Supernovae popping off like firecrackers in Carina

By Phil Plait | May 24, 2011 10:47 am

The Carina nebula is a sprawling, monstrous complex of gas located a mere 7500 light years from Earth. Hundreds of light years across, it’s massive enough to create thousands of stars like the Sun. Tens of thousands.

And churn out stars it does. Embedded in the nebula are several clusters of newborn stars, and many of these stars are so massive they’re nearly at the limit of how big a star can be without tearing itself apart. Stars that big explode as supernovae, and a new mosaic by the orbiting Chandra X-ray Observatory indicate they’ve been popping off in the nebula for quite some time:

[Click to enchandrasekharlimitenate.]

This image is pretty amazing: it’s a mosaic of 22 separate images by Chandra, covering 1.4 square degrees (seven times the area of the full Moon on the sky), and represents an exposure time of 1.2 million seconds! Since it shows X-rays coming from astronomical objects, it’s false color: red is from lower energy X-rays, green is medium energy, and blue from the highest energy photons.

The diffuse glow is from two sources: the stellar winds from those massive stars slamming into surrounding ambient gas at high speed, and from the shock waves generated when supernovae explode. Both are extremely high-energy events, and produce copious amounts of X-rays. That long, horizontal arc is probably the edge of a bubble, a shell of gas piled up from the winds of stars and supernovae like snow piled up in front of a snowplow.

That’s evidence right there that Carina has been cranking out supernovae over the past few million years. Interestingly, it’s what’s missing that provides more proof. Look near the top of the image; see that loose cluster of stars right near the top edge? That’s Trumpler 15, a collection of thousands of stars packed into a volume of space only a few light years across (compare that to the Sun’s neighborhood, where the nearest star is over 4 light years away).

About 900 of the stars in Trumpler 15 are massive enough to produce X-rays and be seen by Chandra, and the highest mass of these stars should be cranking out lots of the highest-energy X-rays. However, this high-energy emission isn’t seen. Those stars should be there, but aren’t. The conclusion is clear: those stars are gone. The most massive stars only live a few million years before going boom, and the cluster is roughly 8 million years old — plenty of time for those stars to have gone supernova. In other words, Trumpler 15 is has been seeing some action lately.

There are other clusters in the nebula as well, and you can see them in the picture (an annotated version is available as well); Trumpler 14 is below and to the right of Trumpler 15; Trumpler 16 is below 15 and just above the curving arc of shocked gas (Eta Carinae, a supermassive star just waiting to explode, can be seen just above that). All told, there are over 14,000 stars detected in this image, and that just includes the ones putting out X-rays. Many, many more can be seen in visible light pictures such as the one inset here (and yes, you very much want to click to embiggen it).

Not only that, but this Chandra survey has shown that the number of massive stars in the nebula is probably twice what we previously thought, and has also revealed six new possible neutron stars — the leftover cores of exploded massive stars. So the big conclusion to draw is that Carina has been churning out massive stars for quite some time, and for the past few million years the most massive of these have been exploding one after the other.

That may sound dangerous — stars exploding like flash bulbs in a nearby gas complex, aiiiee!! — but remember, the nebula is actually pretty far away. A supernova has to be less than 100 light years away to hurt us, and more like 25 light years away to really hurt us, so the nebula’s distance of 7500 light years means we’re safe from death by supernova.

But it does mean we get an excellent view of this star-explodey factory. There’s still much to learn about how stars are born, how they live out their lives, and how they die. Chandra’s X-ray vision is providing us with a big piece of that knowledge.

Image credits: NASA/CXC; Digitized Sky Survey/CXC


Related posts:

- Hubble’s 17th: chaos, birth, and near-death
- Hubble celebrates 20 years in space with a jaw-dropper
- ESO unlocks the Keyhole
- Hubble Heritage diamond gift

Comments (22)

  1. Greg
  2. Mejilan

    Stunningly beautiful, really. Been lurking here for some time now. I appreciate all of the visual and textual treats that this blog offers!

  3. Kim

    I couldn’t find Eta Carina. BTW, some time ago a brazilian astronomer suggested it was a binary system. Has it been proven or disproven?

  4. Hi Phil — I’m having trouble understanding this paragraph:

    “About 900 of the stars in Trumpler 15 are massive enough to produce X-rays and be seen by Chandra, and the highest mass of these stars should be cranking out lots of the highest-energy X-rays. However, this high-energy emission isn’t seen. Those stars should be there, but aren’t. The conclusion is clear: those stars are gone. The most massive stars only live a few million years before going boom, and the cluster is roughly 8 million years old — plenty of time for those stars to have gone supernova. In other words, Trumpler 15 is has been seeing some action lately.”

    If the massive stars are gone, how were they detected in the first place? Do you mean that the stars were found in visible light but not in X-Ray, so they must be supernovae remnants? Have I misunderstood something?

    Fascinating stuff as usual. Keep up the good work!

  5. Cmdr. Awesome

    I’m having the same problem as Saint Aardvark. X-rays should still be bound by the speed of light…so we should not still be receiving light from the stars if they’re gone and we’re no longer receiving x-ray bombardment, correct? Even if we’re getting light from the supernova, we should be getting hit with x-rays generated by that event, shouldn’t we? Or are we seeing light from the remnants after supernova?

    Or maybe are we detecting the existence of these stars indirectly (like gravity lensing, or watching existing stars orbit around black space)? Or is there something really obvious that I’m just completely missing?

  6. JohnDoe

    Trumpler 15 is has been seeing some action lately.

  7. Liath

    So those high mass/energy stars that have gone missing during the last 8 million years, would we not be seeing their remnants as neutron stars? Are they the six additional neutron stars you refer to? I suppose I’ve just answered my own question.

    But then, of course, I have another question. I’m old and cranky and full of questions. With all those stars of assorted sizes all packed into space perhaps not much larger than four light years, what gravitational effect do they have on each other? It would seem to me that stars that size in so small an arena gravity might do some interesting things.

  8. Crux Australis

    An exposure time of 1.2 million seconds; I love it!

  9. PSP

    This is magnificent. Fascinating. Humbling. Frighteningly awesome. (Dang! I pledged I wouldn’t use that totally overused word ‘awesome’ since it’s totally overused, totally.) But – I look at this, and your description, and I’m totally awesomized.

  10. I read Phil as saying that stars come in three sizes, wee, not sa wee and friggin yuge. The wee stars don’t produce X-rays. The not sa wee produce X-rays, but their solar winds slamming into the interstellar medium don’t produce X-rays. The solar winds of the friggin yuge do produce the X-rays. We don’t see those X-rays because the friggin yuge went phutt years ago and all we can see in the X-ray image of Trumpler 15 is the not sa wee that haven’t yet gone phutt.

  11. “enchandrasekharlimitenate” ?

    That just sounds so … degenerate. (rimshot)

  12. Brasidas

    From #4 “If the massive stars are gone, how were they detected in the first place? Do you mean that the stars were found in visible light but not in X-Ray, so they must be supernovae remnants? Have I misunderstood something?”

    Concerning the “missing” massive stars, i think the point is that these stars must have been formed in the nebula but are not detected now so they’ve gone. They were never detected, not that they were detected by one means and not by another.

  13. Messier Tidy Upper

    Superluminous photos once again. The Carina Nebula is the stellar region that never stops giving. :-)

    enchandrasekharlimitenate.

    Nice one – but I’d like to hear you say it ten times in a row real fast! ;-)

    Carina has been cranking out supernovae over the past few million years.

    Plus it will be for a while yet I bet – wonder how long Eta Carinae has left and how many more night’s it will grace our skies for before it explodes too – and what magnitudes it will rise and fall to during its remaining time?

    The most massive stars only live a few million years before going boom, and the cluster is roughly 8 million years old — plenty of time for those stars to have gone supernova.

    Gone in 8 million years! Wow. :-o

    In stellar terms that’s not long at all so those must have been very supermassive and thus very short-lived stars indeed. Can we work out roughly how massive and what spectral types they once were from that?

  14. Messier Tidy Upper

    @3. Kim Says: I couldn’t find Eta Carina. BTW, some time ago a brazilian astronomer suggested it was a binary system. Has it been proven or disproven?

    I’m pretty sure we now think Eta Carinae *is* indeed a binary of two supermassive stars.

    See :

    http://stars.astro.illinois.edu/sow/etacar.html

    Via Kaler’s Stars website or via wikipedia here :

    http://en.wikipedia.org/wiki/Eta_Carinae

    with a photographic star map of Carina here :

    http://stars.astro.illinois.edu/sow/car-t.html

    if that helps. :-)

    Supernovae popping off “like firecrackers” – yeah there’s just a leeetttle bit of diffenrce in the scale of the blast there! ;-)

  15. Messier Tidy Upper

    @3.Kim : James B. Kaler’s superb book ‘The Hundred Greatest Stars’ (which btw. I’d very highly recommend if you can find somewhere) says that Eta Carinae is, indeed, probably two stars :

    Current estimates sugest that the “primary” star (once the secondary) still has around 80 solar masses, while tehsecondary (once the primary) has perhaps 60. The two may have been born with 200 solar masses! Winds from the rapidly evolving stars collide, heat and radiate X-rays. Whether one star or two, Eta Carinae will explode. If the star is indeed double, the invisible secondary will go first (as it is farthest along its evolutionary path). The wisdom is that Eta Car will produce a hypernova, a grander version of the supernova in which the stellar core collapses to produce a black hole.

    - Page 77, Kaler, Copernicus Books, 2002. [Emphasis added. Any tyupos almost certainly mine.]

    The now 60 mass star would be lower in mass than its companion due to the “Algol paradox” where the more massive stars evolves and loses mass quicker – including mass exchange to its partner. The 60 solar mass star is now a Wolf-Rayet type star and its 80 solar mass comrade is a B-type supergiant. The “whether” and “if” are interesting and obviously imply some degree of uncertainty remains.

    Eta Carinae is one of – if not the – brightest star in our whole galaxy witha luminosity an incmprehensible five million times that of our Suns’s (& can you imagine something even just *twice* as bright?) and it is a personal favourite of mine – despite which I’m hoping to see it die by going supernova in my lifetime! :-)

  16. @13.Brasidas — aha, so it’s something like “a cluster this size should have had this many stars that were bright in X-rays — and since we don’t see them, they must have exploded.” Have I got that right?

    @11.Keith Harwood — I think I’m going to use “friggin yuge” as my adjective of choice this week. :-)

  17. chris j.

    my take on the “missing stars” issue:

    trumpler 15 is a young open cluster of stars, all of which are presumably the same age. according to current theories of star formation and accounting for metallicity, a certain percentage of those stars should have been high mass/luminosity, but those high mass stars are not seen. this should not be surprising, because high mass stars have short lifespans, and high enough mass stars can die within a few million years of birth.

    but then why does Phil prelude the missing star discussion with this comment: “About 900 of the stars in Trumpler 15 are massive enough to produce X-rays…” at first, he’s saying those stars are there – he even counted them. but then he’s talking about the stars not being there.

    so the question this raises in my mind is, are there about 900 stars in trumpler 15 that should be producing x-rays, but aren’t?

  18. r0blar

    Yeah, I’m also confused about those missing 900 starts…

    Please explain it – HOW and WHY! :)

  19. jeremy greenwood

    Yeah come on answer it (Trumpler 15). Are you saying that the stars are gone in Xray, but visible in the optical spectrum as longer wavelength light travels slower??

  20. jeremy greenwood

    I can’t help thinking that my last posting had a jeering unpleasant note to it. I’m sorry about that, it wasn’t intended. Your’s is the only blog I read regularly, and I am full of admiration.
    But how about answering the question?

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