Binary Stars Observable with Binoculars: Periodicity

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Discussion Overview

The discussion revolves around the visibility of binary stars using binoculars, specifically focusing on whether any binary stars have orbital periods that can be observed over weeks or months. Participants explore the feasibility of observing such stars and the conditions required for resolution.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that binary stars with short orbital periods would be too close together to resolve with binoculars or even small telescopes.
  • Algol is mentioned as a binary star with a short orbital period of just under 3 days, where the individual stars cannot be resolved, but brightness changes can be observed.
  • Alpha Centauri is discussed as a nearby binary that may be observable, with some participants noting that it can be split with a modest telescope, but uncertainty remains about its visibility with binoculars, especially at its current orbital separation.
  • One participant proposes a hypothetical scenario involving two massive stars at a close distance, suggesting that such conditions would still require a telescope for observation.
  • There is a mention of the historical context of Alpha Centauri's separation, indicating that it is currently near a local minimum, which raises questions about its visibility now.

Areas of Agreement / Disagreement

Participants generally agree that resolving binary stars with binoculars is challenging, particularly for those with short orbital periods. However, there is no consensus on whether Alpha Centauri can currently be resolved with binoculars, and multiple views on the visibility of binary stars remain present.

Contextual Notes

Participants express uncertainty regarding the specific conditions under which binary stars can be observed and the limitations of binoculars versus telescopes. The discussion highlights the dependence on factors such as star separation and orbital characteristics.

thetexan
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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?
tex
 
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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.
 
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.
 
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thetexan said:
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?

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)Dave
 
davenn said:
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)Dave
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).
https://upload.wikimedia.org/wikipedia/commons/e/ee/Orbit_Alpha_Centauri_AB_arcsec.png
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?
 
snorkack said:
Can you now, at the local minimum, resolve Alpha Centauri by binoculars, without excessive shaking?

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.Dave
 
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.
 
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