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  1. #1
    ukastronomy's Avatar
    ukastronomy Guest

    Default New double star and binary star site




  2. #2
    Steven Gill's Avatar
    Steven Gill Guest

    Default newbie question

    How do you know it is a true double, and not just two stars in our line of
    sight but light years apart?

    Steve



  3. #3
    Iordani's Avatar
    Iordani Guest

    Default newbie question

    Steven Gill wrote:


    We can observe their motion around each other.


  4. #4
    Mike Dworetsky's Avatar
    Mike Dworetsky Guest

    Default newbie question

    "Steven Gill" <sfg@arctic.karoo.co.uk> wrote in message
    news:zpudnQleXtMpQy_bnZ2dnUVZ8v2vnZ2d@eclipse.net. uk...


    1. Watch the pair for years or decades and see if there is orbital motion.
    Works best on very close pairs.

    2. Check for common proper motion of wider pairs, since they won't show much
    orbital motion on timescales of a few centuries. If you can use
    spectroscopy to check for common radial velocity that can also help, but
    this is difficult for very faint stars.

    3. Use statistical methods to assign a probability of a pair of given
    magnitude and separation being a physical pair. The famous double-star
    observer Robert G. Aitken offered the formula

    log (separation in arcsec) = 2.8 - 0.2 m

    where m is the magnitude of the double star (I think this is for combined
    magnitude of two nearly equal components). A wide pair of fourth or fifth
    magnitude stars might well be physical (e.g., epsilon Lyrae) by this
    criterion, but the same separation for 11th magnitude stars would not be.

    --
    Mike Dworetsky

    (Remove pants sp*mbl*ck to reply)


  5. #5
    Claudia Marie's Avatar
    Claudia Marie Guest

    Default newbie question

    Question to all re Dark Matter, etc.
    Does Einstein maintain (in his 'M'' equation) that there is no such
    thing as ''empty'' space in the cosmos? Vacuum ??
    tks
    ClaudiaMarie


  6. #6
    Claudia Marie's Avatar
    Claudia Marie Guest

    Default newbie question

    Question to all;
    In some galaxies are some stars only gas & therefore able to pass
    through each other ( without collisions or exerting dominate magnetism
    one over another) ??
    tks,
    ClaudiaMarie


 

 

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