Planets Past Our Galaxy
Date: Prior to 1993
How do you know if there are other planets past our galaxy?
There is as yet no solid evidence for planets around other stars.
Other stars are so far away that we cannot see their planets directly.
Astronomers hope to infer the existence of extra-solar planets by carefully
measuring the slight wobble of a star that has a large planet orbiting it.
Jupiter could be detected this way from nearby stars by looking at our sun.
This is because Jupiter does not orbit around the exact center of the sun:
both the sun and Jupiter orbit around their "center of mass" (we can ignore
the other planets because they are so much less massive than Jupiter).
Update March 2011:
Yes, there are planets past our solar system.
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Update: June 2012