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B Our solar system and its fellows

  1. Jun 5, 2017 #1
    Hello, Im new to this forum, so be brutal :)

    So, Ive tried to find information about earths origin. The nebula, cluster we are a part of etc. but i coud not find the answer I was looking for. For me, it seems logical that we are a part of a cluster. How often do we find a star whos just passing by on its own? Isnt that how most of the universe works, like, you are always a part of and have relstions to something bigger? Ive heard we have relations to Sirius and Alpha Centauri for example. And anyone who knows the name of the nebula who created Earth? I found an earlier thread about this, but it was closed for comments for some reason.

    Im not schooled in this area, so if any of you have any simple thoughts about this subject, please reply
  2. jcsd
  3. Jun 5, 2017 #2


    Staff: Mentor

    The solar system is part of the Milky Way Galaxy. For more details, see, for example, here:


    I don't know that the cloud of gas and dust that originally formed the solar system has any name of its own.

    If you mean, are most objects in the universe part of some larger system, yes. The largest systems we know of are clusters of galaxies.

    Our solar system is in the same galaxy (and the same local region of that galaxy) as these stars, yes, since they are very close to us compared to other stars.
  4. Jun 5, 2017 #3


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    Earth is in the Milky Way Galaxy which is part of the "Local Group" of galaxies. Google the "Local Group".

    EDIT: I see Peter beat me to it.
  5. Jun 5, 2017 #4
    I think you're asking about stars that formed at roughly the same time as the sun, and from the same nebula, and about the nebula itself?

    I have researched this a bit and found nothing that suggests any of those stars are identifiable, they have been scattered around the galaxy so much in the last 5 billion years we can't find them. I could be wrong, and if so, I would be interested to learn otherwise.
  6. Jun 5, 2017 #5


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    I would be amazed if you were wrong about that.
  7. Jun 5, 2017 #6


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    It is difficult to predict the location of solar siblings from the cluster that birthed the sun. By some estimates, it is possible several may still reside within a few hundred light years. The motions of stars in a galaxy are believed to follow a spiral density wave pattern. This could easily disperse them at vast distances from their birth place over ~6 billion years. This is particularly true for stars that form in a spiral arm, as is generally believed in the case of our sun. The problem of finding solar siblings has been likened to finding molecules from a drop of dye added to a whirlpool. For discussion, this may be of interest http://www.sciencemag.org/news/2010/11/can-suns-siblings-be-found
  8. Jun 6, 2017 #7
    So clusters can be ripped apart, and stars may become a part of other clusters? Its quite frustrating, google says that a cluster holds from a hundred to a thousand stars, cant we just observe our closest stars and put our self into this group?
  9. Jun 6, 2017 #8
    Most open clusters, those containing up to a few thousands stars stay together for tens to hundreds of millions years. The cluster our sun was formed in was probably at best loosely gravitationally bound and has been dispersed for billions of years.


    Few if any of the stars nearby us are from the same cluster the sun was formed in
  10. Jun 8, 2017 #9
    Okey, are our closest stars also 'loners' or do they belong to a cluster? And if they dont, and these stars has some relations to our suns lane in the Milky Way, or gravitational pull, what do we call that kind of connection?
  11. Jun 8, 2017 #10


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    Neither the Sun nor its neighbours belong to a cluster. All stars are born in clusters, but then quickly disperse, on a timescale of a few dozens of millions of years (compare with Sun's age of ~5 billion years). More massive clusters remain bound longer.
    So, in order to even observe a cluster, you need to happen to be in the right place at the right time.

    Nearest clusters are Hyades and Pleiades - both readily visible on the northern night sky - respectivelly 150 and 440 light years away. The latter is younger, hence more populated and more compact.

    The Wikipedia article on Hyades includes some general information regarding clusters that you might find interesting.

    Note, the clusters discussed here are 'open clusters'. There's another category called 'globular clusters', but those are quite different and none are present in the closest neighbourghood of the solar system.

    Other than that, all stars, be it in clusters or not, tend to follow the same general pattern of motion around the galactic centre - i.e. they follow similar orbits dictated by all the mass in the galaxy. Stars also have some 'individual' motion, called peculiar motion, resulting from gravitational interactions with their neighbourghood. E.g. if there's a star passing closely by, then it'll attract the Sun, and the Sun will attract the star, so that they end up moving a bit more erratically than one would expect if they were just orbiting the galactic centre.
    This is different from clusters, though, since in clusters the gravitational interactions (due to close proximity and large number of newborn stars) are strong enough to keep the members of the cluster orbit their mutual centres of masses.

    If you want to gain an intuitive grasp on the structure of the Milky Way and solar neighbourghood in particular, then I'd recommend trying out one of the many free planetarium softwares available. Try Celestia, or Digital Universe. The latter is more advanced and better at showing large-scale structures, but its user interface is crap. Celestia on the other hand is very light-weight and intuitive.
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