I am confused about the definition of the period of an eclipsing binary, a binary configuration where one component crosses the other across the line of sight. When people say that an eclipsing binary has a period of T years do they mean that the period of the individual component is T years?

  • 1
    $\begingroup$ No idea where your confusion could be? Both components orbit the centre of mass with the same period. $\endgroup$
    – ProfRob
    Commented Jul 28, 2016 at 17:48
  • $\begingroup$ In binary star configurations, both stars orbit each other with the same period. When they say the eclipsing binary has a period of T years, they mean that both stars complete one orbit in T years and that implies that the eclipse will occur every T years. $\endgroup$
    – zephyr
    Commented Jul 29, 2016 at 17:40

1 Answer 1


The period (at least in physics) is defined the time an oscilating system needs to get back to its starting point (for a sinus curve its 2*pi).

Now when they say an eclipsing binary has a period of T years, it means that its brightness varies as seen from earth when they are eclipsing (thats how we detect eclipsing stars and planets by the way), and that the curve of its brightness is like an oscilation that gets back to its starting point every T years.

The meaning of this is, that this system consisting of 2 stars will be exactly as you see it now again in T years.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .