Two telescopes that are part of the ATLAS project in Hawaii have discovered an unnaturally bright explosion in the sky. The discovery, made in mid-June, was published in Astronomer's Telegram, where the object was assigned the name AT2018cow or "The Cow" for short. Astronomers all over the world quickly got wind of the discovery and focused their telescopes onto the area in which the object was discovered.
So far, at least 24 telescopes have examined the object more closely — and yet it's still not clear what the explosion was caused by.
“I've never seen anything like it in the local universe,” astrophysicist at Queen's University Belfast and director of the ATLAS project, Stephen Smartt, told the Washington Post.
Because of the extreme brightness — about ten times brighter than a normal supernova — the object is thought to have originated from our galaxy but to be in the CGCG 137-068 galaxy, 200 million light years away.
Pictures of the ATLAS telescopes show the point after the explosion on the left, the point before the explosion in the middle and the difference between the two on the right. Stephen Smartt / ATLAS
Too bright and too fast for a normal supernova
After further observation, astronomers found the explosion could be detected on all parts of the electromagnetic spectrum, from X-rays to radio waves, and with unusually bright readings.
The explosion was also unusually fast — with high-energy particles firing outwards at around 20,000 kilometres per second — and very hot, with a surface temperature of up to 9,000 degrees Celsius. Usually it takes several weeks for a supernova to reach its strongest brightness but “The Cow” only took a few days.
Scientists believe it may be a type 1c supernova in which the giant star's nucleus collapses and it loses its outer shell of hydrogen and helium.
“We're not sure what it is yet, but the normal driving mechanism for a supernova is the radioactive decay of nickel — and this event was too bright and too fast,” Kate Maguire, an astronomer from Queen's University Belfast, told New Scientist.
Astronomers will be carrying out further measurements and analyses to find out exactly what the explosion was.