A transiting giant planet with a temperature between 250 K and 430 K

摘要

Of the over 400 known exoplanets, there are about 70 planets that transit their central star, a situation that permits the derivation of their basic parameters and facilitates investigations of their atmospheres. Some short-period planets, including the first terrestrial exoplanet (CoRoT-7b), have been discovered using a space mission designed to find smaller and more distant planets than can be seen from the ground. Here we report transit observations of CoRoT-9b, which orbits with a period of 95.274 days on a low eccentricity of 0.11 ± 0.04 around a solar-like star. Its periastron distance of 0.36 astronomical units is by far the largest of all transiting planets, yielding a 'temperate' photospheric temperature estimated to be between 250 and 430 K. Unlike previously known transiting planets, the present size of CoRoT-9b should not have been affected by tidal heat dissipation processes. Indeed, the planet is found to be well described by standard evolution models with an inferred interior composition consistent with that of Jupiter and Saturn.%在超过400颗已知的太阳系外行星中，大约70rn颗穿越它们的中央恒星，这使得人们有可能观rn测它们的大气层和确定各种不同的关键参数。rn迄今所发现的穿越中央恒星的太阳系外行星都rn有非常短的或偏心的轨道，所以要么非常热，rn要么表面温度会发生极端变化。现在，CoRoTrn空间观测站发现了一颗与太阳系巨型气体恒星rn非常相似的太阳系外行星。编号为CoRoT-9b的rn这颗行星处在一个周期为95天的低偏心度轨道rn上，像水星的轨道，绕一颗类似太阳的恒星运rn行。它的表面温度在-20和150℃之间。根据其rn密度，它的内部组成似乎与木星和土星相似。