Scientists have discovered a new planet that is similar to Earth. The planet, called Kepler-186f, is slightly (no more than 10%) larger than ours and probably has seasons like Earth does. But while this news is exciting, there is a lot that we still don't know about Kepler-186f.

NASA–the research organization that found the new planet–is always looking for planets with similar conditions to Earth's. However, space scientist Thomas Barclay says that we should think of Kepler-186f as an "Earth cousin" and not as an "Earth twin." Like our planet, it is made of rock. It is also likely to have water on its surface, which is unusual, but in many other ways Kepler-186f is different from Earth.

Whereas Earth takes 365 days to go around the sun, Kepler-186f only takes 130 days to go around its star. Earth is brighter, too; at midday on Kepler-186f, the sky would look the same as during our sunset. And scientists don't yet know about the temperature on the new planet. There is a good chance that Kepler-186f is much hotter than Earth.

Unfortunately, humans will not be traveling to Kepler-186f any time soon. It is 500 light-years away, so the journey would take a lot more than 500 years. NASA is still looking for other livable planets which are closer and easier to understand.

科學家已發現了相似地球的新行星。稱為「克卜勒-186f」的此行星，比地球略大（不超過10%），還可能具備如地球般的四季特質。不過，雖然此消息令人振奮，但我們仍不甚了解克卜勒-186f。

發現此新行星的研究機構──美國太空總署（NASA），一直致力於尋找各項條件與地球相仿的行星。然而，太空科學家湯瑪斯•巴克萊表示，我們應該將克卜勒-186f視為地球的「表親」，而非地球的「雙胞胎」。此行星的地質結構與地球一樣，均為岩石，地表也很有可能出現水源，這點實屬罕見。但是克卜勒-186f在許多其他層面，仍與地球大相逕庭。

地球公轉太陽一圈需要365天；克卜勒-186f公轉其恆星一圈僅需130天。地球也較為明亮，克卜勒-186f的午時，天空看起來已如地球的夕陽景象。況且，科學家尚未得知此新行星的氣溫，克卜勒-186f的氣候很有可能比地球炎熱許多。

不幸的是，人類短期內都無法前往克卜勒-186f。它距離地球有500光年之遠，意即這趟旅程需耗費超過500年的時間。NASA仍在尋覓距離較近且更容易了解特性的適居行星。