本帖最后由 其祥 于 2010-1-3 03:20 编辑
In this week’s issue of Nature, astronomers announce the discovery of a planet around the nearby, low-mass star GJ1214 [2]. It is the second time a transiting super-Earth has been detected, after the recent discovery of the planet Corot-7b [3]. A transit occurs when the planet's orbit is aligned so that we see it crossing the face of its parent star.The newly discovered planet has a mass about six times that of our terrestrial home and 2.7 times its radius, falling in size between the Earth and the ice giants of the Solar System, Uranus and Neptune.
在这周的《自然》杂志上所发表的论文中，天文学家宣布发现了这颗绕转小质量恒星--GJ1214的行星。这是继最近发现的系外行星Corot-7b之后，通过掩星（其祥注：掩星是一种天文现象，指一个天体在另外一个天体与观测者之间通过时所产生的遮蔽现象）探测到的第二颗“超级地球”。最新发现的这颗系外行星质量约为地球的6倍，半径约为地球的2.7倍。大小介于地球与太阳系的冰巨人（天王星、海王星）之间。
Although the mass of GJ1214b is similar to that of Corot-7b, its radius is much larger, suggesting that the composition of the two planets must be quite different. While Corot-7b probably has a rocky core and may be covered with lava, astronomers believe that three quarters of GJ1214b is composed of water ice, the rest being made of silicon and iron.
尽管GJ1214b的质量与Corot-7b相近，但是它的半径要大的多，这也表明组构成这两颗系外行星的物质成分会有很大不同。Corot-7b的表面很可能是被岩浆覆盖的岩石地表，而天文学家们坚信GJ1214b上月3/4的地表被水冰覆盖，剩下的很有可能由硅和铁构成。
GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres — 70 times closer to its star than the Earth is to the Sun. “Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid,” says David Charbonneau, lead author of the paper reporting the discovery.
相比于地球绕转太阳的轨道，GJ1214b的轨道半径要缩短了70倍，仅仅只距离它的“太阳”约两百万公里，绕转周期约为38小时。据论文的第一作者David Charbonneau说，因为它距离主星这样近，所以其表面温度约为200摄氏度，如此，水不会以液态形式存在。 |
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