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Space Science

Star Smaller Than Some Planets Found 138

Posted by Zonk from the on-the-way-to-a-hole-in-space dept.
Abhishek writes "Astronomers have found the tiniest full-fledged star known, an object just 16 percent bigger than Jupiter. It is smaller than some known planets that orbit other stars. The star is a companion to a Sun-like star toward the center of our Milky Way Galaxy. It was found and measured by observing changes in the light output of the system when the smaller star passes in front of the larger star from our vantagepoint. This would give a better idea of brown dwarfs or failed stars. The star has been named OGLE-TR-122b. This discovery also marks the possibility of stars that look strikingly like planets."
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Star Smaller Than Some Planets Found More

Star Smaller Than Some Planets Found

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  • Interesting... (Score:5, Insightful)

    by Ianoo ( 711633 ) on Sunday March 06, 2005 @09:37AM (#11858271) Journal
    I've read in other places that there needs to be a critical mass for a big cloud of hydrogen to begin fusion, otherwise it ends up as something like Jupiter. What might be the reason for this star burning when other similarly sized objects do not? Gravitational effects from the companion star imparting extra energy? Any physicists care to speculate?

    • Re:Interesting... (Score:5, Informative)

      by selectspec ( 74651 ) on Sunday March 06, 2005 @09:43AM (#11858291)
      The article is misleading confusing "size" with "mass". This new star has 95 times the mass of Jupiter. However, it's density is so great that its physical size is only slightly larger. Density is the trigger key for fusion.

      • So again, why? (Score:3, Interesting)

        by Mr. Underbridge ( 666784 )
        The article is misleading confusing "size" with "mass". This new star has 95 times the mass of Jupiter. However, it's density is so great that its physical size is only slightly larger. Density is the trigger key for fusion.

        Been a long time since I was I was into nuclear phys, but how can it maintain that density with such (relatively) small mass? The process of fusion, which tends to expand a star, equally balances gravity which tends to contract a star. Seems to me a normal star would expand due to fus

        • Any fusion and it stops being a brown dwarf, by definition.
          • Any fusion and it stops being a brown dwarf, by definition.

            Which still doesn't answer the question of why normal stellar fusion doesn't expand this thing pretty substantially.

            • No, it doesn't. I avoided replying to that point because it baffles me too... I guess that's just the way the numbers work... odd.
            • It's mass is so low that the pressure and temperature at the core can only support a very low rate of fusion. It's radiation pressure from fusion that counterbalances the self-gravity that tries to make stars collapse, so it's no surprise to me that it's pretty tiny. :)
              • It's mass is so low that the pressure and temperature at the core can only support a very low rate of fusion. It's radiation pressure from fusion that counterbalances the self-gravity that tries to make stars collapse, so it's no surprise to me that it's pretty tiny. :)

                I may be off here, but its density seems insanely high though.

          • Close. Brown dwarfs can be hot enough to fuse deuterium, but not normal hydrogen. Any fusion of normal hydrogen and its not a brown dwarf.

            Adrian

        • Re:So again, why? (Score:5, Informative)

          by Ckwop ( 707653 ) * on Sunday March 06, 2005 @01:28PM (#11859507) Homepage

          Been a long time since I was I was into nuclear phys, but how can it maintain that density with such (relatively) small mass? The process of fusion, which tends to expand a star, equally balances gravity which tends to contract a star. Seems to me a normal star would expand due to fusion.

          Basically, it doesn't make sense that it can maintain being 1/10 the mass of the sun and 50x as dense. This means its fusion output must be tiny (little to balance gravity), but why? Is it mainly made of non-hydrogen mass? They should be able to tell the elemental composition from the spectrum. And how could it have such little fusion and not be a brown dwarf?

          Wish this press release had some science in it.

          Actually, you got the right answer! The star has expanded due to nuclear fusion taking place it just hasn't expanded dramatically because it doesn't take a dramatic amount of fusion to support a star with so little mass.

          The reason fusion is needed to support a star is because the heat generated through contraction is radiated in to space. The energy lost through this process needs to be replaced to keep the volume of the star constant - and fusion provides this energy.

          There are two reasons why a star this small can exist. The first is the low mass of the star. The smaller the mass of the star the less heat it takes less energy to raise the tempreture of the entire star. This means it takes less energy to maintain the tempreture of the star and this means less fusion.

          The second reason is surface area. The Sun has a surface area of approximately 6 x 10^20 meters compared with Jupiter's 6.4 x 10^18 meters. This star is only slightly larger than Jupiter in terms of volume and so will have a comparable surface area. This means that the radiation of heat in the star will not be as efficient as in the sun and that means less fusion is required to keep the tempreture of the star constant.

          Since the tempreture, among other things, determines the size of a star both of these factors allow the star to remain balanced and still stay fairly compact. So while it suprising that stars this small exist it is not inconsistent with theory.

          Simon.

          • The second reason is surface area. The Sun has a surface area of approximately 6 x 10^20 meters compared with Jupiter's 6.4 x 10^18 meters. This star is only slightly larger than Jupiter in terms of volume and so will have a comparable surface area. This means that the radiation of heat in the star will not be as efficient as in the sun and that means less fusion is required to keep the tempreture of the star constant.

            No, sorry. The ratio of surface area to heat-generating volume is what you mean. This
      • This makes me wonder, because of it's density, whether or not it has a fission component. Almost like a big hydrogen bomb, a fission triggered, fusion reaction. Is so massive because the hydrogen somehow got so dence? Or is the core composed of heavy elements? Can core composition be determined from spectral lines?

        Could it be a star that was stripped of most of it's mass?

        Could it be a white dwarf that accumulated more hydrogen? If I remember correctly, dwarfs and neutron stars that accumulate mass
        • This makes me wonder, because of it's density, whether or not it has a fission component. Almost like a big hydrogen bomb, a fission triggered, fusion reaction. Is so massive because the hydrogen somehow got so dence? Or is the core composed of heavy elements? Can core composition be determined from spectral lines?

          I doubt fission plays any role here... just plain old fusion. It's just not a very large amount of fusion. Spectral analysis can't peer into the core (you can't see it, silly ;). It must be i
          • A nova is a result of a surface fusion detonation of accumulated material. A star fuses hydrogen inside it's core.

            The reason a nova fuses hydrogen on its surface is that a white dwarf is the heavy remains of a burned out star. Hydrogen is very light, so it remains on the surface of the white dwarf.

    • Quadrupole-induced polarization? (Score:5, Funny)

      by Sheetrock ( 152993 ) on Sunday March 06, 2005 @09:44AM (#11858296) Homepage Journal
      There is a possibility, albeit a small one, that an overload of the phase coupling relay reaction in a solar furnace (star) could trigger a non-catastrophic split.

      If a star is smaller than the conditions necessary for supernovae, and is struck with a star of the same size, you will end up with quadrupoles flying off in different directions. Needless to say this is rare, which makes this quite an exciting find!

    • What might be the reason for this star burning when other similarly sized objects do not?

      Once a gaseous object gets to be the size of Jupiter, adding more material to it causes its diameter to shrink because of the increasing mutual gravitation. As even more matter is added, the shrinking effect is eventually counteracted by thermal expansion caused by fusion once it ignites into a star. After that point, the diameter grows again as the fusion rate increases with more mass.

      Apparently, this object has m

    • Re:Interesting... (Score:5, Funny)

      by LurkerXXX ( 667952 ) on Sunday March 06, 2005 @10:44AM (#11858534)
      Likely it was rebels fleeing from an Alliance Heavy Cruiser. As they were slingshoting around the larger star, they decided to launch one of their thermonuclear torpeados into the gas giant orbiting it, triggering the thermonuclear reaction that the proto-star was incapable of initiating on it's own. Luckily for the rebels the unexpected flood of radition from the new star was enough to temporarily blind the sensors of the Alliance Cruiser, allowing them to escape.

      But that's just my hunch.

    • Re:Interesting... (Score:3, Informative)

      by RobertFisher ( 21116 )
      You can show from basic stellar structure theory that you need a minimum mass of .08 solar masses or so to ignite hydrogen on the p-p cycle. (You can burn heavier isotopes like lithium and deterium at lower masses, but these contribute negligibly to the energy budget of the star because of their low abundances.) .08 solar masses is about 80 Jupiter masses, so this star is over the p-p burning limit. As another author pointed out, the star has a radius comparable to Jupiter. It turns out that due to the phy
      • So how does this explain the discovered planets much "larger" than Jupiter? It the article confusing size and mass? Are the "large" extra-solar planets actually smaller than Jupiter, despite being more massive?

    • Re:Interesting... (Score:4, Funny)

      by Mr. Bad Example ( 31092 ) on Sunday March 06, 2005 @02:23PM (#11859849) Homepage
      > What might be the reason for this star burning when other similarly sized objects do not?

      Sheer impotent RAGE.

    • Pesky monoliths at work again... (Score:2, Funny)

      by Anonymous Coward
      Clear it's evidence of those pesky monoliths at work again.
    • I'm thinking (and IANAP) that this may be something like a white dwarf's configuration where you have a core of denser material with the actual fusion going on on the outside. The heavy central core may or may not contribute to further fusion (perhaps this is where the heavier atoms come from), but it provides the gravity needed to compress the hydrogen to a fusion stage.

      Among other things, I just can't see an object made of mostly hydrogen and helium being almost 100 times the density of Jupiter.

      In any

  • Aren't neutron stars "stars"? (Score:5, Insightful)

    by turnstyle ( 588788 ) on Sunday March 06, 2005 @09:38AM (#11858273) Homepage
    Aren't neutron stars "stars"? And aren't they smaller than planets?

    • Re:Aren't neutron stars "stars"? (Score:4, Informative)

      by nefele ( 654499 ) on Sunday March 06, 2005 @09:48AM (#11858308)
      Neutron stars were stars at one point, but they're not stars in the same sense that the Sun is. When a Sun-like star ends its lifecycle with a (super)nova burst, it gets rid of most of its mass, and the rest collapses into a small neutron 'star', or a black hole if the mass was sufficiently large.

      IANAP, but I think no thermonuclear reactions take place in neutron 'stars' (or maybe just not enough to sustain the emission of light, so they're not easily visible). So basically neutron stars are just dead stars.
      • IANAP, but I think no thermonuclear reactions take place in neutron 'stars'

        Correct. It's not possible to fuse atomic nuclei when the object is itself, one large nucleus.
        • Correct. It's not possible to fuse atomic nuclei when the object is itself, one large nucleus.

          *sigh* So many people on slashdot who think they know everything. Many neutron stars with massive companions have regular thermonuclear flashes of hydrogen on their surface that they accrete from the companion and then heat up. The intensive pressure at the surface plus the heat makes the H fuse.
          • The intensive pressure at the surface plus the heat makes the H fuse.

            Well, that would be fusion *on* a neutron star, not *in* it. It's not just semantics; the process you are talking about does nothing to support the NS against gravity, since it's at the surface. The point is, a neutron star, by itself doesn't have any fusion.

            *sigh* So many people on slashdot who think they know everything.

            LOL, take it easy, man. I have a PhD in astrophysics, how about you? ;)
            • Well, that would be fusion *on* a neutron star, not *in* it. It's not just semantics; the process you are talking about does nothing to support the NS against gravity, since it's at the surface. The point is, a neutron star, by itself doesn't have any fusion.

              OK, you saved your face with semantics, but what you said was very misleading.

              I'm about to get my PhD in astrophysics, so hmmmmph. ;-)
              • OK, you saved your face with semantics, but what you said was very misleading.

                What?! No it wasn't misleading. Neutron stars cannot have nuclear reactions. Period. If one happens to be in a mass-transfer binary, the infalling material will obviously burn, but that's *not* the NS, it's the infalling material!

                Misleading? Sure, the same way saying "Dogs can't fly" is misleading, because you saw one on an airplane once. Sheesh.

                Out of curiosity, what would you say if someone asks you whether nuclear fus
                • Out of curiosity, what would you say if someone asks you whether nuclear fusion takes place in a neutron star?

                  I'd probably take the weasel answer and say, "Well it depends ..." lol.

                  Whether material accreted onto the surface is part of The Neutron Star officially or not is debatable, but I think most people would agree that anything gravitationally bound is part of it. Would you say that the Earth's atmosphere isn't part of the Earth? Because the atmosphere is completely different from the surface, so

      • Re:Aren't neutron stars "stars"? (Score:5, Informative)

        by LokieLizzy ( 858962 ) on Sunday March 06, 2005 @11:34AM (#11858791)
        Not quite. Actually, not at all. A sun-like star doesn't end its life cycle with a nova burst, or anything like that. Rather, it swells into a red giant, and eventually *slowly* puffs out its outer layers and forms a planetary nebula, with a white dwarf at its center. Stars that (go) Nova are typically several times larger than our sun, and stars that go supernova can be hundreds of times larger than our Sun (hence their names: red or blue supergiants). Sirius (brightest star in the night sky) is an example of a blue supergiant, while Antares (the heart of the Scorpion) is a red supergiant. After supernovaing, it's *these* stars that can form neutron stars or black holes. But not our sun, or stars in close mass to our sun -- those form planetary nebulae, and white dwarves.

        Furthermore, neutron stars aren't dead -- they often radiate a hell of a lot of energy. Those that do are called *Pulsars* -- that's where all those directional radio/x-ray waves come from in deep space -- they spin like lighthouses, you see.

        • What I've never grokked is: where does the beam come from? My basic physics suggests that it comes from the poles, but why would the poles sweep like lighthouses?
          • Furthermore, neutron stars aren't dead -- they often radiate a hell of a lot of energy.

          Yes they are. Compare to a dead human body, it too radiates heat until it's at the ambient temperature. That's exactly what's going on with neutron stars, too, a dead body radiating left-over energy (both heat and rotational energy, radiated in different ways).
      • IANAP

        I Am Not A Planetarium?
    • A neutron star is related to a star in the same sense as a black hole is, i.e. at one point it _was_ a star.

      Real life doesnt do
      SELECT * FROM definitions WHERE phrase LIKE '%star%'

  • that's no star... (Score:4, Funny)

    by HawkinsD ( 267367 ) on Sunday March 06, 2005 @09:41AM (#11858284)
    That's no star... That's a space station!

    • Bah. The actual appropriate quote, regarding small stars...

      "Make him a star? What'd he want a star for?"
      "I didn't know you could make stars... I thought they were like, you know, stuck to the sky..."
      "I think he meant to make him a star. You know, him himself. Turn him into a star."
      "How can you make anyone into a star?"
      "I dunno. I suppose you compress them right up small and they burst into this mass of flaming hydrogen?"
      "Good grief!"
      "Yeah! Is that troll mean, or what?"

      - Terry Pratchett: Movin

    • "I think you're right. Chewy lock in the auxilary controls!"

  • They're only small stars (Score:3, Funny)

    by eclectro ( 227083 ) on Sunday March 06, 2005 @09:42AM (#11858287)
    until the Oscar awards.

    Thank you, I'm here all week.

  • Constellation (Score:3)

    by Chemisor ( 97276 ) on Sunday March 06, 2005 @09:43AM (#11858293)
    Was it found in the underdog constellation? Now, what is the latin name for that?...

  • That's so cool (Score:3, Funny)

    by Jugalator ( 259273 ) on Sunday March 06, 2005 @09:53AM (#11858322) Journal
    Wow! Go, OGLE!

    I'm gonna register a website for that...

    No, wait... :-/

  • Stars "looking" like planets ? (Score:4, Insightful)

    by Dozix007 ( 690662 ) on Sunday March 06, 2005 @09:57AM (#11858334)
    I think it should be noted that the way we look at stars and planets could never really lead to that mistake. Radiation emitted by a stellar body is analyzed and it is then determined "what" the stellar body is. It is impossible to misinterpret an extremely hot stellar body with a relatively cool planet.
    • It is impossible to misinterpret an extremely hot stellar body with a relatively cool planet.

      I wouldn't say that. Extremely low-mass stars are very faint and not much hotter than the most massive planets (especially when the body in question receives heat from a much hotter companion star, as is the case with this object).

      There is no sharp distinction, empirically speaking, between a very low-mass star and a very high-mass planet (i.e., a brown dwarf).
      • You also have to consider that Stars are made up of common materials that planets are not composed of. This results in the emission of something that looks like a Perfect Black-Body curve with certain amounts of energy emitted at different wavelengths that are not seen among planets. (And if the planet were hot enough, with those common materials, it would become a star.)
        • What materials are you thinking of? Low-mass stars and high-mass planets should have very similar composition. The only distinction I can think of is that true stars will not have lithium in their atmospheres, because it gets consumed when you have thermonuclear reactions (low mass stars are fully convective, so the surface stuff gets churned down to the center where the burning takes place).

          Anyway, that's something that planets have but stars don't have, the other way around from what you said.
          • The materials vary but it goes down the logical line of fusion. Planets don't have near the mass of stars (not even close). The difference is going to be that a star has the thermonuclear reaction which is going to cause intense radiation to be emmited. This won't happen in nearly the same way on a planet because the thermonuclear reaction isn't there. Remember that with a small increase in energy there is a drastic change all across the frequency spectrum.
            • I'm confused. You were talking about differences in the compositions (the "materials" present in the spectrum); now you're talking about thermal blackbody radiation.

              Planets don't have near the mass of stars (not even close).

              Huh? I guess it depends on whether you consider brown dwarfs to be "planets" for the purposes of this discussion, but by definition, anything that is not massive enough to fuse Hydrogen is not a star, even if that object is just slightly lower than the threshhold mass. There's no
              • I was refering to materials present in stars. Stars are highly dense and large, as the one in this article is. And in reguards to the intense change in Luminosity with even a slight temprature difference, that is true. If the temp. of a star is increased by even a few Kelvin the total luminosity will change across the spectrum. Remember, for even a small temprature change the energy output change is very significant.

    • Re:Stars "looking" like planets ? (Score:4, Funny)

      by Fex303 ( 557896 ) on Sunday March 06, 2005 @10:35AM (#11858492)
      It is impossible to misinterpret an extremely hot stellar body with a relatively cool planet.

      I dunno... After a few drinks I've been known to think all kinds of things have hot bodies.

    • That should make defending cool planets in court a lot easier. "Beings of the court, my client is a peaceful cool planet, not a violent hot stellar body. If the spectra doesn't fit, you must acquit."
    • Actually it could. They are searching for planets by searching for their effect on the local star. The wobble they detect in the host star can now not be assumed to be a planet without futher investigation.

      The only planets we observe via reflected light are those within our own system. To my knowledge no-one has imaged a remote system's plantary bodies yet..

  • Don't panic... (Score:4, Informative)

    by hanssprudel ( 323035 ) on Sunday March 06, 2005 @09:58AM (#11858341)

    Before anyone starts panicing about Juptier collapsing into a companion star to the sun, and screwing over our whole solar system pretty royally - please note that while this star is only 16% larger than Jupiter in volume, it contains 95 times as much mass.
  • Mickey Rooney appeared slightly irritated at a press conference held in his Beverly Hills Mansion earlier today. "I was discovered over 70 years ago, and these astronomers claim they've got a smaller full-fledged star? Well I've got news for 'em."
  • Are we out of names now. They names this little baby : OGLE-TR-122b. May be I should change my address to 127.0.0.1 too. -a
    • Are we out of names now. They names this little baby : OGLE-TR-122b.

      What is the point of naming thousands of stars that you survey at the time of the survey? This is just a code that tells them which in a catalogue it is. Now if it becomes famous, they can give it a stupid name, like karvind. Will that make you happy?
    • Here's a name for the new star: Echidna. I don't know why.
  • We should go get it. It's always good to have a backup...

  • more fuel to the fire of planet X (Score:3, Interesting)

    by master_p ( 608214 ) on Sunday March 06, 2005 @10:49AM (#11858557)
    Planet X is also said to be a small non-ignited brown dwarf circling our sun every 3600 years. What the article describes is quite similar to that. Let the speculation begin! prepare your tinfoil hats!

  • Stars, brown dwarfs, and planets (Score:3, Informative)

    by RobertFisher ( 21116 ) on Sunday March 06, 2005 @11:38AM (#11858806) Journal
    There is an important point to clarify here regarding nomenclature.

    Stars shine by nuclear fusion of hydrogen. That can only be sustained in stars of about .08 solar masses or greater.

    However, smaller mass objects are formed alongside stars with lower mass still. Astronomers call objects with insufficient mass to burn lithium (but enough to burn deuterium) "brown dwarfs".

    At still lower masses, objects which cannot even burn deuterium are labelled (somewhat arbitrarily) according to their environment. If they are orbiting around another star, they are called planets. If they are free-floating, they are given another name -- free-floating objects or planets, depending on the author.

    In the end, this is all a rather arbitrary scheme imposed by humans. For instance, if an object not burning deuturium is ejected from a protostellar disk, it gets changed from a planet to a free-floater in the process!

    This article deals not with mass but with radius. There are in fact many objects which are known to exist with far less mass than the star reported here. They are not called "stars," but in fact the distinction is just one of nomenclature.
  • This should make building a Dyson sphere really, really easy! Right? No?
  • All you need is the ability to trap all the energy from both stars. Some kind of container whose inside is it's outside. I predict this will give rise to a whole new industry in Dyson [nada.kth.se]-Klein Bottles [wolfram.com].


  • This discovery also marks the possibility of stars that look strikingly like planets.

    Not only that, but it also suggests the possibilities of miniturizing these amazing power sources to such a size as to be portable. Perhaps someday we'll each have our own pocket-sun that we can use to supply juice to our laptop computers. Think it's unlikely? These are the same computers that exponentially out-perform computers that took up an entire room some thirty years ago.

  • Tiny aliens... (Score:1, Offtopic)

    by HermanAB ( 661181 )
    well, now we know where these tiny grey alians come from - a tiny star with tiny planets...
  • that solar system is actually the home system of the Aschen (ref: Stargate) - they have converted one of their gas giants into a second sun so that their crops would have higher yield

    XD
  • ...98% of the Universe isn't explored yet. I guess, we'll have to "look" for answers for a long while.

    At least, 600 years ago people believed the World is a Disc.. 100 years ago, people believed that atoms can't be splitted and 10 minutes ago, I didn't know that there is a "star" of almost Jupiter's size... how fascinating! ;)
  • ...is, how hot does it burn? If it is indeed a star, how hot are its surface and its core?
  • > This discovery also marks the possibility of
    > stars that look strikingly like planets.

    We already have those.. examples include John Goodman and Roseanne Barr.
  • I'm going to love it, hug it, and call it OGLE-TR-122b!

  • question about jupiter (Score:3, Interesting)

    by digitalsushi ( 137809 ) <slashdot@digitalsushi.com> on Sunday March 06, 2005 @09:21PM (#11862325) Journal
    if jupiter had ignited into a star, what would it look like from earth? would it be brighter than the light that bounces off the moon?
  • Now for a long and pointless debate over whether it should be called a star or a moon.
  • OK can a real physicist shoot me down?

    This thing is near the galactic core where things are older and funkier. Does this it have to be necessarily fusing hydrogen in there?

    Could the parent star be buggering up any spectrum analysis?
  • This post goes to all you scientist out there. First question, what's to keep Jupiter from being a star it self?

    And second, (this is a serious question so please don't mod me) but what would happen if some one blew up a nuclear bomb in Jupiter's atmosphere? Would it turn into a star or would it just burn out? And how would doing so affect Earth?

    I would think if Jupiter where to turn into a star that it's gravity would increase and effect the entire solar system on a gravitational level.

    What would happ
    • No dude. Gravitational force is just a function of mass, so it would stay the same. Jupiter would keep orbiting (probably, you never really know with anything bigger than a 2 body system) but we'd have another source of light.

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