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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!

 

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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: 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: https://eclipse.aas.org/resources/solar-filters

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)

New Astronomy at the New Year (GW170104)

by Shane L. Larson

Newton’s portrait.

January 4 holds a special place in the hearts of scientists — it is Isaac Newton’s birthday (*). Newton stood at the crossroads that led to modern science, and astronomy in particular. He was the first person to build a workable reflecting telescope, a design that now bears his name and for the past 4 centuries has been the dominant type of telescope used by amateurs and professionals alike. Newtonian telescopes have revealed much about the Cosmos to our wondering minds. Newton was also responsible for the first formulation of a physical law that describes the working of gravity, called the Universal Law of Gravitation. Today we use the Universal Law to launch satellites, send astronauts into orbit, convert the force of your feet on the bathroom scale into your “weight“, and a thousand other applications.  There is much to celebrate every January 4.

(L) Aerial view of LIGO-Hanford Observatory [top] and in Google Maps [Bottom]. (R) Aerial view of LIGO-Livingston Observatory [top] and in Google Maps [Bottom].

But on January 4, 2017 the Cosmos celebrated with us, singing in the faint whispers of gravity itself. On January 4, the signal of two black holes catastrophically merging to form a new bigger black hole washed quietly across the shores of Earth, carried on undulating vibrations of space and time. You were very likely unaware of this cosmic event — it happened at 4:11:58.6 am in Chicago. It was a Wednesday morning, and I imagine most people were blissfully asleep. But two of the grandest pieces of experimental apparatus ever built by humans were paying attention – the twin LIGO detectors in the United States.  For only the third time in history, a gravitational wave signal from the deep Cosmos was detected here on Earth.

The signal was the signature of two black holes (a “black hole binary,” in the lingo of the astrophysicists) merging to form a new, bigger black hole. The black holes, by definition, emit no light themselves. However, astronomers know that black holes can often be surrounded by swaths of interstellar gas. The intense gravity and motion of the black holes can stir the gas into a violent froth that can emit light. At the time of the event, the LIGO team sent out alerts to astronomers around the world, who turned their telescopes skyward looking for a tell-tale signature of light bursting from the energized gas. Our best estimate of the location of the event was canvased by 30 groups, in many different kinds of light ranging from radio waves, to optical light, to gamma rays. No tell-tale emissions of light were seen. The only way we were aware of this event is from the LIGO detectors themselves.

An artist’s impression of two black holes insprialling, near merger. [Image by Aurore Simonnet, SSU E/PO]

The Gravitational Wave Signal. We call the event GW170104, named for the date it was detected. The signal from the black holes registered first in the LIGO detector outside Hanford, Washington, and 3 milliseconds later registered at the LIGO detector outside Livingston, Louisiana. All told, it only lasted about 0.3 seconds. The signal exhibited the characteristic chirp shape expected of compact binaries that spiral together and merge — a long sequences of wave peaks that slowly grow in strength and get closer and closer together as the black holes spiral together.

Comparison of the chirp waveforms from the first 3 detected gravitational wave events. LVT151012 was a very quiet event that was not strong enough for LIGO scientists to be confident it was a pair of black holes. [Image: LIGO Collaboration]

During the early inspiral phase of GW170104, where the black holes are independent and distinct, the heavier black hole of the pair was 31 times the mass of the Sun, and the smaller black hole was 19 times the mass of the Sun. Ultimately, they reached a minimum stable distance (in astrophysics lingo: the “innermost stable circular orbit“) and plunged together to form a new bigger black hole. When that plunge happened, the gravitational wave signal peaked in strength, and then rang down and faded to nothing as the black hole pulled itself into the stable shape of single, isolated black hole. For GW170104, this final black hole was 49 times the mass of the Sun.

All of this happened 3 billion lightyears away, twice as far as the most distant LIGO detection to date. Perhaps these numbers impress you (they should) — they tell the story  of events that happened billions of years ago and in a place in the Cosmos that neither you, nor I, nor our descendants will ever visit. We add them today to a very short list of astronomical knowledge: the Gravitational Wave Event Catalogue, the complete list of gravitational wave signals ever detected by human beings. There are only three.

The current Gravitational Wave Catalogue, of all known events [click to make larger].

Take a close look at the list. There are interesting similarities and interesting differences between the three events. They are all black hole binaries. They are all at least a billion light years away from Earth. Some of the black holes are heavier than 20 times the mass of the Sun, and some are lighter than 20 times the mass of the Sun. Astronomers use those comparisons to understand what the Universe does to make black holes and how often.

This is the most important thing about GW170104 — it is a small but significant expansion to this very new, and currently, very limited body of knowledge we have about the Cosmos. These three events are completely changing the way we think about black holes in the Cosmos, forcing us to rethink long held prejudices we have about their masses and origins. We shouldn’t feel bad about that — evolving our knowledge is the purpose of science. LIGO is helping us do exactly what we wanted it to do: it is helping us learn.

What do we know? There are many things we are trying to learn from the meager data contained in these three signals. The new signal from GW170104 in particular has tantalizing evidence for the spin of the black holes, and some neat assessments of how close these astrophysical black holes are to what is predicted by general relativity. But I think the most important thing about the event from the perspective of astronomy is this: the black holes are, once again, heavy. GW170104 is the second most massive stellar mass binary black hole ever observed (GW150904 was the heaviest).

The masses of known black holes. The purple entries are observed by x-ray telescopes, and represent what we knew about the size of black holes before LIGO started making detections. [Image: LIGO Collaboration]

With the first two events we had one pair of heavy black holes (GW150914), and one pair of lighter black holes (GW151226). There is a great mystery hiding there: where do the heavy black holes come from, and how many are there in the Cosmos? Perhaps they are just a fluke, a random creation of Nature that is possibly unique in the Cosmos. But the detection of GW170104 suggests that this is not the case; we’ve once again detected heavy black holes. The race is on to decide how the Cosmos makes them. The answers to those questions are encoded in the properties of the black holes themselves. How many are there? Are they spinning or not? Are they spinning the same direction as one another? How do their masses compare to one another? GW170104 is another piece of the puzzle, and future detections will help solidify what we know.

How can you help? If you’d like to help the LIGO project out, let me direct your attention to one of our Citizen Science projects: GravitySpy. Your brain is capable of doing remarkable things that are difficult to teach a computer. One of those things is recognizing patterns in images. The LIGO detectors are among the most sensitive scientific instruments ever built; they are making measurements at the limit of our capabilities, and there are all kinds of random signals that show up in one detector or the other — we call them glitches.  It is very hard to teach a computer to tell the difference between glitches and interesting astrophysical events, so we have citizens just like you look at glitches and identify them, then we use that information to train the computer. So far citizens like you have helped LIGO classify more than two million glitches, and they put more on the pile every day.

If you’d like to help out too, head over to http://gravityspy.org/ and try it out; you can do it in your web-browser, or on your phone while you’re sitting on the train to work. We have citizens from kids to retirees helping us out. If gravitational waves aren’t your thing, there are more than 50 other projects in science, arts, history and more at http://zooniverse.org/ you can try out!

A representation of the GW170104 signal, from the scientific paper. These are the kinds of images citizens can classify easily, whereas computers sometimes have trouble. [Image: LIGO Collaboration]

PS: For all of you super-nerds out there, let me point something out if you haven’t already noticed. Suppose you were to parse the name of the signal in the following way: 1701 04. Look familiar? The 4th incarnation of 1701; for the cognoscenti, this event shares the designation of the Enterprise-D. 🙂  Until next time, my friends. Live long, and prosper.

(*) When Newton was born, England had not yet switched to the new Gregorian Calendar, which we use today. They were still using the older Julian Calendar, by which Newton was born on December 25; when converted Newton’s birthday falls on January 4 on the Gregorian Calendar.

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

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Many of my colleagues in the LIGO Virgo Collaboration have also written excellent blog posts about the GW170104 event, and the work we do to make gravitational wave astronomy a reality. You should visit their blogs!

Vampires, Mummies, and Ghost Fears

by Shane L. Larson

By the time I went to college, I had mastered my fear of vampires enough to not have to sleep with my neck covered. Kept my kid sheets, mastered my kid fears.

When I was a kid, I was completely terrified of the dark. I would sleep at night with the blankets bunched up around my neck (to protect me from vampires) and with a bright light on all night long so if I happened to wake up, I’d see anything sneaking up on me.

Don’t get me wrong — I’m still terrified of the dark. I don’t do stupid things like walk into dark rooms without turning the light on, or watch horror movies (in case you’re wondering — 25 years is too short of a gap between viewings of The Exorcist). But as I got older, my fears evolved.

I grew up during the Cold War, and I was terrified of a nuclear holocaust — my nightmares of vampires were replaced by mushroom clouds and warheads unexpectedly raining down on Saturday morning breakfast. There was a lot of general malaise about this, but a particularly strong memory I associate with my burgeoning fear was seeing a 1985 Twilight Zone episode called “A Little Peace and Quiet“. The closing shot of that episode planted enough disturbing imagery in my head to fuel dark dreams for years to come.

The final terrifying scene in the Twilight Zone episode, “A Little Peace and Quiet.” The image of a warhead hanging over a town terrified me.

Today, I still worry about nuclear conflict (moreso lately, given the instability in the United States’ executive leadership). But other nightmares, possibly far more likely, have found purchase in the soil of my psyche. I worry about the resurgence of diseases like measles and whooping cough, the result of peoples’ resistance to vaccinations. I worry a lot about the steady and constant damage we are inflicting on Earth and its biosphere. I worry about the collapse of bee colonies and the massive bleachings of coral reefs. I worry that we see unprecedented changes in climatic patterns, atmospheric chemistry, and arctic ice that herald an uncertain terrifying future not just for humans, but for every lifeform on the planet.

There are lots of problems facing the world. (L) Rampant impact of human civilization on the environment. [Wikimedia Commons] (C) Coral bleaching, one indicator of planetary wide changes due to climate change [NOAA] (R) Viruses once held in check by herd immunity gaining footholds once again amid people disavowing vaccinations [Wikimedia Commons].

But none of this produces the same inconsolable dread in me as vampires. One of my friends was befuddled by this fact. She insisted that climate change and resurgent killer diseases were real threats that should terrify us, whereas vampires and ghosts are figments of our imagination. How could it be that I’m terrified by a figment of our imagination?

A peek inside my (irrational) nightmares.

She’s right — vampires and ghosts are a figment of our imagination, but as such there are no fixed rules about how to deal with them. There are as many ways of conquering and facing the supernatural as there are fiction authors.

But virulent diseases, arms control, and climate change? There are well established ways of finding out what’s at the heart of those threats and figuring out how to combat them. You and I call that science.

Where does my faith in science come from? A long and storied history, written by you and me and 40,000 generations of people before us. Humans, more than any other lifeform we are aware of, look at the world with a critical eye and ask “what do we see happening? what does it mean? what can we learn from this?” The result of that process, pursued relentlessly in the face of superstition and the over-active darkness of our imaginations, are all the wonders of the modern world we see around us — wi-fi and pacemakers and insulated coffee mugs and teflon pans land ballpoint pens and flying drones and digital cameras.

Technology is one of the most obvious manifestations of science in our everyday lives. Simple examples include insulated coffee mugs that exploit a deep understanding of thermodynamics (L), modern pens that utilize fluid dynamics and mechanical interfaces (C), and teflon coated non-stick pans are the product of chemistry and materials science (R).

But the process of science has also resulted in knowledge and discoveries that are as poetic and stunning as the finest piece of porcelain, the most beautiful rhythm of poetry, the most exquisite painting or the most stirring symphony. Consider the lives you and I lead — we live in a world where baseballs and rosebushes abound, we walk around at the pace our feet carry us, and the most extraordinary event most of us ever experience is a thunderstorm or a kiss on a first date.

Some of the everyday extreme events experienced by ordinary humans.

But that same world is a world where people like you and me have left footprints on the Moon. We’ve sent robots to sift the sands of Mars and photograph the far side of a remote icy world called Pluto. We’ve discovered that stars burn at millions of degrees in their hearts and when they die they explode, creating every atom in every cell of you and me. We’ve taken those atoms and broken them apart to discover they are made of smaller particles called protons, neutrons and electrons. We’ve even broken protons and neutrons apart to find they are made of even smaller particles, called quarks.

Well before science turns into ways to improve your golf game or make your life in the kitchen easier, it is simply pushing the limits of what we think is possible. [L] Buzz Aldrin’s bootprint on the Moon; the Moon is the farthest any human has ever been from Earth [NASA]. (C) The New Horizons spacecraft, after a 10 year journey, sent home the most exquisite images of Pluto ever taken. Pluto is the most distant object ever visited by spacecraft from Earth. [NASA] (R) We have the technology to manipulate and image individual atoms, a million times too small to be seen with your naked eye. [NIST]

We’ve got no business knowing any of that, because it has nothing to do with foraging for food, or making babies. It has nothing to do with sheltering from hail storms, or staying warm. It has very little to do with making clothes or making farm implements from rocks and sticks.

So why do we know about the Moon and Mars and Pluto? Why do we care about atomic nuclei and quarks? Because we let our imaginations get the better of us. Unfettered, we let ourselves ask any question we want to ask, and we set out to find the answers. Every time a curious question presented itself, we rolled up our sleeves and we figured out the answer. But discovery and understanding are only the beginning. Once we have the knowledge in hand, then our innovators and engineers can figure out how to bring it into our homes and lives.

That’s how science works.

In the end, science is the most powerful tool we have to solve problems, and we can use it to solve any problem in front of us. We should be convinced of that by the fact that we can visit planets that no human has ever been to, and that we manipulate and image the very atomic building blocks that make up the world even though we cannot see them. We have the ability to use these tools for our own good. We have the choice to use these tools to overcome those dark corners of our imaginations and create a future our children will look back on and remember for all the good that we did to save ourselves from ourselves.

The Saturn Moment

by Shane L. Larson

I just returned from the 33rd annual Winter Star Party, hosted by Miami’s venerable Southern Cross Astronomical Society. Every February, for a week during the new moon, 400 amateur astronomers and their families descend on Camp Wesumkee in the Florida Keys.  During the idyllic days, we sit in lawn chairs, enjoy the gentle sea breezes, watch sandpipers running along the tideline, or beachcomb on the key front looking for pretty shells or little fishies trapped in tidepools.

Sunset over Scout Key, Florida, the site of the Winter Star Party. [Image: S. Larson]

But the real reason we are there becomes apparent as the Sun sinks over the western sea, and the black velvet of night emerges, studded by brilliant diamonds of light. The vast majority of us live our lives under the glaring lights of modern cities, and all too often we forget that the Cosmos is there, hiding behind our artificial fluorescent glow, waiting for us to remember. At the first sunset of the Winter Star Party, it all comes roaring back and you remember what you’ve been missing.

The Milky Way rises over Scout Key around 3am in February. You can watch a timelapse movie of the whole night, including the rising of the Milky Way, on YouTube. [Image: S. Larson]

People often ask me, “are you religious?” My answer is that I am not in the sense of modern churches and institutions, but I do know that we are part of something larger — a Cosmos infinitely vast and wonderful and intricate beyond anything we can imagine or will ever know. The cathedral of night is my church.

In his poem “When I Heard the Learn’d Astronomer,” Walt Whitman espoused the idea that you don’t need sages to know a deep connection to the sky, only the solitude of the night.

When I Heard the Learn’d Astronomer 
by Walt Whitman 

When I heard the learn’d astronomer, 
When the proofs, the figures, were ranged in columns
     before me, 
When I was shown the charts and diagrams, to add,
     divide, and measure them, 
When I sitting heard the astronomer where he lectured
     with much applause in the lecture-room, 
How soon unaccountable I became tired and sick, 
Till rising and gliding out I wander’d off by myself, 
In the mystical moist night-air, and from time to time, 
Look’d up in perfect silence at the stars. 

(http://www.poetryfoundation.org/poem/174747)

But in today’s fast paced world, driven by small screens, instant communication, and more information than has ever been gathered by a civilization before, it is hard to slow down enough to realize those moments of solitude. Living beneath the glare of our cities, there are generations of people who have never truly seen a starry sky and thus never built a deep personal connection to the night.

My telescope (named EQUINOX), on the observing field at Scout Key. [Image: S. Larson]

While the Winter Star Party is dominated by amateur astronomers who, like me, do this as often as we can, there are also a lot of people who are experiencing the dark night sky and the Milky Way for the first time. They walk among the telescopes at night, peering at a nebula here or a star cluster there, all the while being regaled with tales and facts of all that we have learned from 400 years of telescopic study of the sky.

This year, at around 4 in the morning, the Milky Way climbed up above the horizon, it’s center studded by a pale yellow “star.”  A young couple, at their very first star party, had stopped by my telescope for some quiet conversation and some views of the sky.

“Do you want to see something cool?” I swung my telescope over to the pale yellow “star” and let them peer through the eyepiece. The view elicited startled gasps, and loud exclamations of joy.

View of Saturn through the telescope, taken with an iPhone [Image by Andrew Symes; visit his blog here]

There is no way that is real!”  The pale yellow “star” was in fact not a star at all — it was the planet Saturn, a cream colored orb bejeweled by its famous ring, the ring itself narrowly divided by a thin black gap known as the “Cassini Division.”

Delivering a personal experience with the night sky is part of the promise of amateur astronomy. We show people the Moon, stars, clusters, perhaps an occasional galaxy. But nothing moves people like their first view of Saturn through a telescope. Most people who take the time to look walk away remembering that moment for the rest of their lives.

We call this “the Saturn Moment.”

More than any other far away object in the sky, Saturn looks like what people expect. They often respond to their view with incredulity, joking that it looks almost painted, or like a picture that has been taped over the end of the telescope.

The Moon often engenders similar responses, but people expect the Moon to look that way. They can see it with their eyes, and imagine craters and mountains, so they aren’t necessarily surprised by the telescopic view.

By contrast, most people have never seen Saturn, except through the eyes of space probes. The telescope somehow takes the NASA pictures we see on our computer screens, and makes it real and visceral.

At the Adler Planetarium in Chicago, you can see a “20 foot Refractor” similar to the kind used in Huygens time (left). We have it set up so you can look through it, and see the same kind of fuzzy image of Saturn he may have seen (right). [Images: S. Larson]

The first person to have a Saturn Moment was Galileo, who turned his telescope on the skies in 1609. His views of Saturn were not the greatest, as his sketches published a year later in Sidereus Nuncius show. It was clear Saturn wasn’t normal because he could make out blobs on either side. He wrote in a letter to his student Benedetto Castelli that Saturn had “ears.” It wasn’t until 1655 that Dutch astronomer Chrstiaan Huygens, using a much better telescope (though still fuzzy) was able to discern that Saturn was surrounded by a thin, flat ring.

A 57 mm diameter lens, all that remains of the telescope Huygens used to observe Saturn. Around the edge is carved a verse from the Roman poet Ovid: “Admovere Oculis Distantia Sidera Nostris” (They brought the distant stars closer to our eyes). It is an anagram, establishing the details of Huygens’ discovery of Saturn’s moon, Titan. When translated, it reads “A moon revolves around Saturn in 16 days and 4 hours.”[Image: Utrecht Univ. Museum, from APOD]

Today, ordinary people like you and me can own telescopes that would have made Galileo and Huygens swoon with envy. Technology is better, and available to everyone.

My Saturn Moment happened long ago, at a sidewalk astronomy event. An amateur astronomer invited me over to look through her “telescope” — it wasn’t an ordinary telescope, it was a spotting scope for birding that she had pointed at the sky. But what I saw blew my socks off. I was seeing Saturn, with my own eyes, and I could see the rings! Though I don’t remember it, I’m sure the rusty dot of Titan, Saturn’s largest moon, was also lurking nearby.

The ultimate result of that encounter is that today my wife and I are both amateur astronomers ourselves, and we guide people through their own Saturn Moments every year. Each moment is unique, exhilarating, and moving in their own way. Among the most memorable was several years ago, my wife had guided a young boy to our telescope to have a peek at Saturn. The view elicited a loud gasp, and the exclamation, “It looks just like a Chevy symbol!” Yep, it kind of does!

If you’ve never seen Saturn before, go to your local planetarium or astronomy club. They would love to show you Saturn for the first time. And when you’re done, tell everyone what you’ve seen, and encourage them to have their own, first #SaturnMoment, a moment of perfect beauty between us and the Cosmos.

Looking Back 108 Years…

by Shane L. Larson

Today would have been Carl Sagan’s 82th birthday. It is an auspicious year, because after a 108 year drought, the Chicago Cubs have won a World Series title. The Cubs win reminded me of Sagan because his son, Nick, had told a story once of introducing his dad to computer baseball based on statistics, whereby you could pit famous teams in history against one another. Sagan apparently said to Nick, “Never show me this again; I like it too much.”

Today, Carl Sagan would have been 82 years old.

Today, Carl Sagan would have been 82 years old.

It is an instantly recognizable feeling to those of us who do science — a nearly uncontrollable urge to ask, “What if…” and then construct an experiment to answer that question. When faced with the prospect of being able to pit two great teams from baseball history against each other, the little science muse in the back of your mind begins to ask, who would win? What if I changed up the pitchers? Does the batting order matter? What if they played at home instead of away?

This incessant wondering is the genesis of all the knowledge that our species has accumulated and labeled “science.”  And so, to commemorate Sagan’s birthday, and the Cubs win this season, I’d like to look back at what we knew of the world the last time the Cubs won the World Series, 108 years ago, a time well within the possible span of a human life.  The year is 1908…

The title page of Einstein's PhD Thesis.

The title page of Einstein’s PhD Thesis.

In 1908, a young physicist named Albert Einstein, 3 years out from his college degree and after a multi-year stint working as a clerk in the Swiss Patent Office, got his first job as a professor, at the University of Bern. This era was a time in the history of physics where scientists were trying to understand the fundamental structure of matter. Einstein’s PhD thesis was titled, “A New Determination of Molecular Dimensions.” Despite the fact that he could not find a job as a faculty member in the years after he graduated, Einstein worked dutifully at the Patent Office, and did physics “in his spare time.” During 1905, he wrote a handful of transformative papers that would change physics forever. Like his PhD work, some of those were about the invisible structure of matter on the tiniest scales. One explained an interaction between light and matter known as the “photoelectric effect,” which would be the work for which he would win the Nobel Prize in 1921. Physicists had for sometime known that some materials, when you shone a light on them, generated electric current. Einstein was the first person to be able to explain the effect by treating light as if it were little baseballs (Go, Cubs! Go!) that were colliding with electrons and knocking them off of the material. Today we use that technology for devices like infrared remote controls to turn your TV on and off!  By the time Einstein became a professor, he was thinking about new and different things that had caught his attention, sorting out some new ideas about gravity that would, after an additional seven years of work become known as General Relativity.

(Top) Marie Curie in her laboratory. (Bottom) Curie's business card from the Sorbonne. [Image: Musee Curie]

(Top) Marie Curie in her laboratory. (Bottom) Curie’s business card from the Sorbonne. [Image: Musee Curie]

Other physicists were hard at work exploring other aspects of the properties of matter. In 1908, already having earned her first Nobel Prize (in 1903), Marie Curie became the first female professor ever at the Sorbonne in Paris. Her 1903 Nobel Prize in physics was for her work in the characterization of radioactive materials. She and her collaborators were not only trying to understand the nature of radiation and the properties of radioactive materials, but were discovering many of them for the first time. Today, we look at a periodic table of the elements and there are no gaps, but in 1908 there were. Curie and her colleagues discovered radium and polonium. They also discovered that some previously known elements, like thorium, were radioactive and we hadn’t known it. Before this pioneering work, the world knew nothing of radioactivity. At this time, the dangers of radiation were unknown. Curie for years exposed herself to radiation from samples in her laboratory; today, many of her notebooks are still too radioactive to be handled safely without protective equipment. In 1934, Curie died of aplastic anemia, a blood disease brought on by radiation exposure whereby your body cannot make mature blood cells.

We think a great deal of Curie’s exposure to radiation came not just from carrying radioactive samples around in her pockets (something that today we know is a bad idea), but also exposure from a new technology that she was a proponent of: medical x-rays. During World War I she developed, built, and fielded mobile x-ray units to be used by medical professionals in field hospitals. These units became known as petites Curies (“Little Curies”).

Orville Wright (R) and Lt. Thomas Selfridge (L) in the Wright Flyer, just before take off at Fort Myer. [Image: Wright Brothers Aeroplane Co]

Orville Wright (R) and Lt. Thomas Selfridge (L) in the Wright Flyer, just before take off at Fort Myer. [Image: Wright Brothers Aeroplane Co]

There were other technological advances being introduced to the world in 1908.  That year, the world was still becoming acquainted with the notion of flying machines. The Wright Brothers had successfully demonstrated a powered flying machine at Kitty Hawk in 1903, but in May of 1908, for the first time ever, a passenger was carried aloft when Charlie Furnas flew with Wilbur Wright over the Kill Devil Hills in North Carolina. Just as with Curie, the Wrights were in unexplored territory, learning about the art and science of flying for the first time. Dangers and unexpected events abounded — the Wright Flyer experienced a crash late in 1908 after a propellor broke during a demonstration for the military at Fort Myer. Orville Wright was seriously injured, but his passenger, Lieutenant Thomas Selfridge, sustained a serious skull injury and died 3 hours after the crash: the first person to perish in the crash of a self-powered aircraft.

(L) The 60-inch Telescope at Mount Wilson. (R) A young Harlow Shapley. [Images: Mt. Wilson Observatory]

(L) The 60-inch Telescope at Mount Wilson. (R) A young Harlow Shapley. [Images: Mt. Wilson Observatory]

On the opposite coast of the United States, also in 1908, the largest telescope in the world was completed on Mount Wilson, outside of Los Angeles: the 60-inch Reflector, built by George Ellery Hale. The 60-inch was built in an era when astronomers had discovered that building bigger and bigger telescopes enabled them to see deeper into the Cosmos in an effort to understand the size and shape of the Universe and our place within it. One of the biggest discoveries made with the 60-inch was still ten years away — astronomer Harlow Shapley would use the great machine to measure the distances to globular clusters near the Milky Way and discover that the Sun did not lie at the center of the galaxy(see Shapley’s paper here); today we know the Sun orbits the Milky Way some 25,000 light yeas away from the center.

The nature of the Milky Way was still, at that time, a matter of intense debate among astronomers. Some thought the Milky Way was the entire Universe. Others argued that some of the fuzzy nebulae that could be seen with telescopes were in fact “island universes” — distant galaxies not unlike the Milky Way itself.  The problem was there was no good way to measure distances. But 1908 saw a breakthrough that would give astronomers the ability to measure vast distances across the Cosmos when astronomer Henrietta Swan Leavitt published her observation that there was a pattern in how some stars changed their brightness. These were the first Cepheid variables, and by 1912 Leavitt had shown how to measure the distance to them by simply observing how bright they appeared in a telescope. A decade and a half later, in 1924, Edwin Hubble would use Leavitt’s discovery to measure the distance to the Andromeda Nebula (M31), clearly demonstrating that the Universe was far larger than astronomers had ever imagined and that the Milky Way was not, in fact, the only galaxy in the Cosmos. By the end of the 1920’s, Hubble and Milton Humason would use Leavitt’s discovery to demonstrate the expansion of the Universe, the first hint of what is today known as Big Bang Cosmology.

(L) Leavitt at her desk in the Harvard College Observatory. (R) The Magellanic Clouds, which Leavitt's initial work was based on, framed between telescopes at the Parnal Observatory in Chile. [Images: Wikimedia Commons]

(L) Leavitt at her desk in the Harvard College Observatory. (R) The Magellanic Clouds, which Leavitt’s initial work was based on, framed between telescopes at the Parnal Observatory in Chile. [Images: Wikimedia Commons]

Today, it is 108 years later. When I reflect on these items of historical note, I am struck by two things. First, it is almost stupefying how quickly our understanding of the workings of the world has evolved. It really wasn’t that long ago — barely more than the common span of a human life — that we didn’t know how to fly and we didn’t know that the Cosmos was ginormous beyond imagining. The pace of discovery continues to this day, dizzying and almost impossible to keep up with. The second thing that is amazing to me is how quickly we disperse and integrate new discoveries into the collective memory of our society. Flying is no longer a novelty; it is almost as common and going out and getting in a car. Large reflecting telescopes capable of making scientific measurements are in the hands of ordinary citizens like you and me, gathering starlight every night in backyards around the world. Most people know that the Milky Way is not the only galaxy in the Cosmos, and that radioactive materials should not be carried around in your pocket.

It is a testament to our ability to collect and disperse knowledge to all the far flung corners of our planet and civilization. In a world faced by daunting challenges, in a society in a tumultuous struggle to rise above its own darker tendencies, it is a great encouragement to me that the fruits of our knowledge and intellect are so readily shared and accessible. When the challenges facing the world seem to me too daunting to overcome, I often retreat to listen to Carl’s sonorous and poetic view of our history and destiny (perhaps most remarkably captured in his musings on the Pale Blue Dot). He was well aware of the problems we faced, but always seems to me to promote a never ending optimism that we have the power to save ourselves– through the gentle and courageous application of intellect tempered with compassion.  It seems today to be a good message.

Happy Birthday, Carl.

And Go Cubs, Go.

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