Look! This distant galaxy hosted the most powerful explosion since the Big Bang
the little oneThe dim, red dot in the center of the newly released image of a distant galaxy indicates the galaxy underwent one of the most powerful explosions since the Big Bang.
Astronomer Brendan O’Connor and his colleagues recently discovered this as-yet-unnamed galaxy 9 billion light-years away in data from the Gemini North Telescope in Hawai’i, and they say it is the source of a brilliant, bright beam of gamma radiation. brief dazzling NASA. Swift Observatory in late 2015.
Imagine an explosion releasing as much energy as our Sun would in 10 billion years – compressed into an explosion in less than two seconds. Astronomers call this almost unimaginable catastrophe a short gamma-ray burst, and the universe hasn’t seen a brighter or more powerful explosion since the Big Bang. What could cause such an event? The answer appears to involve two colliding neutron stars.
Binary star systems are not very rare in the universe; one of our closest neighbors, Alpha Centauri, is actually a pair of stars quite similar to our Sun. On the other hand, binaries involving two neutron stars — dense balls of neutrons left by stellar deaths that are massive enough to cause a supernova, but not massive enough to collapse into a black hole — appear to be much rarer.
But every now and then, a pair of binary neutron stars will pull each other into a gravitational death spiral, eventually colliding with enough force to release brief bursts of gamma rays that are brighter than the entire galaxy. Astrophysicists say this happens, in most galaxies, several times every million years.
Most of the short gamma-ray bursts observed so far have occurred in bright, nearby galaxies. But 43 of those detected by NASA’s Swift Observatory appear to have come from the middle of nowhere – the distant reaches of intergalactic space with no visible galaxies. O’Connor and his colleagues have recently tracked most of the fast gamma bursts – including the 2015 explosion, dubbed GRB 151229A – to a previously unknown group of very distant galaxies.
Short bursts of gamma rays are exactly what they sound like: short bursts of gamma rays. But they leave behind the remnants of longer wavelength radiation such as X-rays. When Swift detects a gamma-ray burst, it uses an X-ray beam to pinpoint where the explosion is coming from. O’Connor and his colleagues searched through data from Gemini North, its sister observatory Gemini South in Chile, and the Keck Observatory in Hawai’i, looking for anything in the seemingly empty location Swift pointed to.
They discovered galaxies – dim, distant, and old. Most of them, like the one in the image above, are between 8 and 10 billion light years from Earth. And that means the gamma-ray bursts emanating from those galaxies occurred 8 to 10 billion years ago, when the universe was much younger.
Until now, astronomers thought that neutron stars collided even less frequently in the distant cosmic past than is seen in the modern universe. But O’Connor and his colleagues say that the newly discovered ancient galaxy suggests that massive gamma-ray bursts were a common occurrence even in the early universe. It could reshape what we know about the origin of the universe — and when the materials arrived.
Collisions between neutron stars are strong enough to form entirely new elements, including heavy metals such as gold, platinum, and thorium. If neutron stars collided to produce short gamma-ray bursts 8 to 10 billion years ago, then they also seeded the young universe with heavy elements much faster than anyone thought.
“This pushes back the time scale when the universe received the ‘Midas touch’ and was seeded with the heaviest elements in the periodic table,” O’Connor said in a statement.
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