Tuesday, 28 April 2009

GRB 090423: a very long way away

News about GRB 090423 has been spreading rapidly throughout the astronomical community as it's by far and away the most distant object yet observed in our universe. This is the object we were the first to see from the Earth's surface. Press releases are being sent left right and centre by everyone involved in the follow-up observations after Swift first detected the burst. The image above is of the actual Swift observation of the GRB - courtesy of NASA/Swift.

For those unfamiliar with the science, this was a gamma-ray burst. These are objects that are generally awfully distant, they don't occur in our Galaxy or in nearby ones (we might actually be thankful for this - you wouldn't want to be anywhere near such a violent event). The current theory, which is now supported by observational evidence, is that these were massive stars that evolved extremely rapidly in the early universe, as massive stars tend to do, and then died in a sudden and extremely violent manner when their hydrogen and helium fuel was exhausted. GRB 090423 probably left a black hole behind, but also shot some of the heavier elements out into space that our planet and we are all made of.

This GRB occurred just over 13-billion light years away which means it's also taken that long for the light to get here. OK, so some might say it's old news, but there's little we can do about that. It does mean, however, that we observed an unimaginably energetic explosion that occurred when the universe was extremely young - current data suggest the universe is 13.7-billion years old - and observing events such as these will help tell us about what was going on back then and why the universe and our Galaxy are the way they are now. Oh, and perhaps explain why we're here as well!

The Swift satellite detected the burst at 09:55 UTC April 23. The satellite then reorientated itself to observe the burst properly. Within a few minutes we got the alert that there was something going on, but our dome was closed due to high winds and cloud and at this point there was no indication of how distant this object was. We spent the next couple of minutes deciding whether we should risk opening the dome and then went for it. 5-minutes were spent opening the dome and setting up the pointing (calibrating the telescope so it and we knew what it was looking at), another couple of minutes focusing and then we were taking data. Twenty minutes after the initial detection from a satellite in space we were imaging the object at around 2.1 microns (that's in the infrared) - in 50-mph winds I might add!

Our observations confirmed the position and showed that the object was extremely red which meant it was almost certainly very distant. Having done our job we let the other telescopes take over!


Beep said...

This is really fascinating and it is great that you shared it online so even someone like me could understand it :)

Zuzana said...

I went to the BBC link yesterday and your observatory was clearly mentioned in the text.
As I am fascinated by the universe, I think I can understand how excited you must be.;)

Keera Ann Fox said...

Are gamma rays like radiation or something? You must be so happy you decided to open the dome!

and perhaps explain why we're here as well! I was wondering if seeing stuff like this doesn't make you think Big Thoughts. :-)

Tom said...

Gamma rays are radiation, just like any light: infrared, visible, X-rays etc. They're essentially high energy light and very similar to X-rays. It's often the context that determines whether we call them X-rays or gamma-rays, the distinction between them is a little blurry.

And yes, I'm so glad we took a chance and opened the dome for the observations. We wouldn't have opened for a regular observation that we could do another night.