行星状星云Abell 7
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NGC 2440: 新白矮星的茧
2023年12月24日 NGC 2440: Cocoon of a New White Dwarf Image Credit: NASA, ESA, Hubble; Processing: H. Bond (STScI), R. Ciardullo (PSU), Forrest Hamilton (STScI) Explanation: What’s that in the center? Like a butterfly, a white dwarf star begins its life by casting off a cocoon of gas that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest cocoon of all. In the featured cocoon, the planetary nebula designated NGC 2440 contains one of the hottest white dwarf stars known. The white dwarf can be seen as the bright orange dot near the image center. Our Sun will eventually become a white dwarf butterfly, but not for another 5 billion years….
行星状星云Abell 7
2022年5月21日 Planetary Nebula Abell 7 Image Credit & Copyright: Donald Waid, Ron Dilulio Explanation: Very faint planetary nebula Abell 7 is some 1,800 light-years distant, just south of Orion in planet Earth’s skies in the constellation Lepus, The Hare. Surrounded by Milky Way stars and near the line-of-sight to distant background galaxies, its generally simple spherical shape, about 8 light-years in diameter, is outlined in this deep telescopic image. Within its confines are beautiful, more complex details enhanced by the use of narrowband filters. Emission from hydrogen is shown in reddish hues with oxygen emission mapped to green and blue colors, giving Abell 7 a natural appearance that would otherwise be much too faint to be appreciated by eye. A planetary nebula represents a very…
来自蛇夫RS白矮星的新星爆发
2021年8月22日 Explosions from White Dwarf Star RS Oph Illustration Credit & Copyright: David A. Hardy & PPARC Explanation: Spectacular explosions keep occurring in the binary star system named RS Ophiuchi. Every 20 years or so, the red giant star dumps enough hydrogen gas onto its companion white dwarf star to set off a brilliant thermonuclear explosion on the white dwarf’s surface. At about 5,000 light years distant, the resulting nova explosions cause the RS Oph system to brighten up by a huge factor and become visible to the unaided eye. The red giant star is depicted on the right of the above drawing, while the white dwarf is at the center of the bright accretion disk on the left. As the stars orbit each other,…