Bad Astronomy

GORT bags a burst

No, this isn’t a Day the Earth Stood Still reference. Kinda.

GORT in this case is the GLAST Optical Robotic Telescope; it’s a semi-automated 36 centimeter telescope in northern California operated out of the NASA Education and Public Outreach Group at Sonoma State University. That’s the outfit I was part of for six years! We built the telescope to supplement observations by the Fermi gamma ray satellite (which was called GLAST at the time, hence the G in GORT; and in fact we dreamed up the name to match the classic movie robot).

Here’s the image of the gamma-ray burst (GRB) seen by GORT:

The left side is an image taken years ago as part of the Digitized Sky Survey, and the GORT image is on the right, with the gamma-ray burst marked.

It looks rather ordinary, doesn’t it, just your everyday star. But that’s no star. It used to be one, a huge one, maybe even 100 times as massive as the Sun. It ran out of fuel, and its core collapsed. A black hole formed in the very heart of the star, and the forces at play were vast and violent. Twin beams of unbridled fury roared out of the dying star, each containing enough energy to vaporize the Earth a hundred million times over*. They screamed across the Universe, losing energy as they spread out… and eventually touched us here on Earth, so hugely diminished that it took a telescope to notice them at all. Whole planets may have been destroyed by those beams in their home galaxy, but here, on Earth, the amount of energy we received is less than that generated by the beating of a mosquito’s wings.

That energy swept over the Earth just before sunrise on December 3. The gamma rays from the beams were detected by the Swift satellite, which promptly determined the burst’s position and sent the coordinates to Earth. Sent out via the Internet (srsly), telescopes across the planet responded to the call, and in northern California GORT swung its eye to the position of the gamma-ray burst. Within minutes of Swift’s detection of the burst, GORT began taking its images. The picture above was from just 7 minutes after Swift triggered.

I’m very pleased to say that this is the first GRB GORT has imaged; we tried for a long time while I was there to nail one, but irritatingly they were always poorly placed in the sky, or below the horizon, or it was cloudy, or or or. I wished we could have bagged one while I was still at SSU, but I’m still pretty chuffed the system worked!

GRB081203A (named thus because it was the first burst seen on 2008 Dec. 3) is about 10.5 billion light years away, and according to GORT got to about magnitude 12, which is actually pretty bright for a GRB (though about 1/100th as bright as the faintest star you can see with your unaided eye). Imagine something that far away – 100 sextillion kilometers away – that you can see with a small telescope!

GORT is a nice setup, but it’s literally made from off-the-shelf components. You could have a similar observatory yourself in your own yard, though it’ll set you back a few dozen grand. Still, it’s not like a major institutional observatory costing tens of millions of dollars. This kind of thing is affordable by practically any University, and there are a lot of amateurs who have even slicker setups (retired lawyers and doctors have time, money, and interest). Telescopes like GORT are in many ways the equal of much larger telescopes form decades ago. The technology these days is amazing.

My thanks to Kevin McLin at SSU EPO for sending me the images and answering a couple of lingering questions I had about GORT. Also my congrats to him, Lynn Cominsky (the EPO lead) and all the others in the group. Very cool, and well done!

*GRBs are incredibly violent and energetic events, and if one were to happen a few hundred light years from the Earth it would spell the end of pretty much all life on Earth. Happily for us they all seem to be very far away, so we’re not in any real danger. Of course, if you want to learn more, I know a book that has a whole chapter on these titanic cosmic blowtorches…