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Astronomers have found several “cows” in the cosmic meadows — including an especially loud one. They’re a powerful form of supernova — the titanic explosion of a star. They’re named for the first one seen, AT2018cow — the Cow.
Only five have been discovered, suggesting that they’re uncommon. But they shine brilliantly at all wavelengths.
The most recent discovery was the brightest of all. A month after the explosion, AT2020mrf was producing 20 times more X-rays than the Cow had a month after it went off. And almost a year after the explosion, it was 200 times brighter than the Cow.
A possible explanation is that we’re seeing parts of the explosion that had never been seen before.
When a supergiant star reaches the end of its life, its core collapses to form a black hole or a neutron star. Its outer layers then blast out into space as a supernova.
Most of the time, the exploding star is surrounded by a cocoon of gas and dust. That blocks our view of what’s happening in the core. In the case of the cows, though, there was little surrounding material. So when they exploded, we could see all the way down to the core — providing the first direct views of the birth of a neutron star or a black hole.
Cow-like events may be kept bright by radiation from a disk of gas around the black hole, or by the magnetic field of the rapidly spinning neutron star. Either way, they help the cows stand out in the cosmic meadows.
Script by Damond Benningfield