Memento Mori 1: Slip the Surly Bonds of Earth

by Shane L. Larson

From January 27 to February 1 every year is a time of remembrances at NASA: it is the week where we observe the anniversaries of the deaths of three flight crews, all of whom perished in the pursuit of human spaceflight. We remember and celebrate the the fallen crews of Apollo 1, Challenger, and Columbia.

From just an altitude of 30 km, the view of the Earth is different — a planet against the void of space. Once the domain of astronauts, views like this can be obtained with balloons and simple digital technology. [Image: S. Larson & HARBOR Program at Weber State University]

Humans often think of themselves as invincible, as the apex species on planet Earth, but it seems clear that we are more fragile than we like to think. If you take our frail bodies and carry them just 50 miles over our heads, we cannot possibly survive on our own. But we are a curious and clever species, and not prone to accepting the notion that there is something we cannot do. Over the long course of our history, we have harnessed technology to allow us to take our bodies to places they were not designed to go, and to survive. It’s easy to discount our earliest endeavours as mundane: constructing shelters, building fires, and making clothing that permits winter wandering. Such skills ultimately transmuted from simple survival into dreams of mimicking the abilities of other lifeforms. Could we dive deep beneath the waves, or take to the air and fly?

Humans are good at walking the long road to making their bodies do things never intended for. (L) Early diving suits, used to explore the sunken Lusitania in 1935. (R) Samuel Langley’s Aerodrome was an early attempt to construct a powered heavier than air flying machine, prepping for launch test in 1903. [Images: Wikimedia Commons]

By the 1800s, aeronauts had successfully developed ballooning, and by the early 1900s the development of mechanical wings and controls launched the era of human flight that has evolved into the aviation industry we have today. But in the middle of the 20th century other dreams were simmering to the surface, largely in the minds of fiction authors. What would it be like to travel beyond the bonds of Earth? Could we make a remarkable voyage from the Earth to the Moon?

Historians and cultural specialists often frame the conversations about the dawn of the Space Age around the Cold War, the opposition of East versus West in the aftermath of World War II. The Soviet Union and the United States were engaged in a war of ideologies, marked by strutting and preening. Technical achievements trumpeted how each ideology supported progress more, and reaching the Moon was the ultimate prize.  But while the national agenda may have been set that way, and resources committed to the endeavour, that is not what won people’s hearts and minds. Consider all the scientists and engineers who designed and built the great machines, the astronauts who flew in them, and the millions who watched from the sidelines: I’m willing to speculate that only a handful of them were motivated by politics. Far more of them, I think, felt the rapture of the all encompassing dream of reaching out from our small island home, the Earth.

Carl Sagan once noted that knowing the Cosmos is a humbling and character-building experience. Our conceits let us dare leave the Earth, even in the face of a Universe infinitely harsh and relentlessly brutal and unforgiving in ways that are hard for us to imagine. Our successes are soaring, exultant moments that we point to in later days, reminding ourselves of what we are capable of. But the failures, the disasters, are that much more crushing, reminders of how hard our goal is to attain, reminders of how painfully incapable and inexperienced we are in the quest to crawl out of our cradle.

The loss of the NASA flight crews were singularly painful moments — it is impossible to imagine the loss felt by their families, or by their colleagues and friends at NASA who had worked alongside them to make their journey possible. But for the rest of us, who watched the tragedy unfold on smaller than life television screens and brittle leaves of newspapers, those moments are burned in our memories, surrounded by the other parts of our lives we were engaged in that day.

The loss of Apollo 1 occurred just twelve days after the first Super Bowl, where the Green Bay Packers beat the Kansas City Chiefs, 35-10 in the Los Angeles Coliseum. The Vietnam War was still raging and arguably occupied a huge part of the American psyche, dominating the news every day.

The Apollo 1 crew. Left to right: Gus Grissom, Ed White, and Roger Chaffee. [Image: NASA]

On 27 January 1967 (25 days prior to launch) Gus Grissom, Ed White, and Roger Chaffee — the first three person crew in the history of the Space Age — mounted the gantry at launch pad 34 and at 1pm Eastern Standard Time entered the Apollo 1 capsule for their “plugs out test.” Plugs out was a regular ground test NASA ran to assure themselves the spacecraft could operate on its own without being plugged into power and equipment here on planet Earth. After five-and-a-half hours of tests, the crew was still in their capsule, sealed inside and trouble-shooting problems (notably a problem with the communications link). At 6:31:04.7 pm fire broke out on the capsule and a garbled alarm to that effect was called out by one of the astronauts. The fire was fueled by the pure oxygen atmosphere in the capsule, and just 15 seconds passed before the hull of the capsule ruptured at 6:31:19 pm. It took pad crews more than five minutes to get inside the capsule to the crew, who had perished.

It was a horrific tragedy. Later analysis and investigation showed exactly how it happened and what prevented the crew from escaping and rescue crews from getting to them more readily. It was caused, as Apollo 8 Commander Frank Borman later remarked, “by a failure of imagination.” NASA was not unaware of the dangers associated with spaceflight, nor were the astronauts. But up to that point, they had failed to imagine that a regular test on the ground could lead to the death of a crew.

There was an investigation, and Congressional hearings. There are plenty of machinations about why such investigations happen, but I think they happen for a very particular reason — to allow us to understand where we (those left behind) failed those we lost. We often reflect, particularly in the heat of our pain, on whether or not the loss of human life is an acceptable risk in our quest to go where Nature never intended. Gus Grissom himself had weighed in on such risk the year before he perished:

If we die we want people to accept it. We are in a risky business, and we hope that if anything happens to us, it will not delay the program. The conquest of space is worth the risk of life. Our God-given curiosity will force us to go there ourselves because in the final analysis, only man can fully evaluate the moon in terms understandable to other men.

Eventually, the Apollo program restarted, leading to six successful landings on the Moon between 1969 and 1972. The Space Age waxed on, and there were other close calls — nail biting moments when it seemed we might lose another crew — but NASA, with a flotilla of capable engineers and scientists, weathered them all and brought the crews home.

The Challenger crew on walkout. Front to back: Dick Scobee, Judy Resnick, Ron McNair, Mike Smith, Christa McAuliffe, Ellison Onizuka, and Gregory Jarvis.

That changed on 28 January 1986, with flight STS-51L and the space shuttle Challenger. It was the 25th mission of the space shuttle program, and Challenger’s tenth flight. The mission had garnered far more attention from the public than many of the previous flights because of the unique nature of its crew — it was the first flight to include a crew member for the “Teacher in Space” program, Christa McAuliffe. Her inclusion on the crew had electrified students, teachers, and schools across the country, and on the morning of the launch millions of people were glued to their television screens. I was among them, huddled around a large TV screen in our school library with a group of friends.

Launch of Challenger on STS 51L. [Image: NASA]

After three previous scrubbed attempts, and a delay of two hours that day, Challenger launched at 11:38am EST on 28 January 1986. Just 73 seconds into the flight, a small leak in the right solid-rocket burned through a support strut and into the main external fuel tank, leading to a catastrophic failure, and loss of the entire crew: Dick Scobee, Mike Smith, Ron McNair, Judy Resnick, Ellison Onizuka, Christa McAuliffe, and Gregory Jarvis.

It was a devastating moment indelibly etched in the minds of everyone who had been watching. As with Apollo 1 before it, the brought the American spaceflight program to a standstill for 975 days. A six month investigation following the disaster identified a failed O-ring in the solid-rocket as the source of the failure, enabled by poor risk analysis and abetted by colder than normal temperatures that did not delay the launch on the day of the accident (though it should have).

The Challenger crew portrait. L to R: Ellison Onizuka, Mike Smith, Christa McAuliffe, Dick Scobee, Greagory Jarvis, Ron McNair, and Judy Resnick. [Image: NASA]

The loss of Challenger was particularly overwhelming because it was the largest crew ever to perish on a mission — 7 people, most of them civilians or civilian astronauts, not test pilots or military pilots. For all of us with day jobs as teachers, or 7-11 managers, or grocery clerks, or dental hygienists — it put a very real face on the fact that if we ordinary people ever travel to space regularly, there will be undeniable catastrophes that occur. Such realizations dramatically dampen the spirit and enthusiasm for daring greatly.

But the space shuttles did return to the skies, once again, just more than two-and-a-half years later, when the Discovery soared aloft with a 5 person crew for a four day flight. Space shuttle missions continued on apace again, the flights once again fading in the news cycle and noted only by those who were paying attention or soaring alongside in their mind’s eye.

After the Challenger disaster and return to flight the shuttle program had many successes, including visiting Mir, laying the groundwork for the International Space Station. [Image: NASA]

After the loss of Challenger a new orbiter, Endeavour, was commissioned and joined the other shuttles, Columbia, Discovery, and Atlantis. There were 88 more shuttle flights through the start of 2003, beginning with STS-26 by Discovery. There were spectacular successes all along the way, including the launch of space probes like Galileo and Ulysses. The space shuttles deployed the first two of NASA’s “Great Observatories,” the Compton Gamma Ray Observatory and the Hubble Space Telescope. The shuttle began visiting the Russian Space Station, Mir, and assembly began on the International Space Station. Other satellites were launched, and the Hubble Space Telescope was serviced and repaired. In a way, the space shuttles accomplished in that era what NASA had always promised — spaceflight had become common, an everyday experience. Seeing news of the shuttle launching on the backpage of the newspaper was kind of like seeing a story about the latest fleet of city buses or the bio of a new city manager. Spaceflight faded into the background cacophony of modern life.

The Columbia crew portrait. L to R: David Brown, Rick Husband, Laurel Clark, Kalpana Chawla, Michael Anderson, Willie McCool, and Ilan Ramon. [Image: NASA]

But in early 2003, the space shuttle Columbia launched on a 16 day mission, STS-107. The 15-day mission carried out a wealth of experiments. The carbo-bay held the Spacehab module, which provided additional habitable space for the experiments of crew, beyond the space available on the orbiter itself. Prominent experiments included video monitoring and characterization of atmospheric dust, as well as monitoring the web-building habits of orb weaver spiders in microgravity. At the end of the mission, on 1 February 2003, Columbia had reentered the Earth’s atmosphere heading for a landing in Florida. Undetected damage Columbia had sustained on the forward edge of the left wing during launch would be its undoing. During reentry, the damage allowed hot atmospheric gases to enter the airframe, burning through the wing and leading to a catastrophic breakup of the orbiter, killing all seven crew aboard: Rick Husband, William McCool, Michael Anderson, David Brown, Laurel Clark, Kalpana Chawla, and Ilan Ramon.

This has always been my favorite picture of the Columbia crew, the way I’ll always remember them. L to R, Front — Kalpana Chawla, Rick Husband, Laurel Clark, Ilan Ramon. L to R, Back — David Brown, William McCool, Michael Anderson. [Image: NASA]

After the Columbia tragedy, the burden of returning to the skies once again fell to Discovery. Once again, return to the skies we did. On 26 July 2005, Discovery launched on STS-114, carrying a 7 person crew on a 13 day mission to the International Space Station. After the Columbia tragedy, there were 22 shuttle flights, but on 8 July 2011, Atlantis made the last space shuttle launch in history. When its wheels rolled to a stop in the cool morning hours of 21 July 2011 at the Cape, the era of space shuttles came to an end. The shuttles have retired, and like their capsule forebears, have retired to museums and science centers around the country where you can visit them, stare at them, and relive the adventurous journeys they made.

The space shuttle orbiters, now decomissioned, can be visited at various museums around the country. Discovery, responsible for two Return to Flight missions, after the Challenger and Columbia losses, can be visited at the Udvar-Hazy branch of the Smithsonian Air and Space Museum. [Image: S. Larson]

It should be noted that spaceflight is inherently dangerous; fatalities were not confined to the American space program — our nominal competitors in the Space Race, the Soviet Union, also suffered great losses. In 1967, cosmonaut Vladimir Komarov died on Soyuz 1, when the parachute failed to properly deploy on return to Earth; it was the first in-flight fatality of a spacefarer. In 1971, cosmonauts Georgy Dobrovolsky, Viktor Patsayev, and Vladislav Volkov were the first crew to spend time aboard a space station, living for 23 days aboard Salyut 1. They died returning to Earth after an accidental decompression of their capsule; they are the only crew to have died in space.

Today, the human spaceflight program is quieter than it once was. The United States currently does not have a launch system for sending crews to space, though American astronauts travel to the International Space Station aboard Russian rockets. That does not seem to dampen the enthusiasm for nor the mystique of astronauts!

Hero culture is a thing, and it isn’t always a good thing. Joseph Campbell, in his excellent book “The Power of Myth” says that “I always feel uncomfortable when people speak about ordinary mortals because I’ve never met an ordinary man, woman or child.” In general, I think there is deep truth in that. But astronauts are something different: almost universally, they encapsulate what can be good about hero culture. We watch and look up to astronauts the way many of us look up to our parents or our grandparents — as a source of inspiration, a source of motivation, as proof that we can and will be more than we think. Every day, we all do something in the world that matters, but we forget that, crushed under the press of noise from the news, or burdened by the weight of difficulties with our co-workers, our families, our social lives, or making enough money to survive. In some corner of our minds, we aspire to be more. We clamp down on that bright spark of aspiration, perhaps embarrassed by it, and seldom let it shine. Instead we only uncover it when we’re alone at night, gazing at it and daydreaming in the moments before sleep. Our heroes, whomever they are, are a spark we revel in, when we are willing to let it leak out.

For me, space has ever-infused my thoughts and dreams. Every time I see an astronaut spacewalking with the jeweled curve of the Earth reflected in their visor, or watch the long loping hops of the Apollo astronauts on the Moon, or look at the photographs of our lost crews, I still somehow imagine my face among them. Which is weird, because I long ago gave up the quest to be an astronaut, replacing it with other dreams of space in the forms of black holes, surging gravitational forces, and galaxies billions of lightyears away. Despite abandoning the quest, apparently I didn’t abandon the dream. This week every year always shows me that. Revisiting the fallen NASA crews every  year makes me remember what it is about human spaceflight that moves us so.

Kalpana Chawla.

And so, as this week concludes and passes us by once again, I encourage you to dust off your mental photo-album of your heroes and refresh your soul with them once again. For those who are still with us, embrace their vision and mission anew, and go out refreshed in your fight to make the world a better place. And for those who have left us, say farewell once again, to whomever they are. They are the ones that remind all of us that in our brighter moments, we strive to be something better, that we are more than the tribulations in our every day lives may suggest we are. Remember those brighter moments, and stretch for them every day. Kalpana Chawla reminds us, “The path from dreams to success does exist. May you have the vision to find it, the courage to get on to it, and the perseverance to follow it.”

And so, to the fallen crews whose gossamer memories drift in the back of my mind, I say farewell once again. Gus Grissom. Ed White. Roger Chaffee. Vladimir Komarov. Georgy Dobrovolsky. Viktor Patsayev. Vladislav Volkov. Christa McAuliffe. Gregory Jarvis. Judy Resnick. Dick Scobee. Ron McNair. Mike Smith. Ellison Onizuka. Kalpana Chawla. Rick Husband. Laurel Clark. Ilan Ramon. Michael Anderson. David Brown. William McCool.

From the stars we came, and to the stars we shall return, now and for all eternity. Ad Astra Per Aspera.


This post is the first post in a series that explores the ephemeral nature of human life in our quest to understand our place in the Cosmos. The posts in the series are:

Memento Mori 1:  Slip the Surly Bonds of Earth (this post)


The Cosmos in a Heartbeat 3: The End is Just the Beginning

by Shane L. Larson

The fence we walked between the years
Did bounce us serene.
It was a place half in the sky where
In the green of leaf and promising of peach
We'd reach our hands to touch and almost touch the sky,
If we could reach and touch, we said, 
'Twould teach us, not to ,never to, be dead.
We ached and almost touched that stuff;
Our reach was never quite enough.
If only we had taller been,

Ray Bradbury.

So opens Ray Bradbury’s epic poem, “If Only Taller We Had Been…” He had composed it for a panel discussion on 12 November 1971, just before Mariner 9 arrived at Mars, becoming the first spacecraft to ever orbit another planet (here’s a video of Bradbury reading the poem). Bradbury’s poem is an ode of optimism to the future — smiling gently at our ancestors and their grasping reach which didn’t quite reach us on the first try. It is a grand hope for our posterity that they achieve all that we dare to dream. The future is a murky place, fraught with unknown difficulties and challenges, but illuminated by desire and ambition.

Despite the long years that remain between today and tomorrow, you can image what our future selves might do in our quest to understand the Cosmos. The Universe will not change much between now and then, but our understanding of the Universe will change, and change dramatically.  The specific details we cannot know, but we know where the limits of our knowledge are, and we know what the capabilities of our current science experiments are. Scientists already are planning for the future, imagining, designing, and developing the Great Machines of tomorrow.  Let’s spin the clocks forward 30 years and take a glimpse of what we expect.

How my best friend imagines my future personal telescope might be like. [Image: J. Harmon]

In 2048 it is impossible to know what sorts of telescopes amateurs will have. But if history is a teacher, amateurs will have access to bigger telescopes and better technology for capturing light from the sky, whether it be cameras or spectroscopes, or automated robotic mounts, or telescopes that see in light our eyes cannot see. A few amateurs already have such capabilities, and the future will surely make such technology more accessible.

Professional astronomers are also looking ahead toward their next generation of telescopes. On the ground, the next generation of telescopes will be about thirty meters in diameter, three times larger than the current generation and six times larger than the venerable Hale Telescope at Mount Palomar. Thirty years from now, Hubble will be long gone, but its successor, the James Webb Space Telescope (JWST), will have been lofted in its place. Right now, JWST is expected to launch in 2021. It should cast its gaze on the Unvierse for a decade or more, depending on how long its fuel reserves last. As with Hubble, it will see farther and see more than any telescope in history, though we don’t yet know what new things it will teach us. It is a marvel of engineering, designed to fold up and fit inside a rocket for launch, it will unfold like a flower when it arrives in space — 18 hexagonal segments that together comprises a gigantic 6.5 meter diameter mirror that looks out on the Cosmos, all of it sitting in the shade of a multi-layered sun-shield the size of a tennis court. If JWST has a tenure as long and as lustrous as the Hubble Space Telescope’s, then the discoveries in store for us will be extraordinary and transformative for astronomy.

The James Webb Space Telescope (JWST) will be more than two and half times the diameter of Hubble, it’s mirror comprised of large hexagonal segments. [Image by Paul Kalas]

Space affords many opportunities to expand our view of the Cosmos, and this is certainly the case in gravitatioanl wave astronomy. In the early 2030s, the European Space Agency and NASA are planning to launch a gravitational wave observatory called LISA — the Laser Interferometer Space Antenna. It will operate continuously for a decade or more, well into the 2040s, probing new and exotic phenomena, many of which can only be understood or detected at all with gravitational waves. 

LISA will be a triangular constellation of spacecraft separated by 2.5 million kilometers, following the Earth around in its orbit. [Image: S. Barke]

Like its ground-based cousin, LIGO, LISA is a laser interferometer. It shines lasers back and forth between mirrors, timing how long it takes the laser to make the flight. Small changes in that flight-time, changing in regular undulating patterns, are the hallmark of gravitational waves. So what’s so different about LISA?  LISA is about a million times larger than LIGO, which is why it has to be in space. The reason it is so much larger is that the size of a laser interferometer determines the sources of gravitational waves it can detect.  Whereas LIGO can detect small stellar skeletons in the last moments of their lives, as they whirl around each other hundreds or thousands of times a second before colliding, LISA is sensitive those same stellar skeletons when they are much farther apart, earlier in their lives when they speed around their orbits only once every thousand seconds or so. Whereas LIGO can detect black holes that have a few to a few tens times the mass of the Sun, LISA can detect black holes that are millions of times the mass of the Sun (“massive” black holes, like the one at the center of the Milky Way).  Astronomers say that LISA observes a different part of the gravitational wave spectrum. Just as we have different kinds of “light” telescopes (optical telescopes, radio telescopes, x-ray telescopes), we have different kinds of gravitational-wave “telescopes” (LISA, LIGO, and others).

So what will LISA teach us about the Cosmos? Consider the Milky Way. Like many galaxies, the Milky Way is ancient — 10 billion years old. Comprised of 400 billion stars, many stars in the Milky Way have lived their lives and passed on into the stellar graveyard over the long course of its history. Something you may remember from your astronomy learnings is that many of the stars in the galaxy are not single stars, but binary stars — two stars orbiting around each other the way the Moon orbits the Earth or the planets orbit the Sun. That means when both stars die, their skeletons sometimes stay together, orbiting each other over and over and over and over again. The stellar graveyard is full of not just skeletons, but binary skeletons, and in particular binary white dwarf skeletons.

White dwarfs are the size of the Earth, but the mass of the Sun. When they are separated by roughly half the Earth-Moon separation, they emit gravitational waves LISA can detect. [Image: NASA/Chandra X-Ray Center]

A white dwarf is a particular kind of stellar skeleton, created when an ordinary star reaches the end of its life. Most stars — and our Sun is among them — are not heavy enough to explode upon their deaths. Instead they swell up into a red giant, then compress themselves down into a skeletal remnant of their former selves, about the size of the Earth. These white dwarfs are hot and crystalline, mostly comprised of carbon, and will over the remaining history of the Universe slowly cool and fade. Most stars in the Milky Way are ordinary, average stars like the Sun. That means that most of the stellar skeletons in the Milky Way are white dwarfs, created over the ten billion history of the galaxy. All told, there are some ten to fifty million white dwarf binaries, and all of them are going to be emitting gravitational waves that LISA can see. 

A simulation of the stellar graveyard of the Milky Way. [Data by K. Breivik and S. Larson]

Part of preparing for astronomy in the future is imagining what you might observe and discover. We simulate the entire life history of the Milky Way on the computer and ask what does the stellar graveyard look like. Where are the white dwarfs, where did they come from, and what do they tell us about the life and history of stars in the Milky Way? When faced with a view of our home galaxy like this, and you imagine all the vast cacophony of gravitational waves from the stellar graveyard? We often describe this as the “lunch-room problem” or the “party problem.” Imagine you are hanging out in the cafeteria or a crowded restaurant at lunchtime. Everyone there is talking, and what you hear is a dull rumble of noise coming from every direction in the room. You can tell it is people talking and laughing, but by and large all of the sound is mixed together and most of the conversations are indistinguishable from one another. Astronomers call this “confusion noise.” Of course you can hear some conversations. You can hear people that are close to you, and you can hear loud people, even if they are far away. You can always hear these close or loud people, no matter what the background noise is. Astronomers call signals that stand out above the confusion “resolved sources.”

Your ears, and mostly your brain (based on what your ears are telling it), are fully capable of separating resolved sources from confusion noise — you do it every time you go out to eat!  Our job as future gravitational wave astronomers will be to teach computers how to carefully pour over the LISA data and learn to separate resolved white dwarf binaries that are close or loud. Out of the tens of millions of confused skeletons in the stellar graveyard, tens of of thousands will be resolved and studied by LISA. Encoded in that collection of stars are the tales of how stars like the Sun have lived out their lives, and a deeper understanding of how the birth and death of stars has surged and waned over the long history of the galaxy.

Dead stars aren’t the only thing that LISA will observe; it will also be sensitive to black hole binaries — massive black hole binaries. One of the great astronomical discoveries astronomers have made in the last few decades is that big galaxies harbor massive black holes at their centers, black holes of millions or billions of solar masses. As our telescopes have gotten larger and able to see deeper into the Cosmos, we have also started cataloging galaxies in all their shapes and forms, and discovered that sometimes they collide. So what happens when two galaxies, each harboring a massive black hole, collide? 

There are many known examples of colliding galaxies, but this is a personal favorite — the Rose and Hummingbird (Arp 273). The smaller galaxy is throught to have already passed through the larger galaxy once. [Image: Hubble/STScI]

Their stars swarm and merge like a cloud of angry bees, eventually coalescing due to their mutual gravitational attraction and form a new galaxy. Their big black holes slowly sink to the center, where they find one another and begin a slow, spiraling orbit that grows ever shorter as time goes on. When the orbits take only 10,000 seconds or less, they become observable by LISA.

Today, we know galaxies merge, but we know little about the processes that help massive black holes grow. Do they accrete gas? Do they grow by absorbing stars over and over again? Or do they only grow by merging with other black holes? LISA’s observations of massive black holes, together with where in the Cosmos they are found, will begin to provide answers to those questions.  We don’t know those answers today, because we’ve seen that galaxies collide but have yet to see massive black holes merge. In lieu of LISA data, which is still more than a decade in the future, we simulate different ways to grow galaxies and black holes on super-computers, and simulate what LISA would observe.

One massive simulation, spanning the entire age of the Universe, is called the Illustris Simulation. The movie below is a visualization of the Illustris simulation from the Big Bang to the present day. The simulation accounts for gas and dark matter int he Universe, and tracks the formation of stars, galaxies, and black holes across Cosmic time. We use the simulation as a model for the actual Universe, and “observe it” with a simulation of LISA. What do we learn from this? That the sky is going to be alive with massive black hole binaries, visible to LISA in every direction and all the way to the edge of the Observable Universe. In the movie below, we show all the mergers that would be detectable by LISA if it were flying at the right times (data simulation be Michael Katz and S. Larson).

You can imagine, and rightfully so, that all the massive black holes just add to the confused cacophony of gravitational waves created by the millions of white dwarfs in the galaxy. The Cosmos is full with the gravitational chorus, and our job as astronomers is to pick out all the melodies, and harmonies, and individual instruments and voices that make it up.

The miracle of the modern age is that we are suddenly aware that the Universe is sending us messages with a multitude of signals — light, particles, and gravitational waves. It’s an intricate, interlaced story that we are just now learning to interpret. Modern, instrument based astronomy began with the invention of the telescope some 400 years ago. Particle astronomy is only 100 years old, and gravitational wave astronomy has only been successful in the last five years. Our ability to probe the Universe carefully and precisely has existed for only the bareest fraction of Cosmic time — a heartbeat in the life of the Cosmos. We’ve used our ingenuity, our curiosity, and our creativity to spin that short experience into a complex and increasingly sophisticated understanding of the nature of the Universe, and our place within it.


This post is the last of three based on a talk I have given many times over the last few years, updating it each time to reflect the latest coolest things. The complete set posts of the series are:

The Cosmos in a Heartbeat 1: A Love Affair with the Cosmos

The Cosmos in a Heartbeat 2: Coming of Age

The Cosmos in a Heartbeat 3: The End is Just the Beginning (this post)

This post was enabled by a new version of the talk done as a Kavli Fulldome Lecture at the Adler Planetarium in Chicago. The talk was captured in full 360, and you can watch it on YouTube here. If you have GoogleCardboard, click on the Cardboard Icon when the movie starts playing; if you watch it on your phone, moving your phone around will let you look at the entire dome!

I would like to thank all my colleagues at Adler who worked so hard to translate what was in my brain into a story told in the immersive cradle of the Grangier Sky Theater. The talk was given on 9 Nov and 10 Nov 2018.

A Cosmic Collection

by Shane L. Larson

The Cosmos wheels above our heads, far out of reach but well within our powers of perception. Always we wonder, what’s happening now and what does it mean? [Image: S. Larson]

The Cosmos is vast beyond ordinary comprehension, and it is always up to something. Astronomy is our most valiant attempt to observe everywhere all at once, to discover all that is discoverable, to know all that is knowable. We are exceptionally good at it, by any standard you can imagine. The store of cosmic knowledge we have amassed just since recorded human history began (only a few millennia) is extraordinary, and has helped push mathematics, physics, and technology forward in dramatic and unexpected ways. In just the last century and a half, technology has expanded our capabilities by leaps and bounds, allowing us to collect exquisite data that is perplexing and mysterious and revealing. Today we live in an era where we can collect so much data, and collect such complex data, that it cannot be absorbed, analyzed, nor understood with only brief consideration. It requires long and sustained study, intense scrutiny, and expansive modeling.

[L to R] Hubble Space Telescope, the ATLAS detector at the Large Hadron Collider, and LIGO-Livingston. Exquisite technology expands our ability to observe the Universe around us.

Modern science, particularly at the frontiers of knowledge, requires a lot of human brains to make great discoveries. It begins with the great machines themselves. Building something like the Hubble Space Telescope, or the Large Hadron Collider, or LIGO and Virgo requires vast teams of engineers, physicists, materials scientists, construction engineers, titanium welders, chemists, geologists, and a thousand other professions just to build the experiments. Once we start collecting data, there are thousands of others in physics, computer science, signal processing, image analysis, information technology, visualization, and a thousand other professions needed to understand the data!

Big discoveries emerge almost immediately, because the Universe is always up to something, and always up to something that is dramatic and stunning to behold. If you build an exquisite experiment, you’re going to discover something. Such was the case of Hubble’s discovery of the existence of other galaxies, when we constructed the 100-inch Hooker Telescope on Mount Wilson. Such was the case of Rosalind Franklin’s discovery of double-helix structure of DNA with the development of x-ray crystallography. Such was the case of the discovery of the Higgs Boson with the construction of the Large Hadron Collider. Such was the case with LIGO and Virgo, which over the past three years have witnessed six different gravitational wave events.

My personal accounting of every known gravitational wave event, accurate and complete up through GW170817. When we announced GW170608, my page was too narrow to include it!

Today, the LIGO-Virgo Scientific Collaboration announced our first catalog of gravitational wave events — GWTC-1 (Gravitational Wave Transient Catalog). It is the current complete list of every event we’ve discovered in our data. Some of them you know about, because we have talked about them before (even here on this blog: GW150914, GW151226, GW170104, GW170814, GW170817). But since then, we’ve been sifting through the data, looking at every feature, comparing it to our astrophysical predictions, cross-checking it against monitors that tell us the health of the instruments, determining if it appears in all the detectors, and using our most robust (but slow-running) super-computer analysis codes. 

The result is the catalog before you (if you’re curious, you can see the catalog at the Gravitational-wave Open Science Center), that has improved values for the properties of all the previously announced sources, and four new binary black hole sources that were in the data: GW170729, GW170809, GW170818, and GW170823. Additionally a source previously known as LVT151012 (“LIGO-Virgo Trigger“) has been renamed GW151012.

A screen cap of GWTC-1, the first “Gravitational Wave Transient Catalog of Compact Binary Mergers” as it appeared today. The number of events, the amount of data about what the Cosmos is doing, is growing. [Image: LIGO-Virgo Collaboration]

Astronomers are collectors. Every event has an identity, and a long list of everything that we know about it, but there are always going to be a few that are well known and remembered above all the others. GW150914 is always going to be “The First.” GW151226 (“Boxing Day“) was the second and will always represent the moment we all realized this endeavour really was going to be astronomy, not just a single one-time experiment. GW170817 is always going to be remembered as the first multi-messenger gravitational wave detection of a binary neutron star.

But today when you look at the long list of events it strikes me, for the first time, that this is a huge and ever-growing collection. We’ve always known that would be the case, but there is something viscerally pleasing about watching it happen right before your eyes. It is clear that the list is now long enough that it would be challenging to memorize!

We don’t have images of the gravitational wave events, but our artists can imagine what the members of our collection might have looked like at the moment we observed them. [Images: Aurore Simonnet/LIGO-Virgo Collaboration/Sonoma State University]

From the perspective of astronomy, this is a good thing. Having a collection of events is how we learn things about the Universe that can’t be learned from just a few observations. Let’s examine an analogy to explain the necessity of collections. Suppose you were an extraterrestrial visitor who landed on Earth to learn about “humans” and visited someone’s book-club, perhaps five people. What could be learned by just observing five people? A few obvious things might pop out immediately. Humans have five projections from their bodies (two arms, two legs, a head). They have two eyes and two ears. But depending on the five people you may not learn that there is a wide range of hair or eye colors (any redheads in your reading group? anyone with grey hair? what about blue or green eyes?). You may or may not know that there are multiple sexes, nor that there are smaller and larger humans.  Your knowledge would be completely defined by the size of your collected observations.

This is absolutely the case in astronomy — sometimes we have many observations, sometimes we have only a few, but we always want more. Having many observations is paramount to understanding the Cosmos because observations are the only things we have. We are confined to observing the Universe from this small world on which we live, and what we know is built completely on our few, meager observations.

What stands out the most in the new LIGO catalog? We are still letting the implications settle in, but the most important thing the new events do is it makes our estimate of the popuatlion of black holes in the Universe more accurate, and we’ve started to examine those implications is a new study that is being released in tandem with this announcement. But let me highlight the things that personally catch my attention the most.

This shows all the known masses of black holes and neutron stars, detected both by traditional telescopes and using gravitational waves. I’ve highlighted the new black holes in the catalog in green. You can explore this plot with an interactive we’ve created at CIERA. [Image: LIGO-Virgo/Frank Elavsky/Northwestern]

First, remember that every gravitational-wave detection by LIGO-Virgo is not just one black hole, but three — the two black holes that came together, and the black hole that resulted from their merger. That is very important because it means we have three new measurements of the possible masses that black holes can have. If you look at our black hole mass plot you see that black holes come in all masses between five solar masses and 80 solar masses. In fact the new event, GW170729, produced the heaviest stellar origin black hole known to humans, at 80.3 times the mass of the Sun!

Second, it is interesting to look at the black holes that merged and consider how they are different from one another. From the existent data, it looks like the black holes that merge are always close to the same mass. So far, we’ve never seen a smaller black hole fall into another black hole that is five or ten times larger. Does that mean it never happens in Nature? Or does it mean it happens rarely? Or does it mean we’re not good at seeing or recognizing such events yet? The answer is an important one because the sizes of the black holes before they merge tells us something about how they form and grow together. That question is of intense interest to astronomers since black hole formation is tied to stellar evolution, and stellar evolution is tied to how all the stuff around us is made.

Lastly, the trend continues to show that LIGO and Virgo are sensitive to heavier black holes than those that have been previously known from traditional telescopes. The dramatic demonstration that there are stellar-origin black holes near 100-solar masses is stimulating dramatic conversations among astronomers (particularly theoretical astronomers like my group, who study stellar evolution) about how the Cosmos creates these large black holes. 

Left to Right: LIGO-Hanford (Hanford, Washington), LIGO-Livingston (Livingston, Louisiana), and Virgo (Pisa, Italy). All three detectors are currently working toward the start of our new observing run (“O3”) in the Spring of 2019. When new data begins to flow, the catalog is going to start growing once again.

Perhaps the most exciting thing to me, is this is just the beginning. LIGO and Virgo are currently in a maintenance phase, but our third observing run (“O3”) will begin in the spring of 2019. The instruments will be performing at higher precision than ever before, and there are going to be more detections that will make this catalog grow even larger. Our questions are swirling, the anticipation is palpable. But even more importantly, there is a dedicated group of scientists, particularly those who work in signal analysis, computer science, and machine learning, who are developing new and improved techniques for finding signals in data. There are great practical applications to such endeavours (like how do you separate the 25 zillion text messages sent by teenagers every five minutes), but it will once again help grow our gravitational wave catalog, expanding our understanding of the stellar graveyard of the Universe.

Once new data is being collected, the data from our previous observing runs will sit there in the open data archives, waiting for someone to come back and look at it again. Historically, there have always been discoveries made in archived astronomical data long after it was collected. Data is simply too complex to understand everything in it, and we are simply too naive about everything that is going on in the Universe to recognize everything in our data the first time we work with it. There is certainly more in the LIGO-Virgo data than even this catalog. But progress is slow, and only the future will show us what is yet to be discovered, in an every growing tree of knowledge, dividing and growing from our previous discoveries.

Examples of Lichtenberg figures, created by electrical discharges and discovered by the father of experimental physics, Georg Christoph LIchtenberg. Knowledge, like these figures, branch and grow continuously from each other. [Images: Wikimedia Commons]

One of the great physicists of the 16th Century was Georg Christoph Lichtenberg, widely recognized as the first great designer and builder of experiments in physics, our distant ancestor in this game. Today he is most well known for an artform known as “Lichtenberg figures”, the branching shapes burned in materials by surges in electricity — a most suitable metaphor for our growing branches of knowledge. Lichtenberg fully understood the staggering and surging process of scientific discovery, writing “Nothing puts a greater obstacle in the way of the progress of knowledge than thinking that one knows what one does not yet know.” Today’s announcement is just the beginning of what we do not know.

So today, please join us in basking in the glow of new discovery, reveling in the joy that this is just the beginning, and there is no end. Congratulations to my colleagues and friends in LIGO and Virgo; we’ll do this again sometime soon!

Several of my colleagues in LIGO and Virgo have also written about the new catalog — please check out their posts as well!

The Cosmos in a Heartbeat 2: Coming of Age

by Shane L. Larson

Astronomy from your backyard is dominated by naked eye stargazing, and optical telescopes that gather exactly the same kind of light you see with your eyes. There are a few amateurs who ply the skies with radio telescopes, or build cosmic ray detectors in their kitchens, but for the most part it is traditional telescopes. When I first started my studies in astophysics, this was still largely true of professional astronomy, though there were a few advanced experiments that were building the technology needed to survey the Cosmos using astroparticles, and a robust effort to design what would become the world’s first successful gravitational wave detectors.

One of the things that is true of all telescopes, no matter how they are designed to see the Cosmos, you can always build a better instrument that can observe more. In the context of astronomy, “more” means detecting cosmic phenomena that are difficult to perceive, or probing deeper into the distant Universe.

My two current telescopes (both homebuilt). The one on the left is called Equinox (12.5″ f/4.8 Dobsonian Reflector) and the one on the right is called Cosmos Mariner (22″ f/5 Dobsonian Reflector).

For optical telescopes, bigger is better. The larger the mirror, the easier it is for the telescope to capture a few tiny bundles of precious light that arrive on Earth and gather them all together in one place (your eye, or a camera) so there are enough to be bright enough to see. When I first started in backyard astronomy, I had an 8-inch telescope, which is about 30 times larger than the pupil of my eye, and so can gather almost 850 times more light than my eye. That first telescope of mine has been passed down to my daughter as part of her growing interest in backyard astronomy. It has changed its look, but its heart is still the telescope that I spent many hundreds of hours out under the night sky with. I’ve built a new, bigger telescope to replace my old one. Shown above is my telescope called Cosmos Mariner, and has a 22-inch mirror in it. That mirror is about 80 times larger than my pupil, and can gather more than 6000 times the light my eye can!  Mariner can probe deep into the Cosmos, and I use it as often as I can to soak in the wonder of the night sky.

The Hubble Space Telescope. Arguably the most capable and successful telescope ever built by humankind. [Image: NASA]

Professional astronomers have also been building bigger and better telescopes. Shown above is the Hubble Space Telescope, which launched in 1990, and is arguably the most successful scientific instrument in history. It’s mirror is 2.4 meters in diameter, but it peers at the Universe from a vantage point high above the atmosphere of Earth. In its three decades of observing, it has seen farther and seen more than any telescope in history. All told, some 10 to 15 thousand papers have been written about what Hubble has seen in the Cosmos. When we build a machine like Hubble, we always have grand plans for it. One of the tasks we had in mind was to use Hubble’s size and vantage point high above the Earth to take a picture of the Cosmos unlike any other before it. We picked a non-descript region of the sky in the constellation Eridanus, and over the course of a decade, asked Hubble to go back and look at that point over and over and over again, until it had stared at that one spot for a total of 23 days. You take all those individual pictures, and you stack them together to make a single new picture.

The Hubble Extreme Deep Field (XDF). [Image: NASA/ESA]

What you find is that in a region of the sky where you thought there was nothing, there is very definitely something. We call this picture the Hubble Extreme Deep Field. This image covers an area on the sky roughly the size of the eye of needle, held at arms length. Within it, virtually every fleck of light and color you see, is another galaxy. All told there are some 5000 individual galaxies in this image, implying that across the entire sky there are several hundred billion galaxies. This is what we mean when we say the Cosmos is vast beyond our wildest imaginations.

The Hubble Extreme Deep Field is a flat, two-dimensional image not unlike other pictures you are used to looking at. But one of the things we can do in modern astronomy is measure the distances to galaxies, so we can make a movie of what it would be like if you could dive into this image, making the impossible journey from Earth to the most distant galaxy in the image. If we launch ourself on that voyage, the first thing we notice is that over most of the journey, we are travelling through nothing at all.

The Universe, on the grandest scales, is mostly empty of any ordinary matter like you and me or stars or galaxies.  As we plunge deeper, we do encounter groups of galaxies — they tend to cluster and grow together, making a vast cosmic web that fills the entire Cosmos. Many of the galaxies we pass look familiar, like we expect galaxies to look. But as we travel farther and farther into the Deep Field, we are looking back farther and farther in time, until we reach the most distant galaxies in the image. These are the youngest galaxies we’ve ever seen, born barely 450 million years after the birth of the Universe. Astronomy is a special kind of time machine — looking back across the Cosmos is looking back in time. We can see how galaxies were long ago, in an effort to understand how our own galaxy might have been long ago as well.

The surface facilities of IceCube at South Pole. [Image: IceCube Collaboration]

Our colleagues in neutrino astronomy have been building their own new generation of observatories as well. Today, the pre-eminent neutrino observatory in the world is located at South Pole Station, and is called IceCube. IceCube is a series of 86 deep cores drilled 1.4 to 2.4 kilometers down into the Antarctic ice. Long strings with camera modules are lowered into the bores on cables, and the ice refreezes around them; all told there are more than 5000 cameras (“Digital Optical Modules”) in the array.  Observing with IceCube is in principle the same as KamiokaNDE — neutrinos pass through the Antarctic ice, and sometimes interact with the atoms of the ice to produce a burst of light that is picked up by the cameras on the strings. 

The IceCube array is encased in the ice underneath the surface station. [L] The long ice cores contain strings with cameras, and when an event passes through the array the light is detected by some of them. [R] The most energetic neutrino event yet detected, on 22 September 2017. [Images: IceCube Collaboration]

In September 2017, IceCube picked up the most energetic neutrino ever observed. It blasted through the array at  20:54:30 UTC (around 2:54pm Central Standard Time), and was detected by a long sequence of camera modules that stretched from one side of the array to the other. Looking at the shape of the data in the array, and in particular which side of the array lit up first in the detection, allowed astronomers to point backward from IceCube to the point on the sky where the neutrino came from.

An artists impression of a blazar, a type of active galactic nucleus with a supermassive black hole at the center, and an energetic jet pointing at the observer (us, on Earth). This is the type of object the IceCube neutrino event was traced back to. [Image: DESY Collaboration]

Using this pointing information, astronomers searched that region of the sky and discovered a blazar called TXS 0506+056. A blazar is a kind of galaxy that has an active galactic nucleus (AGN). AGN are supermassive black holes that have a swirling maelstrom of gas and material around them that slowly feed the black hole. When gas gets close to the black hole, the gravitational attraction propels it onto high speed orbits around the black hole. All of the gas swirling around together interacts strongly with the rest of the gas and as a result gets very hot; hot gas glows brightly, especially in ultra-violet and x-rays, both very energetic forms of light. The bright light can be seen in telescopes from Earth indicating the presence of a supermassive black hole. As the gas swirls ever inward, some of it eventually falls into the black hole, vanishing forever. Some of it, however, is spining so fast it cannot fall onto the black hole, and gets squirted out into an energetic jet, propelled away from the nucleus of the galaxy at enormous speeds. This is characteristic of AGN; a blazar is simply an AGN where the view from Earth is staring directly down the jet.

All the material being ejected down the jet is moving at very high speeds, and still collides with other material making its own way out through the jet. This energetic environment is not unlike our own particle accelerators here on Earth, and at some point along the jet a collision between particles created the neutrino we detected with IceCube.

This is once again multi-messenger astronomy — observing the same astrophysical object, using both astro-particles and telescopes. What is different in this case is the discovery was led by neutrino astronomers, who guided telescopes toward the right place in the sky.

The twin 10-meter Keck Telescopes on Mauna Kea. [Image: Wikimedia Commons]

Now, most of us know what astronomers know: black holes are AWESOME. Active Galactic Nuclei are not the only big black holes in the Cosmos. There is, in fact, a massive black hole much closer to home, in the center of our own Milky Way. Astronomers on the ground have been building bigger and bigger telescopes, and today among the largest telescopes in the world are the twin 10-meter Keck Telescopes on Mauna Kea, in Hawaii. We’ve been using the Keck Telescopes, togther with others around the world, to peer at the exact center of the Milky Way for the past two and a half decades. The telescopes have been able to detect a small cluster of stars we call the “S-Cluster.” We’ve been watching them long enough now that we have not only seen the stars move on their orbits, but we’ve seen some of them complete their orbits.

Two decades of observations have shown the orbits around the 4 million solar mass black hole at the center of the Milky Way. [NCSA/UCLA/Keck]

If you remember back to your early classes in physics or astronomy, you may remember that someone like me once told you that if we can measure orbits, the Universal Law of Gravitation (published by Newton in 1687) can be used to discover the size of the mass that is driving the orbit. For the S-Cluster of stars, the size and timing of the orbits says there is a 4 million solar mass black hole at the center of the galaxy. How do we know it is a black hole? It is emitting no light, and it is so small it competely fits inside the orbits of the stars!

Among this cluster is a star we call SO-2. It is the star closest to the black hole. Every 16 years, its highly elongated orbit dips down to its closest point (what astronomers call the “periapsis”), and zips around the black hole in a quick slingshot. In just the course of a few months, this 15 solar mass star completely changes the direction it is moving through space. THAT is the power of a massive black hole! In May 2018, we watched SO-2 make the second periapsis pass we’ve seen since observations began (the last was in 2002), giving us the most precise measurements to date of the properties of the black hole. By all accounts, the black hole at the center of the Milky Way has all the properties and behaviours predicted by general relativity.

This story serves to introduce us to one of the emerging wonders of modern astronomy — that we are beginning to understand that we can use gravity itself to probe the Cosmos. In the case of SO-2 we are using the influence of gravity to tell us something about the black hole, an object which by definition emits no light. But a century ago, when general relativity was newly minted and first being pondered by Einstein, he had another notion: perhaps we could observe gravity itself — don’t use telescopes at all, but instead build a machine of some sort that plumbs the Universe with some other sense, a sense that we humans do not posses at all.

This illustrates the basic premise of gravitational wave detection using laser interferometers. [TOP] Imagine a ring of small masses. If a gravitational wave is coming straight out of the screen at you, it distorts and warps the ring, first making it long and skinny, then a bit later making it short and wide, and then back again. [BOTTOM] The idea of detection with an instrument like LIGO or LISA is to use mirrors for three of the masses on the rings. As the distance is warped between the masses, the time it takes a laser to travel between them changes. [Images: Shane L. Larson]

Einstein’s idea was simple. What you and I call “gravity” fills space and can change with time, and so the information about how it is changing must be able to be transmitted from one place in the Cosmos to another at the speed of light or less. That propagating message is what we today call a “gravitational wave.”  It is one thing to deduce that such gravitational signals must exist, and quite another to decide what that means and how to build an instrument to detect them. It took until 1957 for physicists to even come to agreement on what gravitational waves do to the world around us. After much arguing and debating and confusion and aggravation, it was realized that they warp spacetime — they change the proper distance between any two masses in a repeating pattern of stretching the distance out and compressing the distance down.

The effect is extremely tiny, so tiny as to be unnoticeable in everyday life, and so tiny as to be discouragingly small if you want to build an experiment to look for the effect. But physicists are a diligent and resilient bunch, and a few of them began to think about exactly how to build such an experiment. Fast forward to today, and six decades of thinking have culminated in one of the most exquisite astronomical observatories ever built: the Laser Interferometer Gravitational-wave Observatory — LIGO. In 2015, LIGO was the first gravitational-wave observatory that was able to successfully detect gravitational-waves, in that case from two merging stellar-mass black holes. Many more discoveries followed, all of them of black holes, until August of 2017.

Left to Right: LIGO-Hanford (Hanford, Washington), LIGO-Livingston (Livingston, Louisiana), and Virgo (Pisa, Italy).

In late August, people across North America were gearing up for a total solar eclipse that was going to race across the continent from Oregon to South Carolina on August 21. But just four days before, in the early morning hours in North America (7:41am Central Daylight Time), the Universe blasted us with gravitational waves. This particular event was unlike any previous gravitational wave event we had seen. It was accompanied by an almost simultaneous burst of gamma rays, detected by NASA’s Fermi Gamma Ray Telescope, in orbit high above the Earth. The two LIGO facilities, together with our European colleagues using their Virgo detector outside of Pisa, measured the masses of the event telling us we had just observed the merger of two neutron stars — a kind of dead stellar skeleton that can be left over when stars explode at the end of their lives. LIGO and Virgo were able to pinpoint the location of the event to a small region on the sky. By the end of the day, as the Sun set on professional telescopes around the world, the search was on and the fading light of the event was discovered in a small galaxy known by the name NGC 4993. The light gathered by observatories around the world over the next many months (and continues today) showed that this event was an explosive phenomena known as a kilonova. In less than 24 hours, this single event transformed modern astronomy — literally, in the blink of an eye.

The initial detection resolved a great mystery that had confounded astronomers since the 1970s — short gamma ray bursts (like the one detected by Fermi) were the signature of merging neutron stars (detected in gravitational waves). The continuing observations of the kilonova resolved another great mystery — kilonova are the expanding, cooling shattered remains of merging neutron stars. From that cooling and expanding morass of nuclear material that was once the neutron stars, the stuff of us is made in large quantities — the heavy elements on the periodic table, built from the death of dead stars!  All of these ideas are ones that astronomers have speculated about, imagined, and calculated for many years up to now, but the observation, the multi-messenger detection of gravitational waves and light has, for the first time, shown us that some of our thinking is along the right tracks.

It is remarkable to witness this evolution in our thinking about the Cosmos. When I started in astronomy (both in my backyard and in my professional endeavours), our thinking was dominated by telescopes because those were the instruments we had and the tools we had been successful at building and using. We were just starting to try to expand our toolbox, to develop a new repertoire of machines to unravel the story of the Universe and our place within in. Now, at the middle of my life and career, those idle daydreams, those grand ponderings of what might be possible, have come to fruition. 

Now we turn our eyes to the future, and ask “what next?


This post is the second of three based on a talk I have given many times over the last few years, updating it each time to reflect the latest coolest things. The complete set posts of the series are:

The Cosmos in a Heartbeat 1: A Love Affair with the Cosmos

The Cosmos in a Heartbeat 2: Coming of Age (this post)

The Cosmos in a Heartbeat 3: The End is Just the Beginning

This post was enabled by a new version of the talk done as a Kavli Fulldome Lecture at the Adler Planetarium in Chicago. The talk was captured in full 360, and you can watch it on YouTube here. If you have GoogleCardboard, click on the Cardboard Icon when the movie starts playing; if you watch it on your phone, moving your phone around will let you look at the entire dome!

I would like to thank all my colleagues at Adler who worked so hard to translate what was in my brain into a story told in the immersive cradle of the Grangier Sky Theater. The talk was given on 9 Nov and 10 Nov 2018.

The Cosmos in a Heartbeat 1: A Love Affair with the Cosmos

by Shane L. Larson

The night sky over the Pando Forest in central Utah. Pando is an 80,000 year old aspen grove — it has seen almost 30 million nights like this one, far more than any single human will ever live through. [Image: Shane L. Larson]

The Cosmos is vast in ways that are difficult for humans to wrap their brains around. That doesn’t stop us from talking about it, of course, but it is vast, none-the-less. What do I mean by “vast?

The Universe is 13.8 BILLION years old, 100 million times older than the oldest human. When you and I go out at night there are almost 10,000 individual stars we can see with the naked eye, but the Milky Way has some 400 BILLION individual stars, and there are some 500 BILLION individual galaxies in all the Cosmos. If you and I could somehow take a road trip, from one side of the Milky Way to the other, travelling at the fastest speed possible (the speed of light) it would take us 100,000 years to go from one side to the other —1000 times longer than any human has ever lived. And the entire Cosmos itself is far vaster.

These sorts of factoids are fun to know and think about. They melt your brain, and they can impress your friends and family at a dinner party. But what is always remarkable to me is even though you and I occupy only one small part of the Cosmos in space and time, we have still managed to piece together a story about the history of the Universe — its overall size and content, when it was born, how it has lived its long life to date, and what its ultimate future might be.  As a species, we have only been cognizant of the science we call astronomy for a few centuries, though we have been looking outward into the Cosmos for far longer. But in those few centuries, in just a handful of human lifetimes, we have managed to piece the story together. Even though a human only lives through the merest flash of a moment in Cosmic time, less than a single heartbeat in the life of the Cosmos.  This is a story about how we learn what we learn about the Universe around us and our place within it.

Me in elementary school. I’m not sure what I’m doing in this picture, but I’m pretty sure I’m not getting into trouble [Image: Pat Larson]

I am a professional astronomer, but like most of us, my love-affair with the Cosmos began when I was young. I would spend long hours out in the backyard, laying on the ground trying to learn my constellations with an old beat-up paper star wheel. We didn’t have a telescope (they were expensive), but my mom is an avid birder and she had an old spotting scope. She used to let me take it out in the backyard and put it on an old card table, and I discovered there was far more to the Cosmos than my naked eye could see. I looked at the Moon and discovered craters, and mountains and sinuous canyons. I looked at the brightest points of light I could see, and found out they were Mars, and Jupiter, and Saturn — other worlds, tantalizingly close, but so very far away. There were other things to discover as well.

My Mom’s spotting scope (she still has it!). This is the first telescope I ever looked at the sky with.

In the corner of the sky we call Andromeda, there is a smudge of light that looks like a wisp of cloud. It is the most distant object you can see with your naked eye, and we call it the Andromeda Galaxy. It is 2.1 million light years away, which means if you step outside tonight and look at the Andromeda Galaxy, the light that falls in your eye and makes its impression on your mind is ancient light. It left the Andromeda Galaxy 2 million years ago, at a time when the most advanced hominids on Earth were Australopithecus, and the world was dominated by mega-fauna like sabre-toothed cats (smilodons) and mastodons. This is one of the fundamental truths in astronomy: looking out is looking back in time, and the farther we can look, the more about the long history of the Cosmos we can discern. As astronomers we are always on an epic quest to build better tools to help us probe farther out into the Cosmos. 

My first astronomical telescope, an 8-inch reflector I built called Albireo, based on Richard Berry’s excellent book “Build your own telescope” .[Image: Shane L. Larson]

Let’s look back to the time when I decided to become a professional astronomer, sometime during my early years in college. Thirty years ago, in 1988, I was already improving my backyard astronomy. I’d left my mom’s spotting scope at home, and after not too long had built my own telescope. It was bigger than my mom’s spotting scope, and could see much more of the Universe. At the same time, the largest telescope used by professional astronomers was the 5-meter (200-inch) Hale Telescope on Mount Palomar. At that time, it was the largest telescope in the world, a title it had held for 40 years since it was built in 1948. Astronomers are still using it today.

The 5-meter Hale Telescope on Mount Palomar was the largest telescope in the world for 40+ years. This image was taken in the dome on a night in 2009 when one of our observing runs was clouded out. Astronomers still use this telescope today. [Image: Shane L. Larson]

So what do astronomers do with these great machines? On any given night, whether you are looking through a backyard telescope, or looking through a telescope like the Hale, the sky looks much like it did the night before. The stars are still where you remember them, living out their lives slowly, changing little. We find new and interesting things, of course, but what we are often most interested in are the unexpected events — energetic and dramatic events that appear in the sky and then are gone. Astronomers call such things “transients.” Consider a “supernova.” One of the things we have learned over the past century is that stars, like people, are born, they live long lives, and they ultimately perish. When the most massive stars reach the ends of their lives, they die in a titanic explosion that, for a few brief days or weeks, sheds enough light to be visible in the night sky. The last time an explosion like this was seen in the Milky Way was in 1604, before the first telescope was ever used to study the sky!  Four hundred years ago, we didn’t know what supernovae were, but the events were momentous enough to note down.

An astrolabe from the Adler Planetarium collection, showing the Supernova of 1604. [Image: Adler Planetarium, notations from Pedro Raposo]

You can find written notations of the 1604 supernova in paper star atlases of the day, but one of my favorites is shown in the astrolabe above, which is part of the Adler Planetarium’s historical collection. An astrolabe is a mechanical device used to visually measure the positions of stars in the sky by eye. They are elaborate and intricate machines, but also stunning and artistic in their elegance and form.You’ll see on the upper right ring of this astrolabe that Supernova 1604 is marked, preserved forever in the solid copper record of the day. You’ll notice there are other transients on this astrolabe, including the previous supernova observed in the Milky Way (Supernova 1572), as well as the great comet of 1618.  My colleague Pedro Raposo, an astronomy historian at the Adler Planetarium, points out that depicting supernova and comets on an astrolabe is an indicator of how our understanding of the Universe was evolving. At that time, we didn’t know what supernovae and comets were. Their nature was widely debated, with many believing they were atmospheric phenomena. The fact that they were recorded on a mechanical starmap is an indicator that we were slowly coming to the understanding that these events were in the deep, cosmic sky. Our views about the Cosmos were changing.

Supernova 1987a, imaged by the Hubble Space Telescope in 1995, eight years after the explosion. [Image: STScI/NASA/ESA]

Now spool ahead to the 1980s. In 1988 we understood much more about supernovae than we did when that astrolabe was built, but we had never been given the opportunity to study one up close. In the entire 400 year history of telescopic astronomy, there has not been a supernova here in our own galaxy, close enough for us to see all the fine details and study how stars reach the end of their lives. But on 23 February 1987, there was a supernova not too far away, in a small galaxy next door to the Milky Way, called the Large Magellanic Cloud. We called it Supernova 1987A, and it was visible to the eye for several months. Astronomers could see it in their telescopes, and still today the most powerful telescopes can detect the faint echoes of light coming from the explosion.

But SN1987A was special for another reason. When a star dies in a supernova, it not only sheds light, it also releases a cosmic rain of particles called neutrinos. When this supernova exploded, 1057 neutrinos were released (that’s 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 neutrinos!), bursting out in every direction in the Universe. Neutrinos are notoriously hard to detect because they tend to go blasting right through matter as if it isn’t even there. When the neutrino burst from SN 1987A reached Earth, 30 trillion of them went through me and you and every other person on planet Earth, and we didn’t even know it! But astronomers had been thinking about this for a long time, and had constructed a special observatory — a neutrino telescope.

The Kamioka Observatory “KamiokaNDE” experiment, one of the neutrino observatories that captured a few of the neutrinos from SN1987a. [Image: ICRR/University of Tokyo]

A neutrino telescope is not like an ordinary telescope, because neutrinos are very difficult to capture. Instead neutrino telescopes watch for neutrinos interacting with other things. In 1987, the worlds largest neutrino telescopes were enormous tanks of very pure water underground. Sometimes when a neutrino goes through these tanks, their interaction with the atoms in the water generates bursts of light that can be detected with very sensitive cameras lining the inside walls of the tank. In the hours right before telescopes detected the light from the supernova, 25 neutrinos were seen in detectors around the world. Only 25 neutrinos from all the 1057 that were released in the supernova, but it was enough to convince astronomers they had seen neutrinos from the supernova. This was the first time in history that astronomers had detected an astrophysical event with light AND particles; this was the beginning of what we now call “multi-messenger astronomy.” It was a watershed moment in our quest to probe the Cosmos — we had, for the first time, used two machines to probe the Cosmos using different pieces of information together to make one story. It was the beginning of a new way of thinking and learning about the Universe, and it is a story that is still going on today.

This was the frontier of astronomy 30 years ago. In our next post, we’ll fast-forward to today and ponder how we plumb the deep sky with all our modern technology and combine it with the meager knowledge that we’ve gained over the past few decades.


This post is the first of three based on a talk I have given many times over the last few years, updating it each time to reflect the latest coolest things. The complete set posts of the series are:

The Cosmos in a Heartbeat 1: A Love Affair with the Cosmos (this post)

The Cosmos in a Heartbeat 2: Coming of Age

The Cosmos in a Heartbeat 3: The End is Just the Beginning

This post was enabled by a new version of the talk done as a Kavli Fulldome Lecture at the Adler Planetarium in Chicago. The talk was captured in full 360, and you can watch it on YouTube here. If you have GoogleCardboard, click on the Cardboard Icon when the movie starts playing; if you watch it on your phone, moving your phone around will let you look at the entire dome!

I would like to thank all my colleagues at Adler who worked so hard to translate what was in my brain into a story told in the immersive cradle of the Grangier Sky Theater. The talk was given on 9 Nov and 10 Nov 2018.

I also put this post up today to celebrate the occasion of Carl Sagan’s birthday. I, like many around me, was inspired at the right moment by exposure to Sagan’s “Cosmos: A Personal Voyage”. Friday (9 Nov 2018) would have been Carl’s 84th birthday. He left us more than 20  years ago now, but I still hear his voice when I think about and ponder the deep mysteries of the Cosmos around us. Happy birthday, Carl.

The Aquarius Project 2: Into the Deep Void

by Shane L. Larson

When you stand on the shores of Lake Michigan, you cannot see the far shore. Many days of the year, the surf is a gentle lapping over stones or against breakwaters, but there are definitely days when weather whips the water into a frenzy, tossing up waves worthy of ocean waves. You can’t help but notice it is big water. 

Lake Michigan is the second largest of the Great Lakes, covering an area of 58,000 square kilometers and harboring 4918 cubic kilometers of water. In the early morning hours of 6 Feb 2017, a hunk of debris from outer space hurtled into Earth’s atmosphere, somewhere in the skies slightly to the west of Kewaskum, Wisconsin. Leaving a glittering trail of burning dust and shining brightly enough to cast shadows across the dark winter landscape of the Midwest, this space rock broke up and the fragments rained down about 10 miles off-shore in Lake Michigan, near Sheboygan, Wisconsin. Despite happening at roughly 1:30am, 511 people across the midwest reported seeing it. All those reports, together with a few others we had heard, let us make a good guess where it might have fallen in the Lake.

Here “we” are myself and colleagues from the Adler Planetarium, the Field Museum, and the Shedd Aquarium. “We” are a few professional scientists and (sorta) grown-ups, and a remarkable group of young people from the Adler, called “The Adler Teens.”  In the grandest tradition of scientific adventures, we decided it might be fun to go look for fragments of this space rock. On the bottom of Lake Michigan.

Our expedition would be aboard the Neeskay, a research vessel belonging to the University of Wisconsin-Milwaukee.

Scouring the bottom of Lake Michigan for a fallen space rock sounds like fun, but why would we do such a thing?  The answer begins far above our heads, in the inky dark between the planets. The solar system formed from a vast cloud of stuff that eventually accumulated into the planets and other bodies in the solar system. Just like when you clean your house, you don’t get every little fleck of detritus there is — there is always a little bit left over. The solar system is no different — there are bits of stuff floating around everywhere. You may remember from your ponderings of the night sky that there is a lot of such material between the orbits of Mars and Jupiter, called the asteroid belt. There is an additional vast swarm of stuff surrounding the solar system called the Oort Cloud that is the origin of most of the comets we see.

But randomly drifting around there is also other stuff; when space rocks are in space they are called meteoroids. They are interesting because they hold a set of stories, about the early history of the solar system if they are left-overs, and about the historical nature of the other planets and moons if they are fragments blasted off of their surfaces in collisions.  If by chance, one of them should tumble into the Earth’s atmosphere, the tremendous speeds generate tremendous heat and the meteoroid becomes a meteor, a glowing coal of stuff that briefly illuminates the night sky. You and I call these things “shooting stars,” and if they are spectacularly bright, we call them “fireballs.” Finally, if one of these meteors should make it to the surface of the Earth, where it can be picked up and handled and oogled and tested, we call it a meteorite. Meteorites harbour the same stories they did when they were meteoroids, they are just much easier to get your hands on. IF you can find them.

Our sled, on the desk of the Neeskay, waiting to be launched.

So we made a plan to survey the bottom of the Lake looking for this meteorite. While the original concept had been to simply dive down with an amateur ROV (“remotely operated vehicle”), like one from OpenROV, or designing our own, the team rapidly came to the realization that we wanted to keep anything we found and bring it to the surface. A cool idea, but a challenging one at the same time.

As is often the case in science, having a cool idea means you also have multiple competing problems that must be solved. For the Aquarius team, the competing problems were this: how do you cover a vast, VAST area of the lake bottom, find everything that looks interesting, and get it all to the surface. Working your way through such a list of problems is exactly what science is, and it is an iterative process. You imagine a solution, you tinker with it, you build prototypes, and you test them. When the prototypes don’t quite work, or fail dramatically, or succeed in unexpected ways, you take what you have learned and modify or build a new version, and start the testing all over again. Eventually, your efforts stabilize and coalesce around a final product — a plan, an experiment, a workable design. For Team Aquarius that design was a sled we call RV Starfall.

The sled is a scientific device in the grandest tradition. If you just walked up to the sled not knowing what was, then the most apt description of it you might come up with is contraption. A contraption it is. Overall, it is about 1.4 meters long, about 1.2 meters wide, and about 25 centimeters tall. Its made of plastics and metal, with bolts and cables holding it together.  The superstructure of the sled is laid out by four vertical slats that define the shape. The slats are held together by cross-members that provide strength and rigidity. There are two sled-rails on the bottom, bent upward at the front, to help the sled glide over the underwater landscape, no matter what it might encounter (just like the rails on a winter sled or snowmobile). 

A computer model of the sled, viewed from the rear. Note the clear sample capture bins near the front, the curved edge of the sled runner on the bottom, the three magnet wheels across the middle, and the wire capture cages on the back. The red “bricks” on the slats are also magnets. [Model by Annelise Goldman]

Attached at various points on the sled are different devices that were designed to find and recover samples and interesting objects (“possible meteorite candidates”) from the bottom of the lake. The strategy that guided the sled design was passive collection without inspection — pick up everything that is potentially interesting, and bring it back to the surface for later classification and analysis. Look at the back of the sled. There you’ll see three mesh footballs — if they hit something like a small rock (or meteorite!) as they get dragged across the lake bottom, the tines of the mesh spread open and the forward motion of the sled pushes the rock inside, then the mess closes behind it effectively trapping it. A brilliant mousetrap for a meteorite!  There are also magnets all over the sled, strategically positioned to attract metallic fragments and hold onto them until the sled reaches the surface again.

The most active group of magnets are on the three wheels in between the vertical slats. As the sled gets dragged across the lake bottom, the wheels rotate and attach to any metallic fragments they encounter. As a wheel rotates up and over, it encounters a “scraper” that pries off any large bits and drops them into three catch pods (clear acrylic) between the slats. The idea here is that something large might attach itself to a magnet, but if you don’t pry it off and save it, something might later knock if off and you’ll never know you had it. On the bottom of the sled, there are some V-shaped brushes that guide material toward the magnet wheels, as well as a variety of other magnets attached on open surfaces to catch any “just in case” bits the sled might encounter. 

Last but not least, there is an attachment bracket on the front of the sled, where we could mount a video camera to send live pictures of the bottom of the lake back to the surface. The sled is attached to a cable, which is lowered by a crane into the water to the lake bottom. A video cable attached to the camera is clipped to the cable as it is extended, delivering live movie data back to the team in the control room (“Mission Operations Center”) on the Neeskay.

A maritime navigation map of Lake Michigan, east of Manitowoc, with Chris Bresky indicating where we are heading for the sled drops.

We had a boat, we had a meteorite recovery sled, but where do we go? Despite the immense size of the lake, we had a good idea where the meteorite fell from all the reported sightings and the signature on weather radar the morning of the event. Several of the meteorite experts on our team had used codes that they had written as part of their professional research to model the breakup of the asteroid, predict the sizes of fragments, and then simulate how those fragments would fly through the atmosphere and into the water. Those analyses produced a map of the most likely areas to find meteorite fragments of different sizes. One of our meteorite colleagues on the expedition with us, Dr. Philip Willink, took those maps and predictions and estimated the average separation between meteorite fragments on the lake bottom. He estimated that in the areas dominated by 1 to 5 gram pieces (about the size of a marble) we would have to drag the sled about 1.5 kilometers across the lake bottom to encounter 2 fragments. The lake is big, and those aren’t very good odds. But it’s also not impossible!

Phil’s roughed out calculation of how far we’d have to drag the sled to find a piece of the meteorite.

I tried on the survival gear during the safety briefing!

Using Phil’s prediction, we decided to do several mile long drags of the sled (“transects” across the fall field). With that in mind, there was nothing left to do except go out and start searching. The anticipation was palpable — this was literally what we had been waiting more than a year for, planning and imagining.

Scouring the lake depths for fallen space rocks is an all day affair. We arrived bright and early to our expeditionary vessel, the Neeskay. We had a safety briefing from our captain, tried on some of the survival gear, and we set sail. Our destination was off-shore about 16 kilometers, in about 70 meters of water. The Great Lakes are temperamental — soggy days and blustery weather can whip the Lake into a frenzy. But on this day we were lucky — the skies were clear, the winds were gentle, and the Lake was calm.

We loaded all our gear on board, we stowed the sled on the rear launch deck, and before we knew it, Neeskay turned in the harbor, and pointed her bow to the southeast. We were off. The moment we left the harbor was striking to me. Being a kid from a land-locked state, the view off the bow was one of completely open water, with not a speck of land in sight. If I didn’t turn around and look back the way we had come, it could have just been the endless blue expanse of the open sea.

[LEFT] Our expedition leader, Chris Bresky, lays out our plan for the day. [RIGHT] A map of our target area, showing the predicted density of meteorite fragments of a given size on the lake bottom, worked out using a computer model. The blue dashed line near the bottom of the oval shows our first drag, and the purple dashed line shows our second drag.

It was about an hour to our first drop point. On the journey out, we had a briefing about the target area and the drag plan. We would do two mile-ish long transects, one NE to SW, and one N to S. After the first transect, we’d pull the sled up, clean it off and store recovered samples, then drop it for the second run.

[LEFT] The sled is lowered into the water using a hefty steel cable being spooled off of a crane. ][RIGHT] As we let out cable and the sled descends to the lake floor, we clip the cable to our video feed that is bringing live images back to the surface.

When we arrived on site, we attached the sled to a tow harness, we bolted our video camera onto the nose, and we hoisted it up until it hung vertically over the deck. Pivoting it out over the edge of the boat, it hung poised over the water, just waiting for a moment, then cable began to unreel, it slipped beneath the waves, and was gone. The video feed was carried along its own cable. We didn’t want it to get tangled up on something, so every couple of meters we paused and  clipped it to the main tow cable to keep them together.

Pretty much the entire time the sled was in the water, the team huddled around a couple of computer monitors, watching the live video feed, and discussing what we might be seeing, noting down interesting time markers to go back and watch more closely. These were the moments we had been waiting for — having our experiment work successfully, and showing us something that had never been observed before.

In the operations center, the team could watch the video feed as the sled descended into the depths. At first, the image was a brilliant cerulean green, but as the sled descended, less and less sunlight from the surface was making it to the depths, and the images got darker and darker. The meager light from the camera lights revealed only a monochrome murkiness, and the faint shadow of our cable stretching out into the darkness above, where the team waited aboard the Neeskay.  And then….

Live video touchdown image from the bottom of Lake Michigan, 70 meters beneath the Neeskay.

Touchdown! The sled settled onto the bottom of the Lake, churning up a cloud of silt and dirt when it landed, not unlike the landers on the Moon. We had arrived!

As is often the case in science, we discovered something new and interesting immediately. Based on previous surveys of the Lake from two to three decades ago, the depths we were at had very little in the way of a visible macroscopic biosystem — a few lake creatures and fish, but by and large the temperature and light at these depths meant the lake bottom was a bare, open, abyssal plain. But that was not what we were greeted with on the monitors. In every direction, as far as our cameras could see, the lake bottom was covered in colonies of quagga mussels.

The lakescape we could see, as far as we could see in every direction, was dominated by quagga mussels. A few bare spots existed, but they were few and far between.

Quagga mussels, like their cousins the zebra mussels, are an invasive species in the Great Lakes, having been transplanted in the ballast water of ships that plied both the Great Lakes and other waters in the world. Over the past few decades they have been spreading through the Lakes, starting in large colonies in shallow waters, but clearly now also extending into the deeper waters. There are lots of interesting questions that immediately spring to mind. For instance: As we moved across the lake bottom, there are small patches here and there where the mussels hadn’t settled — what were those? Are the mussels not there yet, were they cleared away somehow, or is there something different about those patches? How far into the depths do the colonies extend? Are the depths they are reaching simply growing with time, or correlated with other environmental aspects of the lake (like temperature, lake currents, water chemistry, or other suspensions in the water)? Those are questions for another day, and a future expedition and a future team. As dutiful observers of Nature, we record our findings and the conditions under which we made them, together with thoughts we have, and report them to our scientific colleagues for further consideration.

Once we were on the bottom, we started our run. The captain revved up the Neeskay and we started trundling along our planned transect at about 1 knot (1 nautical mile per hour, which is about 1.15 mph = 1.85 km per hour). But as you might guess, it’s not that easy! We wanted the sled to glide over the bottom in contact with the surface. If we were going too fast, the sled started to “fly” from the hydrodynamic forces of the water lifting it like it was an airplane. We knew when we were on the bottom because we would see occasional puffs of silt and dirt, like the cloud we saw when we landed. If we were going too fast and flying, then we never saw any puffs and the mussels were really flying past fast. 🙂  The video below shows about 2 minutes of what flying over the area was like, extracted from the Aquarius video feed.

So for about an hour, all we could do was watch the video screen, occasionally talking with the captain about speeding up or slowing down by a smidgen. The mussels sailed by — endless lakescapes of mussels. Surprisingly, there were often apparent detritus from our civilization that we could see — bars of metal protruding from the lake bottom or other bits of shattered something. In many ways it was surprising, because you have this sense that the lake is vast and there is no possible way that humans could have somehow made their imprint on so much of it that a random trip across the bottom would turn up some artifacts from our civilization. But we have. It is a testament to how much time humans spend on the lake, and how far reaching our influence likely is.

Two examples of interestings “things” that passed with the field of view of the Aquarius sled camera. Possibly natural (wood?) and possibly anthropogenic (metal?). The team noted where they were, in case we ever want to go back and look at them too.

Eventually, we decided to haul the sled up, clean it off, and preserve any samples we found. The ascent was a little slower than the descent because as we hauled it up, we had to separate the video cable and the tow cable. Separating the two was not nearly as straightforward as clipping them together — while the sled is in the water and the cable is under tension, the two cables wind around each other, so as they come out of the water and are separated, all of the twists remain in place! The result is a giant spaghetti ball of cable that you have to manage as the sled ascends. It’s only 70 to 100 meters of spaghetti cable, but it’s a plenty big mess! If you’re watching on the monitor, eventually the sled video can see us up through the water as it ascends, a distorted fun house view of the team, peering eagerly into the water to see what secrets had been pulled up from the depths.

[TOP ROW] As we raise the sled, we have to cut the video cable free from the tow line, but it turns into a big spaghetti mess that must be managed as the sled returns home. When it is near the surface, it can see the mess above it! [LOWER ROW] When the sled is clear of the water, it drops all kinds of mud that it has been dragged through. We have to grab the sled, and pivot it back onto the deck so we can begin cleaning it.

As the sled emerges from the water, there is a flood of mud that is released as water sheets off of it, but we move it aboard and finally it is laid down on the deck. What happens next is a burst of activity: every member of the team moving to do something to get us ready for the next transect. The captain turns the boat and heads to our next drop point. A group grabs the spaghetti ball and takes over an entire side of the Neeskay to untangle it and lay it out, untangled, for the next drop. A cadre of people with cameras and smartphones are taking pictures of everything, documenting what is going on. And the sled itself is surrounded by a pack of the Aquarius team, shoulder to shoulder, digging in to clean the sled and preserve the recovered samples.

[LEFT] The moment the sled was on the deck, the Aquarius Team was swarming all over it. No known force in the Universe could have kept them away. [RIGHT] Getting the mud off was a chore; spraying it off worked well, but then the mud had to be gathered off the deck and sifted through.

The philosophy of the sled clean-off stage is simple: keep everything for later. Set aside interesting stuff for careful consideration later.

There is a lot of mud. Some of it we spray off, carefully sifting through it for anything that was surrounded by the gooey stuff. The cleaning teams grabs great gobs of the stuff and mashes their hands through every little bit of it, looking for anything small and solid. We find rocks, we find clear bits of metallic somethings. We keep it all, and toss it in big 5 gallon buckets. The buckets are marked with the day of the expedition, and the transect that we made, so when we get back to the lab we’ll know where the samples came from. We find stuff stuck to the magnets — all the magnets — so we pull it off, and stick it in the buckets. Every now and then we find a mussel; what do you do with that? You see if it sticks to a magnet! If it sticks, you keep it — it probably has eaten something metallic (possibly a meteorite fragment) and we want to know what it is! If it doesn’t stick, we toss it back into the Lake. If something looks particularly interesting, we show it to one of our meteorite experts, who decide to toss it in the general buckets, or keep it in a special “oooo interesting” container. 

[TOP ROW] The magnets collected plenty of material. Notice the fine grain black stuff — this is “magnetic mud,” the kind of stuff you can pick up in a sandbox with a magnet, comprised largely of metallic rich grains. [LOWER ROW] We mash through ever little bit of mud with our hands, looking for fragments and interesting bits. With the mud cleared away, there are a variety of different things we find, almost all of which we keep.

The entire clean-up takes 30 to 60 minutes, and by the time we’re done, the spaghetti cable is untangled, and we’re ready to make a second drop. We hook RV Starfall back onto its cable, pivot out over the water, and drop it in for a new run. Wash, rinse, repeat!

Really interesting looking samples are set aside, to make sure we look at them more closely later, and to insure that we don’t lose them in all the detritus.

But all too soon,  you discover the day has wiled itself away. The Sun is heading toward the horizon, you have buckets of samples, thousands of pictures, hard drives full of video, and notes, thoughts, and observations from everyone on the team that need to be collected, collated, read over, pondered, and speculated with. 

With the happy melancholia that accompanies the end of any adventure, the team looks to shore as the captain turns the bow of the Neeskay to the west, and we begin to steam toward home.

Now, the samples are back in the lab, and the next long bit of hard work is happening — consulting with scientific colleagues who are experts in meteorite identification, and figuring out what all this stuff is!

Now, our samples are in the lab. Fall is winding away and winter will be here soon. This is the time for careful lab work and analysis of all the samples we’ve found. There are, perhaps, fragments of our meteorite in the collection. If there are, we will be beyond excited. But if there are not, the samples still represent a treasure trove of knowledge about one small part of Lake Michigan. Contained in those carefully preserved samples is a story, yet to be understood, about the geology and history of human influence in that part of the Lake. We’re going to find out what we can learn from that hard earned haul — truly a treasure, valued in the sweat and joy and mystery of its recovery.


This post is the second of two describing my adventures with the Adler Planetarium’s AQUARIUS team. The first post was here:

You may also enjoy listening to the Adler Planetarium’s podcast series about Aquarius, it is excellent. You can hear them online here: 

The Aquarius Project 1: The Cosmos Beneath the Waves

by Shane L. Larson

The wind is brisker, the nights cooler and crisper, and something about the slanting misted light of morning says autumn is here. Over your morning nibbles, with your family prattling around you in the kitchen and the hum of a weekend just getting underway, you look back through your memories on social media, and it’s like “Wow! I had some awesome adventures this summer!”

During the daily grind, when the morning commute is doing its best to wear down the gears of your soul, and the daily maintenance of jobs and life stretches well beyond the length of a reasonable ToDo list, I sometimes despair that there are no great adventures to be had. But those are just little demons whispering, preying on weariness. In reality, I think there are always new adventures launching without you even knowing it. Some of them lead to great friendships and growth for your community around you. Some of them bring great good to the world, even if it is just a small group of people around you. A few indelibly ink a memory in your heart and soul that you will carry around with you to the end of your days in this Cosmos. This is an adventure story with all of these. Like most adventures, it arrived unexpectedly, and grew from humble beginnings. It started one winter night in the northwest suburbs of Chicago.

I’m a bit of a short sleeper, so I’m always up late at night, long after the rest of my family and friends are slumbering. It’s always quiet, just me and the cats. When it’s nice, I can do a bit of backyard astronomy, but if the weather is inclement, I can wheedle away hours in the workshop or at the Lego table.  More often than not, I have papers from my students to read, or lectures to write, or homework to grade. The latter was the case in the early morning hours of 6 February 2017. My study is on the second floor of our house, and I have my writing desk situated to look out over the wetlands north of our home. 

I don’t recall exactly what I was doing, but I was up and at my desk. At 1:25am I just happened to be looking north and witnessed one of the awesome transient events you can see in the sky, a fireball. I’m an active amateur astronomer (I’m also a professional astronomer, but that’s a discussion for another day), so I’ve literally spent thousands of hours out under the night sky. I’ve seen fireballs before, but they are not common enough to simply shrug your shoulders when one graces the skies overhead. They are all of them dramatic, bright, beautiful, colorful, and awesome to behold. This one was no different. It had a brilliant teal colored head and a streaky tail that was long and “sparky” with a yellowish color. It was BRIGHT. So bright that it lit up the walls inside the house and cast shadows, like a long duration flash bulb had gone off.

I’m one of those amateur astronomers who has a strong habit of writing everything down when it happens; if you have a birder friend who keeps a lifelist of all the birds they’ve seen, I’m of the group of amateur astronomers who do the same thing only with objects in the night sky.  I try and immediately write down everything interesting I see happening in the sky. I note everything I can — the time, how “big” it looked in the sky, how long it lasted, and anything I noticed like its color or shape or behaviour. All those details are important to write down in the moment before your brain thinks about it and embellishes it. Colors are completely subjective, but for an event like this, they are the best description you can usually give. The size is also not precise, but you can use old astronomer tricks to estimate the size of an object, either by referencing other things you can see in the sky (like the positions of stars) or using your hands. In this case, the fireball was perfectly framed in my window, so I used my hands to estimate angles. I also like to simply write down my responses — from my journal entry above, you can see I was pretty excited.

When you need to quickly estimate angles in the night sky, use your outstretched hands. The width of your fist is about 10 degrees, and your spread hand is about 20 degrees fingertip to thumbtip. [Image: S. Larson]

It is all well and good to keep your own notes about what you see, your personal dialogue of your relationship with the sky, but if no one ever hears about what you saw in the sky we can’t use your experiences to learn more about the Universe and our place in it. There is something special in the sharing of communal experiences with the Cosmos, and sometimes we can learn something new at the same time. When that fireball lit up the night that winter morning, I did two things. The first was to ping all of my local friends on email and social media, on the off chance someone had also seen it. The second was to report the event to the American Meteor Society, which collects observations and collates them together. 

My initial query to my friends to see if any of them saw the event.

In the end, hundreds of people all over Illinois, Wisconsin, Michigan and Indiana reported the event, and collating all of our reports generated a good guess about what the fireball did, pointing to something I had speculated: it probably came down in Lake Michigan. You can see the report at the AMS online here.

The American Meteor Society map showing people in northern Illinois and southern Wisconsin who saw the fireball. Reports came in from a much larger area than this, but in this view you can see the estimate of the meteorite’s trajectory (between the green and red pins). [Image: American Meteor Society]

My email to my friends and colleagues at the Adler Planetarium ended up being the seed for this particular adventure story. One of my hobbies is constructing underwater robots (ROVs — remotely operated vehicles), which is also another story for another day. But in my email, I speculated on whether or not we could use such a “hobby” to perhaps dive down to the floor of Lake Michigan and take a look around on the off chance that we might find something.

The early email, speculating that maybe an ROV could be used to look for any possible fragments from the meteorite.

Now why would we do that? Material from outer space rains down on the Earth all the time. On any given night, if you spend enough time looking up, you’ll see numerous quick streaks of light slashing across the sky — the “shooting stars” you learned about when you were young. Most of these are small, no bigger than a grain of sand, and burn up in the atmosphere high above you, leaving only the flash of light and your memory of its existence. Throughout the year, we have regular “meteor showers” when the Earth sails through the trail of dust and debris left behind by comets as they blaze their journey toward the Sun, dropping fragments of ice and dust that we see as their tails. Such events are not unique to Earth — they also happen on other worlds (one of my first scientific papers was about using comet orbits to predict when you might see meteor showers if you lived on other planets in the solar system). Larger fragments of stuff also hit the Earth, though less frequently, with fewer and fewer instances as the size gets larger and larger. Things the size of baseballs and laundry baskets will light up the night sky and while they can cause damage, aren’t devastating. Most events of this size are over the ocean and out of sight of stargazing humans because 71% of the Earth is covered by water!

A typical shooting star (this one is a meteor during the Perseid Meteor Shower). [Image: S. Larson]

NASA estimates that around 100 tons of material hits the Earth every single day. But most of that is small flecks that vanish in a sparkling flash of light, sometimes seen by someone like you looking up from their backyard. But a few pieces — a precious few — make it all the way down. Something about the size of your fist has a good chance of making it to the ground. Meteorites are not as common as everyday rocks, but not so rare that ordinary people like you and I can own small fragments purchased in museum gift shops or from reputable dealers.  Never-the-less, they are rare enough to still be of intense scientific interest. After tracking this random fireball through the skies of the Midwest it seemed, perhaps, we knew where one had come down in Lake Michigan, and maybe a little adventure was in order.

Me and the indomitable Chris Bresky, off on an adventure.

The adventure started innocently enough, because my Adler colleague, Chris Bresky, thought pitching ROVs into Lake Michigan to look for sunken space rocks not only sounded cool, but would be a great way to engage area teens in some science investigation. It has all the hallmarks of what science is all about. It begins with a phase of Big Thinking, where there are no boundaries. You put a group of interested people together in a room or on an email thread, and you just talk. The rules are simple: no idea is too whacky, no question is too silly, everything should be put out there for discussion. During the Big Thinking phase there are no limits or considerations of limits, there is no quarter given to practicality or logic, there is no worry about regulations or costs or anything. That is all for later. In the beginning, you want to let your imagination run wild, and let your curiosity and excitement drive what you are thinking and talking about. Why? Because good ideas come from unfettered imaginative thinking. There are many ideas and hypotheses that are untenable or wrong. There’s nothing wrong with exploring those ideas — that is the pathway to finding out what is possible and what is true. When we are first embarking on a journey of scientific investigation, we do not know where fundamental insights will come from, or what will spark them. 

It’s not that all the squirrel-brained ideas that come out of the Big Thinking phase are workable or even reasonable. That’s not the point of Big Thinking. The point of Big Thinking is to have conversations about the ideas that form around all the squirrel-brained ideas. For this project, we started with simply the idea of an ROV to photograph whether there was a piece of this space rock on the bottom of Lake Michigan. That simple question opened up a remarkable spectrum of questions that would ultimately be an important part of our adventure.

Big Thinking started early, even in email. Chris’ imagination was captured early on.

What was the bottom of Lake Michigan like? Probably rock and dirt, as the depths in the target zone are too deep for sunlight to penetrate and support plant life.  Is it mud or hard packed surface? If it’s mud, will we see little divots from meteorites or will they sink in the mud? If it is hard packed will the meteorite sitting on the surface just look like another rock? What is the Lake really like in the area where the fall happened? No one really knows, because 99% of the Lake hasn’t been seen, only surveyed by sonar and most of that at low resolution. Do we just want to take pictures? What if there is a big rock we want to recover? Can we make a robot arm to pick it up? Will we need to dig on the bottom of the Lake? Can an ROV even lift a giant space rock?

And so on. Over time, we coalesce together into a team, and we develop some common language and ideas, and a plan begins to emerge. In this case:

  • we didn’t even know where there was a space rock, only a huge area that it could be in. If we were going to search, we had to be able to search vast areas.
  • we absolutely wanted to recover some space rocks if they were on the bottom of the lake. Anything was probably small, so we’d have to recover material and separate it on the surface
  • like outer space, the bottom of the lake is not amenable to humans hanging out, so we’d have to do this space-exploration style — with uncrewed, mechanical entities
  • we’ve never done ANY of this before; few if any people have looked for space rocks in deep water before. So we’re going to have to figure out how to do it, teach ourselves, learn from our mistakes, and then execute our search on the true frontier — the unexplored depths of Lake Michigan.

After that, it’s time to start rolling. You get your hands dirty and your feet wet and you make your brain tired, for months. Not exhausted tired; happy tired. So tired you can’t fall asleep at night because you’re still turning a problem over in your head tired. The core team in this endeavour are a group of kids from Chicago we call “the Adler Teens” (follow them on Twitter, and Instagram). Like all teens, they are extraordinary. They’re excited, they’re passionate, they’re full of boundless energy, and they want to learn how to solve cool problems. There are also a few of us grown-ups around too, but we try to stand back and let the team push the project forward. The beauty of science is there are as many ways to solve a problem as there are people trying to solve them. Some solutions work better than others, but no solution is right and no solution is wrong. I’ve been a science educator my entire career, and while I could go and figure out a way to find and recover space rocks on the bottom of Lake Michigan, I long ago learned that some of the most inventive solutions to problems come from students who are learning to flex their scientific skills.

Doing science requires talented minds with all kinds of skills. The AQUARIUS Project, like all great exploration missions, has a patch and logo, developed by our talented graphics designers at the Adler Planetarium [Images: Orilla Fetro]

Our project became known as “AQUARIUS” (suitably nautical and astronomical at the same time — you can follow their progress on OpenExplorer), and over the course of the next year it grew into an extraordinary voyage of discovery. The first part of the journey involved the team figuring out clever ways they could recover meteorite fragments from the bottom of the Lake. The team settled on the idea of a towed sled with scoops and magnets that could be pulled behind a boat in long transects across the fall field on the bottom of the Lake. They made simulated meteorites in the lab, threw them in shallow water and tested their sled repeatedly. When their design didn’t work quite as expected, or it ran into an unexpected problem, they rolled their sleeves up again and went back into “Big Think” mode, and thought of a way to fix the problem. They deployed and retested. 

After more than a year of work, the team was ready to take their equipment and hit the open water, searching the depths of Lake Michigan for fragments of a space rock that had fallen more than a year before, waiting quietly and patiently to be found in the dark depths of the Lake. I had the great honor of accompanying them on a sunny day in July 2018.

Our port of call was Manitowoc, Wisconsin. Our ship was the SS Neeskay, a research vessel owned and operated by the University of Wisconsin-Milwaukee. Built in 1953, the vessel had served many roles during its time at sea, but was converted into an expeditionary scientific ship in 1970. This summer, it carried a group of us on a hunt for space rocks on the bottom of Lake Michigan…


This post is the first of two describing my adventures with the Adler Planetarium’s AQUARIUS team. The rest of the story is in the next post:  Into the Deep Void (