美国康奈尔大学的研究人员称，月亮不是唯一围绕地球轨道运行的天体。其它更小一些的物体也一直有规律的运行在地球轨道上，有时它们会离开几个月，但仍然会回来继续绕地运行。在这个科学家都忙着研究地外星球的时代，这项研究被认为具有重大的意义。不过由于这些临时月亮太小，以至于太空飞船也不能在其上着陆，因此，科学家只能等它们距离地球较近时通过天文望远镜进行研究。

其实，早在2006年，美国卡特里娜巡天系统已经发现有一颗这样的临时月亮绕地运行一年。但，康奈尔大学的科学家认为，还有更多的“秘密月球”没有受到应有的关注。科学家认为，除了月亮外，在任何时候，地球都会有至少一颗直径超过1米的非人造卫星环绕左右。

There are at least two moons orbiting Earth at any given time.

Researchers at Cornell University say that what we know as the Moon is in fact not the only one orbiting our planet at any given time. Smaller objects regularly inhabit the Earth's orbit, usually leaving after a few months to continue on their celestial journeys.

The discovery is considered a major breakthrough for space research because scientists had been working toward visiting asteroids outside of Earth's orbit for research. While these temporary moons are too small for a shuttle landing, they are prime for research from a relatively close distance.

However, it's still to be determined whether the announcement will capture the public's attention like previously revealed New Moons. Either way, it should be a decidedly more pleasant experience for all involved.

The new paper titled "The population of natural Earth satellites," from Cornell University's Mikael Granvik, Jeremie Vaubaillon and Robert Jedicke states that these "secret moons" enter and exit the Earth's orbit without notice.

"At any given time, there should be at least one natural Earth satellite of 1-meter diameter orbiting the Earth," Granvik writes.

Scientists have confirmed at least one such temporary moon, discovered by the Catalina Sky Survey in Arizona in 2006.

"Our results are consistent with the single known natural [temporarily-captured orbiter] 2006 RH120, a few-meter diameter object that was captured for about a year starting in June 2006," the report says.

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(Agencies)

（英语点津 Rosy 编辑）