Friday, January 25, 2013

if the orbital velocity of an eclipsing binary is 153 km/s and the smaller start becomes completely eclipsed i?


Question by sarah v: if the orbital velocity of an eclipsing binary is 153 km/s and the smaller start becomes completely eclipsed i?
if the orbital velocity of an eclipsing binary is 153 km/s and the smaller star becomes eclipsed in 2.5 hours what is it's diameter?


Best answer:
Answer by Simon van DijkIt is just it takes 2.5 hours = 8000 seconds to eclipse. With 153,000 m/s it travels 1.224.10^9 m.
This could be the diameter of the star. But this implies that the bigger star has a negligible velocity. That is not the case. In a binary the 2 stars must have the same angular velocity: they must be opposite each other relative to the center of gravity. If the heavy star is 10 times heavier than the other one. The center of gravity is at 10 to 1 distance from the big star, so their orbits are 1 to 10 relative, That makes the orbital speed 10 to 1.

So the 1.2 million kilometer (about 90% the size of the sun) is only an estimate.

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