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Astronomers say they have found evidence for the first time of a planet orbiting a star outside our Milky Way galaxy.
天文学家表示，他们首次发现证据表明有一颗行星围绕银河系外的一颗恒星运行。
The evidence was observed by a telescope operated by the American space agency NASA.
该证据是由美国国家航空航天局的望远镜观测到的。
It is called the Chandra X-ray Observatory.
它被称为钱德拉X射线天文台。
NASA says the orbiting observatory is the world’s most powerful X-ray telescope.
美国国家航空航天局表示，该轨道天文台是世界上最强大的X射线望远镜。
NASA recently announced that the observatory might have discovered a new planet in the galaxy known as Messier 51 or M51.
美国国家航空航天局最近宣布，该天文台可能在星系中发现了一颗被称为梅西耶51或M51的新行星。
The galaxy is popularly known as the “Whirlpool” galaxy.
这个星系通常被称为“涡状”星系。
The research recently appeared in the publication Nature Astronomy.
这项研究最近发表在《自然·天文学》杂志上。
The possible planet is considered an exoplanet.
这颗可能存在的行星被认为是系外行星。
These are planets that orbit a star outside of our own solar system.
这些行星围绕我们太阳系外的恒星运行。
NASA says that so far, more than 4,500 exoplanets have been discovered and are considered "confirmed."
美国国家航空航天局表示，到目前为止，已经发现了4500多颗系外行星，并被认为是“已确认的”。
Thousands of other "candidate" exoplanets have been detected, but require additional study.
数千颗其他“候选”系外行星已经被探测到，但还需要进一步的研究。
But all of these have been observed in the Milky Way galaxy.
但所有这些行星都已在银河系中被观测到。
And NASA says almost all of them are "less than about 3,000 light-years from Earth."
美国国家航空航天局表示，几乎所有这些行星“距离地球不到3000光年”。
Scientists estimate that an exoplanet in the M51 galaxy would be much farther, about 28 million light-years away.
科学家们估计，M51星系中的一颗系外行星要远得多，距地球大约2800万光年。
Exoplanets are hard for telescopes to identify.
天文望远镜很难识别系外行星。
This is because the bright light of the stars they orbit can hide them.
这是因为它们所环绕的恒星发出的明亮光线会将它们隐藏起来。
The identification process involves searching for drops in the light levels of stars.
识别过程包括寻找恒星亮度的下降。
Such drops could be caused by a planet passing in front of a star.
这种亮度下降的现象可能是由一颗行星从一颗恒星前面经过造成的。
This method has been used in past observations by NASA telescopes to confirm the presence of planets crossing in front of stars.
美国国家航空航天局的望远镜曾在过去的观测中使用过这种方法，以在行星在恒星前面穿过时确认行星的存在。
These movements—of planets partly blocking light from stars—are called "transits."
这些行星部分阻挡恒星光线的运动被称为“凌日”。
NASA's latest finding is based on a transit detected by the Chandra X-ray Observatory.
美国国家航空航天局的最新发现是基于钱德拉X射线天文台探测到的一次凌日现象。
But unlike other NASA telescopes which search for drops in observable light, Chandra is designed to detect X-rays.
但与美国国家航空航天局的其他在可观测光线中寻找亮度下降的望远镜不同，钱德拉是为探测X射线而设计的。
The observatory "searched for drops in the brightness of X-rays received from X-ray bright binaries," NASA said in a statement.
美国国家航空航天局在一份声明中说，该天文台“寻找从X射线明亮双星接收到的X射线亮度的下降。”
These binaries are defined as bright systems that usually contain a neutron star or black hole pulling in gas from a closely orbiting star.
这些双星被定义为明亮的系统，通常包含一个中子星或黑洞，它从近距离环绕的伴星中吸收气体。
A neutron star is the unimaginably dense result of a supergiant star that has collapsed on itself.
中子星是超巨星坍缩后的产物，密度高得难以想象。
The researchers said the activity of binaries causes the material near the neutron star or black hole to become superheated and glow in X-rays.
研究人员说，双星的活动导致中子星或黑洞附近的物质变得过热并发出x射线。
However, the area producing the X-rays is small.
然而，产生X射线的区域很小。
It is so small that a planet passing in front of it could block most or all the X-rays, they added.
他们补充说，它是如此之小，以至于从它前面经过的行星可以阻挡大部分或所有的X射线。
This method could permit exoplanets "to be detected at much greater distances" than other light-searching systems that depend on optical telescopes, the NASA statement said.
美国国家航空航天局在声明中说，与其他依赖光学望远镜的光搜索系统相比，这种方法可以让系外行星“在更远的距离被探测到”。
Rosanne Di Stefano is an astrophysicist at the Center for Astrophysics, Harvard & Smithsonian in Cambridge, Massachusetts.
罗珊·迪·斯特凡诺是马萨诸塞州剑桥市哈佛和史密森尼天体物理中心的一名天体物理学家。
She said in a statement that the research team is seeking "to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths."
她在一份声明中说，研究小组正在寻求“通过x射线波长搜索候选行星，为寻找其他世界打开一个全新的舞台。”
Such methods could be used in the future to discover other new planets in distant galaxies, Di Stefano added.
迪·斯特凡诺补充说，这种方法将来可以用来发现遥远星系中的其他新行星。
The researchers say more data will be needed to confirm the observation as an actual "extragalactic exoplanet."
研究人员说，还需要更多的数据来证实这是一颗真正的“星系外系外行星”。
They say one problem is that the planet candidate has a large orbit.
他们说，问题是这颗候选行星的轨道很大。
This means it is not expected to pass in front of its binary partner for at least 70 years, blocking any confirmation attempts anytime soon.
这意味着它至少在70年内不会在其恒星前面穿过，从而阻止了任何短期内的确认尝试。
However, one co-writer of the study said the team is very confident with its findings.
然而，该研究的一位合著者表示，该团队对其发现非常有信心。
"We know we are making an exciting and bold claim, so we expect that other astronomers will look at it very carefully," said Julia Berndtsson of Princeton University in New Jersey.
新泽西州普林斯顿大学的朱莉娅·伯恩特森说：“我们知道我们正在做出一个令人兴奋和大胆的声明，所以我们期待其他天文学家会非常仔细地观察它。”
She added "We think we have a strong argument, and this process is how science works."
她补充说，“我们认为我们有一个强有力的论点，这个过程就是科学的运作方式。”
I'm Bryan Lynn.
布莱恩·林恩为您播报。
译文为可可英语翻译，未经授权请勿转载！
