Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands.
Nature. 2010 Jun 24;465(7301):1049-51. doi: 10.1038/nature09111.
For extrasolar planets discovered using the radial velocity method, the spectral characterization of the host star leads to a mass estimate of the star and subsequently of the orbiting planet. If the orbital velocity of the planet could be determined, the masses of both star and planet could be calculated using Newton's law of gravity, just as in the case of stellar double-line eclipsing binaries. Here we report high-dispersion ground-based spectroscopy of a transit of the extrasolar planet HD 209458b. We see a significant wavelength shift in absorption lines from carbon monoxide in the planet's atmosphere, which we conclude arises from a change in the radial component of the planet's orbital velocity. The masses of the star and planet are 1.00 +/- 0.22M(Sun) and 0.64 +/- 0.09M(Jup) respectively. A blueshift of the carbon monoxide signal of approximately 2 km s(-1) with respect to the systemic velocity of the host star suggests the presence of a strong wind flowing from the irradiated dayside to the non-irradiated nightside of the planet within the 0.01-0.1 mbar atmospheric pressure range probed by these observations. The strength of the carbon monoxide signal suggests a carbon monoxide mixing ratio of (1-3) x 10(-3) in this planet's upper atmosphere.
对于使用径向速度法发现的太阳系外行星，对母恒星的光谱特征进行分析可得出恒星的质量估计值，进而得出环绕该恒星运行的行星的质量。如果能够确定行星的轨道速度，就可以利用牛顿引力定律计算出恒星和行星的质量，就像对恒星双星的凌日观测一样。我们在此报告对太阳系外行星 HD 209458b 凌日现象的高色散地面光谱观测结果。我们观察到行星大气中一氧化碳的吸收线出现了显著的波长位移，我们推断这是由于行星轨道速度的径向分量发生了变化。母恒星和行星的质量分别为 1.00 +/- 0.22M(Sun)和 0.64 +/- 0.09M(Jup)。相对于母恒星的系统速度，一氧化碳信号的蓝移约为 2 km s(-1)，这表明在这些观测所探测到的 0.01-0.1 mbar 气压范围内，存在着一股从受照的白天面流向未受照的黑夜面的强风。一氧化碳信号的强度表明，在这颗行星的高层大气中，一氧化碳的混合比为 (1-3) x 10(-3)。
