Solar System Planets: Freaks of Nature?
The nearly circular orbits of most planets in our solar system may be the exception rather than the rule. Of the 17 known extrasolar planets, the 9 that lie farthest from their parent stars have elongated, egg-shaped paths.
"For the first time, we have enough extrasolar planets out there to do some comparative study," says Geoffrey W. Marcy of San Francisco State University and the University of California, Berkeley.
Marcy suggests that the oval orbits may not bode well for life around these stars. As massive planets in such orbits careen close to their parent stars and swoop back out again, they may sweep aside smaller orbs that circle the same star, including any with Earthlike temperatures. "The big bullies may wipe clean the terrestrial planets, rendering [the systems] void of any Earth analogues," he says.
Astronomers, however, have only been able to detect planets that lie relatively near their host stars, notes William D. Cochran of the University of Texas at Austin. For instance, all nine of the planets with oval orbits venture considerably closer to their parent stars than the distance between Mercury, the solar system's innermost orb, and the sun. It remains unclear whether extrasolar planets that orbit at greater distances also have elongated paths. …