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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Comments (18)

  1. Nathan

    But if it’s 5,000 years old and 6,000+ light years away, would we be able to see it? Doesn’t its distance from Earth tell us its minimum age since we can see it?

  2. Chris

    Since it is only 5000 years old and fairly close, I wonder if the supernova could have been seen on Earth? Would be interesting if there were any records from Ancient Egypt, although any records would be very hard to find. Would this be close enough to leave a trace in ice cores or tree rings?

  3. Michael

    We only wake you up for the important supernovae.

  4. Pete Jackson

    I assume that the blue spots are discrete X-ray sources, appearing blue because the X-rays are harder (more energetic) than the supernova remnant X-rays. Interesting that only one of them, at 8 PM, has an optical counterpart.

  5. Mac

    Looks like it’s time for you to dust off that PhD and write a scholarly article. You’ve certainly got enough throw weight to get some VLT time, perhaps even some Hubble. You’re a rare beast, a self supporting astronomer, and you’ve got friends in a lot of unlikely places. You should carve out some time to work on things like this that interest you. I realize that the self-supporting and time are mutually exclusive, but there are also relatively few astronomers out there interested in super nova remnants. Besides, an occasional scholarly paper will keep your CV interesting.

  6. Pete Jackson

    @1Chris: This supernova remnant is in the far southern sky, at -50 degrees declination. 5000 years ago, it would have been further north, but still quite low in the southern sky even for Egyptian, Chinese, or Babylonian observers. Stars that far south are above the horizon for only a few hours out of 24 hours; and there will be a six-month period out of the year when those few hours are all in daylight.

    Australian native peoples have been around for a long time, and probably observed the supernova, but haven’t left written records as far was we know.

  7. I wonder what the top asymmetry of the explosion is all about? Could there have been a large planet in the way?

  8. Frost Bite

    Do these type supernova give an idea of the Heliosphere of the star? Can they show the Bow shock in this example with the bow to the bottom right of the image and the tail beginning to pull off material in the upper left? Or is this too “new” for Bow shock to start to degrade?

  9. Infinite123Lifer

    A horrible new species of goo ball? ;)

    Who is that darn Sign Painter anywho?

  10. Terry

    @1 I think the policy is that nothing happens until we see is; so if something happened 5000 years ago and it 6000 light years away; then that means that it ‘actually’ happened 11000 years ago.

  11. But geez, next time, someone let me know before a decade passes, OK?” Betelgeus, 21 December 2012. Alas, its rotation axis does not point at Earth. A supernova’s optical shock wave oozes from its collapsed core through the star. A supernova’s ~10^58 neutrino pulse diffuses through the core implosion region, then propagates hard by lightspeed through the rest of the star. Super-Kamiokande will give a few hours advance warning if it is running. IceCube, not so much (sensitive for 10^11 to 10^21 eV neutrinos. Betelgeus’ thermal neutrinos will be a detector-wide, brief, correlated rise in noise rates. (It already happened some 600 years ago vs. local time. How can you doubt?)

    Do Chanukah rather than Christmas this year. The Beiwe Festival (Sami people) has some nice butterworks. Chawmos (Kalash people) for fetishists. Dzon’ku ‘Nu (West African Papaws) for the giddy.

  12. Chris

    Phil, the light from a distant supernova is on its way to Earth as we speak. Just to give you a heads up.

  13. Jeff S.

    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

    You are so correct. Electromagnetism in fact is the most fascinating force to me and is behind a lot of this; but of course gravity and nuclear are involved. It’s just that to life, EM is the most important force.

    Life, non-life, supernovae, they all boil down to the same thing: this amazing quantum universe of which life is only a part.

  14. Jeff S.

    In three months I’ll do my annual chore of teaching students EM, but I love it; still, it is so hard a subject, it is tough to learn. Still, EM is the most fascinating to me. Look forward to it again.

  15. Interesting that a supernova so relatively recent is so obscure and little studied. Certainly wouldn’t have expected that.

    Spose as (#6.) Pete Jackson suggests the southernly location may be its problem.

    (Incidentally Australian aboriginal skylore is known to some extent for some groups & some aboriginal rock art depicts it although I’m far from an expert on this.)

    @12. Chris :

    Phil, the light from a distant supernova is on its way to Earth as we speak. Just to give you a heads up.

    Well sure but from which star and celestial co-ordinates and when that’s what I want to know! ;-)

    @11. Uncle Al : I know Betelguex / Betegeuse / Alpha Orionis has a variety of spellings but that’s a new one for me! ;-)

    Cool as it’d be if Betelgeuse were to go supernova – as for instance James Kaler describes (linked to my name here) I’d kinda miss it in the sky if it goes.

    Just as I’d miss Antares too – which right near its rival Mars for handy comparison over lats night or so!

    So I’m personally hoping for Eta Carinae and definitely hoping to witness a supernova in my lifetime. 8)


    “…about 40 supernovae are exploding somewhere in the universe every second. However, light from most of these events won’t reach Earth for billions of years, if ever.”
    – Page 73, “Ask Astro” column in ‘Astronomy‘ magazine October 2008.

  16. #1 Nathan:
    When we say “it happened 5000 years ago”, we mean that’s when it was observed*, i.e. when its light reached Earth. The light by which we see it now has taken the same time to reach us, so we are now seeing the remnant as it was 5000 years after the supernova.
    Which is, after all, what matters to us. What the remnant actually looks like now is irrelevant to us, because we can’t see it!

    *I’m talking hypothetically there – as in, when the supernova’s light reached Earth, irrespective of whether or not any humans actually observed it! Astronomers can work out the remnant’s age, by studying its size and rate of expansion.

  17. Nathan

    Thanks for the explanation Neil – that makes sense now. I knew I was missing something easy in the explanation…

  18. Sanjaya

    Good to see such an amazing picture however, in what year did the star explode?
    what was happening here on Earth when the star exploded?


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