NAn illustration of two neutron stars colliding
- For the first time, astronomers have detected a neutron-star collision.
- Gravitational waves heard by two detectors pinpointed the source to a galaxy 130 million light-years away.
- The collision produced a radioactive "kilonova" that forged hundreds of Earths' worth of platinum, gold, silver, and other atoms.
- The discovery solves a longstanding mystery about the origins of heavy elements.
Platinum and gold are among the most precious substances on Earth, each fetching roughly $1,000 an ounce.
However, their allure may grow stronger - and weirder - thanks to a groundbreaking new finding about their violent, radioactive, and cosmic origins.
On Monday, scientists who won a Nobel Prize for their discovery of gravitational waves, or ripples in the fabric of space, announced the first detection of the collision of two neutron stars.
The team alerted astronomers all over the world to the event right after it happened, helping them point telescopes directly at the scene of the crash and record unprecedented observations of the aftermath in visible light, radio waves, X-rays, and gamma rays.
These images revealed a radioactive soup giving birth to unfathomable amounts of platinum, gold, and silver - not to mention elements like the iodine found in our bodies, the uranium in nuclear weapons, and the bismuth in Pepto-Bismol - while shooting those materials deep into space
The two neutron stars most likely merged to form a black hole, though the tiny bit of neutron star that escaped - and formed new elements - could get recycled into planets like Earth where aliens may eventually dig up the metals as we have.
"The calculations we did suggest most of the matter that came out of this event was in a swirling disk around a black hole. Half of that matter fell in, and half of it got ejected," Brian Metzger, an astrophysicist at Columbia University who's one of roughly 4,000 researchers involved in the discovery, told Business Insider. "The matter that ended up in your wedding band could have just as well fallen in."
Astronomers detected the merger from 130 million light-years away, in the galaxy NGC 4993, on the morning of August 17.
"This is going to have a bigger impact on science and human understanding, in many ways, than the first discovery of gravitational waves," Duncan Brown, an astronomer at Syracuse University who's a member of the research collaboration, told Business Insider. "We're going to be puzzling over the observations we've made with gravitational waves and with light for years to come."
When two city-size atoms collide
Albert Einstein first predicted the existence of gravitational waves a century ago, but he didn't believe they'd ever be detected because of their extraordinarily weak energies.
The Laser Interferometer Gravitational-Wave Observatoryin the US defied Einstein in September 2015 when it "heard" the elusive phenomenon for the first time. Europe's new Virgo gravitational-wave detector has also come online since then and worked with LIGO to make this fifth detection possible.
Unlike the four previous events, the latest one - which emanated from the constellation Hydra and was dubbed GW170817 - wasn't created by colliding black holes. Its signal was weaker and closer to Earth by hundreds of millions of light-years, and it lasted 100 seconds as opposed to one second.
Brown and others think GW170817 is revolutionary in part because it provides clues about how the heaviest elements we find on Earth formed in space.
For example, giant stars that explode as supernovas - blasts that are brighter than billions of suns - are thought to form iron and lighter elements.
"Some of the heavy elements are made in supernova explosions, but it turns out this can't explain the abundances," Brown said of heavier elements. "They didn't appear to be coming from supernova explosions, and so people have wondered for a long time where they came from."
Researchers eventually hypothesized that pairs of colliding neutron stars could do the trick.
Most stars in the universe form in pairs, and the same is true of massive stars. Unlike the sun, however, big stars become supernovas when they die. At that point, their gravity crushes them into one of two forms: a black hole if they're heavy or a neutron star if they're light.
The latter is essentially one big atomic nucleus, since its gravity is powerful enough to squash all the particles together into an orb roughly the width of a metropolitan city - just one teaspoon of a neutron star weighs billions of tons.
"You smash these two things together at one-third the speed of light, and that's how you make gold," Brown said. "Turns out it's not the philosopher's stone - it's not the things alchemists were looking at thousands of years ago."
100 Earths' worth of gold forged in one second
Metzger was among the first to seriously explore the physics of how this could happen.
He said neutron star mergers are a "messy process" that spill some of the stars' guts into space, like "squeezing a tube of toothpaste" and having it shoot out of both ends. The collisions also accelerate thrown-off particles to a fraction of the speed of light while heating them to 10 million degrees.
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