Why Some Planets Orbit the Wrong Way; Extrasolar Insights Into Our Solar System
Excerpt: More than 500 extrasolar planets--planets that orbit stars other than the sun--have been discovered since 1995. But only in the last few years have astronomers observed that in some of these systems, the star is spinning one way and the planet is orbiting that star in the opposite direction. "That's really weird, and it's even weirder because the planet is so close to the star," said Frederic A. Rasio, a theoretical astrophysicist at Northwestern University. ... It so obviously violates our most basic picture of planet and star formation."