View Full Version : Optical doubles and eclipses

2012-Jan-29, 05:31 PM
There are plenty of optical double stars in heavens.

What is the closest known optical double - i. e. NOT physically nearby, at least 0,1 lightyears away in the direction to Sun?

If the disc of a fixed star were to move directly in front of another star tens or hundreds of lightyears beyond, as a result of the independent proper motions of these stars, what would the event look like?

Obviously, the probability of any single star getting physically eclipsed by another star is tiny - by virtue of Olbers Paradox. What is the fraction of heaven covered by the discs of all fixed stars?

But there are many stars in sky. The count of stars to magnitude +6,5 is about 9000. What is the count of stars to, say, +20? +25?

Has any star ever been seen eclipsed by an unrelated star?

2012-Jan-29, 05:41 PM
The most interesting part of your question is about independent eclipses, and yes they have been observed by MACHO and OGLE. The nearby star acts as a gravitational lens for the other and the brightness of the other increases and falls following a bell curve (more or less) with some superposition brought in by parallax from the Earth going around the Sun. This can take a few months to a few years depending on alignments and velocities, and can also include short spikes if near-field planets also pass near the more distant star.

This works even if there is not a direct eclipse.