Are there any stars that do not have a planetary system?

  1. At first, scientists found stars with planets and think that there are suns with planetary system. But it seems now that every sun has planets. My questiion is are there any suns without a planet.
     
  2. jcsd
  3. Chronos

    Chronos 9,986
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    Blue giants seem to be poor breeding grounds for planets. Perhaps because they blow off their accretion disc before sizable planets can coalesce, or they are too massive for companion planet detection. Otherwise, it appears planetary companions are the norm for nearly every star. Planetary companions have even been detected orbiting neutron stars, which is pretty weird. They are, however, probably not good candidates for SETI study.
     
  4. Borg

    Borg 1,139
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    Stars that form around the central black holes of galaxies could also be good candidates.
     
  5. LURCH

    LURCH 2,514
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    I suppose a good place to start exploring this question would be to ask, " do we currently have the technology to look at a star and say, with any degree of certainty, that it does not have a planet orbiting it?" Until we can do that, we cannot say for certain that there is any star without a planet.
     
  6. negitron

    negitron 842
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    Given the sheer number of stars in the universe, it's a safe bet that there exists at least one star with no planets. While it seems likely that most, if not all, stars form with planets around them, things can happen to remove them later such as a close encounter with another star.
     
  7. How many man on Earth over 50 yrs old and has no kids? Plenty of them. Can't i say this for stars? Without planets? I can't give you any evidence at the moment but i'm pretty sure there must be plenty of stars without planets. However if we think planetary systems and atoms structures are more similar than above example, then we can't see any atom nuclei without elcetrons at the first look, but actually we find places in universe where there are plenty of atom nuclei together and without electrons around, like in neutron stars. So still there are high possibilities for existence of stars without planets.
    According to a scientific article first stars had no planets. Only later generations of stars, that contain more metal, were able to have planetary companions. To reach this conclusion astronomers looked at 754 nearby stars. Some of surveyed stars had planets but most did not. To read more: BBC News, Science/Nature, First Stars Had No Planets
     
  8. I think those gas blobs that have rotation movement would from stars with acretion disks and planets may form from that.
    Those gas blobs that have no rotation movement will never have an acretion disk and no planets are from.
     
  9. Vanadium 50

    Vanadium 50 17,750
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    This is unanswerable. If you see a star that seems not to have planets, how do you know that it really doesn't have planets rather than planets that are too small, too far out or too close in to detect?
     
  10. negitron

    negitron 842
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    Those half-dozen or so stars at the center of our Milky Way galaxy which are whipping around what is presumed to be a supermassive black hole with 2-3 million solar masses having orbital periods measure in mere days probably don't have any planets now, even if they once did.
     
  11. DaveC426913

    DaveC426913 16,230
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    I think this is an exceedingly bold claim.
     
  12. I'm going to say yes. Given the vast number of galaxies, and the vast number of stars within a galaxy, surely at least one sun in the universe has no planets. The problem is, you need to find an example to really prove the answer. I don't think we have the technology to prove that a star has no planets. It's often difficult to prove a negative.
     
  13. DaveC426913

    DaveC426913 16,230
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    I'm going to guess that the OP wasn't looking for 'only one in the universe', but was looking for 'is it rare'.
     
  14. negitron

    negitron 842
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    You're probably right, on further thought. Claim retracted.
     
  15. Why make a guess that changes the clear meaning of the stated question? However, if guessing is allowed, then you should guess that I didn't really mean that there is only one in the universe, but only that they are probably rare. The main point is that it is very difficult to determine just how rare they might be. Any star that shows no sign of a planet, might still have one. It's much easier to prove that a star has a planet, than prove that it does not.
     
  16. DaveC426913

    DaveC426913 16,230
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    Because I think even the OP knows that the answer to his question - if taken literally - is trivial.

    Of course, there is at least one planet somewhere in the entire universe, for one reason or another, that has no planets. End of thread.

    Only looser interpretations of the question lead to further discussion.
     
  17. I guess you missed my subtlety. What I was trying to say was; why did you give the OP the benefit of the doubt by guessing that his question should not be interpreted literally, and not do me the same favor in interpreting my answer? My point was not that there is one star without a planet, but that determining the rarity is difficult.
     
  18. Integral

    Integral 7,345
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    I thought that it was nearly impossible for a binary star system to have planets. Binary star systems are very common.
     
  19. negitron

    negitron 842
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  20. Vanadium 50

    Vanadium 50 17,750
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    55 Cancri A has 5 discovered exoplanets and is part of a binary system.
     
  21. tony873004

    tony873004 1,562
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    Any star that happened to randomly pass within ~5 AUs of another star will have all its planets ejected into interstellar space, likely leaving both stars with no planets. But how often does this happen? Using the close stellar encounter formula from the abstract of Joan Garcia-Sanchez's paper "Stellar Encounters with the Oort Cloud based on Hipparcos", available in calculator form here:
    http://orbitsimulator.com/formulas/cse.html ,
    stars in the sun's neighborhood are likely to have such an encounter about every 400,000 Billion years. So in the last 4 billion years, one out of every 100,000 stars should have suffer such a fate. That makes thousands of planetless stars per galaxy by this process alone. The odds are probably much higher as many stars begin their lives in clusters, where close stellar encounters are more frequent.
     
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