Fireball in Chelyabinsk
No pictures here on my blog, but the videos are amazing--you could call it "dashcam astronomy." I'm sure Slate and other news sites will be updating.Here is some speculation from my astro artist friends about determining the size and energy of the meteorite, which blew out a LOT of windows from the shockwave:
How does one ascertain the size of something that has broken into pieces and burned? Was it air traffic or defense radar, or based upon the net effect of the blast?
Pat: No idea how the estimate was derived!(note:"the size of a bus") A cumulation of effects, ranging from the brightness, the size of the shock wave, (the reports I am hearing on the radio this morning are saying nearly a thousand people have been injured from broken glass caused by that shock wave) would be my guess. I doubt there is a way to know definitively. From Dan:
There is a system of US DoD satellites that monitor the IR signatures of, uh, 'events' in the atmosphere. They are watching for man-made 'events' of course, but are naturally well-tuned for these kinds of big meteors. We in the asteroid community used to have access to scrubbed versions of these data and used that to determine that things like this happen about once a month or so somewhere on the planet (usually over open ocean, of course). The releases of the scrubbed data were turned off a few years ago, but be assured that somewhere right now someone is using calibrations from similar known events to get a very good estimate of the total energy. Another source of information that will go into that is from infrasound. Big booms leave a barometric signature that also gives information on the energy. Peter Brown at the University of Western Ontario in London, Ontario is one of the experts on this and you will likely see press reports in the coming days with his name in them... So, we all just wait to see what the numbers tell us in the coming days. My initial, 'gut' feel from this (could well prove wrong) is that, while very spectacular, this may be one of those once-every-month or once-every-few-months event. But coincidentally timed as it is with all the press about the close pass by 2012 DA14 it should serve as a good wake up education for some/many on the realities of the cosmic shooting gallery we're living in...
(This is Epsilon Eridani, but it was the only meteorite painting I had handy)