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B Binary stars

  1. Apr 3, 2016 #1
    Are there any binary stars that can be seen with binoculars which have orbital periods you can observe from week to week or month to month?
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  3. Apr 3, 2016 #2


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    Not that I know of. I don't even know of any of that orbital period where you can resolve both stars through a telescope. For such a short orbital period the two stars would have to be very close together. Somewhere on the order of 1 au or less, depending on the masses of the stars. There are no telescopes for visual observation able to resolve two stars that close.
  4. Apr 3, 2016 #3

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    Algol has a period just under 3 days. You cannot resolve the individual stars, but you can see the decrease in brightness - even with the naked eye - when the dimmer star eclipses the brighter. Algol goes from a bright second magnitude star to a relatively dim third magnitude star. This dim period lasts for 10 hours.
  5. Apr 3, 2016 #4


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    Not that I am aware of ....unless they were substantially sized bino's ( haven't personally tried the BIG ones)

    Alpha Centauri is easily split with a modest 6" reflector or a reasonable refractor ( been doing that and showing others since I was a kid)

  6. Apr 4, 2016 #5
    Is it still possible?
    Being the nearest binary, Alpha Centauri should be the easiest to see moving. (Any more distant, and a binary is either hard to resolve if short period, or slow moving if long period).
    The separation of Alpha Centauri was at a global maximum around 1980. It is now near the local minimum. The global minimum is due in 2037.
    Can you now, at the local minimum, resolve Alpha Centauri by binoculars, without excessive shaking?
  7. Apr 4, 2016 #6


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    haven't tried over the last few years
    I was looking at Alpha Cent. on Saturday nite with a group of people I took out for their first telescope and deep sky imaging session.
    Used it as one of the 3 alignment stars for the GOTO scope. Looked at it so quickly, I cannot remember if I could split it or not.

  8. Apr 4, 2016 #7


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    I calculated somewhat optimal conditions: let's imagine we would have two 100 solar mass stars orbiting each other at a distance of just 4 light years to us. We do not have those, of course. To get an orbital period of 1 month with circular orbits, the separation would be 1.1 AU, about 0.9 arcseconds in the sky. That still needs a telescope.

    Edit: fixed missing factor of 2.
    Last edited: Apr 7, 2016
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