天文學家發現比煤炭還黑的行星

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。據英國《每日郵報》8月13日報道，天文學家發現已知最黑行星。

這顆行星被命名爲TrES-2b，它僅反射低於1%的恆星光線，這使得它比迄今發現的任何行星或衛星都要暗。

TrES-2b基本如木星一般大小，距離地球大約750光年。

以木星爲例，TrES-2b之所以與其它與之大小相近的行星不同，是因爲木星周圍被能反射超過1/3太陽光的氨雲層所籠罩。

而酷熱的 TrES-2b上缺少能反射光線的氨雲層。

相反，TrES-2b的大氣層由氣態鈉、鉀和三氧化鈦這些可以吸收光線的化學物質組成，不過這也並不能爲該行星極黑提供解釋。

儘管如此，TrES-2b並非完全漆黑，炙熱的高溫意味着它可發出淡紅色的光輝。

TrES-2b繞恆星運行時發散出的光線與月球繞地球所散發出的光線很相似，來自哈佛史密鬆森天文物理中心的的大衛•基平和他的團隊通過對這種光線的測量及對TrES-2b在繞軌運行時“可見”與“黑暗”面的研究得出了這一結論。

對該發現的詳盡介紹發表在《皇家天文學會月刊》上。