Astronomy Picture of the Day

Explanation:

裡頭滿是神秘絲狀物的蟹狀星雲，是1054年一顆恆星爆炸的產物。 這例壯觀的超新星爆炸事件，曾由中國和（很可能是）阿納薩齊印第安人的天文學家所記錄。 這些絲狀物之所以神秘難解，則是它們看起來比原始超新星釋出的質量少，擴張速度又比自由爆炸要高。 在上圖裡，以顏色代表蟹狀星雲不同區域裡的電子行為。 紅色表示電子正在與質子結合形成中性氫，而綠色則表示電子正在繞著星雲內的磁場旋轉。 星雲的中心有顆孑遺的脈衝星，這顆中子星的自轉高達每秒30次。

The Crab Nebula, filled with mysterious filaments, is the result of a star that exploded in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while green indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.