NASA Astrobiology Magazine | Cosmic Evolution | 08 July 2010
Recent discoveries of gas giant planets in unusual orbits challenge the generally accepted theory of planet formation. While these discoveries do not disprove the theory, they have opened our eyes to chaotic solar systems quite unlike our own.
Over the past two hundred years, a standard model emerged to explain how solar systems form. Using our own solar system as a guide, the model explains the existence of a central star (our Sun), an inner system of rocky, “terrestrial” planets, and an outer system of “gas giant” planets, all orbiting in nearly the same plane of rotation as the central star.
Recent discoveries of planetary systems around other stars have challenged this model. These exoplanet discoveries have included gas giant planets in close orbit around their stars, some of which are in radically different planes of rotation from their primary stars.
... if planetary systems with renegade gas giants turn out to be common, life as we know it may be very rare.