Astronomy:
Worlds Around Other Stars Shake Planet Birth Theory
James Glanz
Starting just 20 months ago, observers began detecting planet after planet around other sunlike stars, throwing planet-formation theory into turmoil. Many of these new worlds dwarf the giant planets we know, orbit much closer to their parent star than Mercury, or follow wildly eccentric paths. Now theorists are coming up with scenarios that might explain this strange bestiary. Among them are planet-forming mechanisms that would flout all the standard assumptions about planet size, proximity to the parent star, and orbital eccentricity.