Tag: XMM-Newton

A whole star exploded, and no one told me?

By Phil Plait | September 24, 2012 7:00 am

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


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The cold arms and hot, hot heart of the fuzzy maiden

By Phil Plait | January 5, 2011 12:15 pm

Hot (and cold) on the heels of my posting the infrared view of the nearby spiral M33, the European Space Agency just published this incredible picture of our other spiral neighbor, M31, the Andromeda Galaxy!

[Click to galactinate.]

Oh my. This is a composite of two orbiting observatory images: the far infrared using Herschel (colored orange), and the X-ray emission using XMM-Newton (blue). There’s so much to see! That’s not surprising, since at 2.5 million light years away, Andromeda is the closest big galaxy to us, and presents itself with loads of detail.

First, shown here is Robert Gendler’s magnificent visible-light image of the galaxy. You can see it’s tilted almost edge-on to us, but you can see the central bulge of old stars, the spiral arms winding out, the dark lanes of dust. This image has roughly the same orientation and border as the big one above, so you can compare them.

The infrared observations trace the presence of cold dust, created when stars are born and when they die. And by cold, I mean cold: much of it is just a few degrees above absolute zero. That dust is opaque in visible light, as you can see in Gendler’s shot. But it glows in infrared! The X-rays, on the other hand, are from incredibly hot gas heated to millions of degrees by neutron stars, black holes, and newly-born massive stars; you can see several individual objects in the galaxy’s core. Read More

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