最冷恒星被发现 表面温度相当于地球夏天

伤我心太深

天文学家发现了一颗温度仅为370开氏度的褐矮星

恒星就是恒星，行星就是行星，两者永远都没有交集，不是吗？

答案并非如此。

当谈到质量和温度，褐矮星的分类应当介于恒星与行星之间的某个地方。

褐矮星是所谓的不成功的恒星，它们因为太小而无法维持稳定的氢燃烧。

如今，研究人员已经发现了两颗褐矮星，它们的温度比之前观测到的任何褐矮星都要低——因为是如此之冷以及如此之小，这两颗褐矮星几乎就像是巨行星。

在3月20日发表于《天体物理学杂志快报》上的一篇论文中，美国大学公园市宾夕法尼亚州立大学的天文学家K. L. Luhman和同事报告说，一颗距离地球约63光年的褐矮星，其温度仅仅为300开氏度。

这一温度比之前的纪录保持者低了200开氏度，大约相当于地球上的一个温暖的夏日。

在发表于即将出版的《天体物理学杂志》上的第二项研究中，美国纽约市康奈尔大学的天文学家Michael C. Liu和同事描述了另一颗非常寒冷的褐矮星(如一部红外望远镜拍摄图像所示)，据估计其温度约为370开氏度。

这两颗天体将成为一类极冷的褐矮星，即Y级褐矮星的第一批例证。

原文：

科学家近日发现一颗叫做WD 0806-661 B的星球的表面温度与地球夏天的温度差不多，只有27~80℃，要知道它可是不是行星，而是一颗恒星。这个星球属于褐矮星，距太阳系63光年，质量只有木星的6~9倍，它目前围绕着一颗白矮星运动。

Artists impression of what the brown dwarf discovered with the Nasa spitzer telescope would look like - the tiny, cold star orbits a white dwarf, the burnt-out remnant of a star like our sun

Artist's impression of a brown-dwarf object (left foreground) orbiting a distant white dwarf, the collapsed-core remnant of a dying star

The temperature of the surface is like a hot summer's day in Arizona or Seville - and would be quite pleasant for humans. It's the coldest object ever photographed outside our solar system.

But WD 0806-661 B is not a planet - it's a very small star. Its mass is just six to nine times the gas giant Jupiter.

Penn State Associate Professor of Astronomy and Astrophysics Kevin Luhman, who discovered the object said, 'It is a very small star with an atmospheric temperature about as cool as the Earth's.'

The astronomers used Nasa's Spitzer space telescope - the most sensitive space telescope on Earth - to find the cold star, scanning 600 near-earth stars for objects orbiting them. Infrared telescopes are used because cold objects 'shine out' brightly in the images. The record-breaking star is 63 million light years from Earth and orbits a dense, collapsed 'white dwarf' star.

The star is a brown dwarf - and formed, like other stars, out of a cloud of dust and gas.

But because it failed to accumulate enough mass from the dust cloud, the thermonuclear reaction that 'lights up' normal stars fail to ignite.

The new brown dwarf's surface is between 27 and 80 degrees centigrade - so in places, it's a temperature humans might enjoy.

The new brown dwarf has a surface temperature between 27 and 80 degrees centigrade, and orbits a white dwarf star

Ever since brown dwarfs first were discovered in 1995, astronomers have been trying to find new record holders for the coldest brown dwarfs - the objects are seen as valuable laboratories to help us understand the atmospheres of extrasolar planets with Earth-like temperatures.

Astronomers have named the brown dwarf ‘WD 0806-661 B’. It orbits the ‘white dwarf’ core of a star . The white dwarf would have shone like our sun until its outer layers were expelled into space in the final stages of a star's life.

‘The distance of this white dwarf from the Sun is 63 light-years, which is very near our solar system compared with most stars in our galaxy,’ Luhman said.

The orbit of the brown dwarf is huge, about 2,500 times the distance between Earth and the sun.

Luhman and his colleagues presented this new candidate for the coldest known brown dwarf in a paper published in spring 2011, and they now have confirmed its record-setting cool temperature in a new paper that will be published in the Astrophysical Journal.