One of the most violent and catastrophic events in the history of the universe took place in October. It was found to be two billion light-years away from Earth. 20 billion trillion kilometers away from us is a decent amount of the observable universe.
The meaning of close is different to the astronomer. It was so close that it was detected by a fleet of observatories both on and above the Earth. It was bright enough to spot its visible-light emission in smaller amateur telescopes, and was able to affect our upper atmosphere, even though it was so far away from us. There is no danger posed by this burst. I'm glad they don't go too far.
A GRB is an intense blast of the highest-energy form of light that lasts from a fraction of a second to a few minutes. Since the 1960s, when the first burst was discovered, astronomy has been puzzled by it. Since then, over 1,700 have been seen. It took decades to pin them down in the sky so that they could be observed with more conventional telescopes. Each GRB has quirks that make them hard to understand as a group.
We have a good understanding of their basic nature. Short-duration bursts come from two superdense neutron stars colliding and blasting out fierce energy, whereas long-duration ones last several minutes. A black hole is formed by the collapse of the star's core. A swirling disk of material that wasn't immediately swallowed by the black hole rapidly forms around it, funneling twin beams of intense energy out into space. The rest of the star explodes as a very powerful supernova when these eat their way through it.
The amount of energy that can be released in a few seconds is almostincomprehensible. Thin beams concentrate the energy in a narrow direction. If the beam is pointed in your direction, you can see a flash of gamma rays that are bright enough to be seen billions of light years away. There is a more typical supernova outside the path.
A telescope is needed to see most of the bursts that are so far away.
The first flash of GRB 221009A was detected by the space telescope, designed to detect and locate GRBs. The Neil Gehrels Swift Observatory, a set of telescopes designed to observe bursts, spotted another blast of gamma rays. It took nearly an hour for the second peak to happen, indicating just how much power the GRB had.
Astronomers all over the world responded by pointing their own telescopes at the burst. This was the closest GRB ever seen because of the fading glow of visible light caused by the beams slamming into the dying star.
There are lightning detectors in India and Germany that show how the GRB energy hits our planet. The electrons were stripped from their host atoms in the upper atmosphere. It is likely that the blast physically affected the atmosphere of the planet. It is extraordinary from two billion light-years away.
Astronomers can analyze the light they see from it in more ways than usual because of the close proximity. The central black hole engine that forms during a burst and the incredibly complex nature of the physics surrounding them could be better understood by this specimen.
It can give us information about the stars. Dust clouds located between 600 to 12,000 light-years from Earth caused the Swift observatory to see x-ray light coming from the GRB. When light hits dust clouds just off our line of sight to the GRB, we see them to the side. It takes light from the blast to reach the dust clouds, and it takes light from the center to reach them. Calculating the distances to the clouds was made possible by measuring these rings.
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Since then, great strides have been made, but there is still a lot we don't know about them. GRB 221009A is still being observed by telescopes around the world, and it is possible that it is a Rosetta stone.
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