什麼是脈衝星

全名脈衝無線電星（pulsating radio star）

宇宙天體的一類，表現出發射極度有規律的無線電波脈衝的特徵。少數幾個也發出可見光、X射線和伽馬射線的短州週期脈衝。1967年休伊什和貝爾.伯奈爾（Jocelyn Bell Burnell）用專門設計的無線電望遠鏡發現了它們，認爲是快速自旋的中子星。至今已發現的脈衝星達五百顆以上。所有的表現都相似，但脈衝之間的間隔不同，範圍在1秒鐘的千分之一到4秒鐘之間。從表面發出的帶電粒子進入星體的磁場，磁場將它們加速，使得它們產生輻射，從磁極處以強粒子束釋放出來。輻射束的方向與脈衝星自轉軸方向不一致，因此當星體自旋時，輻射束像燈塔般來回擺動，看起來就像是脈衝。已經證明無線電脈衝星一直在減速，典型的減慢速度爲每年百萬分之一秒。計算得知約一千萬年後脈衝星的磁場變得足夠弱時，脈衝星就會「熄滅」。

pulsar

Any of a class of cosmic objects that appear to emit extremely regular pulses of radio waves. A few give off short rhythmic bursts of visible light, X rays, and gamma radiation as well. Thought to be rapidly spinning neutron stars, they were discovered by Antony Hewish and Jocelyn Bell Burnell in 1967 with a specially designed radio telescope. More than 500 have been detected since. All behave similarly, but the intervals between pulses range from one-thousandth of a second to four seconds long. Charged particles from the surface enter the star's magnetic field, which accelerates them so that they give off radiation, released as intense beams from the magnetic poles. These do not coincide with the pulsar's own axis of rotation, so as it spins the radiation beams swing around like a lighthouse and they are seen as pulses. Radio pulsars have been shown to be slowing down, typically by a millionth of a second per year. It has been calculated that pulsars “switch off” after about 10 million years, when their magnetic fields weaken enough.