又多五粒

NASA 的 Kepler 望遠鏡又發現多五粒天外行星，其中四粒比木星還大，一粒介乎木星與地球之間。詳情不在這裡重覆，自己看連結吧。
來源：Five New Exoplanets Run the Gamut From Styrofoam to Ice, ScienceNOW, 4 Jan 2010

探測天外行星的方法很多，昨天的文章有介紹（Kepler 是用 transit 方式的）。每種辦法有其「擅長」探測的行星種類，簡單來說，radial velocity（亦即下圖所謂的 doppler）和 transit 善於探測質量大和接近母恆星的行星，microlensing 則適合一些離母恆星較遠的。儀器不斷進步，發現的天外行星質量應該愈來愈小。
來源：The detection and characterization of exoplanets, Physics Today, May 2009

行星根據其質量和溫度大致上可分為 gas giant 和 super Earth 等數種，以下是截至 2009 年 3 月的分佈。

A “discovery space” plot of known extrasolar planets according to their mass and distance shows all three classes of planets familiar from our solar system — gas giants (orange), cold super-Earths or ice giants (blue), hot and warm super-Earths or terrestrial planets (green) — as well as hot Jupiters (red) and brown dwarfs (brown). One astronomical unit (AU) is the mean distance of the Earth from the Sun. (Credit: The Extrasolar Planet Encyclopaedia)

來源：Brave new worlds, physicsworld.com, 2 Mar 2009