天文学家发现比煤炭还黑的行星

Astronomers have discovered the darkest known planet。

The planet, known as TrES-2b, reflects less than 1 per cent of light, which makes it darker than any other planet or moon。

The planet, roughly the size of Jupiter, is around 750 light years away。

The reason it differs from other similar-sized planets is that Jupiter, for example, is surrounded by ammonia clouds that reflect more than one third of its sunlight。

TrES-2b has no ammonia clouds to reflect light because it is extremely hot。

Instead, it has an atmosphere made up of chemicals such as vaporized sodium, potassium and gaseous titanium oxide, which absorb light, but that still does not explain the planet's extreme blackness。

However, TrES-2b is not entirely black. Its extreme heat means it gives off a faint red glow。

David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA) and his team arrived at the discovery by measuring the light TrES-2b emitted as it orbited its star, much like our moon does with earth, studying both the “visible”side and its“dark” side during orbit。

The discovery was detailed in the journal Monthly Notices of the Royal Astronomical Society。

据英国《每日邮报》8月13日报道，天文学家发现已知最黑行星。

这颗行星被命名为TrES-2b，它仅反射低于1%的恒星光线，这使得它比迄今发现的任何行星或卫星都要暗。

TrES-2b基本如木星一般大小，距离地球大约750光年。

以木星为例，TrES-2b之所以与其它与之大小相近的行星不同，是因为木星周围被能反射超过1/3太阳光的氨云层所笼罩。

而酷热的 TrES-2b上缺少能反射光线的氨云层。

相反，TrES-2b的大气层由气态钠、钾和三氧化钛这些可以吸收光线的化学物质组成，不过这也并不能为该行星极黑提供解释。

尽管如此，TrES-2b并非完全漆黑，炙热的高温意味着它可发出淡红色的光辉。

TrES-2b绕恒星运行时发散出的光线与月球绕地球所散发出的光线很相似，来自哈佛史密松森天文物理中心的的大卫•基平和他的团队通过对这种光线的测量及对TrES-2b在绕轨运行时“可见”与“黑暗”面的研究得出了这一结论。

对该发现的详尽介绍发表在《皇家天文学会月刊》上。