Astronomers Observe a New Kind of Massive Cosmic Collision for the First Time

NSF/LIGO/Sonoma State University/A. Simonnet
NSF/LIGO/Sonoma State University/A. Simonnet

For the first time, astronomers have detected the colossal blast produced by the merger of two neutron stars—and they've recorded it both via the gravitational waves the event produced, as well as the flash of light it emitted.

Physicists believe that the pair of neutron stars—ultra-dense stars formed when a massive star collapses, following a supernova explosion—had been locked in a death spiral just before their final collision and merger. As they spiraled inward, a burst of gravitational waves was released; when they finally smashed together, high-energy electromagnetic radiation known as gamma rays were emitted. In the days that followed, electromagnetic radiation at many other wavelengths—X-rays, ultraviolet, optical, infrared, and radio waves—were released. (Imagine all the instruments in an orchestra, from the lowest bassoons to the highest piccolos, playing a short, loud note all at once.)

This is the first time such a collision has been observed, as well as the first time that both kinds of observations—gravitational waves and electromagnetic radiation—have been recorded from the same event, a feat that required co-operation among some 70 different observatories around the world, including ground-based observatories, orbiting telescopes, the U.S. LIGO (Laser Interferometer Gravitational-Wave Observatory), and European Virgo gravitational wave detectors.

"For me, it feels like the dawning of a next era in astrophysics," Julie McEnery, project scientist for NASA's Fermi Gamma-ray Space Telescope, one of the first instruments to record the burst of energy from the cosmic collision, tells Mental Floss. "With this observation, we've connected these new gravitational wave observations to the rest of the observations that we've been doing in astrophysics for a very long time."

A BREAKTHROUGH ON SEVERAL FRONTS

The observations represent a breakthrough on several fronts. Until now, the only events detected via gravitational waves have been mergers of black holes; with these new results, it seems likely that gravitational wave technology—which is still in its infancy—will open many new phenomena to scientific scrutiny. At the same time, very little was known about the physics of neutron stars—especially their violent, final moments—until now. The observations are also shedding new light on the origin of gamma-ray bursts (GRBs)—extremely energetic explosions seen in distant galaxies. As well, the research may offer clues as to how the heavier elements, such as gold, platinum, and uranium, formed.

Astronomers around the world are thrilled by the latest findings, as today's flurry of excitement attests. The LIGO-Virgo results are being published today in the journal Physical Review Letters; further articles are due to be published in other journals, including Nature and Science, in the weeks ahead. Scientists also described the findings today at press briefings hosted by the National Science Foundation (the agency that funds LIGO) in Washington, and at the headquarters of the European Southern Observatory in Garching, Germany.

(Rumors of the breakthrough had been swirling for weeks; in August, astronomer J. Craig Wheeler of the University of Texas at Austin tweeted, "New LIGO. Source with optical counterpart. Blow your sox off!" He and another scientist who tweeted have since apologized for doing so prematurely, but this morning, minutes after the news officially broke, Wheeler tweeted, "Socks off!") 

The neutron star merger happened in a galaxy known as NGC 4993, located some 130 million light years from our own Milky Way, in the direction of the southern constellation Hydra.

Gravitational wave astronomy is barely a year and a half old. The first detection of gravitational waves—physicists describe them as ripples in space-time—came in fall 2015, when the signal from a pair of merging black holes was recorded by the LIGO detectors. The discovery was announced in February 2016 to great fanfare, and was honored with this year's Nobel Prize in Physics. Virgo, a European gravitational wave detector, went online in 2007 and was upgraded last year; together, they allow astronomers to accurately pin down the location of gravitational wave sources for the first time. The addition of Virgo also allows for a greater sensitivity than LIGO could achieve on its own.

LIGO previously recorded four different instances of colliding black holes—objects with masses between seven times the mass of the Sun and a bit less than 40 times the mass of the Sun. This new signal was weaker than that produced by the black holes, but also lasted longer, persisting for about 100 seconds; the data suggested the objects were too small to be black holes, but instead were neutron stars, with masses of about 1.1 and 1.6 times the Sun's mass. (In spite of their heft, neutron stars are tiny, with diameters of only a dozen or so miles.) Another key difference is that while black hole collisions can be detected only via gravitational waves—black holes are black, after all—neutron star collisions can actually be seen.

"EXACTLY WHAT WE'D HOPE TO SEE"

When the gravitational wave signal was recorded, on the morning of August 17, observatories around the world were notified and began scanning the sky in search of an optical counterpart. Even before the LIGO bulletin went out, however, the orbiting Fermi telescope, which can receive high-energy gamma rays from all directions in the sky at once, had caught something, receiving a signal less than two seconds after the gravitational wave signal tripped the LIGO detectors. This was presumed to be a gamma-ray burst, an explosion of gamma rays seen in deep space. Astronomers had recorded such bursts sporadically since the 1960s; however, their physical cause was never certain. Merging neutron stars had been a suggested culprit for at least some of these explosions.

"This is exactly what we'd hoped to see," says McEnery. "A gamma ray burst requires a colossal release of energy, and one of the hypotheses for what powers at least some of them—the ones that have durations of less than two seconds—was the merger of two neutron stars … We had hoped that we would see a gamma ray burst and a gravitational wave signal together, so it's fantastic to finally actually do this."

With preliminary data from LIGO and Virgo, combined with the Fermi data, scientists could tell with reasonable precision what direction in the sky the signal had come from—and dozens of telescopes at observatories around the world, including the U.S. Gemini telescopes, the European Very Large Telescope, and the Hubble Space Telescope, were quickly re-aimed toward Hydra, in the direction of reported signal.

The telescopes at the Las Campanas Observatory in Chile were well-placed for getting a first look—because the bulletin arrived in the morning, however, they had to wait until the sun dropped below the horizon.

"We had about eight to 10 hours, until sunset in Chile, to prepare for this," Maria Drout, an astronomer at the Carnegie Observatories in in Pasadena, California, which runs the Las Campanas telescopes, tells Mental Floss. She was connected by Skype to the astronomers in the control rooms of three different telescopes at Las Campanas, as they prepared to train their telescopes at the target region. "Usually you prepare a month in advance for an observing run on these telescopes, but this was all happening in a few hours," Drout says. She and her colleagues prepared a target list of about 100 galaxies, but less than one-tenth of the way through the list, by luck, they found it: a tiny blip of light in NGC 4993 that wasn't visible on archival images of the same galaxy. (It was the 1-meter Swope telescope that snagged the first images.)

A NEW ERA OF ASTROPHYSICS

When a new star-like object in a distant galaxy is spotted, a typical first guess is that it's a supernova (an exploding star). But this new object was changing very rapidly, growing 100 times dimmer over just a few days while also quickly becoming redder—which supernovae don't do, explains Drout, who is cross-appointed at the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto. "We ended up following it for three weeks or so, and by the end, it was very clear that this [neutron star merger] was what we were looking at," she says.

The researchers say they can't be sure if the resulting object was another, larger neutron star, or whether it would have been so massive that it would have collapsed into a black hole.

As exciting as the original detection of gravitational waves last year was, Drout is looking forward to a new era in which both gravitational waves and traditional telescopes can be used to study the same objects. "We can learn a lot more about these types of extreme systems that exist in the universe, by coupling the two together," she says.

The detection shows that "gravitational wave science is moving from being a physics experiment to being a tool for astronomers," Marcia Rieke, an astronomer at the University of Arizona who is not involved in the current research, tells Mental Floss. "So I think it's a pretty big deal."

Physicists are also learning something new about the origin of the heaviest elements in the periodic table. For many years, these were thought to arise from supernova explosions, but spectroscopic data from the newly observed neutron star merger (in which light is broken up into its component colors) suggests that such explosion produce enormous quantities of heavy elements—including enough gold to put Fort Knox to shame. (The blast is believed to have created some 200 Earth-masses of gold, the scientists say.) "It's telling us that most of the gold that we know about is produced in these mergers, and not in supernovae," McEnery says.

Editor's note: This post has been updated.

Did NASA Ever Consider Women for the Mercury, Gemini, or Apollo Programs?

Russell L. Schweickart, Keystone/Getty Images
Russell L. Schweickart, Keystone/Getty Images

C Stuart Hardwick:

Unambiguously, no.

This was not sexism. NASA decided early on, and quite correctly, that early astronauts must all be experienced high-performance jet test pilots. To anyone who understands what the early space program involved, there can be little question that choosing all men was the right call. That's because there were zero women in the country with high-performance test flight experience—which was due to sexism.

You may have heard of the so-called “Mercury 13” or the Women in Space Program, both of which are misleading monikers invented by the press and/or American aviator Jerrie Cobb.

Here’s what happened:

Randy Lovelace’s laboratory tested astronaut candidates to help NASA select the initial seven Mercury astronauts. He later ran Jerrie Cobb through the same Phase I (biomedical) tests (though not through the other tests, as he didn’t have access to equipment owned by the military). Contrary to some reports, Cobb did not test superior to the men overall, but she did test as well overall. And while that should not have been a surprise to anyone, it was in fact a surprise to many.

Lovelace published a paper on the work in which he suggested that women might actually be preferable candidates for space travel since they weigh less on average and consume less oxygen, water, and other consumables, a fact which I exploited in my book, For All Mankind, and I can tell you that on a long duration mission (of several months) the difference really does add up.

This had no effect on Mercury, Gemini, or Apollo, all of which were short little jaunts in which the mass of the astronauts wasn’t terribly critical, and all of which were always going to be flown by high-performance test pilots anyway.

However, it attracted the attention of famed aviation pioneer Jackie Cochran, who agreed to fund further research on the suitability of women for space.

Pioneer American aviator Jacqueline "Jackie" Cochran in the cockpit of a Curtiss P-40 Warhawk fighter plane
Jackie Cochran in the cockpit of a Curtiss P-40 Warhawk fighter plane
Public Domain, Wikimedia Commons

Cochran and Cobb recruited several more women, mostly from the ranks of the Ninety-Nines, a women aviator’s professional organization founded by Amelia Earhart. These women also went through the initial biomedical testing, and 13 passed at the same standard as met by the Mercury astronauts.

So far so good. Cobb, Rhea Hurrle, and Wally Funk went to Oklahoma City for an isolation tank test and psychological evaluations, and Lovelace secured verbal agreement through his contacts to send another group to the Naval School of Aviation Medicine for advanced aeromedical examinations using military equipment and jet aircraft.

However, no one had authorized the use of the military facilities for this purpose—or the costs that it would entail. Since there was no NASA request behind this effort, once Lovelace tried to move forward, the military refused his access.

Meanwhile, Cobb had been enjoying the attention she was receiving and, according to some, had gotten it into her head that all of this was going to lead to some of the women actually flying in space. In fact, I’ve found no evidence that Lovelace ever implied that. This was a small program of scientific study, nothing more. Nevertheless, Cobb flew to Washington, D.C. along with Jane Hart and was given a meeting with then-vice president Lyndon Johnson.

Johnson was congenial—Cobb has always claimed he pledged his support—but immediately afterward, he sent word to have all support for the experiments withdrawn.

Far be it from me to defend the motives of LBJ, but consider this: The president had publicly committed the nation to returning a crew from the moon by the end of the decade—and this was at right about the same time when enough work had been done for Johnson to have a handle on just how hard that was going to be. He may or may not have supported the idea of women astronauts in general—we have no idea—but Jerrie Cobb standing before the press, pushing for “women in space” was definitely, irrefutably a distraction he didn’t need. And any resources devoted to it were being pulled directly away from the moon shot—which, to Johnson, was the goal.

Jerrie Cobb poses next to a Mercury spaceship capsule
Jerrie Cobb poses next to a Mercury spaceship capsule
NASA, Public Domain, Wikimedia Commons

Cobb has always maintained the women were misled and betrayed. I’ve found no evidence of that. Testimony of many of the other participants suggests that Cobb simply got carried away—not that anyone could blame her. Let’s remember that at that time, she couldn’t have known what was really involved in space flight or what the program would look like over the next decade. No one did.

Of course, American women did start flying in space with the Space Shuttle. Do not for a moment think this means they didn’t face the same prejudices at NASA that they did everywhere else. The first class of women astronauts was, according to my sources, invited to help design an in-flight cosmetics kit—an offer they immediately and forcefully shot down. Thirty years later, women remain a distinct minority in the U.S. astronaut corps ...

The bigger question is not whether Cobb was betrayed, but why, in 1961, not a single U.S. woman had been hired to work in high-performance flight test—considering that so many (like Cobb, for example) had performed test flight and ferry duties during the war.

Why weren’t women welcome in the post-war aerospace economy, and why—even today—are so few women granted degrees in engineering of any sort? I don’t know the answer, though sexism is unquestionably in the mix, but it’s a question we need to address as a nation.

This post originally appeared on Quora. Click here to view.

True or False: Was This Object Left on the Moon?

SECTIONS

arrow
LIVE SMARTER