AstroAlert: Type Ia supernova in M101!

By Phil Plait | August 25, 2011 1:30 pm

Attention all astronomers! There is a new Type Ia supernova that has been seen in the nearby spiral galaxy M101, and it’s very young — currently only about a day old! This is very exciting news; getting as much data on this event as possible is critical.

Most likely professional astronomers are already aware of the supernova, since observations have already been taken by Swift (no X-rays have yet been seen, but it’s early yet) and Hubble observations have been scheduled. Still, I would urge amateur astronomers to take careful observations of the galaxy.

[As an aside, I’ll note that this supernova won’t get bright enough to see naked eye and poses no threat at all to us here on Earth. It may be visible in decent-sized telescopes, though, and as you’ll see this may be a very important event in the annals of astronomy.]

[UPDATE: Joseph Brimacombe took a very nice shot of the new supernova using a 20" telescope in New Mexico. Thanks to Surak who left a comment below about this.]

So why is this a big deal?

First of all, a supernova is an exploding star — one of the most violent events in the Universe. There are different kinds of supernovae, but a Type Ia occurs, it’s thought, when a superdense white dwarf — the remnant core of a dead star — siphons material off a companion star. If enough material piles on top of the white dwarf, it can suddenly start to fuse hydrogen into helium. This starts a runaway effect, and the entire star explodes. This supernova can release so much energy it can actually outshine its host galaxy! If you want more details, I’ve written about Type Ia supernovae before: Astronomers spot ticking supernova time bomb and Dwarf merging makes for an explosive combo.

So this kind of supernova is incredibly bright, making them easy to spot over vast distances. These events are very important, because we think that each Type Ia supernova is very similar in the way it explodes, making them useful as benchmarks in gauging distances to very distant galaxies. In fact, it is the study of these explosions that has helped us nail down how fast the Universe is expanding, and also led to the discovery of dark energy. Clearly, the more we know about them, the better.

M101 is a spiral galaxy only about 25 million light years away, making it one of the closest big spirals in the sky. It’s also huge, boasting a trillions stars, ten times the mass of our Milky Way. You can read all about it in an earlier post featuring the image at the top of this article.

Given M101’s close distance, this new supernova will be relatively easy to study. And the best part is that the exploding star was caught young: most of the ones we see are far away, and too faint to be seen until they start to reach their maximum brightness after a few days. Getting data on them early is absolutely critical for understanding them, and it’s the hardest part of all this. I am not exaggerating to say this new supernova could be a linchpin in our understanding of these events.

Interestingly, Hubble took images of this galaxy in 2002, and astronomers dug up the archived images and looked at the spot of the supernova to see if anything was there back then. Nothing shows up in the blue filter, but in the red (shown here) there are two stars very close to the position of the future supernova (the circle is centered on the best measurement of the supernova’s position). From their brightness and color, both of these stars are red giants, stars like the Sun but near the ends of their lives. That would fit with the Type Ia supernova: red giants are so big that if there’s a white dwarf nearby, it could suck up their matter and start the chain of events that led to its doom. Further observations may pin this down. If one of these stars is what fed the supernova, that’s seriously cool; there are only a handful of supernova progenitor stars that have ever been seen*.

All in all, this is pretty much a big deal. The galaxy is close, pretty, a bit odd, and is hosting the nearest Type Ia supernova seen in decades which was caught when it was less than a day old. I’m excited! I know a lot of telescopes will be aimed at the northern skies over the next few days, and I’ll be very interested to find out what they see.

Image credits: Hubble M101 image: NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana), and STScI; Type Ia art: NASA/CXC/M.Weiss; Hubble image: NASA/ESA/Hubble. Tip o’ the dew shield to paulwarren73.

* Technically, if one of the red giants was behind this event, it wasn’t the star that actually exploded — the white dwarf which actually blew up was far, far too faint to be seen here. Still, very cool.

Related posts:

Dwarf merging makes for an explosive combo
The heat of the Pinwheel
Hubble delivers again: M101
The Universe is expanding at 73.8 +/- 2.4 km/sec/megaparsec. So there.

CATEGORIZED UNDER: Astronomy, Pretty pictures, Science

Comments (90)

Links to this Post

  1. AstroAlert: Supernova tipo Ia en la Galaxia M101! [Eng] | August 25, 2011
  2. Nueva Supernova de tipo Ia | Pablo Della Paolera | August 25, 2011
  3. AstroAlert: Type Ia supernova in M101! – Discover Magazine (blog) « Technology « Direct Global Media | August 25, 2011
  4. AstroAlert: Type Ia supernova in M101! « EIU Astro | August 25, 2011
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  15. chill sends this quote from a news release by the Lawrence Berkeley National Laboratory: « Bitter Harvest | August 31, 2011
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  21. Supernovas and Neutrinos « physics4me | September 20, 2011
  1. How far away, guesstimate-wise, do you suppose the dwarf is from its companion star? Haw far away from each are are these types of pairs typically?

  2. Aaron

    So it occurred 25 million years ago today? Let’s declare this “Supernova Day” and all go get drunk!

  3. Zombie

    How does the apparent magnitude of this supernova compare to 1987A? I’m curious if SuperK etc will be able to detect neutrinos from this (it will probably take some time to determine if there was a statistically significant spike compared to normal background radiation though).

  4. X

    “If enough material piles on top of the white dwarf, it can suddenly start to fuse hydrogen into helium”

    Err, I think you mean it starts fusing carbon in the core. Standard white dwarfs are mostly C/O on the inside.

  5. Clearly the supernova caused Tuesday’s earthquake.

  6. Bggeek

    @X, I think he means that the hydrogen captured from the nearby star is what fuses on the surface of the white dwarf. Not the core material.

  7. Scott Hurst

    M101 is roughly a mag 8 galaxy. I’ve been trying to look at lately in a small scope, but light polution has been making it impossible. It’s right where the tip of the handle of the big dipper would be if the handle were straight.

    In the linked announcement “The supernova was discovered on Aug. 24 UT when it was at magnitude 17.2 in g-band” That means “green” if I’m not mistaken (quite possible).

    I don’t know, is that still ramping up at mag 17? It’s got a long way to go to be as bright as the galaxy.

    For comparision, 1987A was a Type II-P a mere 168k ly distant and peak magnitude of 3. That would be easily visible by naked eye but pretty sketchy near any large city.

    All things being equal (but they’re not and I have no idea how Ia compares to II-P), it is about 150 times further away, so should be about 22k times fainter. That is about 11 magnitudes dimmer. Or about mag 14.

    I hope I’ve screwed that up or that a Ia is way brighter or I’ve got no hope to see it.

  8. Travis L

    Keep us posted Phil!

  9. XRBfan

    @#4 X, no Phil is correct. The material streaming in from the companion star is mostly H. This fuses into He on the surface of the white dwarf (WD). The C/O is degenerate material and is not fusing until just before the SN. When enough mass is accreted, the electron degeneracy pressure in the core can no longer support the WD against the gravitational collapse and BOOM. In some systems, the WD tries to save itself and releases mass and energy. This the from the fusion of H to He over a period of time.

  10. andy

    If enough material piles on top of the white dwarf, it can suddenly start to fuse hydrogen into helium. This starts a runaway effect, and the entire star explodes.

    Nope. The case where the accreted hydrogen fuses at the surface is a nova, and the white dwarf typically survives.

    A type Ia supernova is starts as a deflagration flame from the core (powered by carbon fusion) as the star approaches the Chandrasekhar limit.

  11. XRBfan

    Yeah, what andy said. :) See also cataclysmic variable.

  12. Grimbold

    @10- “Nope. The case where the accreted hydrogen fuses at the surface is a nova, and the white dwarf typically survives.”

    It is possible to get stable, continuous burning of accreted hydrogen on the surface of a white dwarf. But the accretion rate needs to be juuuust right and the accreting material needs to be of very low metallicity.

  13. XRBfan

    @12, not likely. Accretion rates are not generally constant and the accretion stream tends to be blobby.

  14. Kelly

    @1 That Neil Guy, If we assume the progenitor was a cataclysmic variable (thought to be the progenitor in the white dwarf + normal star scenario), it is in a very tight binary. Orbital periods are generally about 80 min to 10 hours, meaning they have an orbital separation of about a few solar radii (~10^9 m) or less than 10 microarcsec on the sky.

  15. Keith Bowden

    This is obviously why I have a headache today. :)

  16. Chief

    Of course, secretly everyone is hoping for one that turns night to day for months on end to really jazz up the sky.

  17. Peter Blanch

    I’ve seen models in which the the accreted hydrogen starts to fuse, as in an ordinary nova, but the presure wave from that triggers the fusion of carbon in the core. From there, it’s a runaway deflagration / detonation. So maybe everybody is right…

  18. Kelly

    @13, White dwarfs accreting at just the right rate so that they steadily fuse hydrogen on their surface are a type of cataclysmic variable called super-soft sources. The name comes from the fact that temperature of the white dwarf puts peak of its emission in the soft X-rays, and in softest bands of X-ray satellites like ROSAT. They are the favorite type 1a progenitor in the white dwarf + normal star scenario. They exist and we observe them, although not enough to mach the number of 1as we see!

    If you go below this accretion rate, you get novas, where the accreted hydrogen undergoes periodic, explosive fusion. If you above this rate, you begin to build up a red giant or lose a bunch of mass in winds. All of these different types of nuclear burning white dwarfs could be potential type 1a progenitors.

  19. andy

    Of course, secretly everyone is hoping for one that turns night to day for months on end to really jazz up the sky.

    I kind of hope Betelgeuse at least doesn’t blow up any time soon. For starters it’d ruin the aesthetics of the Orion constellation…

  20. Doug Little

    I wonder if there were any civilizations in the vicinity of the supernova that just got wiped out. I guess we will never know.

  21. Aliandre_D

    So, am I the only Lovecraft geek who saw “Ia” and thought, “Ia! Ia! Cthulthu ftagn!”?

  22. Scott Hurst

    A little more digging, 1987A had an absolute magnitude of -15.5. Type Ia has -19.3.

    It should be brighter 3.8 magnitude brighter intrensicly, and 11 magnitude dimmer for being further away. That gets from mag 3 for 1987A to about mag 10 for this new one.

    I won’t see it. I hope someone comes along and points out I’m doing this wrong.

  23. Swift, my favorite scope wins again! I watched it launch in 2004 :)

    anyway, if there was a dwarf star between the two proposed red giants, what happened to the red giants? Would they be destroyed by the SN? Would that make for an extra big planetary nebula?

  24. Chris

    Actually how sure are we that a type Ia supernova is really from a white dwarf? As far as I know we haven’t seen any confirmed white dwarfs explode. Is this the result of modeling a white dwarf explosion once it passes the Chandrasekhar limit and matching up the observations with theory?

  25. Jim

    Wait, so we see it and an earthquake happens at nearly the same time? Obviously the two are connected. I would say this proves it sent supercharged gravitons our way and disrupted earth’s gravity which in turn caused the earthquake. It’s the only logical explanation.

  26. Cool.

    17. Doug Little Says:
    August 25th, 2011 at 3:02 pm
    I wonder if there were any civilizations in the vicinity of the supernova that just got wiped out. I guess we will never know.


  27. Jim

    Great…an earthquake, a hurricane, and now THIS

  28. XRBfan

    @19 Scott, I get about 10 too. m = 5*log(7.2e6)-5-19.3, in case I need to show my work. :)

    @20 Chris, yes well…never mind that man behind the curtain! :)

  29. Boddhisatva

    A very nice discovery and I hope it adds to our knowledge of the cosmos and all, but I always have to wonder when I hear about supernovas if another sentient race got wiped out?

    We have no idea how likely it is for life to develop on a planet and even less idea of how likely it is for intelligence to appear. There could have been one or more planets too near that blast for its inhabitants to survive.

    Has anyone ever done a survey stars near Earth for this sort of pre-type Ia configuration? Is there a ticking bomb in our neighborhood? How near is too near?

  30. Stormy
  31. So, the white dwarf is next to two red giants, accretes hydrogen from one or both until critical then explodes. The question is this: because of the proximity, does the white dwarf take out the two red giants? First of all, cool! Second of all, you guys take it from here, I’m an idiot.

  32. Sam H

    The sweetest thing is that I saw this very galaxy, my own retinas absorbing the dim waves of photons which were both newborn and 125 times older than humanity itself, at a pristine dark site on a desolate country road almost 100 km south of my city only 25 days ago. As I gazed at the dim, unthinkably distant core of that vast city of stars, even more massive than our own, a dim light that I new was made of the collected light of ten hundred thousand ancient suns surrounding a literal hole in space and time, as I thought of the life, and hopefully the intelligences that almost certainly exist in and amongst the ocean of worlds that populate that faint island universe, and how alien their actions must be to the inhabitants of this lonely star – all the while as I looked, the photons from that massive explosion heralding the end of a seven billion-year life, an event that provides a beacon for all the inhabitants of the universe to learn of its vastness and realize their insignificance – all the while, those photons were travelling toward me, and I could have never known…

    My God… 😮

    “Life’s such a beautiful mistake…”

  33. Relativity

    @22 Jim, don’t forget Steve Jobs on your list. 😉

    What I don’t understand (I am a astronomy neophyte after all) is that if this neutron star (leftover core) sucked up too much material from the red giant neighbor, fused that hydrogen to helium, then went Ka-Bloooey!! to kingdom come?

    But when it was a normal star, the core was already doing that fusing cha-cha and did not go Type 1a. So, why did this time?

    Relatively confused…

  34. Bill

    @ 20 Andy It wouldn’t ruin Orion at all. Just think of the new nebula it creates as a war wound on his shoulder. We’d be the envy of every ancient Greek astronomer to see that.

  35. chris j.

    whoa, we can actually resolve the host star system for a supernova 25 m.l.y. away. that blows my mind.

    Aliandre_D @22:
    yes, you are (and it’s fhtagn).

  36. loud

    @21 Doug Little:
    You mean wiped out 25 million years ago.

  37. Joseph Brimacombe as usual has nabbed a great image of the event:

    He’s measured the magnitude as being 14.9

  38. Wow. That is really close. By my estimate that’s only about a factor of 10 away from being able to detect the neutrinos, although I seem to remember that Ia supernovae don’t produce nearly as many neutrinos as type II. Is that correct? If so, then presumably the distance needed to detect the neutrino signature over the background noise would closer, yes?

  39. John
  40. Jess Tauber

    Actually, since the white dwarf is blowing the whole thing off, one could say that the star is both fusing and refusing hydrogen nearly simultaneously.

  41. John (41): And yet you had time to leave an insulting comment on the blog.

  42. Chris Jeske

    On the one hand there’s the comments section of a Yahoo or CNN News story and its blithering idiocy.

    On the other hand is a place like this that makes my head spin.

    I need to find the middle place somewhere on the interwebs.


  43. LSandman24

    The light left this supernova just as the first deer were evolving on this planet. Mmmmm, venison. We have yet to determine if deer have evolved on any other planet or if the evolution of deer caused the supernova.

    Hey, if humpback whales can answer space probes, why not antler-induced supernovae?

  44. Sam H

    @45 Lascas: Merci bien :)

    FYI, the quote is from this awesome song: the little girl singing it on the outro just melts hearts.

  45. Chief

    I think John (41) was waiting for Betelgeuse to go, anything else is just a waste of time to him.

    How about something closer to home, the collision of two brown dwarfs 1 ly away.

  46. Loopback

    Long ago, in a galaxy far, far away… a star explodes.

    John (41): I care.

  47. @^ Chief : Um .. there are no brown dwarfs or indeed any other stars at all as close as 1 light year away. Nearest star we know of – Proxima Centauri is 4.2 ly distant.

    Nearest brown dwarf – I think unless WISE has discovered a closer one yet – is orbiting Epsilon Indi – and is actually a binary but in no danger of collision.

    Pretty sure that the collision of a brown dwarf duo would NOT lead to a supernova but simply the formation of a new star which given their individual low masses would probably only be a red or at best for high mass L type brown dwarfs maybe an orange dwarf star. (Could the most massive ones get up to forming a yellow dwarf like our Sun? Hmm ..that’d be pushing it I think!) Sure would be interesting and spectacular to observe though.

    We do know that contact binary stars (W Ursae Majoris) will end up merging forming fast-spinning, dramatically star-spotted FK Comae Berenices variables. Other stellar collisions create blue stragglers in globular clusters. :-)

    To form a supernova you need a mass in excess of the Chandrasekar limit of 1.4 solar masses. White dwarfs colliding or aquiring enough matter to push themselves over this limit, high mass red & blue supergiants (and bigger still hypergiants) and Wolf-Rayet stars are what you need for a supernova as I understand it.

  48. See :


    for more info.

    Correction :

    .. contact binary stars (a.k.a. W Ursae Majoris variables) will end up merging ..

    for clarity.

  49. @2. Aaron : “So it occurred 25 million years ago today? Let’s declare this “Supernova Day” and all go get drunk!”

    I second that suggestion and will have a beer or two in its honour later tonight. :-)

    Of course, there are other days related to supernovae that are arguably more significant – the anniversary’s of Tycho’s supernova, Kepler’s one and SN1987 A frex – but then I’m happy for them to be made holidays too! :-)

    @41. John : Who cares?

    Astronomers, the BA, myself and millions of others who find this stuff fascinating and wonderful. If you don’t feel that way yourself, if you’re NOT interested even a little then what the blazes are you doing on this blog? :roll:

    Did you just come for the politics or something? 😉

  50. Sion

    Lets not forget the billions of aliens wiped out by this event.

  51. Randy Owens

    @^Sion: You’re right, better have a beer for them, too.

    “I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened. “

  52. zeke

    @32 Evonne Marietta’s paper in 2000 has shown that red-giant that feeds the white-dwarf to near the Chandrasekar limit can survive the resulting blast. The core of a red giant is tough to dissemble.

    The near the center of the white dwarf, the C/O ignites and burns uncontrollably (but sub-sonically) then transitions to a detonation wave as it moves outward as described by Wheeler. The details of the transition to a detonation wave is a subject of active research and modelling. The debris from deflagration only or detonation only models do not match observations. A mix of the two, deflagration to detonation, is a much better fit. This close, very early look at Type Ia supernova will certainly help.

  53. Kelly


    17. Doug Little Says:
    August 25th, 2011 at 3:02 pm
    I wonder if there were any civilizations in the vicinity of the supernova that just got wiped out. I guess we will never know.


    Ahh, think positive. If there were a civilization there who knows how long they would have known this was coming.

    I think it’s more likely it would be a story of triumph and tragedy then just tragedy.

  54. Steve

    Is “explosion” really the right way to explain what happens when this type of supernova occurs? How does the light curve reaching the Earth reconcile with an explosive (very short duration) event? Is this actually more like a “meltdown” since it generates photons over a longer period?

  55. Captn Tommy

    56 Sion

    Actually, they were the Natives… we are the Aliens :)

    Have a good Day and remember after the flash comes the shock wave. Though after 20 million or so light years in might have disappated a little.

    Hard hats on Mister!

  56. Wzrd1

    No, Phil. You’re not ENTIRELY correct about the supernova posing no danger.
    There is grave danger to every amateur astronomer with even a half decent telescope losing a night’s sleep if the sky is clear! 😉
    Of course, that is a danger that is worthy of being an accepted danger. 😀
    Keep looking up, all!

  57. Matt

    Speaking of the locals… I wonder what the “danger zone” around an event like this is?

  58. Doug Little

    loud @38,

    Doh, Yes that’s what I meant. I wonder what the nebula looks like right now? How long do nebula’s last before they either re-collapse or dissipate? Can they Re-collapse?

  59. Kafernusse

    Buy stock in Celestron, Orion, and Meade…

  60. Robert Berta

    Aliandre_D …your post #22….hmmm.
    If you have the Lovecraft “Cthulhu Live” check out the cover of the book and the photo credit inside the book 😉
    Robert Berta

  61. KC

    @Relativity: The processes are different…in a regular star all the hydrogen & helium has been present for billions of years – in this case hydrogen is being dumped relatively quickly on to the white dwarf (not a neutron star, which is a whole different animal).

    May be this is a poor analogy: the gasoline in your car doesn’t explode when you start it – but if you toss a bucket full of gasoline onto a fire – FOOOM!

  62. First time I seen a star being eat by a black hole :)

  63. anna

    whats the neerest star in ursa major, is it alkaid???

  64. GRBjunky

    If the red giants are not red herrings, the double degenerate model will face serious challenge.

  65. Rick

    This is really cool… If we can pin-down the growth part of the luminosity curve it’ll go a long way to improving/validating the models of these events!

  66. Colin

    What are the chances I’ll ever be able to see this with my Celestron IYA2009 First Scope telescope?

  67. Tangleoak

    The locals that may have once inhabited the worlds that orbited these two Red Giants may have been very old civilizations of up to twice the age of our intelligence. If this was the case they definitely did see it coming and started to migrate to their respective outer planets millions of years before they were in any real danger of cataclysmic extinction. After we learn to colonize and teraform the outer planets and moons then it becomes much more feasible to begin the process of transporting our knowledge base and peoples to other suitable star systems. It’s this basic survival instinct that will ultimately take us to the stars and transform us into what Carl Sagan referred to as class IV or V civilizations that have learned to harness all of the available energy from their galaxies. This is why we should all call about our star systems, how they work as younger healthy systems and how they die as older systems to make way for new star nurseries.

  68. Wzrd1

    I remember seeing a deflagration to detonation model from LANL ages ago. The pressure wave generated by the deflagration increased, pressing inward, as the point where deflagration initiated expanded, surface boundary density differences caused the wave to reflect back “in” toward the center of the mass, until sufficient pressure was generated that the center detonated, with the detonation wave expanding outward.
    While, the model was on high explosive, the overall principle is much the same, the added compression changing a simple deflagration into a detonation source.

    As for those asking about the fate of the two red giants, they’ve both a black eye a piece. Some of their matter was ablated by the shock wave, but most of their mass will remain.
    But, the resultant nebula will have two cone shaped holes in it, resulting from their “shadow” in the shock front.


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