Star Exploded Too Early, May Blow Apart Supernova Theory

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NASA’s Hubble Space Telescope has identified a star a million times brighter than the sun that exploded as a supernova in 2005 — well before it should have, according to current theories of stellar evolution.

The doomed star, estimated at about 100 times our sun’s mass, was not mature enough, according to theory, to have evolved a massive iron core of nuclear fusion ash. This is the supposed prerequisite for a core implosion that triggers a supernova blast.

“This might mean that we are fundamentally wrong about the evolution of massive stars, and that theories need revising,” says Avishay Gal-Yam of the Weizmann Institute of Science, in Rehovot, Israel. The finding appears in the online version of Nature Magazine.

The explosion, called supernova SN 2005gl, was seen in the barred-spiral galaxy NGC 266 on October 5, 2005. NGC 266 is about 200 million light years away, in the constellation Pisces.

The progenitor was so bright that it probably belonged to a class of stars called Luminous Blue Variables (LBVs), “because no other type of star is as intrinsically brilliant,” says Gal-Yam. But there’s a wrinkle: as an LBV-class star evolves, it sheds much of its mass through a violent stellar wind. Only at that point does it develop a large iron core and ultimately explodes as a core-collapse supernova.

“The progenitor identification shows that, at least in some cases, massive stars explode before losing most of their hydrogen envelope, suggesting that the evolution of the core and the evolution of the envelope are less coupled than previously thought, a finding which may require a revision of stellar evolution theory,” co-author Douglas Leonard, from California’s San Diego State University, said in a press release.

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One possibility is that the progenitor to SN 2005gl was really a pair of stars — a binary system — that merged. This would have stoked nuclear reactions to brighten the star enormously, making it look more luminous and less evolved than it really was.

“This also leaves open the question that there may be other mechanisms for triggering supernova explosions,” says Gal-Yam. “We may be missing something very basic in understanding how a superluminous star goes through mass loss.”

Gal-Yam and Leonard located the progenitor in archival images of NGC 266 taken in 1997. They then used the Keck telescope to precisely locate the supernova on the outer arm of the galaxy. A follow-up observation with Hubble in 2007 unequivocally showed that the superluminous star was gone.

Extremely massive and luminous stars topping 100 solar masses, such as Eta Carinae in our own Milky Way Galaxy, are expected to lose their entire hydrogen envelopes prior to their ultimate explosions as supernovae.

“These observations demonstrate that many details in the evolution and fate of LBVs remain a mystery,”  said Mario Livio, of the Space Telescope Science Institute in Baltimore. “We should continue to keep an eye on Eta Carinae – it may surprise us yet again.”

MOSAIC CAPTIONS: [Top Center] 2005 ground-based image of the supernova; [Bottom Left] 1997 Hubble archival visible-light image of the region of the galaxy where the supernova exploded, with white circle marking the progenitor star; [Bottom Center] Near-infrared light photo of the supernova explosion taken on Nov. 11, 2005, with the Keck telescope, with the blast centered on the position of the progenitor; [Bottom Right] Visible-light Hubble follow-up image taken on September 26, 2007. The progenitor star is gone. Credit: NASA, ESA, and A. Gal-Yam (Weizmann Institute of Science, Israel)

Source: HubbleSite

30 Replies to “Star Exploded Too Early, May Blow Apart Supernova Theory”

  1. Intriguing to be sure… Could open up some very interesting vistas of exploration if it bears out.

  2. Exactly what type of supernova was this? Neither the article nor the Hubble press release mentions what type of SN this was. If this was a Type Ia SN, I’ve long suspected these ‘standard candles’ might not be that “standard’ after all. Certainly this object deserves an intensive follow up. This certainly could have huge implications.

  3. Or was there some outside force or object which it collided with, like a wandering black hole? Was the generation of the star misinterpreted? Was it simply a defect? A lot of answers to work through yet.

  4. Jon Hanford: Exactly what type of supernova was this?

    The article mentions it still had most of its hydrogen envelope so it would have been a type II supernova.

  5. i am just curious as to the 1997 data which is so noisy and the 2007 data which is so good…Both of them seem to be from the same camera…so it cant be an instrumental effect…so why is the data looking so different???

  6. I am a bit confused by this. This galaxy is so far away, and i’m assuming that most images of it are very pixellated like the one in the article. If we know that many stars in our own galaxy are binary, including massive stars, then how can we assume that stars from galaxies that we can barely pick out are single?
    The 1997 image of the progenitor ‘star’ looks to me like a big blog of light, how do astronomers pick out an individual star from this when we have trouble even in our own galaxy?

  7. @ alan: Thanks for the info on 2005gl’s type. After checking the Hubble site a second time I found a version of the paper published in Nature here: http://hubblesite.org/pubinfo/pdf/2009/13/pdf.pdf .Turns out the supernova was indeed a Type IIn and it appears most of the ejecta fell back in the newly formed black hole. If Luminous Blue Variables (LBVs) can indeed be precursors of some types of supernovae, then Eta Carina bears close watching. @ vino The paper mentioned above states that the 2007 image was indeed a longer exposure than the 1997 image.

  8. @ Becky WS In their published paper the authors only point out that the system ‘may’ have once been a binary star that ended up merging before going supernova. The star may have also been a LBV with a white dwarf, neutron star or black hole companion, but this is still just speculation. Heck, SN 1987a was also an LBV before detonation, and its’ binary nature is still being debated. And for Eta Carina, evidence of its’ binarity is now a hot topic in astrophysics. BTW, the authors also applied rigorous research to address the problem of this event being caused by a much fainter, subluminous progenitor that by chance lies in this region of NGC 266. To sum up, some but not all supernovae may be binaries. More research is clearly needed.

  9. Could it be…maybe…gosh no it can’t be…or can it?…that there was some external force that caused this supernova to occur billions of years before its time – like maybe the tiny temperature fluctuation of an infinitesmal bit of rock within a hundred million miles or so somehow caused the star to heat up just enough to explode.

    We’d better coronate algore and hansen to save us before it happens here too. I’m sure they could come up with a computer model that would prove it’s inevitable if we don’t.

  10. @ Papa Smurf:

    I don’t think so. The SN was really far away and thus only few neutrinos should have hit us, I guess too few to be detected in the “noise” of the sun’s neutrinos.

    Low-massive stars are very well understood. There is much work to be done concerning high-massive stars. Very interesting, indeed.

  11. Nah… thats simply stellar engeeniring (damn, who do I spell this?) from a high advanced species. They need some extra energy… so… bang!!!!

    Hmm… it can give a good novel!!! 🙂

  12. Not likely!
    Any advanced species capable of harnessing the energy created by the death of a star, would have no need to! in terms of energy. other reasons maybe! but as far as useable energy goes a species that advanced would have already figured out monatomics a free energy! Now I dont know much about black holes but if they gobble up energy as well as matter. then you could look at a black hole as a kind of 4 dimensional gift wrapped preserve of viable energy!!!!!! a refueling station in space if you will !!!!! I would’nt think o hard on it though .The human race won’t advance past what we are today! maybe if we would have setteled are differences a 1000 years ago. we would be 1 race now and far more advanced then we can fathum.

  13. OH NO! Darth has developed a death star that can knock out a solar mass!

    One event does not end a theory; but given that the expected sequence leading up to these events has always been theory and never been observed means it is past time to rethink the science: So what has the observed polarity of supernova events been trying to tell us for decades?

  14. Someone might have discovered the Omega Particle:

    Omega Particle: Omega particle is very unstable and even the destruction of one particle can blow up subspace for many light years around it, rendering faster-than-light travel impossible.

    LOL

  15. Maybe the electric current powering the star got a bit too strong, the circuit overloads and boom!! Supernova.

  16. @ Dr. Flimmer.

    Thanks.

    I once read that SN 1987a had become opaque to neutrinos briefly during it’s collapse. Considering that the 1/2 value thickness for neutrinos is over a light year thick that is some really dense stuff.

    When I read that, I had the same thought that I had standing at the edge of Sedan crater after having just visited Meteor Crater in Arizona. For some reason the crew at the NTS was really proud of their big hole.

    As Darth Vader said, “Don’t be too proud of your technological terrors…”

  17. Depending on what elements we have detected from the debris and what proportions they are in, it could have been triggered by pair instability, though if that is the case it would have had to have been heavier than it appeared. The conditions in such an event would tend to result in a large amount of non hydrogen/helium elements being tossed out.

    Just tossing out an idea. Most people i know don’t even know about that mechanism for stellar death which is not surprising since it doesn’t happen often at all (I think there’s only one suspected so far).

  18. Lo and behold, 2 more disappearing stars mentioned in a previous story ( SN 1993J & SN 2003gd in “Disappearing Stars Confirm Supernova Origins” UT 3-19-09 by Anne Minard ) finally released a paper on arXiv.org here: http://arxiv.org/PS_cache/arxiv/pdf/0903/0903.3772v1.pdf . This flurry of pre-supernova observations will surely be carefully scrutinized by observers and theorists alike. Now theorists have hard data that must be accounted for in stellar evolutionary models.

  19. Also noted, both SN 1993J and SN 2003gd were Type II supernovae, as was SN 2005gl. Just food for thought.

  20. @ Dave: Thanks for the heads up concerning the Pair-instability Supernova mechanism ( supernova astronomy is not my specialty ). This SN (2005gl) looks to be massive enough for this to be a real possibility (see my link above for SN 2005gl for a look at the light curve & progenitor mass estimate) A good primer on Pair-instability Supernova (with reference to the candidate 2006gy) can be found here: http://en.wikipedia.org/wiki/Pair-instability_supernova .

  21. From reading the two papers mentioned in the links above, it is noted that 1) SN1993J in M 81 & sn2003gd in M 74 were both moderate mass M & K red supergiants, metal rich (Type IIn & IIP, respectively) but too small for Pair-instability mechanisms to come into play (It should also be noted that SN 1993J has a still visible blue giant companion!). 2) SN 2005gl and SN 1987A (as well as SN2006gy) are a different breed of SN. All three appear to have been LBVs just prior to detonation, were very massive and metal poor, just the prerequisites for Pair-instability to proceed.

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