Dawn of an Era: Astronomers Hear and See Cosmic Collision

By Eric Betz | October 16, 2017 9:00 am
Two neutron stars merge into a kilonova. (Credit: Illustration by Robin Dienel, courtesy of the Carnegie Institution for Science)

Two neutron stars merge into a kilonova. (Credit: Illustration by Robin Dienel, courtesy of the Carnegie Institution for Science)

For hundreds of millions of years, two city-sized stars in a galaxy not-so-far away circled each other in a fatal dance. Their dimensions were diminutive, but each outweighed our sun.

They were neutron stars — the collapsed cores left behind after giant stars explode into supernovas. Closer and closer they spun, shedding gravitational energy, until the stars traveled at nearly the speed of light, completing an orbit 100 times every second.

By then, dinosaurs reigned on Earth, and the first flowers were just blooming. That’s when, 130 million years ago, the dance ended. 

The collision was fast and violent, likely spawning a black hole. A shudder — a gravitational wave — was sent out across the fabric of space-time. And as the stars’ outer layers launched into space, the force formed a vast cloud of subatomic particles that would cool into many Earths’ worth of gold, platinum and uranium.

Seconds later, a blast of high-energy gamma-rays – the most energetic kind of light – punched through the erupting cloud.

The space-time ripple and the light crossed the cosmos together, and finally arrived at 6:41 a.m. Eastern on Aug. 17. The gravitational wave first reached Italy’s freshly finished detector Advanced Virgo before stretching and squeezing the lasers at America’s two LIGO sites.

Two seconds later, NASA’s gamma-ray detecting Fermi spacecraft caught the blast.

In the weeks since, hundreds of astronomers on all seven continents have turned their telescopes and spacecraft to watch the cosmic collision play out in all manner of light – radio, infrared, optical, ultraviolet, X-rays, gamma-rays. The Spitzer and Hubble space telescopes are still watching the event, as is the Very Large Array in New Mexico. Right now, it’s the greatest show in astronomy.

“What was surprising with this one was it was extremely close to us, and so it was an extremely strong signal,” says LIGO scientist Jolien Creighton of the University of Wisconsin-Milwaukee. “We were figuring with our full Advanced LIGO sensitivity we might see something like this every few years.”

Ground-based observatories all over Earth, as well as a handful of orbiting space telescopes, caught the neutron star merger. (Credit: LIGO and Virgo collaboration)

Ground-based observatories all over Earth, some 70 in all, as well as a handful of orbiting space telescopes, caught the neutron star merger. (Credit: LIGO and Virgo collaboration)

In February 2016, LIGO announced they’d detected gravitational waves for the first time, almost exactly a century after Albert Einstein predicted these events as an outcome of his theory of general relativity. Astronomers said that initial detection was like hearing the cosmos for the first time. And they hoped for the next breakthrough — to hear and see the cosmos simultaneously, or so-called “multi-messenger astronomy.”

That’s now happened.

The Multi-Messenger Age

“This is the first real multi-messenger astronomy,” says astronomer Josh Simon of the Carnegie Observatories. “There are things you can discover with gravitational waves that you could never see with electromagnetic light, and vice versa. Having that combination should provide us with insights into these extreme objects.”

And this neutron star mash-up uncorked a jug of scientific firsts. A press briefing Monday morning outlined some of the dozens of research papers appearing in scientific journals — the main discovery one boasts a whopping 3,500 co-authors.

Those discoveries include:

Whew.

Carnegie Observatories' Swope telescope was the first to image the neutron star merger in optical light. It's a small, decades-old telescope at Chile's Las Campanas Observatory. (Courtesy Ryan Foley)

Carnegie Observatories’ Swope telescope was the first to image the neutron star merger in optical light. It’s a small, decades-old telescope at Chile’s Las Campanas Observatory. (Courtesy Ryan Foley)

A Race For Photons

Ryan Foley and his partner were wandering Copenhagen’s historic Tivoli amusement park on what turned out to be an explosive Aug. 17. They’d been in Denmark for a month at a gravitational waves conference but Foley, an astronomer at the University of California, Santa Cruz, had yet to see the sights on his trip. It was a day to relax; a text message would change that.

It was from Foley’s grad student, David Coulter. LIGO had caught a binary neutron star merger – and so had the Fermi spacecraft.

Foley says he was certain his apprentice was just screwing with him on his first day off. After all, the week before, Foley had sounded a pessimistic tone in a room of young researchers as he detailed his plan to use ground-based telescopes to catch any LIGO-detected neutron star mergers.

Foley left the amusement park and raced back to campus on his bike. If this was indeed the real deal, there were only a few hours to prepare before nightfall in Chile, where his Carnegie Observatories team had time on a small, 45-year-old telescope called the Swope. Because the signal came from a region of sky close to the sun, it would only be visible for a little while after twilight. And they’d be racing against observatories around the world.

The potential payoff: a Nobel Prize.

Coulter set to work creating a list of about 100 possible galaxies to target based on LIGO’s estimates. Meanwhile, Foley called up two colleagues – Carnegie Observatory astronomers Josh Simon and Ben Shappee – who were each operating one of the twin 6-meter Magellan telescopes that night.

“When big things happen, you call in every favor you can get,” Foley says. “You’ve only got one shot, you either view it or it’s gone.”

Meanwhile, back in Santa Cruz, team member Charlie Kilpatrick downloaded images of their targets. The three telescopes would quickly image each galaxy and send the data back to California. There, Kilpatrick would compare the new pictures to existing ones looking for signs of a cosmic explosion.

Just 20 minutes after twilight, the Swope telescope struck gold with its ninth image.

“Found something,” Kilpatrick punched into a Slack group message. There was an enormous bright spot in the galaxy NGC 4993.

“Wow!” Foley replied.

Astronomers on the optical light discovery team used Skype and Slack to message across three continents as they imaged the sky. (Courtesy Ryan Foley)

Astronomers on the optical light discovery team used Skype and Slack to message across three continents as they imaged the sky. (Courtesy Ryan Foley)

Lights, Camera, Action

As the target galaxy inched closer to the horizon, Shappee and Simon each turned their titan telescopes to capture its light spectrum – astronomers’ method for capturing an object’s chemical fingerprints.

Telescope operators usually don’t let their instruments point so low for fear of over-rotating and breaking them. Shappee kept observing until the Magellan shut itself down.

“I’ve never seen telescopes point so close to the horizon,” says UW-Milwaukee astronomer David Kaplan.

It’s a good thing, too. Other telescopes also caught the event that night, but Foley’s group caught the only spectra. That data went to Maria Drout, also from Carnegie Observatories, who processed it within half an hour, revealing a spectrum unlike anything astronomers had seen before.

All the Galaxy’s Gold

You and me, my pet dog, the apple that fell on Issac Newton’s head – we’re all made from matter that’s created in supernovas, which happen about once per century in our galaxy. We’re standard star stuff. But supernovas create sparse amounts of heavy elements, like the gold and platinum on your wedding ring, or the uranium world leaders are always fighting over.

So how did all the heavy stuff get here?

“All the other elements on the periodic table we knew where they came from in the universe,” says Columbia University astronomer Brian Metzger. Neutron star mergers were the leading contender.

Metzger predicted these collisions would form a “kilonova,” an event 1,000 times brighter than a standard nova. And other astronomers had showed these kilonovas could produce huge amounts of the heaviest elements. The trouble is, no one had ever seen one. So a fundamental question has gripped astronomers for decades.

“Is it the really common thing that makes a little? Or is it the rare thing that makes a lot?” says Kaplan, a co-author on research appearing Monday in the journal Science.

That answer arrived on Aug. 17.

Colliding-Neutron-Stars-Produce-Gold

An artist’s illustration of two colliding neutron stars. (Credit: NASA/Swift/Dana Berry)

By the time Foley’s team caught the first images of the collision – just 11 hours later – the cloud of material had already expanded as far out as Neptune is from our sun. Those subatomic particles cooled as they pushed outward, and they started combining into heavier and heavier elements.

Astronomers involved in Monday’s announcement say this one neutron star merger created somewhere between 10 and 100 Earth masses’ worth of gold. And based on how often neutron stars collide, scientists can extrapolate to say there should be roughly something like 100 million Earths’ worth of gold in the Milky Way galaxy.

“It’s essentially a way to take a neutron star’s material and turn it into gold,” Metzger says. “And not just gold but platinum and uranium and anything you see at the bottom of the periodic table.”

Considering that this collision happened 130 million years ago in its own galaxy, all those heavy elements have likely already mixed in with interstellar gas clouds that will someday form new solar systems like our own.

And here on Earth, this one event has settled decades of scientific debate. “At least for the heaviest elements, this issue has been put to bed,” Foley says.

Multi-messenger astronomy is just getting started. When LIGO comes back online next year after another round of upgrades, scientists expect to see one of these mergers every month or so. In the years to come, that number could grow to once a week – though astronomers don’t expect many more neutron stars to merge this close to home.

“We’ve created a new field of astronomy,” Foley says. “We’ve been walking around for all of humanity being able to see the universe but not being able to hear it. Now we get both.”

He adds: “It’s even hard to predict where this field will go, but I can tell you now it’s going to be exceptional.”

CATEGORIZED UNDER: Space & Physics, top posts
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  • Dan Lipford

    Cool!

    • Wade Carmen

      Shouldn’t we get a creationist report first before making a decision?

      • Dan Lipford

        Creationist usually argue that God works in mysterious ways, but they also usually reject evolution as one of the mysterious ways in which he/she/it might be working — and every other “mysterious way” that doesn’t seem to agree with their theology. Just as Groucho wouldn’t join any club that would allow rabble like him to become a member, I can’t conceive of believing in any God that I could fully understand.

  • ersliva

    I STILL DONT BELIEVE IT TAKES LIGHT TO TRAVEL THAT FAR THAT LONG…WHEN WE OPEN OUR EYES AT NITE TO SEE THE STARS PAST….I THINK ITS ACTUAL TIME WE ARE SEEING AND NOT SOME PAST TIME SPECIALLY WHEN THERE IS NO DIMMING OR BRIGHTNING JUST TWINKLES OF THINGS MOVING IN IT WAY NOW AND NOT BACK THEN…I THINK EINSTIEN IS WRONG ABOUT HOW LIGHT TRAVELS WHEN IT COMES TO OR EYES….I FEEL WE ARE SEEING THE PRESENT AND NOT THE PAST….WE CAN SEE OBJECTS THAT WOULD TAKE YEARS TO REACH US COMING AT US AT PRESENT TIME SO WHY IS IT DIFFERENT WITH STARS AND SUCH THEN….IT DOESNT MAKE ANY SENSE….

    • Tayvl

      And what makes you think that light doesn’t take time to travel? Its speed has been measured scientifically with precision for the last century by scientists who know what they’re doing. On what do you base your belief?

      • ersliva

        open and close your eyes when you look at the stars…there is no variation in the lite…and when you look at the stars at night dont you sometimes see lites zipping around out in space…..if you dont look straight up around 10 to 10:30 pm on a december nite and you will…lol….and im not alking about satalites that circle our earth…these are farther out in space for the most part….you can watch them travel great distances across the nite sky or go short distances till they are no longer visible…but they zip across the sky and and around defying physics on how they move stop and move again…..and you can see them with just your eyes so that alone defies just how fast lite actually is…

        • Tayvl

          On another note, would you mind telling me what age you are?

    • Hillary (WTF Happened) Clinton

      If you look towards our sun, do you believe you are seeing light emitted instantaneously a moment ago?

      Light from the sun takes approximately 8 minutes to reach earth.

      • ersliva

        then why does it take a solar flare much longer to reach us then….and we can see objects trillions of miles away and tell just how fast they are moving towards us…furthermore the age of everything will once again be put farther back once we get larger and stronger telescopes out into space….the fact is their is no end to space itself and we will find voids until the next stronger and better telescope is built showing more galaxies beyond the so called end of space voids….unless they come up with the idea that we are seeing another big bang…lol…that created that side of space…and odds are thats what they will say to counter voids that have galaxies at the other end of them when its all just actually just one endless space with galaxies scattered about forever…in all directions and that there is no true center…..furthermore to go fast in space all we need to do is create a heater coil like system that turns the temp of space absolute zero to a warmer temp that is pushed out the tail end of a craft…if you look at a space heater and run its fan it feels it gets faster and pushes more once you turn the heater coils on….so if you can have a system that warms absolute zero to 100 degrees you have an increase of 400 being forced out against the coldness of space which then would cause you to go faster then any gas rocket engine could……and it all could be run by magnetics that create electricity….for the craft….and if the craft is going faster then anything else around it and is fully pressurized inside….objects that hit it should simply bounce of it for the most part depending upon it overall size that is to the craft….because there idea of solar sails wouldnt work do to all the objects it would be hitting along the way if its not pressurized and only going the same speed as everything else in space…the sails would be pitted with holes beyond belief before it even left or solar system….lol….and if not it would then be collecting every ice and rock particle and building up like frost on a car window does on cold winter nites and mornings….but the heat coil system should get a craft to go at least 400 times as fast as any object in space its size can move depending on just how hot the coils get or you want them to get then double that by how much exhaust speed you add to it as well….so you should be able to jump that 400 times more to actually 800 times more or greater even….and if an object can travel lets say 22,500 miles per hour times 800 then….you then are moving at 18,000,000 miles per hour…..trips in or solar system are not done in years then anymore….lol…but hours to days….and the hotter the coils and the faster the fans…the greater speed you go and all done by magnets to begin with….the cost is nothing except for parts to have around….in case….and then no real fuel weight considerations and the more of other things that can be carried…..at greater distances….

    • Hillary (WTF Happened) Clinton

      Please publish your thesis and mathematical equations to disprove Einstein. You could become very famous.

    • Hillary (WTF Happened) Clinton

      From your vantage point, everything you see is in the present even though the source of light took billions of years for you to see.

    • Chris

      Again, if troll..Lol
      If not, you have a significant misunderstanding of the speed of light and I recommend you enroll in your nearest physics classes asap.

      • Hillary (WTF Happened) Clinton

        A physics class is way too in depth for that one.

        • Chris

          One can never have too much physics education.

          • Hillary (WTF Happened) Clinton

            When you run a marathon, you don’t start at the FINISH line.

          • Chris

            I do.

            No, but seriously, I would argue that the classes would be the marathon. Just giving him the answer is the finish line. The classes are much more difficult and time consuming.

    • BoundlessExistence

      Are you even able to walk and breathe simultaneously?

    • mholdcraft

      Duh!

  • ersliva

    AND HOW IS IT WE CAN NOW SEE THE LITE SHOW OF THESE TWO STARS WHEN WE JUST FELT THE SHOCK WAVE IF THEY TRAVEL AT TWO DIFFERENT SPEEDS AS WELL….THE LITE WAVE IS TO TRAVEL FASTER NOT THE SHOCK WAVE…THUS THERE IS A PROBLEM IN HOW FAST THINGS TRAVEL…..THE SPEED OF LITE AND SOUND ARE WRONG THEN WHEN IT COMES TO SPACE….ITS ACTUALLY FAR MORE FASTER THEN ACTUALLY CALCULATED BY EINSTIEN….

    • ersliva

      IMO ITS AS FAST AS IF IT WAS ON EARTH THEN WITH SPACE NOT HAVING ANY THINGS TO SLOW IT DOWN AS IT IS ON EARTH…THUS MAKING THINGS ALMOST CONSTANT…SPECIALLY SINCE SOUND WAVES TRAVEL FAR LESS SLOWER IN SPACE THEN LITE DOES…..BECAUSE THERE IS DISTRACTIONS IN THE SOUND WAVE FIELDS….TO CAUSE SOUND WAVES TO GO MUCH SLOWER…..

      • Glaisne

        Your Caps Lock is on.

        • ersliva

          so what

          • daniel letterman

            Sad :(

      • Necromancer

        Turning your caps lock off might help with the stupid also. I hope. You’re a lousy troll.

        • ersliva

          too freaken bad nimrod

          • daniel letterman

            Aaaaand the troll is revealed. Go back to trying to sell infinity machines in the classified section of Popular Science.

      • mholdcraft

        Sound does not travel through the vacuum of space. A gravitational wave is not sound. Sound is vibrations within an atmosphere (like our atmosphere here on earth).

    • Chris

      I hope you’re a troll, but if not… The shockwave was not sound, which doesn’t travel in space, but the gravitational waves themselves. These travel at light speed.

      • MEOIRS

        Mate, genuine question from a non troll.
        We had a sequence of:
        1.Grav Waves
        2.Gamma Radiation (1st form of light?)
        3. X-rays
        4. UV
        5. Optical
        and on and on and on…

        In the emptiness of the space vacuum, shouldn’t all of these travel at the same speed?
        What makes this sequence? The energy of each radiation form?
        Why do gravitational waves travel faster than anything else?

        Just a curious mind (illustrator for 20 years but everytime I hear this I want to break my pencils and go do astronomy) :)

        • Chris

          I believe your answer is twofold:
          1. Gravitational waves travel at the speed of light, unhindered by anything. This is because they are perturbations in space-time itself.
          2. Light waves also propagate at light speed, however, light waves interact with matter as it travels through the universe (the universe is not a true vacuum), thus slowing their true propagation speed. The amount of interaction is inversely related to the frequency of the light, thus higher frequency waves propagate faster. Therefore, we would see the spectrum in order from highest frequency to lowest, as you described.

  • Prof Quill

    I have to chuckle at the subject line in my email about this article: “BREAKING NEWS: Two neutron stars collide”. ….and read that this happened 130 million years ago. Rather old news, I’d say ;-). Or was that the point of a tongue-in-cheek headline?

    • mholdcraft

      Happened 130 million years ago, but the light and gravitational wave just arrived here. Can’t detect it until the wave and light arrive here. Braking News to us, old news to that Galaxy.

      • Prof Quill

        Sure, I quite get that, just poking a little fun at the phrase ‘breaking news’. To be more accurate, the headline could have added ‘detected’. It’s rather like what does ‘now’ mean. When we perceive it or really like, NOW. We can’t quite know until we perfect ‘subspace communication’. Not being real serious, just wondering whether the subject line author was being a wee bit sarcastic.

  • ersliva

    SO HOW CAN WE BE SEEING THE AFTERMATH RIGHT AFTER COLLISSION THEN UNLESS WE ARE ACTUALLY CLOSER THEN EXPECTED TO SAID STARS

    • Tayvl

      The same way they saw the collision. Same distance, same time.

    • Hillary (WTF Happened) Clinton

      When you watch reruns of “I Love Lucy” do you believe you are watching her perform live?

  • Todd Holland

    Thanks to Eric Betz for an eminently well written explanation of these monumental observations. The piece helps me understand the broad significance of this breakthrough.

  • Hillary (WTF Happened) Clinton

    “They’d been in Denmark for a month at a gravitational waves conference…..

    SInce almost nothing is known about gw, how can you spend a month talking about almost nothing?

    • Tayvl

      Who said almost nothing is known about gravitational waves?

      • Hillary (WTF Happened) Clinton

        They have been theorized by Einstein since 1915, but it was only this year that the first wave was detected.

        Wouldn’t you say not much is known if they were only detected months ago?

        • Tayvl

          Then people have been talking about it for over a century. Why ask how anyone could spend a month talking about it.

          • Hillary (WTF Happened) Clinton

            I did not say they were talking about this for over a century.

            Where do you get your misinformation from?

            But if they were talking, here’s how the dialogue probably sounded for 100 years.

            Scientist #1 “What do you know about gravity, gravitons, and gravity waves?”

            Scientist #2 thru # 1000
            “Nuthin'”

            Scientist #1 “Okay, I’ll check back next year”

          • Tayvl

            So they knew about it but nobody talked about it all that time then?

          • Inimical Jim

            They talked about it. It has taken this long for it to reach us. Duh.

          • Tayvl

            No idea what that even means.

      • Hillary (WTF Happened) Clinton

        Name one scientist who claims to understand Quantum Mechanics.

  • Robert Johnson

    You have to be a cosmologist to really understand fully what it means, otherwise, to most it is meaningless or to some,”the so- what- department”.

    • lheid

      Be kind! Trained in the biological sciences and still counting on my fingers when it comes to math I greatly appreciate articles like this. It helps me understand material that would otherwise be out of my reach. It lets me know what is happening in fields very far from my own. I am not a cosmologist but I am not stupid and I come away with feelings of awe and an urge to learn more. I am certain I am not alone.

      • Gerald Wonnacott

        Well said, thank you…

  • http://www.Rataway.com ricksuddes

    Read this… https://www.universetoday.c

    •Edit•Share ›

  • http://www.tjbooks.com/ John T. Jones, Ph.D.

    This is thrilling to this old man. My father was an astronomy nut and he passed his enthusiasm along. Congratulations to all the observers watching this great although common event.

  • Clear#4213

    Awesome. What a glorious, delicious, juicy universe we live in.

  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    Build one (longer!) Australian LIGO to trilaterate sources.
    Land around -31.649468, 126.077045 is not doing much.

    46.455144, -119.407656) LIGO Hanford
    (30.562894, -90.774242) LIGO Livingston
    (-31.649468, 126.077045), LIGO Australia
    H to L, 1880 miles
    H to A, 8885 miles
    L to A, 10,265 miles

    The interested reader can calculate chord distances, the ones that matter.

    • Keith Hebbard

      That location isn’t going to happen, they won’t let anyone build on the nullabor plain! you’re going to have to find a better spot

  • Robert Bamford

    “- the cloud of material had already expanded as far out as Neptune is from our sun. Those subatomic particles cooled as they pushed outward, and they started combining into heavier and heavier elements.”
    How does that work? The particles are moving out from a point source, which means that they are expanding away from each other – and cooling. To make a different element requires protons to combine in the same nucleus. We’ve been trying for years to produce fusion energy but it requires immense pressures and heat, so how do these cooling particles fuse to make heavier elements?

    • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

      The merging neutron stars also far ends fragment, centripetally hurling out many Earth masses of impossibly neutron-rich nuclear lumps absent gravitational stabilization. Said lumps furiously beta-decay, turning neutrons into protons, walking down the Periodic Table into stable or long half-life heavier elements.

      • Robert Bamford

        OK – that makes sense. Thanx for the clarification.

  • Chuck Johnston

    This is very cool.

  • Ali

    How did they indicate that there is collision between two neutron stars. The picture shows the shining of one object. this can happen because of an event like glitch that happens in pulsars or neutron stars.

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