On June 21, an intense blast of X-rays from a distant explosion slammed into NASA’s Swift satellite, and was so bright it actually temporarily blinded the observatory!
Swift is a satellite designed to look for gamma-ray bursts (GRBs); incredibly violent cosmic explosions that occur when black holes form. We think there are several ways this can happen, but the most common is when a massive star explodes at the end of its life. Forces in the star’s core can create unbelievably destructive power; essentially packing all the energy the Sun emits in its entire lifetime into two narrow beams that march across the Universe. A GRB beam can be so intense that from a hundred light years away it would blowtorch the Earth, and so bright it can be seen from clear across the observable Universe.
For once, I’m not exaggerating. In the case of last month, the GRB was about 5 billion light years away. Called GRB 100621A (from right to left, the first GRB seen on the 21st of June in 2010), it was unusually, amazingly bright in X-rays. A lot of GRBs emit light across the spectrum, from radio to super-energetic gamma rays, but this one really overachieved in the X-ray department. Swift, normally easily able to handle the X-ray load from these explosions, was overwhelmed, and actually shut down temporarily when software detected that the cameras onboard might get damaged by the flood of light. That’s never happened before.
The burst was so bright in X-rays it put other GRBs to shame: slamming Swift with 143,000 X-ray photons per second, it was 5 times brighter than the previous record holder, and nearly 200 times as bright as a typical GRB! Weirdly, it didn’t look out of the ordinary in visible light.
So why was this burst such an overachiever? At the moment, that’s not clear. The good news is, GRBs don’t just blink on and off, they fade over time, allowing for long observations, and for other observatories to take a peek at other flavors of light (like radio, optical, and infrared). With a fleet of telescopes keeping their eyes on this prize, I expect the journals will soon see their own flood of papers being submitted to explain this extraordinary event.
I can’t help but add that for several years I worked on the Swift team, doing education and public outreach. Whenever we got an extraordinary burst like this one – and we did see a few whoppers! – everyone got very excited and the email and phone calls would fly. Neil Gehrels, the Principal Investigator of Swift (think of him as Big Daddy) was always particularly gung-ho about these, and was really supportive and willing to give time to talk to me about them. He was incredibly helpful to me when I wrote the GRB chapter of my book, and is just an all-around good guy. I’m really glad to see that Swift – one of NASA’s all-time most successful satellites – is still cranking out the hits, and the team is still jumping into action when it does.
Tip o’ the Cesium-iodide X-ray detector to my old pal Dan Vergano. Image credits: NASA/Swift/Stefan Immler, NASA