@nasa : Blue Bubble: Sparkling at the center of this beautiful Hubble Space Telescope image is a Wolf-Rayet star known as WR 31a, located about 30,000 light-years away. The distinctive blue bubble appearing to encircle WR 31a is a Wolf-Rayet nebula - an interstellar cloud of dust, hydrogen, helium and other gases. Created when speedy stellar winds interact with the outer layers of hydrogen ejected by Wolf-Rayet stars, these nebulae are frequently ring-shaped or spherical. The bubble - estimated to have formed around 20,000 years ago - is expanding at a rate of around 220,000 kilometers (136,700 miles) per hour! Unfortunately, the lifecycle of a Wolf-Rayet star is only a few hundred thousand years - the blink of an eye in cosmic terms. Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt #nasa #hubble #hst #nebula #planets #stars #nasabeyond #astronomy #science
โพสต์เมื่อ 27 ก.พ. 2559 | 05:53 น.
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