Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing
Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing
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DOI：
10.1038/nature04441
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发表时间：
2006-01-26
期刊：
影响因子：
64.8
通讯作者：
Yoshioka, T
中科院分区：
文献类型：
--
作者：
Beaulieu, JP;Bennett, DP;Yoshioka, T
在行星系统形成的核心-吸积模型中，固态微行星积累形成行星核心，如果质量足够大，则会吸积星云气体。在M-矮星（银河系中最常见的恒星）周围，这个模型倾向于形成地球质量（M+）到海王星质量的行星，其轨道半径为1到10个天文单位（Au），这与已知的少数气体巨行星围绕M-矮星运行（1-4）是一致的。迄今为止，已经发现了170多颗太阳系外行星，它们的质量和轨道周期都有很大的不同，但迄今为止还没有发现海王星质量或更小的行星与正常恒星的距离超过0.15 Au。在这里，我们报告发现了一个5.5（-2.7）（+5.5）M（+）的行星伴侣，距离0.22（-0.11）（+0.21）M（.）M-矮星星星，其中M-。指的是太阳质量。(We建议将其命名为OGLE-2005-BLG-390 Lb，表示微透镜事件的透镜星星的行星质量伴星。）质量低于GJ 876 d（参考文献5），尽管误差条重叠。我们的探测表明，这种冷的，亚海王星质量的行星可能比气体巨行星更常见，正如核心吸积理论所预测的那样。
In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars ( the most common stars in our Galaxy), this model favours the formation of Earth-mass (M+) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (AU), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars(1-4). More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15 AU from normal stars. Here we report the discovery of a 5.5(-2.7)(+5.5)M(+) planetary companion at a separation of 2.6(-0.6)(+1.5) AU from a 0.22(-0.11)(+0.21)M(.) M-dwarf star, where M-. refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory.