Eclipsing Binary is type of a Binary Star.

Eclipsing binaries: Italian astronomers have noticed in the late 1600’s that some stars occasionally drop their peak luminosity in their brightness to 1/3. Later measurements showed that these reductions ranged from hours to days and were intermittent. It is now understood that these variations in light are due to one star being eclipsed by another (as they cross in front of each other).

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Eclipsing binaries are studied by monitoring their light curves (shown below), the brightness changes over time. There is a deep minimum when the smaller, dimmer star passes in front of the brighter star. When the dimmer star passes behind the bright star there is a minimum of a second, less deep.

Eclipsing binaries are very rare, because the stars’ orbits must be edge-on to our solar system. Note that the only direct method for measuring a star’s radius is an eclipsing binary, both the primary and the secondary from the time the light curve reaches and rises from minimum.

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