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沙漏星云内部能源耗尽 “天空之眼”大限将至

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小编摘要:沙漏星云(MyCn18)是位于南天的苍蝇座,距离地球8000光的年轻行星状星云。因星云中心有沙尘般的物质外溢,好似沙粒在沙漏中移动而得名。当其内部核燃料耗尽,这个如同太阳般的恒星会首先在中心冷却,褪变成为白矮星。

导读:沙漏星云(MyCn18),还有一个动人的名字“天空之眼”,因天文学家通过哈勃太空望远镜观测距地球8000光年远的外太空时,它像极了上帝凝视的眼睛。据悉,MyCn18内部原子能已耗尽,“天空之眼”将消失,最终冷却成白矮星。MyCn18由Annie Jump Cannon和Margaret W Mayall在扩编HD星表(1918-1924)时发现,沙漏形状的成因是MyCn18在低速膨胀的云气之内有高速膨胀的星风,而云气在赤道的密度又比两极高。

Exhausted: Located 8,000 light-years away from Earth in the southern constellation Musca, MyCn18's core is in the process of becoming a cooling, fading white dwarf

Exhausted: Located 8,000 light-years away from Earth in the southern constellation Musca, MyCn18's core is in the process of becoming a cooling, fading white dwarf

The sands of time are running out for the central star of this hourglass-shaped planetary nebula.

With its nuclear fuel exhausted, this brief but spectacular closing phase of MyCn18 - better known as the Engraved Hourglass Nebula - occurs as its outer layers are ejected.

Located 8,000 light-years away from Earth in the southern constellation Musca, the sun-like star's core is in the process of becoming a cooling, fading white dwarf.

Astronomers used the Hubble Space Telescope to make a series of images of planetary nebulae in the mid-1990s, including this one.

Delicate rings of colourful glowing gas - nitrogen-red, hydrogen-green, and oxygen-blue - outline the tenuous walls of the hourglass.

The unprecedented sharpness of Hubble's image has revealed surprising details of the nebula ejection process.

And it is these that are helping scientists to resolve the outstanding mysteries of the complex shapes and symmetries of planetary nebula.

MyCn18 was discovered by Annie Jump Cannon and Margaret W Mayall during their research on an extended Henry Draper Catalogue, an astronomical star encyclopedia compiled between 1918 and 1924.

The astronomers described it as a small faint planetary nebula, but the march of technology allowed scientists Raghvendra Sahai and John Trauger of the Jet Propulsion Laboratory to capture this stunning image using Hubble in January 1996.

MyCn18's hourglass shape is thought to have arisen from the expansion of a fast stellar wind within a slowly expanding cloud which is denser near its equator than its poles.

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2011-08-09 15:06 编辑:jeannn
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