NASA9s Kepler spacecraft has racked up thousands of exoplanet discoveries since its launch in 2009, but before Kepler, the workhorses of exoplanet identification were ground-based instruments that measure tiny stellar wobbles caused by the gravity of an orbiting planet. They are now undergoing a quiet renaissance. The new generation of these devices may be precise enough to find a true Earth twin: a planet with the same mass as ours, orbiting a sunlike star once a year. That9s something Kepler—sensitive to planet size, but not mass—can9t do. Over the past few months, two new third-generation instruments have opened their eyes to the sky and nearly two dozen others are either under construction or have recently begun service.

中文翻译：

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地球行星探测器通电

自 2009 年发射以来，NASA9 的开普勒航天器已经发现了数千颗系外行星，但在开普勒之前，系外行星识别的主力是地面仪器，用于测量由轨道行星引力引起的微小恒星摆动。他们现在正在经历一个安静的复兴。新一代的这些设备可能足够精确，可以找到真正的地球双胞胎：一颗与我们质量相同的行星，每年围绕一颗类似太阳的恒星运行一次。这是开普勒——对行星大小敏感，但对质量不敏感——做不到的。在过去的几个月里，两台新的第三代仪器已经向天空开放，还有近两打正在建造中或最近开始使用的仪器。