The Crab pulsar, the best-known example of a bright pulsar wind nebula, is about 950 years old.
蟹状星云脉冲星是脉冲星风星云中最为著名的一个,但它已经950岁了。
2
Also known as Abell 21, this Medusa is an old planetary nebula some 1, 500 light-years away in the constellation Gemini.
也被称作阿贝尔21,水母星云是双子座中一个1500光年远的年老行星状星云。
3
Since open star clusters disperse after only a few hundred million years, this one must be exceptionally old to have one of its member stars evolve to the planetary nebula stage.