Spotting Betelgeuse

By Phil Plait | January 12, 2010 10:31 am

If you go outside around midnight tonight and look to the south (north for you standing-on-your-head southern hemispherites), it’ll be hard to miss Orion standing tall over the horizon. If you look at the star at the upper left, marking his right arm, you might note that it glows a ruddy orange-red. That star is the famous Betelgeuse, one of the brightest in the night sky.

But your view of it probably isn’t as good as that of some French astronomers who got this awesome shot of Betelgeuse:

betelgeuse_interferometry

Cooool. Literally. Betelegeuse is a red supergiant, a massive star nearing the end of its life; in a few millennia (or a few hundred) it’ll explode as a supernova. But for now it’s a swollen monster, cooler than the Sun, but intrinsically a lot more luminous because, simply, there’s so much of it.

Even with our most powerful telescopes, most normal stars would be an unresolved dot at a distance of 640 light years. But because Betelgeuse is so frakkin’ big, we can resolve using a technique called interferometry. This uses several different telescopes to collect light and adds them together in a way such that extremely small objects — well, apparently small, that is — can be resolved.

At its mind-numbing distance of over 6 quadrillion kilometers (4 quadrillion miles), mighty Betelegeuse is diminished to a mere 0.045 arcseconds across. To give you an idea of how small this is, the full Moon is about 1800 arcseconds across in the sky. An arcsecond is 1/3600th of a degree, and Betelgeuse is a tiny fraction of even that. Hubble’s resolution is about 0.1 arcseconds, so Betelgeuse is unresolved even using that famous ‘scope (though using some fancy tricks some features on the star can be seen using Hubble).

Obviously, interferometry is a powerful method for looking at big stars! Using it, the astronomers were able to see two large, bright features on the surface of Betelgeuse, most likely convection spots, where hot gas is bubbling up from the star’s interior. The bigger of the two spots is about 500 K hotter than the rest of the 3600 K surface, and accounts for about 8.5% of all the light the star emits! The other is smaller and unresolved, and contributes about 5% of the light.

Mind you, the bigger of the two hot spots really is ginormous: it’s bigger than the distance of the Earth from the Sun!

Did I mention Betelegeuse is frakkin’ huge?

Techniques like this reveal a huge amount of information on objects that are otherwise far too small in apparent size to measure. We already knew Betelgeuse is a dynamic star — it changes its brightness over time, for example — but this particular image shows us the scale of the changes on the star’s surface, which can lead to models of how its interior behaves, which in turn will help us understand how supergiant stars live out their lives and eventually explode. At 640 light years away, Betelgeuse can’t hurt us when it goes supernova, but it’ll be an amazing light show… and the more we know about it, the better.

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (59)

  1. George Martin

    Yeah, but what happened to Pharyngula? All I get is a blank page. (9:38 AM PST).

  2. George — Me TOO.

    Phil — At 640 LY away, is there any chance it has already blown up and we don’t know about it yet? Or will there be tell tale signs for months/years/decades.

  3. Pierre

    It just happens that Wikipedia’s featured picture for today is a size
    comparison of stars (and planets). You can find Betelgeuse there.

    http://en.wikipedia.org/wiki/File:Star-sizes.jpg

  4. Dan I.

    I read somewhere that they think Betelgeuse might be shrinking and going into its collapse. How awesome would it be if the thing blew up in our lifetime. They said it would outshine the full moon by a substantial amount.

  5. Justin

    That’s cool! Is Betelgeuse the only star we can resolve?

  6. bmoloney

    So is this an optical interferometry image? That’s pretty cool alright, didn’t realise it had gone past Hubble resolution!

    ….radio interferometry allows us to resolve well below 0.001 arcseconds (perhaps even to ~millionths of an arcsecond), so there’s quite a way to go yet!!

  7. ricardo

    Nope, Justin, there’s also Mira

  8. It defintely is an amazing image, to see a star near its end, and considering that for the last two weeks, I have been observing the Hunter in the Heavens, as it passes over.

  9. Awesome stuff! By the way, is it just me, or is Orion one of the best constellations with all sorts of really cool stuff in it to turn a telescope towards? And if it isn’t IN Orion to observe, it’s pretty close! The winter sky is my favorite for observing (or Summer sky if you are one of those upside down people).

  10. XMark

    I reaaally want to see Betelgeuse going nova during my lifetime. That would be amazing! A giant bright light in the sky for months, lighting up the night sky more than a full moon. And then when it finally died away I could talk to little kids, point to an area in the sky and say “when I was your age there was a star right there”.

  11. rob

    i call dibs on Betelgeuse. it’s mine…all mine!!!

    bwa ha ha.

  12. Nemo

    This makes me wonder, can we get similar or better images of smaller-but-closer stars? Besides Sol, I mean.

  13. iHunger:

    At 640 LY away, is there any chance it has already blown up and we don’t know about it yet?

    Yes. Since it is 640 light years away, we are seeing it as it was 640 years ago. Whenever it does (“did”?) blow up, we won’t know until 640 years after the fact.

  14. @#5 Justin:

    Nope, (for instance) the CHARA interferometric array managed to resolve the surface of the nearby A-type star Altair using similar techniques. See my link. They’ve also done it with a whole bunch of other stars, mostly stars that, like Altair, rotate so rapidly they’re actually puffed out at the equator. They’re not the only telescope doing this sort of thing, either.

  15. Another astronomy story man I thought this site was only for Doctor Who, Randi Worship, antivaxx bashing and politics. I might have to go to another website.

  16. To give an idea of the size of Betelgeuse, if you plunked it down in place of our Sun, it would go out well past the orbit of Jupiter. Big star. Big.

  17. Pericles

    That’s a really cool image of Betelgeuse.

    Along the lines of Nemo’s comment (12. “… can we get similar or better images of smaller-but-closer stars?”), can we use this technique to get similar images of huge stars that are a few thousand light-years away (e.g. Eta Carinae and VY Canis Majoris)?

  18. MuscaDomestica

    Cool surprised there were no Ford Prefect references yet.

  19. Dan I.

    @ 16. Carey

    And what’s really mind boggling is that it’s no where near the biggest star we know of.

    VY Canis Majoris for the win there I think.

  20. amphiox

    re: 1 and 2,
    Something funny is going on at Scienceblogs. A number of the blogs there are turning up blank pages. Last I checked Pharyngula was back up.

    If the big B goes supernova, would it screw up any significant ongoing astronomy projects from the several months of sustained light pollution? (I don’t imagine astronomers to be all that upset, though, in the event)

  21. Simon Richard Clarkstone

    After the video last year, I calculated the density of VY Canis Majoris, and it turned out to be very low. Alas I do not have the result around any more, but the poster who used the phrase “red hot vacuum” was not far off:
    http://blogs.discovermagazine.com/badastronomy/2009/06/12/scale/#comment-191750

  22. reidar

    I was also wondering if these’s any chance it has already gone supernova, that we can get to see it in our lifetime?

  23. T_U_T

    the thing kept shrinking for 16 years. If it continues shrinking, it will go kablam within a few decades at most given the rate its diameter decreases. Or, more exactly, there is a fair chance that it has already exploded at least 600 years ago.

  24. MadScientist

    I want to see a nearby star go “kablooie!” Not fair – I even missed some of the best comets because I happened to be in the wrong hemisphere at the time.

    Even with interferometry it’s quite remarkable to resolve the star as they have done. I’ll have to see what comprises the IOTA set.

  25. Noel

    Just for clarification, when you say, “in a few millennia (or a few hundred)”, do you mean “(or a few hundred millennia)” or “(or a few hundred years)”? (Hoping, like others above, that it’s the latter!)

  26. Sean McCorkle

    Pierre@3:

    I’m quite fond of these two size comparison images myself:

    Rigel, Aldebaran, orbit of Mercury
    http://commons.wikimedia.org/wiki/File:1e10m_comparison_Rigel,_Aldebaran,_and_smaller_-_antialiased_no_transparency.png

    Betelgeuse, R Doradus, Rigel, Aldebaran & the solar system:
    http://commons.wikimedia.org/wiki/File:1e11m_comparison_R_Doradus_and_Betelgeuse,_and_smaller_-_antialiased_no_transparency.png

    I grew up slurping over these kinds of illustrations in astro books that I perpetually checked out of the local library. It just never gets old (although I did).

  27. locke

    @davidlpf Well said! There’s more info on the story at universetoday and the preprint itself is available at http://arxiv.org/PS_cache/arxiv/pdf/0910/0910.4167v2.pdf. It’s written well enough that one doesn’t have to be an expert on IR interferometry to learn a lot (more) from it.

  28. ND

    I’m not sure if I want Betelgeuse to supernova. Then we won’t have Betelgeuse anymore :( Not to mention something will be missing from Orion. Let some other star blow up.

  29. Lars

    I sense an epic role playing game here. “Betelgeuse is about to blow up, and only YOU can stop it!”

    Ok, now, you’ve got a short sword, a piece of flint and you’re in the middle of the forest. What do you do?

  30. Mister Earl

    @Lars:

    Insert the flint into the quantum vacuum initiator and fire it, triggering a quantum metastability event, and thus destroying the entire universe. It’s the only way to be sure.

  31. Messier Tidy Upper

    Awesome picture and amazing to get get it! :-D

    @ those talking about size comparisons – this, from earlier on the BA blog, is a great one & my personal fave :

    http://blogs.discovermagazine.com/badastronomy/2009/06/12/scale/

    @ ND : Let some other star blow up.

    Like y’know one of the potentially dangerous ones? Such as T Pyxidis or Wolf Rayet 104 or what is apparently the record holder for most dangerous star of all – HR 8210?

    See :

    http://blogs.discovermagazine.com/badastronomy/2010/01/07/no-a-nearby-supernova-wont-wipe-us-out/

    http://blogs.discovermagazine.com/badastronomy/2008/03/03/wr-104-a-nearby-gamma-ray-burst/

    &

    http://jumk.de/astronomie/special-stars/hr-8210.shtml )

    (Hope that’s not too many links ..)

    Personally I’m hoping to see Eta Carinae go hypernova – but without a deadly Gamma Ray Burst in our direction. ;-)

    I did read somewhere in some particular book by an author whose name escapes me something about a disaster scenario where Eta Carinae blew up and caused major catastropic issues .. What was it now something about “skies” and “death” by a Dr P-something!? ;-)

    I do recall hearing something once that Betelgeux is so large – and its outer layers so red-hot vacuum like that it actually has another star orbiting inside it! Is that true? Anyone got more info on that?

  32. Gary Ansorge

    30. Mister Earl

    “quantum vacuum initiator”,,,Man, that would really suck.

    “triggering a quantum metastability event, and thus destroying the entire universe.”

    Oh sure, like nobody has ever done THAT before.

    How to stop a super nova:
    1) Take one medium size black hole.
    2) Place in close orbit of the incipient super nova.
    3) Wait until enough mass has been removed to reduce the burgeoning super nova to a more manageable size.
    4)(and this is VERY important) Remove black hole.

    See: Simple, when you know how.

    GAry 7

  33. Plutonium being from Pluto

    One greta source of info. for Betelgeuse and just about every other star in the sky is Kaler’s stars website see : http://stars.astro.illinois.edu/sow/betelgeuse.html

    Betelgeuse has been shrinking lately & been very interesting to follow, I saw it as extremely bright not too long ago and perhaps got a bit carried away – see :

    http://www.bautforum.com/space-astronomy-questions-answers/93070-betelguex-much-brighter-than-usual-tonight-maybe.html

    (Yes, I’m also known as StevoR – my only tag on the BAUT forum.)

    But it is one of the most interesting stars to follow.

    I’m wondering if Betelgeux keeps shrinking it is presumably getting hotter and changing – does this affect its spectral type? It is (was?) currently listed as an M1 Ia red supergiant but has or could its shrinking and changing turn it into anotherspectral type eg. an M0 or K9 supergiant instead?

    Anyone know?

  34. StevoR

    @ 32. Gary Ansorge Says:

    … How to stop a super nova:
    1) Take one medium size black hole.
    2) Place in close orbit of the incipient super nova.
    3) Wait until enough mass has been removed to reduce the burgeoning super nova to a more manageable size.
    4) (and this is VERY important) Remove black hole.

    See: Simple, when you know how. – GAry 7

    Now you have to give us your method for removing black holes … ;-)

    How about this alternative & even simpler method :

    1. Accelerate fairly massive object (or series of objects) to near light speed then slam it (them) into the incipient pre-supernova star thus ejecting a quantity of mass and reducing mass to the levels where the star will just become the usual planetary nebula & white dwarf .

    2. (optional) Repeat if necessary until job done. ;-)

    Works best on red supergiants with their extended tenous outer layers.

    Can you (theoretically) shatter a white dwarf star with its immense density without triggering a supernova via the pressure (shock) wave I wonder?

  35. Astroquoter

    I do recall hearing something once that Betelgeux is so large – and its outer layers so red-hot vacuum like that it actually has another star orbiting inside it! Is that true? Anyone got more info on that?

    “A star inside a star. A 1986 study by three Harvard-Smithsonian astronomers gave evidence for a companion star orbiting the famous red giant [sic - its actually a supergiant.] Betelgeuse … Their data suggest that this close companion is in an elliptical orbit that dips inside the red-glowing, outermost atmosphere of Betelgeuse. In one interpretation … the companion star could be a blue-white companion of a few solar masses. Such a system could form when the red giant [sic] expands and engulfs part of the orbit of the second star: The system would last only a short time, astronomically speaking, since drag forces will cause the second star eventually to plunge far into the giant [sic] and to merge with it.

    Source : Page 36, ‘Cycles of Fire: Stars, Galaxies and the Wonder of Deep Space’, William K. Hartmann & Ron Miller, Workman publishing, 1987.

    No other source seems to mention this companion or at least not that I can find or remember.

    Does anyone know if this study was refuted or confirmed anywhere and whether this “star within a star” really exists?

  36. db

    must be the result of runaway global warming

  37. anon

    Wikipedia says (citing an EarthSky podcast) that when Betelgeuse goes kaboom it will be brighter than the Moon in Earth’s sky.

    However, it will still be a point source, right?
    I’m trying to imagine what this’ll look like.

  38. Radwaste

    Phil, how is it that the bright areas shown on the surface of Betelgeuse are not artifacts of the imaging process? These areas would seem not to be the only bright patches – there would be others not facing us.

    And do you have the period of rotation, by which the bright masses can be resolved?

  39. DigitalAxis

    @35 Astroquoter

    I see no mention…

    I took a quick look through the SIMBAD database entry for Betelgeuse, and there hasn’t been anything definite published about a companion in the last 20 years. It DOES have ADS (Aitken Double Star, from the 1930s) and CCDM (Catalog of Doubles and Multiples) designations, but those may be historical and refuted. There are plenty of entries in there about the winds from, dust around, changing size (Charlie Towne’s work), changing shape, and sunspots on Betelgeuse. That, combined with the sheer brightness of Betelgeuse, makes me wonder HOW anyone could find a companion to a star that’s basically a big messy blob of cool gas with no definite edge, and tons of detritus spewed out around it.

    On the other hand, the enveloping binary scenario is one I’ve heard of before. It’s possible, and thought to be the way you get really tight white dwarf pairs; the star that gets enveloped spirals in slowly, leaving it much much closer to the remnant of the other star by the time the outer layers poof off the star.

  40. Cool. Unfortunately I probably couldn’t see it because of all the damn trees around my house.

  41. Haymaker

    Thanks Phil for posting about this star. I have been wondering for the past month or so, and tonight even, why that star on Orion’s shoulder was so reddish/orange and bright. Now I know!

  42. Lars

    anon said: “However, it will still be a point source, right?”

    If that is the case, I’m wondering if it can cause (naked) eye damage.

  43. MarkW

    In case anyone is wondering, there are sixty arcthirds in an arcsecond.

    So Betelgeuse has an apparent diameter of just under 3 arcthirds.

    Can I add my vote to the “will Betelgeuse please go kablooie in my lifetime” petition?

  44. Pi-needles

    @ ^ 43. Mark W.

    Can I add my vote to the “will Betelgeuse please go kablooie in my lifetime” petition?

    Sure you can … but how do you expect to get that petition to the star in time* & why do you think Betelgeuse will do as you ask? ;-)

    ______________________________

    * 640 years to get there and another 640 back travelling at the speed of photons (a.k.a. ‘c’ / “lightspeed”) for a total of 12,800 years plus the time it takes for Betelgeuse to consider your petition and decide to reply …or not. How long do you plan on living for? ;-)

  45. Magnum

    “Click to exponentiate” hey? That will just reverse the logarithm process.

  46. Magnum

    oops wrong thread :oops:

  47. Shawn

    Yay! I learned something today. If you’d asked me yesterday, I’d have told you that we could not resolve any stars to any more than a single pixel. I am embarrassed by the gaps in my knowledge sometimes.

  48. Jamie

    I hope Ford has his towel at the ready……

  49. bouch

    Great timing on this post, Phil. Just last night I was looking up at Orion while walking my dog at 10PM on a 10 deg F, moonless night, looking up at the stars as I usually do. I couldn’t believe how red Betelgeuse appeared, and I was wondering if we had ever resolved the disk of a star, or if they were always “point” light sources. Bingo, this AM you answered my question. Its like you’re psychic, or something ;)

    Of course, I was also wondering if my cheap 4.5″ newtonian ‘scope would pick up the Orion Nebula on a night like that…

  50. Petrolonfire

    & why do you think Betelgeuse will do as you ask?

    Because I’ve said his name three times? ;-)

  51. Gary Ansorge

    34. StevoR

    To move black holes around:
    1) Inject a LARGE number of electrons into the BH(charge is conserved, even for a BH).
    1a) You will then have a large number of protons from your electron source
    2) Accelerate the proton source and the negatively charged BH will follow meekly along.

    On the other hand, to weaponize a super nova, (ie, to explode it on demand), build a large(sic) proton accelerator, inject 800 Mev protons into a deuterium/tritium target to create negative muons. Accelerate these to about 99.999999 % light speed and impact the target star. Negative muons facilitate fusion reactions so, if we hit the star with about 100 Giga Tonnes of negative muons, it should go nicely blowie uppie and wipe out our competitors.

    See: easy when you know how.

    GAry 7

  52. Mike

    oh
    sweet
    merciful
    crap

    O_O

  53. mike burkhart

    I have seen this star thro my teleascope in fact I find Orion to be the most interesting constelation it has some thing for every one the only problem is it only showes up in the winter and I have to freze to see it

  54. WJM

    Can I add my vote to the “will Betelgeuse please go kablooie in my lifetime” petition?

    Start a Facebook group!

  55. StevoR

    @ 51. Gary Ansorge :

    Okay. Thanks. :-)

  56. Charlie in Dayton

    “…If you look at the star at the upper left, marking his right arm…”

    Hmmm. Way back when, I remember being taught that we’re looking at The Hunter’s back, not his front. For me, Betelgeuse will always mark his LEFT side.

  57. astroquoter

    @ 39. DigitalAxis Says:

    @35 Astroquoter: I see no mention… I took a quick look through the SIMBAD database entry for Betelgeuse, and there hasn’t been anything definite published about a companion in the last 20 years. It DOES have ADS (Aitken Double Star, from the 1930s) and CCDM (Catalog of Doubles and Multiples) designations, but those may be historical and refuted. There are plenty of entries in there about the winds from, dust around, changing size (Charlie Towne’s work), changing shape, and sunspots on Betelgeuse. That, combined with the sheer brightness of Betelgeuse, makes me wonder HOW anyone could find a companion to a star that’s basically a big messy blob of cool gas with no definite edge, and tons of detritus spewed out around it.

    On the other hand, the enveloping binary scenario is one I’ve heard of before. It’s possible, and thought to be the way you get really tight white dwarf pairs; the star that gets enveloped spirals in slowly, leaving it much much closer to the remnant of the other star by the time the outer layers poof off the star.

    Thanks for that. :-)

    Belated but no less sincere for that – hope you get to see this .

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