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A rocky composition for an Earth-sized exoplanet

机译：地球大小的系外行星的岩石组成

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人们目前已经发现少数几个与地球的大小或质量差不多的太阳系外行星。现在，它们当中一个的大小质量首次同时被确定。于今年8月被首次描述的Kepler-78b靠近其主星，它绕后者每8.5小时转一圈。两个小组得以能够利用行星和恒星之间的近距离来对Kepler-78b的质量进行多普勒光谱测定。由Andrew Howard和Francesco Pepe领导的这两个小组采用不同天文望远镜分别对该行星的质量做出了估计，其结果分别为1.69 ± 0.41和1.86+0.38/-0.245个地球质量。他们计算出该行星的平均密度分别为5.3和5.57gcm~(-3),这非常像地球的平均密度，并且说明它具有与地球相似的岩石和铁组成。%Planets with sizes between that of Earth (with radius R_(+)) and Neptune (about 4R_(+)) are now known to be common around Sun-like stars. Most such planets have been discovered through the transit technique, by which the planet's size can be determined from the fraction of starlight blocked by the planet as it passes in front of its star. Measuring the planet's mass-and hence its density, which is a clue to its composition-is more difficult. Planets of size 2-4R_(+) have proved to have a wide range of densities, implying a diversity of compositions, but these measurements did not extend to planets as small as Earth. Here we report Doppler spectroscopic measurements of the mass of the Earth-sized planet Kepler-78b, which orbits its host star every 8.5 hours (ref. 6). Given a radius of 1.20 ± 0.09R_(+) and a mass of 1.69 ± 0.41M_(+), the planet's mean density of 5.3 ± 1.8 g em~(-3) is similar to Earth's, suggesting a composition of rock and iron.
机译：人们目前已经发现少数几个与地球的大小或质量差不多的太阳系外行星。现在，它们当中一个的大小质量首次同时被确定。于今年8月被首次描述的Kepler-78b靠近其主星，它绕后者每8.5小时转一圈。两个小组得以能够利用行星和恒星之间的近距离来对Kepler-78b的质量进行多普勒光谱测定。由Andrew Howard和Francesco Pepe领导的这两个小组采用不同天文望远镜分别对该行星的质量做出了估计，其结果分别为1.69 ± 0.41和1.86+0.38/-0.245个地球质量。他们计算出该行星的平均密度分别为5.3和5.57gcm~(-3),这非常像地球的平均密度，并且说明它具有与地球相似的岩石和铁组成。%Planets with sizes between that of Earth (with radius R_(+)) and Neptune (about 4R_(+)) are now known to be common around Sun-like stars. Most such planets have been discovered through the transit technique, by which the planet's size can be determined from the fraction of starlight blocked by the planet as it passes in front of its star. Measuring the planet's mass-and hence its density, which is a clue to its composition-is more difficult. Planets of size 2-4R_(+) have proved to have a wide range of densities, implying a diversity of compositions, but these measurements did not extend to planets as small as Earth. Here we report Doppler spectroscopic measurements of the mass of the Earth-sized planet Kepler-78b, which orbits its host star every 8.5 hours (ref. 6). Given a radius of 1.20 ± 0.09R_(+) and a mass of 1.69 ± 0.41M_(+), the planet's mean density of 5.3 ± 1.8 g em~(-3) is similar to Earth's, suggesting a composition of rock and iron.

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  • 来源
    《Nature》 |2013年第7476期|381-384|共4页
  • 作者

    Andrew W. Howard; Roberto Sanchis-Ojeda; Geoffrey W. Marcy; John Asher Johnson; Joshua N. Winn; Howard Isaacson; Debra A. Fischer; Benjamin J. Fulton; Evan Sinukoff; Jonathan J. Fortney;

  • 作者单位

    Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA;

    Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts institute of Technology, Cambridge, Massachusetts 02139, USA;

    Astronomy Department, University of California, Berkeley, California 94720, USA;

    Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA;

    Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts institute of Technology, Cambridge, Massachusetts 02139, USA;

    Astronomy Department, University of California, Berkeley, California 94720, USA;

    Department of Astronomy, Yale University, New Haven, Connecticut 06510, USA;

    Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA;

    Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA;

    Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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