Ineffable Images of the Space Age

by Shane L. Larson

The arrival of each new year always engenders a brief moment of reflection on how we all would like to improve and change our lives, and very often with a recounting of how transitory life actually is.  I was reminded of this yesterday when I was reflecting on the sad fact that on December 21, astronaut Bruce McCandless II passed away at the age of 80. He was a Naval Academy graduate who joined NASA in April 1966 as part of Astronaut Group 5.

McCandless joined NASA during the Apollo era, but never flew until the Space Shuttle era, logging 312 hours on two flights: STS-41-B aboard Challenger in 1984, and STS-31 aboard Discovery in 1990. It was on his first flight that he gained notoriety: he made the first untethered spacewalk in history, flying the MMU (Manned Maneuvering Unit) some 300 feet away from the Challenger. The image of McCandless, flying free over the Earth, has become one of the most iconic images of the Space Age.

Bruce McCandless, flying the MMU about 300 feet from the space shuttle Challenger during STS-41B in 1984. It was the first untethered spacewalk in history. [Image: NASA]

There is something timeless and awe-inspiring about this image. What is it? Is it the ever-blue curve of the Earth behind him? Is the loneliness of a single human, flying in the void far from any others? Is it the thrill of the the adventure or a surge of voyeuristic fear, the “fun thrill” letting your mind roll around how you would feel in that same situation? I think it is a little bit of all of those. Just show the image to some friends at your next dinner party and ask, “Would you do that?” or “Can you imagine?” and listen to the direction of the conversation!

When McCandless made his historic untethered spacewalk, I was in high school and dreamed of being an astronaut. I didn’t become an astronaut, and likely will never travel to space, but the dream lingers in my mind and surges forward every time I see images like this one.  This isn’t the only image from the Space Age that has such an effect on me. Some photographs, some moments suspended in time on celluloid or pixels, somehow capture ephemeral emotions that are indescribable by any other means.

Many such photographs come from the astronauts themselves. Astronauts have had a singular, unique experience that is transformative to their consciousness. Nothing molds a person’s worldview more dramatically than first hand experiences, there are no first hand experiences quite like those of the astronauts. They have seen the Cosmos, seen the world, from a perspective that the rest of us can only catch elusive glances of in stunning photographs delivered from the shoals of space.

Take a look at this photo. Almost exactly 49 years before Bruce McCandless passed away, the crew of Apollo 8 made the first voyage from the Earth to the Moon. They completed ten orbits around the Moon, and on their fourth orbit were the first humans ever to see the Earth emerging from behind the Moon — the first Earthrise ever witnessed by the human species.

“Earthrise” shot by Apollo 8 astronaut Bill Anders on 24 December 1968. A recreation of the moment, with mission audio has been created by Goddard Spaceflight Center [Image: NASA]

The world first saw the image in the 10 January 1969 issue of Time Magazine, burning it indelibly into our collective consciousness.

Like so many moments captured on film and revisited with reverence and awe, the Earthrise photo was taken by chance; Apollo 8 just happened to be rolling at the moment, and the image just happened to be visible through the tiny windows on the front of the capsule. In retrospect, the moment could have been predicted, but every story told of that moment when Apollo 8 rounded the limb of the Moon describes the first sight of the Earth as an unexpected and ineffable moment — the first time in human history that we had ever seen our world in Cosmic context, behaving in relation to the rest of the Universe in ways that our minds had only previously considered for other worlds.

One of the most famous pictures returned from the Apollo missions was of Buzz Aldrin’s bootprint in the lunar soil, made and imaged by Aldrin to record the properties of the lunar soil. [Image: NASA]

Just seven months later, Apollo 11 made the first crewed landing on the surface of the Moon, leaving humanity’s first footsteps on another world. Buzz Aldrin famously took a photograph of his bootprint on the Moon to illustrate the behaviour of the lunar surface soil; it is an image that is universally recognized as being from our first journey to another world. Most of us have made footprints, in snow or mud or soft dirt. Often alongside many other footprints, a cacophony of shapes and patterns, each one a remnant of a journey from somewhere to elsewhere. The next time we cross that particular trail or particular riverbank, the prints have changed and tell new tales of new journeys. But the footprints on the Moon are different — so far, there are only 12 sets of prints, laid down five decades ago by the few humans who crossed the gulf. And they will persist for millions of years, untold aeons beyond my life and your life and the times in which we live. If some future traveller should happen upon them, perhaps laying down their own prints alongside, what will they know of the journey that first left the prints there? Will they know of Aldrin’s famous footprint, and cast about debating which one was The Print? Or will they have utterly forgotten us and these days, the remains of Apollo on the Moon just curious forgotten relics of a civilization wiped away by time? What will they remember and know of us?

After 21 hours and 36 minutes on the surface of the Moon, Armstrong and Aldrin lifted off to rejoin Michael Collins, who had remained in lunar orbit. On their approach to dock with Collins, he snapped this picture of the lunar module over the surface of the Moon, with the Earth in the background sky. Collins famously remarked that this photograph was a picture of every person in the human race, except him. What a stunning observation, a perspective that reflects how small and alone we all can be in the face of the immensity of the Cosmos.

Apollo 11 image of the Earth and Moon behind Lunar Module Eagle, carrying Armstrong and Aldrin back from the lunar surface to command module Columbia. Michael Collins, aboard Columbia, noted that this was a picture of every human being except him. [Image: NASA]

Such images are not confined to cameras held by humans. Over the past six decades, we have hurled many robots into space, mechanical emissaries designed to carry our senses to places we cannot easily visit ourselves. Among that mechanical flotilla are eight explorers sent into the outer reaches of the solar system, to visit the giant, gaseous planets and even tiny Pluto. Among them is an 800 kilogram spider of wires, foil, antennae and cameras called Voyager 1. Today it is still faithfully travelling outward, gently probing the space around it to map out the invisible bubble that defines here, the neighborhood of the Sun, from there, the wildlands of interstellar space.  On 14 February 1990, a little more than nine years after its encounter with the planet Saturn, Voyager 1 was commanded to make one last photographic survey of the neighborhood it came from — a Family Portrait of all the worlds of the Sun.  Turning inward one last time, it snapped off sixty frames. Laid side by side, one over the next, the last pictures from Voyager built a unique and humbling portrait of our homeworlds.

Voyager 1’s family portrait of all the planets of the solar system. [Image: NASA]

Buried on one of these frames is a pale point of light, small and blue, easy to miss in the flared light of the Sun bursting though Voyager’s lens. That’s the Earth, our home in the vastness of the void. That small meager point of light inspired Carl Sagan to write one of the most poignant and eloquent  assessments of human nature ever penned. The “Pale Blue Dot” soliloquy can be found in the book of the same name, but in one of the great magics of the modern age, a recording of Sagan reading it has been found and preserved; it is as moving to listen to as it is to stare at the delicate fleck of light captured by a simple robot from 6 billion kilometers away.

The Pale Blue Dot; an image of Earth from Voyager 1’s “Family Portrait” sequence, and arguably one of the most famous pictures ever taken of Earth, noted for showing the smallness of the Earth in the immensity of the Cosmos. [Image: NASA]

When leafing through stacks of images from the Space Age, I’m struck by one very clear fact: there are no boundaries to the grandeur and ineffable wonder that can be captured on film. Each frame, each snapshot, each pixel, is a gift to future generations, a record of what we attempted, a record of what we aspired to, a record of what we risked during this time in history. On most days achievements like this stand in stark contrast with the lows our civilization has sunk to, and it is difficult to understand how both can be the legacy of the same species.

Some people look at images like these, and are nonplused. For them I weep. I hope they find wonder and awe in some other visions of the world, because the emotions and exhultations that these images evoke hearken to something deep in the soul, something I think we have lost in the modern morass of social media, reality TV, consumerism, and soundbites that claim to capture the quintessence of life. There is something deep and abidingly important in being able to see and experience amazing things and tremendous accomplishments, even in the face of serious and possibly overwhelming challenges to our way of life and our future on this planet. It provides a focal point for our aspirations to be better. It provides a poignant bludgeon of hope for the better selves that we aspire to be.

Other people look at these images, and all they see are dollars spent on endeavours they regard as frivolous. I can’t help but feel agony at such narrow visions of the world. In no small way, today’s world was made by these images. Not the images themselves, of course, but the thousands and thousands and thousands of hours of problem solving, prototyping, invention, innovation, creativity, and imagination required to make every one of these possible. We didn’t strap a gazillion dollars onto the side of Voyager and catapult it into space. We paid an army of engineers and as a result fed their families and sent their kids to school. We created entire new technologies, birthed companies that today make the backbone of the trillion dollar aerospace industry. We inspired a generation of children who wanted to be astronauts, but became enamoured with science and went on to become computer scientists, cancer specialists and brain surgeons, molecular biologists, ecological physicists, and aerospace engineers. I bet if you talk to many of today’s technical professionals, there is a time in their past where they swooned over pictures of the Moon.

The point is pictures are just one small return on each of the investments that were made to send people to the Moon, or to send a robot into the depthless void of space. Maybe you don’t think they’re interesting or the cost was worth it, but consider this: these are pictures we unfailingly recognize and know of — that simple recognizability is an indicator of the intrinsic and often unspoken value we as a society put on these ephemeral moments, captured forever as a frozen memento of places we once visited and knew and experienced.


Journey to a Northern Ocean

by Shane L. Larson

Polar bear on the shores of Hudson Bay, near Churchill, Manitoba. [Image: S. L. Larson]

I’m an active professional scientist and also a university professor. One of the things about my job that I enjoy the most and take quite seriously is the opportunity to talk with everyone about science. We talk about why science is an important human endeavour, how science impacts our daily lives, and how science helps us to improve our lives. We also talk about how science helps us understand the world around us, and what our purpose in the world is. At the end of October, I had the great opportunity to join a trip to the shores of Hudson Bay to observe the annual congregation of polar bears waiting for the return of the sea ice. Ostensibly I was there to give a science talk about the aurora borealis, but I was also representing my university with the group of travellers who were largely our alumni. Our destination was Churchill, Manitoba.

Churchill has a thriving tourist industry that in the early winter focuses on polar bears, and in summer focuses on beluga whales that congregate in the Churchill River; many businesses exist to help people experience these aspects of the natural world (we were hosted by the Lazy Bear Lodge). While people come for the wildlife, there is a lot to see in the area.

I was there late in the fall, on the verge of winter; walks on the shores of Hudson Bay were fun, but the weather was bleak and the landscape was windswept and cold. The surfline was beginning to freeze, leaving long gelatinous burms of frozen seafoam as the tides receded, a harbinger of the coming ice.

The shores of Hudson Bay, at the onset of winter. The foam from the surf is freezing at the high tide line. [Images: S. L. Larson]

Outside town there is a crashed Curtis C46 Commando, known to the locals as “Miss Piggy.” It went down in 1979 trying to return to the Churchill airport after its port engine went out on take-off. Miraculously, everyone walked away from the crash, but the plane is still there on a hillside outside of town.

Miss Piggy is the wreck of a Curtis C46 Commando, left where it crashed in 1979, on the outskirts of Churchill, just north of the airport. [Images: S. L. Larson]

 To the east of town, near the mouth of Bird Cove are the hulking remains of a derelict ship known as the Ithaca. It ran aground in 1969 during a storm, after 47 years at sea; the crew walked ashore at low-tide, and the ship was left to rust away into oblivion.

The wreck of the Ithaca, grounded at the mouth of Bird Cove since 1969. [Image: S. L. Larson]

All of this and more exist in the region, but we were there to see polar bears. The scientific name for polar bears is Ursus maritimus, Latin for “sea bear,” because the bears spend much of their lives on the arctic sea ice, largely in the areas where it interfaces with the land that fronts the Arctic Ocean. The area around Churchill is the home of one of the 19 recognized sub-populations of polar bears, numbering around 1000 individual bears. The story of why there is a population of bears in this area is a magnificent tale of biology, the planet, and the changes of the season.

The boundaries of the 19 recognized individual polar bear populations. [Image: C. Brackley, Canadian Geographic]

Polar bears are generally classified as carnivores, but they are perhaps more properly called lipidivores — their main sustenance is fat, primarily the fat of seals. Seals are primarily sea-going, occasionally crawling out onto rocks during the warm season and frequenting the surface of the ice in the cold seasons. The bears have the easiest time of hunting during the cold season, when they can stalk seals on the ice.

Polar bears are well adapted to life on the ice and in the sea. These bears were at Assiniboine Park Zoo and Leatherdale Polar Bear Conservation Center in Winnipeg. [Images: S. L. Larson]

Polar bears are well adapted to a life on the sea ice, with insulative fur and wide paws suited to walking on snow and ice. Their feet sport large claws and stippled pads for traction on frozen surfaces. They have insulative layers of fat that keep them warm when they are swimming in cold arctic waters. Compared to their cousins, the grizzly bears or brown bears, polar bears have long conical heads and necks, well adapted to lunging through breathing holes on the ice and hauling out a seal.

During the northern hemisphere winter, Hudson Bay is frozen over. The sea ice extends down from the arctic cap to the north and merges with shorefast ice that forms all along the coastline. During this time of year, the polar bears live on the ice, hunting seals. It is estimated that during this time, polar bears consume about 75% of their yearly intake of food, processing and storing it away as fat reserves for the ice-free season.

The average seasonal ice coverage on Hudson Bay. Red is the thickest ice, blue is open water. [A] June 18; with the onset of summer ice begins to recede across Hudson Bay. [B] July 30; by midsummer the last shorefast ice is gone, and the bears have come ashore in southern Hudson Bay. [C] September 17; around this time, arctic sea ice has reached its minimum extent. [D] November 5; by the start of November, shorefast ice begins to form in the Churchill region [E] November 26; the ice season has begun, and the polar bears migrate out onto the sea ice. [F] January 1; deep winter and the whole of Hudson Bay is frozen. (Images: Environment Canada)

What happens in the ice-free season? The ice recedes from the center of Hudson Bay, with the shorefast ice in the vicinity of Churchill being the last to disappear. The slow, seasonal recession of the ice drives the Churchill polar bears off the sea and onto the land, where they roam the boreal forests and tundra during the Arctic spring and summer. During this time of year, their primary food source — the seals — remain at sea and are more or less inaccessible, so the polar bears embark on a seasonally enforced fast while they are landbound. They will eat some vegetation, and possibly feed on carcasses if they happen upon them, but they consume little in the landbound months because their biology is largely optimized for the consumption of fat.

While they are landbound, waiting for the return of the sea ice, the bears wander around, and can sometimes be seen! [Image: S. L. Larson]

The Churchill population of polar bears comes off the sea-ice across the shores of Hudson Bay in northern Manitoba, but as summer wears on toward fall they migrate to the area around the Churchill River estuary. More than a mile across at the mouth, the Churchill River drains a large area of Alberta, Saskatchewan, and Manitoba into Hudson Bay, about 1.2 million liters (around 317,000 gallons) of freshwater on average each second. Fresh water freezes at higher temperatures than salt-water, so the large flow of freshwater into Hudson Bay from the Churchill River insures the sea-ice appears around the river outlet first, in late October and early November. The polar bears have learned this, and their seasonal circulation brings them to the area around Churchill when the first ice appears, so they can head out onto the bay and start their seasonal feeding again.

When the polar bears are landbound, they do not expend tremendous amounts of energy. This bear was started by humans who were trying to scare it away from their home. [Image: S. L. Larson]

This seasonal pattern of feeding and fasting has influenced other aspects of polar bear biology, particularly with regard to young bears. Polar bears mate in the spring (mostly in April and May), while the bears are still on the sea ice. The females experience a delayed impregnation — after mating, they harbor fertilized eggs that do not implant or begin developing. In late September, around the time the sea-ice is reappearing, a female polar bear’s body makes an assessment of how much fat reserves she has; if it is enough, the fertilized eggs implant, and the embryos begin to develop. The gestation period is very short — only about three months. During this time, the female bear begins to look for an area to den. In the Churchill area, she typically excavates a large, protected hollow in the peat that covers the northern shores of Manitoba above the permafrost layer. Sometime around December or January, cubs are born. Generally two cubs are born, but singles or triplets are not unheard of. The cubs are feeble and small when they are born, usually around half a kilogram, covered in short fur but blind and toothless.

A mock-up by Parks Canada of a mother bear, denning in the peat with her cubs. [Image: S. L. Larson]

The mother bear remains in her den with her new cubs for several months, continuing the enforced fast that began when she came ashore with the vanishing of the sea-ice the previous spring. The cubs nurse, growing rapidly on a diet of milk that is typically about 31% fat. Within a few months, the cubs have grown to about 10-15 kilograms, have developed thicker fur coats, and are able to move around. With the arrival of spring, the mother leads them out onto the sea-ice. This is usually around the time the seals have delivered their own pups. Seal-pups are born on the ice, and spend about eight weeks of their early days in dens in the ice and snow, near breathing holes their parents use to access the sea. The pups, despite being covered in snow dens, are not quiet and make easy prey for the polar bears. Uncovering the poorly protected pups in large quantities provides an easy, exploitable source of food for a mother bear to rapidly grow her cubs before they are forced off the sea-ice in the summer months. For the seals, vast numbers of pups insure they survive this season of hunting by bears.

Schematic of a seal pupping den. The adult seals access the den from a breathing hole; the pups live out of the water, but under a crust of snow that polar bears can break through.

All told, in our two days on the tundra, we saw five bears. The last bear we saw had been tranquilized and was being airlifted to the Churchill Polar Bear Holding Facility, where it will be held for a week or more and then released far from town (ideally so it can move onto the sea ice, once it forms). Managing the interface between people and bears is part of life in Churchill. For the most part, the bears are not habituated to the humans, but they are sometimes captured and moved away from town to protect both people and the bears themselves. The bear we saw being airlifted was near town on the afternoon of Halloween — we suspect the action was taken to prevent a bear from thinking that a trick-or-treater was a delectable substitute for a seal pup.

[left] A red fox we saw; sadly, we saw no arctic foxes. [right] The best ptarmigan picture I could get! (Images: S. L. Larson)

The tundra is replete with other life as well. In addition to the bears we saw several red fox, as well as plethora of birds (including ptarmigans). My favorite other animal we saw were lemmings frolicking in a snow bank, but they are frickin’ fast and difficult to photograph. 🙂

The remoteness of this area is not to be underestimated. The town of Churchill has a population of about 1000 people. Historically, the area has been populated by indigenous people, notably the Cree and the Dene. Europeans came to the area in the 1600s, when the Hudson Bay Company built the Prince of Wales Fort at the mouth of the Churchill River, across the estuary from the location of the modern town. The port of Churchill affords access via sea during the short ice-free months. Rail service has traditionally existed, running through the forests and tundra of northern Manitoba from Churchill to Winnipeg. During the spring of 2017, many sections of the rail line have been washed out, and it is uncertain if they are going to be repaired or if the rail line will be abandoned in place. In light of this, the only reliable access to the town is via air.

Aerial view of Churchill, with the Lazy Bear Lodge in the foreground. (Image: Wikimedia Commons)

For those of us who grew up in small towns, or in remote parts of North America, Churchill feels like a typical small town — people know almost everyone in town; there is only a small business district; lots of cars and trucks that are decades old instead of a year or two old; there are only a couple of roads and few multi-lane highways. The wilderness is within walking distance of anywhere in town.

To the southeast of Churchill, hugging the shores of Hudson Bay, is the Wapusk National Park (“Wapusk” is a Cree word for polar bear), but it is not a park like Yellowstone or Banff, criss-crossed with roads and full of amenities for people who seldom emerge from urban areas. Wapusk National Park has no roads leading into it, and encloses the largest protected polar bear denning area in the world. It is 11,475 square kilometers of boreal forest and tundra with more polar bears than people who frequent it.

Maps showing Manitoba, Churchill, and Wapusk National Park. (Maps: Parks Canada)

Nestled as it is on the shores of the northern ocean, the area around Churchill and Wapusk National Park are an ideal region to study and understand the changes our planet is experiencing, particularly as anthropogenic activities drive the global climate to warmer temperatures. Already the seasonal cycles of ice growth and recession are noticeable in the Churchill area, with sea-ice forming later in the fall and melting earlier in the spring by measurable lengths of time. This expansion of the ice-free season is part of the larger pattern of global arctic sea-ice decline.

Graph showing the projected decline in arctic sea ice as Earth’s climate warms. The grey and black show model predictions, and the red line shows current observations. [Graph from National Snow and Ice Data Center]

These kinds of environmental changes ripple through the ecosystem of the area, particularly the polar bears — a shortening of the sea-ice season is a shortening of the season where they do most of their feeding and building of fat reserves, complemented by a longer fasting season. Worldwide, there are growing numbers of bears who are starving or in declining health. Currently the Churchill polar bear population appears to be stable, though other bear populations in the arctic are declining. Whether or not the global polar bear population is stable or not is highly uncertain, since a significant portion of it inhabits the shores of Siberia, and the Russians are not forth-coming with environmental data about their area of the world.

If you are a scientist who would like to study ecology, or climate, or wildlife in the tundra and boreal forests of the region, Churchill is also home to the Churchill Northern Studies Centre. The Centre is a scientific and educational institution dedicated to a deeper understanding of life in the north — the physical environment, the ecology of the flora and fauna, and the interface with humans and human cultures. The Centre resides on the grounds of the Churchill Rocket Range, which used to launch sub-orbital sounding rockets to study atmosphere and aurorae, housed in a modern LEED certified building, with lab and workspace for scientists, and residential space that allows you to come and stay for weeks at a time while working at the center.

I was in Churchill for only 3 days, and barely scratched the surface of what there is to see and experience in this remote part of the world. Beyond the ecology of the polar bears, the summer months bring vast migrations of beluga whales who birth their young in the Churchill River. The area is part of the wide territories of the indigenous people of the Arctic that have inhabited these lands for thousands of years. Sitting on the boundaries of the Arctic, the area is showing and will continue to experience the early and rapid onset changes brought on by the changing climate, and represents an area where a person can learn and focus attention on this pressing problem.

I’ve been home for a month now, but I still think every day of those windswept days I spent on the shores of the Northern Ocean. I’m going to have to go back, sometime soon.

Songs from the Stellar Graveyard (GW170817)

by Shane L. Larson

Bernie Capax meets Death in Brief Lives, by Neil Gaiman.

In Neil Gaiman’s transcendent literary comics series The Sandman,  the Endless are echoes of the patterns of force and existence that define the Universe. Among them is Death, who at the end of our lives, collects us and escorts us from this Universe. As she says to Bernie Capax, who had walked the world for some 15,000 years, “You lived what anybody gets… you got a lifetime.”  (issue 43, contained in the collection “Brief Lives“).

If there is any truth in astronomy that we have learned over the last few centuries, it is that the Universe itself evolves. The stars are born, they live their long lives, and ultimately they perish and decay away. Death waits for them too. The galaxy is littered with the remains of stars that once were. From our vantage point here on Earth, we peer out into the Cosmos and glean what we can with the meager view we have in our telescopes. We have mapped billions of stars, and millions of galaxies. But in the stellar graveyard, we have only seen a handful of objects — we know precious little about the skeletons of the stars, because they simply don’t emit much light.

On 17 August 2017, at 7:41:04 am CDT, a faint whisper from the stellar graveyard washed across the shores of Earth. It showed up first in the LIGO-Virgo gravitational wave network, which was deep in our second observing run (what we call “O2”). At that particular moment, we were all wound up and celebrating because just three days before, we had made our first joint detection with LIGO and Virgo together (a pair of black holes called GW170814). When signals register in our network, the automated software (we call them “pipelines“) generates initial numbers about what the source might be, and that morning we knew we had something special. Our group lead at Northwestern was spinning us all up to start doing computer simulations, and in an early email to us she said what we all knew: this is life changing.

On the first day, we were sending emails that had the inkling already of how important this discovery was.

Why? Because the mass of the objects in the new signal were smaller than anything we had seen in gravitational waves before — all together less than about 3 times the mass of the Sun. Our predisposition from all our years of experience in astronomy said that could mean only one thing: the LIGO-Virgo network had just detected the first binary neutron star merger in history. Today, we call this event GW170817.

Spectrograms show how the frequency of the signal (vertical axis) changes in time (horizontal axis) in each of the three detectors. The long swoop up and to the right is called a chirp. [Image: LIGO-Virgo]

But the story gets better. 1.7 seconds after the gravitational wave signature, the Fermi Gamma-ray Burst Monitor (GBM), in orbit high over the Earth, registered an event — a short gamma-ray burst, now called GRB170817A. This was hugely significant, because we have often speculated about what causes gamma-ray bursts. For short gamma-ray bursts we’ve long thought it must be colliding neutron stars.

The discovery of GRB170817A by Fermi-GBM. [Image: NASA/Fermi]

What are these neutron stars? They are the dead skeletons of stars, one possible outcome of a colossal stellar explosion known as a supernova. They are extreme objects. They have about one and a half times the mass of the Sun packed inside a sphere about 20 kilometers across (about the size of a city). That means they are extraordinarily dense — a tablespoon of neutron star matter would weigh 10 billion tonnesabout 30 times the mass of all the humans on planet Earth. Gravity on the surface is outrageously strong — about 190 billion times the strength of gravity on the surface of the Earth; if you had the misfortune of falling off a 1 millimeter high cliff, you would be travelling almost 220,000 kilometers per hour when you hit bottom (136,000 mph).

A neutron star (diameter 20 km) scaled to the Chicago skyline. [Image: LIGO-Virgo/Daniel Schwen/Northwestern]

One thing we know about the lives of the stars is that many of them live together with a partner, orbiting one another in a fashion similar to the Earth orbiting the Sun. Like human life partners, one star inevitably reaches the end of its life first, and expires in a supernova. Some such stars become neutron stars. Eventually, the second star in the pair also dies, and if it supernovas, then one end state is two neutron stars, left in an orbital dance with the skeleton of their partner. One might think that is the end of the story for such stars, but there is still one final chapter in this tale from the stellar graveyard. The orbit of the two neutron stars can and will shrink over time through emission of gravitational waves. Of course, we’ve detected gravitational waves before (GW150914, GW151226, GW170104, GW170814), but this time it’s different. Why? We’re talking about neutron stars instead of black holes, which means there can be light, and indeed there was.

The collision of the neutron stars smashes all the matter together, and under such energetic circumstances, matter generates light. The gamma-ray burst was only the beginning. The collision sheds matter into a volume around the merging pair. This matter, suddenly free of the strong nuclear forces involved in the dense matter of the neutron star, recombines and makes heavy elements (physicists call this “r-process nucleosynthesis“). This recombination also creates light, and is called a kilonova. Following the gamma-ray burst there is also a long term afterglow, from the energetic jet of the gamma-ray burst blasting through the surrounding interstellar medium.

Different phases of emission of electromagnetic radiation from the binary neutron star merger. (L) The initial gamma ray burst. (C) The kilonova from nucleosynthesis. (R) Long term afterglow from energized material around the event. [Images: NASA-GSFC SVS]

The LIGO error ellipses plotted on a skymap of the Hydra-Virgo region. The galaxy NGC 4993 is visible in amateur telescopes. [Image: S. Larson]

Together, the LIGO and Virgo detectors can determine where on the sky a source comes from, though not perfectly. They can point to a region called the gravitational-wave error ellipse. For Gw170817, the ellipse on the sky was narrowed down to just about 30 square degrees — an area about the size and shape of a small banana held out at arms length. The error ellipse spans the boundary between the constellations Hydra and Virgo, with a little tail that stretches into Corvus. This was a difficult position in the sky because at the time of the discovery in mid-August, it sets very shortly after sunset. Never-the-less, telescopes around the world began an intensive imaging search, and just 10.9 hours after the detection of GW170817 and GRB170817A, an optical signal was discovered by the Swope telescope in Chile — a pinpoint of light on the outer fringes of the galaxy NGC 4993 that was not there before. Over the course of the next 10 days, the kilonova faded away; in the end more than 70 observatories worldwide imaged and measured the kilonova.  It has been a historic discovery and observing campaign. This is the beginning of multi-messenger astronomy with gravitational waves.

An image of the kilonova associated with GW170817; the fuzzy blog is NGC 4993. [Image: TOROS Collaboration, M. Diaz]

So what can you do with gravity and light together? As it turns out, an awesome amount of science! Today there is a virtual raft of papers being published (the first wave of many, I expect) outlining what we have learned so far. There are too many to explain them all here, but let me just outline a few that stand out to me.

Probably the most important outcome is the confirmation of the connection between short gamma-ray bursts and binary neutron star mergers. Gamma-ray bursts have been a mystery for more than 40 years. First discovered in the 1960s by the military using satellites meant to monitor nuclear weapon tests, the discovery that they were of cosmic origin was revealed to the scientific community in the 1970s. Since then many ideas and models to explain their origin and intense energy have been explored, but none have been confirmed because the engines — the astrophysical systems that drive them — are far too tiny to resolve in telescopes. The LIGO-Virgo detection of gravitational waves confirms that neutron star binaries are the progenitor of short gamma-ray bursts.

The result that I’m most excited about is we used GW170817 to measure the expansion of the Universe. The expansion of the Universe was first noted by Hubble in 1929, by measuring the distances to other galaxies. This was being done just 5 years after the discovery that there were other galaxies! Fast forward 88 years to 2017 — we’ve measured the expansion of the Universe independently using the distance to a galaxy with gravitational waves and light from telescopic observations together. This measurement comes just two years after the discovery of gravitational waves!  It gives me no small amount of pleasure to echo that historic discovery so close to the beginning of this new era of astronomy. 🙂

Top shows Hubble’s original 1929 diagram (from PNAS, 168, 73[1929]); bottom shows the location on this diagram of the GW170817 measurements, at the + mark. [Image: W. Farr/LIGO-Virgo]

We try and write public accessible versions of our papers in the LIGO-Virgo Collaboration. If you’d like to explore some of the science we’ve been doing, try out some of our science summaries.

There are of course many things we still don’t know about the discovery. Foremost among them is this: what is the thing that formed after the merger of the two neutron stars? Some of us in the astrophysics community think it might be some kind of exotic super-neutron-star, larger than any neutron star ever detected. Some of us in the astrophysics community think it  might be some kind of exotic light-black-hole, smaller than any black hole ever detected. Whatever it is, it lies within a very fuzzy range of masses that we call the mass gap — a range of masses where we have never seen any stellar remnant. What is the lightest black hole Nature can create in the Universe?  What is the heaviest neutron star Nature allows? These are questions we would very much like to know the answer to. At least for the moment, it seems we may not learn the answer from GW170817, but with future detections of binary neutron star mergers we may.

The masses of known stellar remnants discovered by both electromagnetic and gravitational wave observations. Between the black holes and the neutron stars is the “mass gap.” [Image: LIGO-Virgo/Frank Elavsky/Northwestern]

So here we are. We are all simultaneously exhilarated, relieved, joyous, and eager for more discoveries to be made. We’re very tired from late nights analyzing data, arguing about results, writing papers, and furiously preparing ways to tell our story to the world.

We could all use a nap. And a pizza.

Because this is only the beginning, the culmination of decades of hard work, difficult hardships, and anticipation. And the best is yet to come. I’m so happy that I’ve seen these days. Being tired doesn’t bother me, all the struggles getting to this point don’t bother me either, because I got to watch it unfold. As Death said, we get what anyone gets; we get a lifetime. These are the moments, the discoveries, that are filling that lifetime up.  Onward to the next one.


This post is the latest in a long series that I’ve written about all the LIGO detections up to now.  You can read those previous posts here:

The Harmonies of Spacetime – GW150914

My Brain is Melting – GW150914 (part 2)

The Cosmic Classroom on Boxing Day (GW151226)

New Astronomy at the New Year (GW170104)

Focusing our Gravitational Wave Attention (GW170814)


I have many LIGO and Virgo colleagues who also blog about these kinds of things. You may enjoy some of their posts too!


Focusing Our Gravitational Attention (GW170814)

by Shane L. Larson

Nature guards her secrets jealously, and wresting them from her grasp is an arduous, and frustrating task. One of the great difficulties of the modern world is that knowledge is so easy to pull up, with the flick of a finger across a screen, that we forget how hard it was to obtain that knowledge in the first place. Every bit of knowledge that you and I take for granted was earned, at great cost, by a long line of humans who came before us.

Knowledge is hard to come by, a fact that we often forget in an age where virtually any and all information is readily available on demand with a handheld device. [Image: S. Larson]

For just more than two  years now, we have lived in a new astronomical era, where astronomers have the ability to sense minute deviations in the shape of spacetime and use them to discover the secrets of the Cosmos. We call this science gravitational wave astronomy.

This new branch of observational astronomy burst on the scene with much fanfare in early 2016 when it was announced that the two LIGO gravitational wave observatories had detected a pair of black holes merging far across the Cosmos. We knew roughly where it was in the sky, but only roughly in the same sense that “Kansas is roughly in North America.” The physics of how an instrument like LIGO works means detection is easier than pointingpointing to a gravitational wave source on the sky is hard, because Nature guards her secrets jealously.

We call gravitational wave detectors “observatories“, but they are very different from traditional telescopic facilities that you and I are familiar with. Telescopes work more or less like your eyes — they point in a given direction, and are sensitive to a narrow space in front of them (what astronomers call the “field of view“).

A daytime picture of the Moon, taken by holding my phone up to the eyepiece of my backyard telescope. The field of view is not much bigger than the Moon, which is very small on the sky. [Image: Shane L. Larson]

By contrast, gravitational wave detectors are largely omnidirectional — they can sense gravitational waves from every direction on the sky, though some directions are easier than others.  They are much more like your ears in this way. If you close your eyes, you can hear sounds in front of you, above you, to the sides, or behind you. You can usually point at a source of a sound, but that is because your brain is using both of your ears together to triangulate the position of the source of sound. Here’s an experiment: close your eyes and plug one of your ears. Have one of your friends stand somewhere in the room and sing “The Gambler” (here’s a version I particularly like, by First Aid Kit) and see if you can point to them. It’s not so easy to point with only one ear.

We use this same method of triangulation in gravitational wave astronomy — multiple detectors can point better than single detectors alone. The more detectors, the better a source of gravitational waves can be found on the sky.

The Virgo gravitational wave observatory, outside of Pisa, Italy, looking roughly northward toward the Monte Pisano Hills. [Image: Virgo Collaboration]

For the past two decades, at the same time LIGO was being built, our colleagues in Europe were constructing another gravitational wave observatory outside of Pisa, called Virgo. On 1 August 2017, the Advanced Virgo detector joined the two Advanced LIGO detectors in the search for gravitational waves.

There was much celebration in the LIGO-Virgo Collaboration that day, because gravitational wave detectors are not easy to build. Getting to the moment where all three advanced detectors were online together was a tremendous accomplishment, and one that held much promise. With three detectors, we should be able to pinpoint gravitational wave sources on the sky better than ever before. The holy grail of events would be to make a detection, and narrow the skyview to an area so small that one could reasonably point a telescope there and possibly see a simultaneous signal in light.

Doing directed astronomy with gravitational wave detectors requires a network of many facilities. As time goes on, more are being built around the world.

We held our breath, and dared not hope. That’s the nature of astronomy — it’s a spectator sport. All we can do is turn on our instruments, and sit here on Earth and wait for the Universe to do something awesome.

As it turns out, we didn’t have to wait long for something awesome. On 14 August 2017, all three detectors registered the gravitational wave signature from a pair of merging black holes.  At about 5:30am CDT in the United States (10:30:43 UTC), a signal came sailing through the Earth, ringing off each of the three gravitational wave detectors that were diligently collecting data, hour after hour, minute after minute, waiting for the Cosmos to do something. Nature did not let us down. The signal was a strong series of spacetime ripples, with the same pattern, showing up in each of the three detectors. We call the event GW170814 (here is a LIGO-Virgo factsheet on the event), and it brings the total number of events in the gravitational wave catalog to 4.

The GW170814 signal, as gravitational wave astronomers like to represent it. The top row shows the spectrograms, showing how the frequency (analogous to the pitch of a sound) evolves in time, chirping as you go from left to right. The lower row shows the waveform traces in time from left to right, growing stronger as the black holes approach and merge, then tapering away. [Image: LIGO-Virgo Collaboration, from our paper]

Below, I show a table I keep of events, and it is getting harder to manage! I like to take it out and stare at it sometimes because you can see a story beginning to emerge, and for a scientist there is nothing more exciting. A story is exactly what we’ve been trying to learn from Nature, but you can seldom figure it out from just one astronomical event. It is only the long, slow accumulation of happenings in the Cosmos that lets us begin to see the tantalizing patterns of what is going on. Lots of black holes. We’re beginning to get a sense for some trends in their masses. We’re beginning to figure out how many there might be, and how common they are in the Universe. Scientists, as a general rule, are a cautious lot. It will still be a while before there are definitive statements on Wikipedia or in astronomy textbooks. But buy your favorite gravitational wave astronomer a bag of jelly donuts (I also like Dr. Pepper), and they’ll talk your ear off about what we’re beginning to figure out.

My updated gravitational wave catalogue. [Image by Shane L. Larson]

But the real story of GW170814, is Virgo. Virgo came roaring on the scene, and transformed our ability to point on the sky. The sky location graphic below shows all of the gravitational wave events seen to date (including one interesting signal, called LVT151012 that wasn’t quite strong enough for us to make out perfectly in the data, but looks an awful lot like a black hole pair).  In every previous detection, the source was known to lie in some great banana shaped region of the sky that we call an error ellipse. With the addition of Virgo to the network, and the arrival of GW170814, we see the dramatic and awesome difference it makes, collapsing the giant banana of an error ellipse into a much smaller bubble on the sky. This bubble lies near the southern end of the constellation Eridanus (if you’d like to look at a starmap, it came from an area around RA = 3h 11m, DEC = -44d 47m). At the moment of the event, the source was directly overhead southern Chile.

The sky location of all gravitational wave events to date. [Image: LIGO/Virgo/NASA/Leo Singer (Milky Way image: Axel Mellinger)]

There were no detected signals with light associated with the event, but these were after all, black holes. By definition, black holes emit no light; if there is going to be something for traditional telescopes to see, there is going to have to be some kind of matter involved. And so, we wait for the next one. We can tell we’re on the cusp of a tremendous new era of astronomy. We still haven’t found the holy grail, an event seen with both gravitational waves and light, but we continue to look. With our growing network of detectors, and scientists around the globe, we will eventually make that discovery too.

Until then, my heartfelt congratulations to my colleagues and friends who I work with on LIGO and Virgo — here’s to many more long years of searching the Cosmos. Viva Virgo!


You can read about the previous LIGO detections in my previous posts here:

The Harmonies of Spacetime – GW150914

My Brain is Melting – GW150914 (part 2)

The Cosmic Classroom on Boxing Day (GW151226)

New Astronomy at the New Year (GW170104)


A Majestic End for a Faithful Friend

by Shane L. Larson

We live in an age where digital technology can make anything seem real. Movies have become immersive experiences where any landscape, real or imagined is possible. Physics defying stunts are rendered on screens as tall as buildings and with sound louder than thunder. Creatures long extinct or completely imagined spring to life, and actors long since passed from the world magically return to the screen, appearing as they did in their youth. Anything seems possible, and the boundaries of reality are blurred, to say the least.

Anything can be given realism with modern technology, whether they be long dead creatures, imagined aircraft, or an architectural plan for a new building. [all images from Wikimedia Commons]

We are so used to this, that when confronted by real pictures of the real world, we often forget what we are looking at. Fantastic and awe-inspiring pictures slip past us and don’t always capture our attention. Photographers capture massive migrations of animals across the land and sea, forlorn sights of abandoned corners of our cities, and the vibrant colors of rainbows and autumn leaves. When we see those pictures, at just the right moment, we experience a visceral moment of joy and set our phone screens and computer desktops to the image, to remind us of that moment of wonder. But more often than not, we don’t remember that real pictures of the real world can evoke emotional responses in us. Some small part of our brain remembers, of course, else we wouldn’t takes selfies in front of restaurants where we enjoy fantastic dinners, or pictures of sunsets against the skyline of our backyards.

On many days, as the woes of the world sidle past me on my computer screen, I am reminded of something that I became aware of in my youth: the true masters of real pictures of the real world are the folks at NASA. They have long been part of the storytelling narrative, reminding us that we are part of a far larger Universe, showing us that with concerted effort and imagination and perseverance, we can overcome tremendous obstacles, solve incredibly difficult problems, and discover that the world around us is filled with unimagined and awe-inspiring grandeur. The Cosmos is alive and breathing around you, reminding you that you are part of something greater that the usual bibble-babble washing out of your device screen.

NASA’s digital artists are masters of putting us at the center of the action, even if it is impossibly far away. L to R: Curiosity skycraning onto Mars; Juno arriving at Jupiter; Cassini arriving at Saturn. [Images by NASA]

In the last few years, our friends at NASA have upped their game. Not only have they regaled us with real pictures of the real world, but they’ve picked up the story-telling torch, and as masterfully as any filmmaker in the world catapulted us into the drama of exploring the Cosmos. You may remember this when they told us about the Seven Minutes of Terror as we lowered the Curiosity rover onto Mars using a robotic, rocket-powered skycrane. Last year, they told us the tale of returning to the unknown regions around Jupiter with a hearty spacecraft called Juno, diving into the radiation belts where anything could happen. But recently, they turned their attention to a far-away world called Saturn, and a steadfast spacecraft we sent there called Cassini….

Saturn has been known to humans since antiquity, one of the bright moving lights in the sky known as the planētes asteres, the “wandering stars.” Like the other naked eye planets, Saturn moved slowly among the stars, tracing out a path along the band of constellations known as the Zodiac, cementing itself in the folklore and mythology of sky-gazers who watched it closely. In the 17th century, the era of Saturnian exploration began when the first telescopes were pointed skyward. The first fuzzy, warbling views of the world showed it was not like the stars at all. Telescopes improved rapidly, as did the views they showed of this far away planet, until at last we discovered the truth — Saturn was magnificently bejeweled by a brilliant, encircling ring. Since that time, Saturn has reigned supreme among all the planets for the awe it evokes at its splendor and beauty. More than any other planet, it looks like it is supposed to look. Today, millions of telescopes around the world are set-up in backyards and on sidewalks on clear nights, giving ordinary people like me and you views of one of the Cosmos’ great spectacles — you can have your own Saturn Moment.

View of Saturn you will have through a modern backyard telescope, taken with an iPhone [Image courtesy of Andrew Symes]

Like most things in space, Saturn is unfathomably far away. At a distance of 1.3 billion kilometers from Earth, it would take you about 1400 years to drive to Saturn’s orbit in your car, or about 150 years to fly there at the speed of a passenger jet. We are, by and large, restricted to staring at it from afar, gleaning what we can from the meager light gathered in our telescopes. The arrival of the Space Age put a new possibility on the table: travelling across the void. Suddenly, we had the chance to see Saturn up close.

While there are effervescent dreams to send humans, Saturn is still too distant to imagine easily crossing the void ourselves, so our attention has been focused on sending quasi-intelligent emissaries in our stead: robotic explorers whose sole purpose is to gather as much information and take as many pictures as possible, and transmit all of that information back to Earth.

Our robotic emissaries, Pioneer 11 (left) and Voyagers 1 and 2 (right). These are the only spacecraft to have ever visited the gas giant worlds of the Solar System. [Images by NASA]

In the 60 years since the start of the Space Age, only 4 spacecraft have ever visited Saturn. The first was a resolute robotic explorer called Pioneer 11.  In 1979, it flew by Saturn skimming through just 20,000 kilometers above the cloud tops, returning the first up close pictures of Saturn, but only a few. It was followed by Voyager 1 in 1980, and Voyager 2 in 1981. The Voyagers returned wide planetary views of Saturn that became iconic to an entire generation of humans, and showed us an ensemble of moons that are each unique and tantalizing, demanding their own careful program of exploration. All of these missions flew past Saturn, returning quick passing views before sailing onward. Today, Pioneer 11 and Voyagers 1 and 2 are on an unknown voyage, destined to drift in the great cosmic dark between the stars for a billion years.

Closeup views of Saturn by Pioneer (left) and Voyager (right). Their time with Saturn was short because they were doing flybys (try taking a picture of your friend on the sidewalk as you drive by at 50 miles per hour…). [Images by NASA]

The most recent of the quartet of august explorers is a two tonne spacecraft called Cassini. It spent seven years crossing the void to Saturn, and has spent the last 13 years circling Saturn, probing the ringworld and its remarkable moons. Twenty years ago, it was cocooned up inside its rocket, and hurled into space. No human has seen it since.

This image is one of the last pictures taken of Cassini in 1997, before launch; the whole spacecraft, together with a few of the people who gave it life. Not soon after, the rocket fairing was lowered into place and closed, cocooning Cassini inside. That was the last any human ever saw of it. [Image by NASA]

For more than a decade, we have been treated to remarkable images, ranging from the strange divided faces of Iaepetus, to the mangled surface of small, tumbling Hyperion. We saw stunning views of the blue-white ice of Enceladus, and ephemeral views of Saturn and its rings, backlit by the distant Sun.

The images returned by Cassini have been stunning, and are far too numerous to do justice to here. A few favorites include: Hyperiod (top left), Enceladus (top center), Iapetus (top right), and Saturn backlit by the Sun (lower). [Images by NASA]

But never among these has there been an image of Cassini itself. Unlike its siblings, the Mars rovers, Cassini cannot take a selfie. But our artists have continued to insert Cassini into imagined views of the Saturnian system, seen as if we were sailing along side it, snapping pictures for the family photo album. Cassini cruising over Titan; Cassini plummeting through the ice plumes of Enceladus; Cassini looking back toward a distant blue star that is Earth.

Artist imaginings of Cassini during its decades long exploration of Saturn. [Images by NASA]

Now, after a two decade journey, we are nearing the end. Cassini’s tasks are nearly over. Unlike Pioneer 11 and Voyager 1 and 2, Cassini is bound to Saturn forever; it will not embark on a lonely voyage to the stars, and in fact, it can’t: there simply isn’t enough fuel in its rockets. Instead, the humans who lovingly crafted it and meticulously planned its journey have planned a magnificent send-off. We call it The Grand Finale. The end of the journey is stunning, worthy of an adventurer as bold and brave as Cassini. But we won’t be able to see it, so once again we turn to our artists to illuminate the images in our minds eye.

Some images from Cassini’s Grand Finale. (L) Saturn’s polar regions, up close as Cassini loops over the top of the planet for another ring pass. (C) One of the highest resolution images of the rings ever taken. (R) The small moon Daphnis, carving out a corridor in the rings. [Images by NASA’s Cassini Imaging Team]

In a series of slowly descending orbits, Cassini will voyage closer to Saturn than any spacecraft before. Looping high over the planet, it will plunge down through the rings for the first time, then loop back around and do it again. Over and over again, it will pass through the rings and skim the top of Saturn’s atmosphere. In all, the Grand Finale consists of just more than 22 orbits. On each orbit it dutifully records what it finds, and relays that information back to us here on Earth. Already we have received stupendous views of the rings, of the cloudtops from closer than we’ve ever seen, and the nearby moons framed by a sky simultaneously more majestic and more alien than any we could imagine in a Hollywood studio.

But at the very end, when there is no where else to go, Cassini will finally succumb to the inexorable gravitational pull of Saturn, and be drawn down into the atmosphere. Travelling more than 75,000 miles per hour, it will burn up in a colossal fireball. One of a thousand meteors that might hit Saturn on any day, but this one from a nearby world. We won’t see Cassini. As it falls, it will be linked to Earth only by the tenuous thread of its radio link, faithfully relaying the last of its observations as it sinks forever into the ocean of Saturn’s atmosphere.  At some point, we don’t know when, Cassini will be gone. With no one to see it, Cassini will disintegrate into nothing. Out of our sight, the last of our dreams and aspirations for Cassini will come to an ultimate end.

Will will mourn. But always we will return to the vast photo album we have assembled over its 20 year life. Like a long time friend departing for the other side of the veil of death, we can’t help but be simultaneously overwhelmed by sadness together with admiration for everything that this little robot has accomplished, against all odds. Cassini has forever transformed our understanding of Saturn. Saturn is a real place, as much a part of the story of our solar system and our home as anything we have ever seen.

Once again our artists capture what we cannot see, rendered in NASA’s End of Mission video, using the tools of entertainment to tell us the story of our long departed emissary in it last moments over Saturn. More than any other art or video I’ve seen, they’ve succeeded in evoking how truly huge and majestic Saturn is, and how tiny Cassini is by comparison. All that we know, all that we’ve discovered, we owe to a tiny robot immeasurably dwarfed by the planet it has so faithfully explored.

You owe it to yourself to go watch this video; reflect on all that Cassini is and was, and know that we are capable of doing tremendous things.

Ad astra per aspera. Fare thee well, Cassini.

Total Eclipse: On the Far Side of Totality

by Shane L. Larson

How do you describe the indescribable?

I’ve been a skywatcher for more than half of the years of my life. I’ve literally spent thousands of hours with my telescope, watching the sky, making sketches to remind me of what I saw, keeping notes about appearances, and making lists of favorites to look at again. I’ve seen the rings of Saturn, and the Great Red Spot. I’ve observed supernovae, seen comets stretch across the sky, and watched the aurora borealis storm overhead. I’ve seen a transit of Venus, a once in a lifetime event.

But nothing prepared me for what I saw on Monday, standing on a hillside in Casper, Wyoming. For a brief two minutes, the Moon covered the Sun in the total solar eclipse of 21 August 2017.

Our morning started early, arriving at 5:30am. We weren’t tired now; that was later, after the eclipse was over and the adrenaline wore off! [Image by S. Larson]

My family and I, together with eight of our long time friends, set up on the grounds of Casper College, together with a vast number of our amateur astronomy colleagues who had been in Casper for the  2017 Astrocon Convention. The eclipse was due to start at 11:42am MDT, so we arrived on site early to set up: 5:30am!

By 6:00am the horizon began to glow with the scarlet tones of sunrise, and at 6:19 the Sun rose slowly over the distant horizon. We couldn’t see it, but we knew the Moon was right there too, steadfastly churning along its orbit, its shadow streaming through space, like a needle waiting to poke the Earth.

Sunrise and the appearance of the Sun. This was the moment when we knew in our cores that we were going to witness the total solar eclipse, without fail. [Images by S. Larson]

We had a row of tripods — some set up to image, some with binoculars, some with telescopes, all with solar filters. Every one of us had eclipse glasses that we constantly watched the Sun with, waiting for the first moment when the Moon would slowly begin to move between us and the Sun.

Eclipse glasses. This is pretty much how we looked all morning once the Sun came up. [Images by S. Larson]

We knew we were in for a wait, as the eclipse wasn’t due to start until 10:22am, and totality wouldn’t start until 11:42:42am!  So we paced back and forth restlessly. We took selfies with each other. We joked around. We checked the traffic, wondering if the slug of red between Denver and Cheyenne would make it to the path of totality on time. We played games. We make cookie art to track the eclipse.  You know — normal nerd herd stuff.

Just passing the time, tracking the eclipse by making art with cookies. [Images by S. Palen (L) and K. Larson (R)]

The folks down the row from us had an old Astroscan telescope, outfitted with a DIY homebuilt funnel projection screen (here are instructions from NASA) that was ideal for letting everyone see what was going on, and for taking pictures of what the Sun looked like during the partial phase of the eclipse. There was an excellent group of sunspots arcing across the middle of the Sun, and another small group down near the limb.

Our observing neighbors had an Astroscan fitted with an observing funnel (top left). The Sun had some great sunspot groups that day (top right). The screen made it easy to see the progression of the partial eclipse (lower 4 photos). [Images by S. Larson]

We also watched the progression with pinhole projections, looking at the shadows of anything with tiny holes in it. Every one showed a dazzling array of small crescent Suns, slowly being eaten by the Moon.

“Pinhole projection” is an easy way to enjoy the progress of the partial eclipse. We used a cheese grater and a Ritz cracker (Left), and also watched the dappled light in the shadows of the trees (Center and Right). [Images by S. Larson]

And then, we knew the moment was coming. We were all watching. The light got really flat and dim all around. It started getting darker, quickly. At the last moment before the Sun was completely covered, the left side burst out in a brilliant flare we call “the diamond ring.” Simultaneously, I remember the right side illuminated with a sharp edged circle, rimming the edge of the Moon. And then the Sun was gone. The total solar eclipse had begun.

We were on that hillside with maybe a thousand other people, and it erupted with cheering, screaming, whistling, and shouts of joy and astonishment. There are a million photos on the web of these precious few moments of darkness, suffused with the effervescent, gossamer glow of the Sun’s corona. They are fantastic pictures, but none of them capture everything I remember now in my mind’s eye.

The shapes are right, with two streaming horns pointing up and to the right and one down and to the left. Many of them show the bright red spot of a solar prominence peeking out from behind the limb of the Moon. A few that have been processed show the amazing interlaced structure in the corona.  My lifelong observing buddy (Mike Murray) and I agreed that the word we would have used to describe the view is translucent.

The best representation of the color I remember is the translucent blue of this plastic, in the middle of this cup (above the dark blue in the bottom). [Image by S. Larson]

But even more what I remember was it did not look white to me. It looked kind of pale blue. I’ve observed a lot of objects in the sky, and the diaphanous light of the corona reminded me all the world of the color in some planetary nebulae or bright, hot stars. I’ve been struggling to find something this same color, or a better way to describe the color. That night at dinner with my wife and daughter, I stumbled on a drinking cup whose translucent plastic comes close to being right.

But in the end, all of these attempts to describe the event fall far short of what I remember. There is nothing quite so profound as standing in the shadow of the eclipse, and it’s over before you even know it. The memory, while powerful, feels slippery — I want to cement it somehow, because it would be horrible to forget what I felt in those few moments. I immediately wrote down my notes (images of them are included at the bottom of this post), but they are pale by comparison to what is in my head. I recently met a psychologist named Kate Russo who studies and writes books about people who watch and chase solar eclipses. She names this feeling we all have about our solar eclipse experiences: ineffable.

I had resolved not to make a considerable effort to set up equipment and try to photograph the event. It was my first total solar eclipse, and I didn’t want to be distracted by the equipment and miss it. I did throw my phone up and snap a couple of pictures, but no more. It is small and grainy, but it looks like an eclipsed Sun. Knowing how fast it went, and how much more I wanted to just LOOK at it, I’m not sure I’ll ever go the route of taking pictures.

Totality. The best photo my iPhone could take? I dunno — the best photo I could take for the time I was willing to spend looking at the screen and not the eclipse! [Image by S. Larson]

In the day since the eclipse, I’ve seen many fantastic pictures of the eclipse from friends. Every single one, no matter how technically awesome it was shot, is spectacular. Why? Because they capture that ineffable moment that every person was trying to capture for their mental review later. Each one is a tiny memento, small and bright, captured on silicon and in digital pixels, that reminds the photographer what it was like to stand, just for a moment, in the shadow of the Moon.

During that same day, I’ve been looking at all those pictures, scrolling through what I had on my phone, talking with my wife and daughter, and talking with friends on social media. Always trying to cement the experience in my head. But quite by chance, I did something that I am thankful for. I set up my video camera (a little Sony Handycam) pointed at the Sun for about a half hour around totality. I didn’t know what it would capture on video, but what I wanted it for was audio.

I couldn’t have asked for any better record and memory of the event than that audio record. I’ve listened to it many times now, and each time I’m transported back to that moment on a hillside in Casper, surrounded by friends and a thousand other of my fellow humans, gazing up at the sky in stupified awe. Nothing shocks my memory with better clarity than this audio. A good friend of mine who is a psychologist in Colorado told me listening to this audio fired off mirror neurons in her brain. Mirror neurons are neural responses in your brain that respond from observing something going on as if you were there doing it yourself.

So I close this meager recounting of my experience with the audio of me and my friends, immersed in the moment. I hope you glean from it some of the joy and awe and ineffable wonder that we all felt standing there for those two minutes, and reminds you of similar moments you may have experienced and shared.

Mirabilis sole!


I’m a fastidious note-taker. Here are images of my notes I took in the hours immediately after the event.

Notes Page 1. When big things happen, I often have my friends who are with me sign my observing log, so I remember they were there. [Image S. Larson]

Notes page 2. [Image by S. Larson]

Notes page 3. [Image by S. Larson]

Notes page 4. [Image by S. Larson]

Here is the previous post I wrote leading up to this solar eclipse: Total Solar Eclipse: Anticipation (20 Aug 2017)

Here is a previous post I wrote about the astronomy behind a total solar eclipse: Stand in the Shadow of the Moon (25 Aug 2014)

Total Eclipse: Anticipation

by Shane L. Larson

There are many amazing sky events that happen to pique the interest of amateur astronomers. I went out in 1994 and watched the shattered fragments of Comet Shoemaker-Levy 9 plummet into Jupiter, scarring the giant planet’s atmosphere with dark swaths of discolor larger than the Earth.  In 2001, I sat up all night in a campground in Cloverdale, CA counting Leonid meteors in one of the best storms in recent memory.  I’ve sat cross-legged in an empty field just off of I-80 in Kearney, Nebraska, peering through a small spotting scope at a bright supernova in spiral galaxy M101, just detectable at the edge of my vision.

All of these events, and many more like them, are important and interesting to those of us who forego sleep regularly to stand out under the dark and look at the night sky. There is something exhilarating about hunting for a few photons that just happened to cross the great gulf of space and fall to Earth at the exact moment I was looking up. But it is not for everyone.

Total solar eclipse progression. [Image by Justin Ng]

Tomorrow, people living in North America will be witness to one of the most profound spectacles the Cosmos has to offer: an eclipse of the Sun. Everyone in North America, if their skies are clear enough, will be able to see something. For a couple of hours, on 21 August 2017, the Moon will pass between Earth and the Sun, partially blocking the view of the Sun.  If you stand along a pathway roughly 70 miles wide that stretches from Oregon to South Carolina, there will be about two minutes during your day when the Sun is completely hidden behind the Moon. The skies will get dark, and the day will feel cooler — it will, for two minutes of your day, feel like night. You are standing in the shadow of the Moon.

Standing in the shadow of a total solar eclipse is one of the most profound personal experiences with the Cosmos you can have. Those comets and supernovas I mentioned before are cool to witness, particularly if you know what you’re looking at and can be reflective about the profound distances those little photons of light have travelled.  But a total solar eclipse is different.

Our lives, whether we think about it or not, are ruled by the Sun.

It is impossible to be unaware that our lives on Earth are acutely connected to the Sun. We bask in its warmth, play in its dappled rays, and soak up its energy every day. But during totality it will completely vanish from your view — you can’t help but notice that it is just gone from its normal place in the sky and our lives. People struggle to explain the ephemeral and visceral reaction they have to the sight and raw beauty of these singularly moving events.

For this eclipse, there are more people who live near the path of totality, and more people that can get to the path of totality, than possibly any eclipse in history. The eclipse tomorrow will be one of the most viewed natural events in the history of our civilization.  You owe it to yourself, no matter where you are, to at least take a moment and #lookUp and share in the spectacle with your fellow humans.

What can you expect?  In your local media you should be able to find the times when you can see something going on in your area. There are great online tools; I like the Astronomy Magazine widget (here is the link!) that gives you eclipse times for any place you click on a map.

For most people, the partial eclipse will last a couple of hours, and any time during those couple of hours you can see the Sun looking like a cookie with a bite taken out of it.

Eclipse glasses are a cheap, convenient, and easy way to be #EquippedToEclipse. [Image by Adler Planetarium]

During the partial eclipse, the Sun will be too bright to look at! You wouldn’t normally look at the bright Sun, so you won’t feel compelled to now!  If you want to see the partial eclipse, then a pair of the ubiquitous eclipse glasses are needed to look at the partially covered Sun. There has been a lot of concern about safety of glasses found from various outlets and vendors, and the debacle with Amazon has not helped. The American Astronomical Society (our professional society) has produced a page with vetted sources of glasses — this page includes BRANDS OF GLASSES that are certified, and also has a list of stores (e.g. Lowes etc) that are selling glasses that are safe for the event. That page is here:

But what if you never got some glasses, you lost your glasses, or your dog ate your glasses?  Well never fear. Eclipse glasses are not the only way to enjoy this!

The dappled light streaming between the leaves on trees will make thousands of little eclipse images in the shadows. Watch for them! [Image by John Armstrong]

During the partial eclipse you can see what is going on by projection. Look in the shadows of trees – the dappled light will be mini eclipses. Hold up a spaghetti colander – the light in the shadow will be mini eclipses. Hold up a Ritz cracker – light thru the holes will show mini eclipses in the shadow. People have used straw hats and lacy sweater sleeves! Be creative, and enjoy the eclipse.

Also — the partial phase lasts almost 3 hours. If your friend next to you has eclipse glasses, you can share. 🙂

My image of the Ring of Fire on 20 May 2012, taken with my iPhone held up to a filtered telescope. [Image by S. L. Larson]

I have never seen a total solar eclipse (though I had the good fortune to observe the Annular Solar Eclipse on 20 May 2012 in Cedar City, UT). We watched that event in a city park, surrounded by maybe a thousand residents of the town who were watching with us. Everyone had eclipse glasses, there were projections with spoons and meshes, and we had our filtered telescopes there and talked to hundreds of people who just happened to be walking by and took a look.

What I remember most, was at maximum when there was a perfect ring of fire visible through your glasses in the sky, there was a tremendous swelling mass of cheering and shouting and joy. There was no big sporting event, no blockbuster music stars inciting that reaction.

Just a thousand humans, witnessing together one of the most beautiful spectacles the Cosmos has to offer, unable to control their joy and emotions.  It was awesome to be standing there shoulder to shoulder in that crowd.

My daughter was in kindergarten when she saw the annular eclipse in 2012, and still remembers it. Now she’s going into 6th grade, and I think she’s going to become an eclipse chaser. 🙂 [Image by S. L. Larson]

I wanted to just get a few thoughts down here about what it is like leading up to the event, musing on how it will feel on the far side.  Will I feel compelled to travel the world for the next possible one I could view (2 July 2019, over the Southern Pacific, Chile and Argentina)? Will I become an eclipse chaser, racking up 10 or 20 total solar eclipses over my lifetime? Or will I just be like, “cool, put it in the log book; when’s the next cool something to happen?” I honestly don’t know.  But we’re about to find out.

Catch you on the other side of totality….

Here is a previous article I wrote about the astronomy behind a total solar eclipse: Stand in the Shadow of the Moon (25 Aug 2014)