One of my favorite things to do in the whole world is look at astronomical images. They are a source of great beauty, insight into our Universe, and wonder that we can understand them.
As it happens, I spent a solid chunk of my professional research career looking at supernovae remnants, the expanding debris after a star explodes. Everything about them is cool: the extraordinary energy released, the amazing beauty and symmetry they posses, the fact that many of the elements necessary for life are created in them.
So I’m pretty familiar with images of these things. Which is why I got a good surprise when the European Space Agency posted this picture of the supernova remnant G272.2-03.2, taken with the XMM-Newton observatory:
[Click to corecollapsenate.]
This is actually a composite image; the starry background is from an optical telescope, but the remnant itself is seen in X-rays by XMM-Newton. X-rays are emitted by very hot gas – heated to a million degrees or more – so you know right away this was an energetic event. I mean, duh, a star exploded.
The two colors (green and orange) tell you the gas is at two different temperatures. The outer rim is probably a thin shell of gas compressed as it slams into the very thin material between stars, while gas heated by shock waves fills the shell. My eye went right away to the bright bit at the right. That’s very common in objects like this when the expanding gas rams into a slightly denser part space (like some other floating cloud of gas) – you get a "dent" in the shell and it gets a bit brighter.
What surprised me most about this particular object is that I had never heard of it! That’s a little unusual; I try to keep up with such things. Then I found out this image was taken in 2001! So it’s not like I ever had a chance to see it. Weird.
So I did what I always do in these situations: looked for references to it in professional journal research papers. And what I found was… almost nothing. There’s a good paper analyzing it by my friend Ilana Harrus, but not much else. Her paper came out a few months before this XMM-Newton observation though, and I couldn’t find a paper with these observations in it.
So I don’t have a lot of information about it. It’s probably about 5000 years old, and may be somewhere between 6000 and 16,000 light years away; pinning down these numbers is very difficult. The star that blew up was probably 8 – 10 times the mass of the Sun, actually a bit of a lightweight for a supernova progenitor. The nebula itself is clearly a shell with hot gas in the interior, but it’s hard to know much more about it. From Ilana’s paper I read that it has some features that make it look old, others younger. But the lack of deep observations keeps this object something of a mystery. I’d love to see some long exposures from Hubble or the Very Large Telescope in Chile. There really aren’t very many good examples of moderate age supernova remnants, and this looks to be a pretty nice example of one.
But geez, next time, someone let me know before a decade passes, OK?
Image credit: XMM-Newton/ESA
I deal with superginormously ridiculous energies, velocities, and sizes all the time as an astronomer. You get used to it after a while… then something like this’ll slap you upside the head: a star that exploded more than 5000 years ago launched two epic bullets. One is a cloud of gas screaming away at thousands of kilometers per second, and the other is the cinder of the star itself, an octillion-ton cannonball blasting through space in a totally different direction.
This is a composite picture of the supernova remnant N49: an expanding lumpy sphere of gas about 30 light years across (300 trillion kilometers, or 180 trillion miles)*, located in the Large Magellanic Cloud, a satellite galaxy to our Milky Way. The blue in the picture is the emission from gas heated to millions of degrees, and shows X-rays detected by the Chandra observatory. The yellow and purple are from Hubble data, showing gas being whipped and beaten by shock waves slamming around insides the remnant.
Turn your attention to the little blue blob to the right, marked by the red arrow. It’s outside the main bubble of the nebula, meaning that it must be moving faster than the gas in general. This is seen sometimes in supernovae remnants: a bullet or focused blob of gas screaming away. It may be caused by magnetic fields in the expanding gas just after the star explodes, launching the octillions of tons of matter away in all directions, or it may be due to focusing from shock waves, which can sculpt the gas and create little pockets of denser knots.