Giant Planets to Brown Dwarfs: What Is in Between?

摘要

The discovery of planets orbiting nearby sunlike stars has shown that planetary systems can be surprisingly diverse and has raised many new questions about how they formed. The initial discovery in 1995 of the planet around the star 51 Pegasi by Mayor and Queloz at the University of Geneva was a surprise because it is a planet with mass about that of Jupiter's and an orbital period of only 4.2 days. This implies that it is 20 times closer to its star than Earth is to the sun. The method of detection is based on the observation of periodic variations in Doppler shifts of the light from the star caused by wobbling, because of the gravitational pull of the planet. Although this method gives an accurate measurement of the object's orbital period and eccentricity, the mass deduced represents only the minimum possible mass.