Sep 212011
 

We take a break from astroimaging for a moment to talk about things that go bang. We all know about fireworks, smash-em-up derbies, and an obscure rock group from the early 70s. But I’m talking about things that go bang in the sky.


We have two things going on in September, 2011 that are not exactly rare, but they are things that you don’t get to experience more than a few times in a lifetime. The first is the explosion of a star in the Pinwheel Galaxy (M101) and the second is the crashing to Earth of the NASA UARS satellite. First things first – the supernova.

SN 2011fe is a medium sized star that went bang in the Pinwheel Galaxy. It’s only 20,000,000 light years from Earth, so about the time that Giraffes first put their necks up to the trees to eat the leaves at the top of the canopy, this star blew up. Its light has been racing towards us ever since. About a month ago, we got to see it. Or you did if you have a really good Time Machine.

M101 is so far away that it takes a Time Machine about twice as large as Astropotamus’s to be able to even see it. The supernova itself looks like any other middle-bright star in the night sky though my Time Machine. But I know better. There was no star there in July. Then there was one in August and September. Now it’s fading, just in time for the rain that’s coming over the next five nights or so. The Internet is full of information about the supernova, so I won’t pretend to tell you anything new here, but just keep in mind that a single star from a galaxy 1,900,000,000,000,000,000,000 kilometers away (damn, that’s far) briefly shown bright enough to look like a star only 5,700,000,000,000,000 kilometers away. Makes it feel positively close, doesn’t it?

I didn’t take this image, but it’s a good one to get an idea as to how bright the overall supernova is. Remember, in this image, all of the other dots that look like stars are stars that are no farther away than 25,000 light years. Most are more like 2500 light years or closer. The supernova is almost 8000 times farther away than any of the other stars, yet shines just as brightly. Look closely near the middle, about 1/3 from the bottom, and you’ll see two white lines that indicate where SN2011fe lies.

Moving from things 20,000,000 light years away to things less than 200 miles away, we come to the NASA UARS satellite. As I write this, it’s about 72 hours away from crashing into the planet, even though we’re still not quite sure where it will crash. It reminds me of when Skylab did something similar on July 12, 1979 – 4 days shy of the 10th anniversary of the launch of Apollo 11, which put men on the moon.

So far, no one has the unfortunate honor of being the first known human killed by falling man-made space debris, but there is often damage when things come crashing out of the sky. Skylab was a randomly moving, hulking piece of metal that was not under control when it crashed. It rained parts of itself down on Australia, putting charcoal sized pieces of supersonically heated debris through people’s roofs.

Mir Falls to Earth

Mir Falls to Earth

Mir was another space station that came down, but it did so after Russian engineers gave it an intentional push with a rocket burn that caused it to go into a decaying orbit and land in the Indian Ocean. That was in March of 2001. And here we are 3800 days later getting ready for UARS to lumber out of the sky and fall…well, we don’t know.

It’s not falling in a controlled manner like Mir did. It’s more like Skylab. Luckily, it’s not quite as big. But it’s still expected to spew its debris over a 500 mile long track somewhere between 57 degrees North latitude and 57 degrees South latitude.

That’s roughly most of Canada, Greenland, Denmark, Sweeden, Latvia, all of the UK, the bottom half of Russia, and everything south until you get to the southern tip of South America. So, roughly speaking, every populated place on the planet is a potential space-based smash-em-up derby.

Actually, truth be told, NASA and NORAD, which track the 20,000 estimated pieces of space junk have a pretty good idea what the track of UARS is and where it will end up. You can see it at this web site. Pay attention to the yellow lines. That’s where the satellite will be during its presumed death plunge. Most likely, it will be off the coast of South America and shower a few llamas with debris. One of those tracks, however, shows it going right over Astropotamus’s neck of the woods so there’s a chance we’ll be in the fall zone.

Personally, I think the odds are more likely I’ll get killed by a radioactive rabid monkey, so I’m not too worried about it. But if a piece of of UARS junk hits my backyard, I’m going to go collect it and put it in a nice Lexan case on my mantle as a reminder of all the other things that have gone bang in the sky.