蛇妖星云

蛇妖星云

ByNASA中文

2021年03月26日 The Medusa Nebula Image Credit & Copyright: Josep Drudis Explanation: Braided and serpentine filaments of glowing gas suggest this nebula’s popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula some 1,500 light-years away in the constellation Gemini. Like its mythological namesake, the nebula is associated with a dramatic transformation. The planetary nebula phase represents a final stage in the evolution of low mass stars like the sun as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation from the hot star powers the nebular glow. The Medusa’s transforming star is the faint one near the center of the overall bright crescent shape. In…

行星状星云Abell 78

行星状星云Abell 78

ByNASA中文

2020年10月16日 Planetary Nebula Abell 78 Image Credit & Copyright: Bernhard Hubl Explanation: Planetary nebula Abell 78 stands out in this colorful telescopic skyscape. In fact the colors of the spiky Milky Way stars depend on their surface temperatures, both cooler (yellowish) and hotter (bluish) than the Sun. But Abell 78 shines by the characteristic emission of ionized atoms in the tenuous shroud of material shrugged off from an intensely hot central star. The atoms are ionized, their electrons stripped away, by the central star’s energetic but otherwise invisible ultraviolet light. The visible blue-green glow of loops and filaments in the nebula’s central region corresponds to emission from doubly ionized oxygen atoms, surrounded by strong red emission from ionized hydrogen. Some 5,000 light-years distant toward the…