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Space Science

Three Largest Stars Identified 354

Posted by timothy from the larry-curly-and-moe dept.
mOoZik writes "BBC News is reporting that astronomers have identified the three biggest stars known to science, having diameters of more than 1.5 billion km. If they were located in the same place as our own Sun - at the centre of the Solar System - the stars would stretch out further than the orbit of Jupiter!"
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Three Largest Stars Identified More

Three Largest Stars Identified

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  • The three widest stars? (Score:4, Funny)

    by gbulmash ( 688770 ) * <semi_famousNO@SPAMyahoo.com> on Wednesday January 12, 2005 @01:30AM (#11331924) Homepage Journal
    The three largest stars with huge diameters? That's easy... Louie Anderson, Bruce Bruce [bruce-bruce.com], and Roseanne.

    Thanks folks, I'll be here all week. Try the veal.

    - Greg

  • just wondering (Score:3, Interesting)

    by adamruck ( 638131 ) on Wednesday January 12, 2005 @01:30AM (#11331926)
    Why wouldn't these huge starts turn into black holes?

    • Re:just wondering (Score:3, Informative)

      by roseblood ( 631824 )
      Large dosen't mean heavy. LARGE RED stars are going to be very thin, not much density. All of their material will be spread out over quite a large area. A LARGE BLUE star on the other hand, would be quite dense (and short lived...they burn their fuel much faster and die in billiant novas, or if they are TOO heavy, as blackholes.)

      • Re:just wondering (Score:2, Insightful)

        by Anonymous Coward
        And the Green and Yellow stars have the best chance of finding inhabitable planets. Unless of course you are the Silicoids, in which case you can colonize anywhere.

        • Re:just wondering (Score:4, Interesting)

          by techno-vampire ( 666512 ) on Wednesday January 12, 2005 @02:14AM (#11332212) Homepage
          Alas, there are no green stars. Even if their temperature is such that their radiation peaks there, green has such a narrow band of frequencies that either yellow or blue will always predominate.
          • I've been wondering why there are no green stars for like years. What a bummer, I think that'd be the coolest star.

            Damm you Roy. G. Biv. for not fulfilling my dreams.

            • Re:just wondering (Score:3, Interesting)

              by LuxFX ( 220822 )
              ditto! I have always been curious and dissappointed about the lack of pretty emerald stars.

              fortunately, since moving to the midwest (Kansas City) and seeing the sun set over flat land instead of the mountains where I used to live, I have now seen sunsets with discernable green bands in them. That was my other hope for green.

              Now, if I can just witness a green flash [sdsu.edu] sometime....
          • When I was soldering my leads to the stereo using a propane torch, the copper turned the flame green.
            Want a nice color change in the hearth?
            Put a copper tube drilled with holes and stuffed with rubber hose into the fire.

            I imagine there might be conditions similar in not so common sequences of stars; perhaps containing the right recipe of elements?

            No doubt some stellar race has already toyed with the idea. :->

            So maybe there would be purple plants under a Green Star?

      • Re:just wondering (Score:2, Interesting)

        by Phil Urich ( 841393 )
        ah, apparently you beat me to it. That's pretty much the point; speaking of, that's why our sun won't be going supernova, right? My knowledge is a bit far in the past, now, but I remember learning at some point that the eventual fate that our Sun will endure, ie. swelling out into a red giant or something of that like, then shrinking down and simmering out its final cold years as a white dwarf, is entirely related to exactly that: it's a medium density star, thus it will last a rather average time, and en
      • Can a star really be that thin? Doesn't its own gravity dictate a minimum density to maintain that volume?

    • Re:just wondering (Score:4, Informative)

      by albn ( 835144 ) on Wednesday January 12, 2005 @01:35AM (#11331984) Journal

      Why wouldn't these huge starts turn into black holes? This URL may help you [slashdot.org]

      According to the web site: A star of 15 solar masses exhausts its hydrogen in about one-thousandth the lifetime of our sun. It proceeds through the red giant [slashdot.org] phase, but when it reaches the triple-alpha process [slashdot.org] of nuclear fusion [slashdot.org], it continues to burn for a time and expands to an even larger volume. The much brighter, but still reddened star is called a red supergiant. Betelgeuse [slashdot.org], at the shoulder of Orion, is the best-known example. Absolute luminosities may reach -10 magnitude [slashdot.org] compared to +5 for our sun.

      Some of these supergiants are unstable and form the very important Cepheid variables. In their final stages, supergiants may explode into supernovae [slashdot.org]. The collapse of these massive stars may produce a neutron star [slashdot.org] or a black hole [slashdot.org].

    • Re:just wondering (Score:3, Informative)

      by tm2b ( 42473 )
      Light pressure and the heat of fusion.

      Stars don't become black holes until they burn up their fuel, collapsing (and perhaps exploding, perhaps even multiple times) in on themselves until they are much more dense than any visible stars. Then, assuming they they haven't blown off so much of their mass that they no longer have enough mass and will instead become a dwarf or a neutron star, they can collapse to become a black hole.

      Link: HOW BLACK HOLES ARE FORMED [geocities.com]

      • Re:just wondering (Score:4, Informative)

        by coyote-san ( 38515 ) on Wednesday January 12, 2005 @12:20PM (#11336854)
        Stars don't become black holes until they burn up their fuel, collapsing (and perhaps exploding, perhaps even multiple times) in on themselves until they are much more dense than any visible stars.

        You might want to check university pages, not just some guy's geocities page.

        Stars collapse once the core has exhausted its available fuel. This is only a minute fraction of the star's total mass, but it's critical. When the core goes dark the rest of the star falls on it.

        According to an article in Discover magazine a few years ago, parts of the star will fall towards the center with a speed as high as a third of the speed of light! This causes enormous pressure, during the "big crunch" the density of the star may be 5-6 higher than the density of a neutron star. IIRC the massive neutrino flux is produced at this time. BTW this "core" is substantially far larger than the core mentioned earlier.

        Matter can't be compressed this hard for long and the core "bounces" back. That is what flings the outer layers of the star into space. But force goes both ways - what throws stellar masses into space also increases the pressure on the remaining core. If the density gets too high a black hole is created and it quickly consumes the core, but the outer layers have already been ejected. Otherwise the core eventually bounces back entirely and you have a neutron star. A neutron star is a core of degenerate matter covered by a layer of normal matter.

        You do not get cycles of explosions.

        (I seem to recall hearing about flares on neutron stars after enough normal mass has fallen to trigger fusion, but those flares are fall smaller than supernovas.)

    • Shh... Don't give them any ideas.

    • More info for the non-physics folk... (Score:5, Informative)

      by TiggertheMad ( 556308 ) on Wednesday January 12, 2005 @02:39AM (#11332336) Journal
      Several other posts have danced around the question a little bit, without answering it directly. It's a good question.

      While these stars are big, filling a large volume of space, the article doesn't mention their mass. This is the ultimate determinant of what becomes a black hole and what doesn't.

      Stars have gravity trying to pull everything into the center off it's mass. In physics pressure is basically equal to temapture, so as all the mass is squezed together, it heats up and begins nuclear fission. This creates a lot of heat, and the star's mass tries to expand. Gravity and pressure find a happy meidum and that is how the star ends up a particular size.

      As the star burns it's fuel, it has to get hotter or it will stop 'burning', due to the way nuclear fusion works. Eventually it will burn up its fuel and prssure will not balance gravity, and the whole star will collapse. If it is really heavy, say several times the mass of the sun, it will probably collapse into a black hole. If it is slightly heavier than our sun, it might end up as a very dense neutron star. Otherwise, it will end up as a white dwarf, a small star that is somewhat like a ember left over after a campfire. If a star is really massive it can also explode in a supernova to lose some weight and avoid becomming a black whole.

      As I mentioned, the article doesn't say what the mass of the star is, but it's probably a safe bet that is above the black hole limit. When it finishes burining its fuel, it will likely go supernova and/or become a black hole.
      • You're wrong in two points:
        a) Turning into a black hole is determined by
        mass/radius ratio. You could even turn out sun
        into a black hole by "somehow" ( :-) ) pushing
        its radius below the Schwarzschild radius.
        b) "it heats up and begins nuclear fission."
        -> You mean "fusion", as fusion needs heated-up
        gas (plasma) to start. Fission is what happens
        in nuclear power plants ;-)
      • Good post! we need more posts like that to explain science in laymans terms.

        Here is another question: let's say that we have a star that is 50% hollow at its center, i.e. there is an empty sphere around its center with its radius being at 50% of the radius of the star.

        Would the star still collapse towards its center?

    • Re:just wondering (Score:5, Insightful)

      by physicsphairy ( 720718 ) on Wednesday January 12, 2005 @02:48AM (#11332370)
      This is a bit reverse logic, but the reason they don't collapse is because they're still burning.

      You can think of the fusion reaction in a sun as it's 'defense' against collapse. The force driving the future collapse, gravity, is what's sustaining the fusion reaction, which creates internal photonic pressure, which in turn pushes the mass of the star outward, counteracting the force of gravity.

      The reason these stars are so large is in fact directly related to the photonic pressure produced by this reaction. If the gases are very hot it prevents the gas from codensing, i.e., you need a lot of it (a big star) to combat gravity. Once these go supernovae and leave clouds of elements that burn at a lower temperature, smaller stars will be able to form.

    • My understanding is that while these stars are certainly more massive and probably just as dense (if not denser, contrary to what some posters have speculated) than our sun they are much, much hotter. A star can be thought of as a dynamic equilibrium between the force of gravity pulling the material together and the pressure produced by the heat of fusion pushing it apart. Therefore, the bigger a star is, the hotter it must be to equilibriate. This happens naturally, since the kinetics of the fusion reac

      • Not very dense (Score:3, Insightful)

        by hpa ( 7948 )
        Red supergiants may be large, but their density have been described by e.g. Larry Niven as "red-hot vacuum." At least their outer layers are very tenuous at best. Given that the masses are typically only a few orders of magnitude more than the Sun, at most, but that their volumes are enormously much bigger, there can't be that

        This means (surface) gravity is low and they can get by with less hydrostatic pressure to maintain their bulk.

        The *core* is typically very dense, much denser than the Sun. Higher

      • Re:just wondering (Score:3, Informative)

        by jnik ( 1733 )
        > certainly more massive
        Correct.

        > probably just as dense (if not denser
        Incorrect, both in the sense of mean density and in the sense of the density of most of the star.

        > they are much, much hotter
        Incorrect.

        > the bigger a star is, the hotter it must be to
        > equilibriate
        The more massive a star is. Not bigger. The discussion is big in terms in volume. And it's only hotter while it's on the main sequence/during the hydrogen burning phase.

        > contrary to what you might expect, the bigger a
        >
  • The mass of these stars must be outrageous. Could it be possible that they are already black holes that we are able to see only because we are already within the event horizon of the stars' gravitational pulls?
    • You know, large dosen't mean heavy. A Peacock feather is alot larger than my wedding ring. My wedding ring is (slightly) heavier though.

    • Re:Visible black holes? (Score:3, Informative)

      by mOoZik ( 698544 )
      It seems they were able to measure temperature and luminance, thus making them red [super]giants.

    • No.

      No, it couldn't.
    • no. The mass of the stars is big, but they are very far away.

      Consider:

      density of sun = ~1400 kg/m^3

      let us assume these stars have the same density (they don't, it will be lower, but that is ok for our purposes here)
      diameter 1.5 billion km = 1.5E12 m

      volume (assume a perfect sphere) = 4/3 pi r^3 ~ 1.8E36 cubic metres
      giving a mass of 2.5E39Kg (about 1 billion times that of the sun)

      the gravitational field strength on an object obeys an inverse square relationship
      F=GM/r^2
      The nearest of these stars is 5200 l

  • I'd like to announce the official... (Score:5, Funny)

    by The Ultimate Fartkno ( 756456 ) on Wednesday January 12, 2005 @01:34AM (#11331964)
    ..."Name Three Fat Women In Entertainment" thread right here. Skill points will be deducted for all mentions of Delta Burke, Oprah, and Anna Nicole Smith. You have thirty seconds from the time you read the headline and pounced on the "reply" button.

    Go.

  • I feel really insignificant now. Not even a *large* electron do we live upon... it's really tiny!

  • My only wish (Score:3, Funny)

    by nihilogos ( 87025 ) on Wednesday January 12, 2005 @01:36AM (#11331987)
    Is that at least one giant goes supernova in my lifetime. I don't think that's too much to ask
    • You might be in luck. I hear the Vogons have got a contract for another Interstellar Overpass...

    • Re:My only wish (Score:3, Funny)

      by daeg ( 828071 )
      Dear nihilogos: We're sorry, but all intelligent designers are currently assisting other beings. Your request will be tended to in the the order that was receieved. The current wait time is: /pause/ 3 billion years. Please hold.

    • Re:My only wish (Score:3, Informative)

      by NormalVisual ( 565491 )
      Already happened, back in March of 1987 in the Large Magellanic Cloud in the Southern Hemisphere. Sure, it was 100K light years away, but it's still pretty substantial.
    • I don't supposed Supernova 1987a don't count?
      • I don't supposed Supernova 1987a don't count?

        No. Must have a magnitude of at least -5. Or is that at most -5? Something like Supernova 1006 would be good.
    • Well, even if it does happen, you won't know about it until 1 million years later.
      • Remember, we're limiting the question only to the milky way. The Milky Way galaxy is basically a sphere (diameter of 50,000? light years) surrounded by a disc with diameter of 100,000 light years. The earth is about 1/2 of the distance from the outer edge to the core. That means that the most distant part (from earth) is the other edge of the disc. This means it would take you 3/4 * 100,000 = 75,000 years to see the most distant suprnovas.
    • That'll just bring down the MPAA and their legion of lawyers around again and the suprnova will have to shut down.
    • I wasn't born until October of 1987, so I missed out on SN 1987a.

      But there is always Eta Carinae to hope for.
    • ...my goal is to blow up one giant in my lifetime. Right after I finish this time machine, now where is that damn flux capacitator again...
    • Astrophysicists used to think that a supernova occured once in the Milky Way (on average) every 100-300 years, but there was some work done in the early 90s that indicated it was more like once every 30 years or so.
    • Carefull what you wish, one a little to close give the whole planet a <I>very</I> bad sunburn.
      Of course if it happens in our lifetime we won't have to deal with*, and hopefully those that do will get the dysonsphere's force shields up soon enough.

      * Unless it's REALLY close, in witch case we still won't have to deal with, we won't even know it. just a bright flash and it's all over.

      Mycroft

    • Stars go supernova all the time. I saw a documentary with one person who has made it his hobby to observe them and does it with just a normal telescope.

      Aparently he became quite skilled at it and was finding quite a few each year.

      The reason we don't see them is they are too far away
    • A supernova from a star like those would wipe out the region of space around it and create an immense black hole. Possibly wiping out alien civilizations and lifeforms in systems distant from it.

  • Betelguese! Betelguese! Betelguese! (Score:3, Interesting)

    by Ralph Spoilsport ( 673134 ) on Wednesday January 12, 2005 @01:37AM (#11331998) Journal
    they had a picture of Betelguese! there, but only the vaguest idea as to when it's supposed to blow.

    Anyone heard ahything that way?

    I've heard anything from tomorrow afternoon to 2 milion years. I've heard it's been getting increasingly variable since 1940.

    If it goes supernova (and it's WAY big enough) what would be the results here? Genetic disorders? Extinction? Has anyone done the math on this?

    RS

    • No worry -- the world will not end (Score:5, Informative)

      by helioquake ( 841463 ) on Wednesday January 12, 2005 @02:03AM (#11332156) Journal
      Don't worry about it. These giants are big, but not necessarily massive enough to go supernova at the end of their lives.

      Besides, hypothetically, even if it were to explode like a supernova, it won't affect us much. Here is the number:

      d = distance to the closest giant (5200light-yr)
      E = total energy arising from supernova (1e51erg or something like that)

      The energy receied at the Earth is

      E / (4 *pi *d*d).

      Now compare this number with the energy we receive every second from the Sun:

      E_sun / (4 * pi * r*r)

      where r is the distance between the Earth and the Sun (1.5e13 cm). You do the math, then the ratio of these two quantities comes out to be:

      [E/(4*pi*d*d)] / [E_sun/(4*pi*r*r)] ~ 2.4

      So all we get from this supernova is about 2 seconds worth of energy received from the Sun. And I'll tell you that the actual energy received from the supernova is much, much smaller.
    • Well, you can Google for more details, but the last time a star went supernova close enough, it caused the biggest mass extinction in history.

      The short story goes like this: The pulse of gamma radiation completely wiped out the ozone layer, and replaced it by an opaque layer of nitrous oxide. That is, opaque but not to UV. So most living being on the surface _and_ in shallow water got deep fried by the Sun's UV. (UV goes a long way through water.) Additionally, that brown shell around the atmosphere caused

  • Non Red Giants (Score:3, Interesting)

    by bobobobo ( 539853 ) on Wednesday January 12, 2005 @01:40AM (#11332031)
    It would be interesting to find the largest non-red giant stars. As once our own sun turns into a red giant, it's radius is supposed to extend out past Jupiter as well.

  • Saturn too... (Score:2, Informative)

    by tigersaw ( 665217 )
    This puppy would actually eclipse Saturn, whose mean orbit is about 1.43 billion km.

  • Imagine a cluster of stars... (Score:2, Funny)

    by Anonymous Coward
    ... and the astronomers name it the Beowulf Cluster.

  • Largest?

    Biggest?

    Are we talking about diameter, magnitude or mass?

    My guess, from reading the article, is diameter. I'd be interested in the highest mass stars, since there is an inverse relationship between mass and lifetime. What's the shortest time that a star can exist for?

  • Largest? (Score:3, Interesting)

    by marevan ( 846115 ) on Wednesday January 12, 2005 @02:31AM (#11332302)
    Correct me if I'm wrong, but isn't red giants dencity pretty low? So when a star transforms into a red giant, it's bound to get much larger. So wouldn't it be cooler to find actually non-dying star of this magnitude?

    (Well definetly not cooler)

    • Re:Largest? (Score:2, Funny)

      by RajivSLK ( 398494 )
      So wouldn't it be cooler to find actually non-dying star of this magnitude?

      What the hell? You act like the universe is your backyard sandbox. What's out there is what's out there. Sure it would be cool if we found a 3 foot tall leprichan that could shoot fireballs out of his ass running around on mars but it's just not going to happen buddy.

      <retard>Wouldn't it be cooler though? </retard>

      And for god sakes who modded him up?

  • If they were located in the same place (Score:5, Funny)

    by frovingslosh ( 582462 ) on Wednesday January 12, 2005 @02:33AM (#11332312)
    If they were located in the same place as our own Sun - at the centre of the Solar System - the stars would stretch out further than the orbit of Jupiter!"

    Shows what little they know. If they were located in the same place as our own Sun, Jupiter would burn up and not have an orbit!

  • SO666, or perhaps Rosie O'Donnell for short
  • Not the guy who forwarded it to Slashdot's fault; the BBC got it wrong. According to the Lowell Observatory's site, it's 7 au in radius, or about 1.3 billion MILES. That's B-I-G.

    And dang, you'd expect the BBC to keep their units right.
  • When will the artists rendition competition begin for what it looks like on the surface? Should be able to see Saturn on the horizon, since it only goes out to Jupiter's orbit.

  • Wrong Units (Score:4, Funny)

    by willpall ( 632050 ) <{moc.oohay} {ta} {todhsals-lliwllap}> on Wednesday January 12, 2005 @03:29AM (#11332521)
    "1.5 billion km across" means nothing to me. How many Libraries of Congress could the star hold?
  • imagine earth that size.
    plenty resources, more than enough land, so no reason to fight over that and the internet spanning earth would be BIGGGGGG

  • Thanks for the tip! (Score:3, Funny)

    by po8 ( 187055 ) on Wednesday January 12, 2005 @04:02AM (#11332636)

    If they were located in the same place as our own Sun - at the centre of the Solar System...

    So that's where I left it!

  • Its all just smoke and mirrors.

    I'm sure there may not be many anomalies between us and 9800ly, however, it would be smart to keep an open mind about the possibility.

    Sounds like they are making some progress ;
    "With close stars, scientists can calculate stellar sizes from their temperatures and luminosities."

    So does this formula not work for distances beyond say 1,000,000ly?
    Where is the transition and why?

    01/14/04 Blog 4: -- You Are Here -- SpaceCanada.org [spacescience.ca]
  • I hereby declare that "the orbit of Jupiter," much like the popular trend of referencing an arbitrary number of Volkswagons as a benchmark for indicating "pretty heavy", is becoming a new unit of measure indicating "pretty far away".

    You heard it here first.

    As far as I know.

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