本帖最后由 gohomeman1 于 2009-7-6 12:54 编辑
The binary black hole AGN, OJ287 continues to provide astronomers withsurprises. Long term monitoring of OJ287's optical brightness now indicates that the system may be precessing very rapidly, setting arecord for general relativistic precession of orbits.
双重黑洞系统AGN, OJ287继续给天文学家以惊喜。对OJ287光学亮度的长期观测显示,整个系统在超高速旋转,并记录到相对论性轨道进动。
OJ287 is thought to be a binary black hole in the centre of a distant galaxy. Both black holes are very heavy -- one equivalent to some 18 billion times the mass of the Sun, while the other weighs in at a mere 100 million times the mass of the Sun. The smaller black hole is believed to be in a quite eccentric orbit around the heavier, and prediodically passing through the regions close to the centre of the system, where gas has collected into a so-called accretion disk. The passing of the lighter black hole through this disk causes huge outbursts of energy in the system, showing up at all frequencies from radio to optical and X-ray. The outbursts are seen approximately every twelve years and occur as double peaks. OJ287 is going through such an outburst at the moment, and observatories world-wide are closelymonitoring it during this particularly interesting phase.
OJ287是遥远星系中心的双重黑洞系统。两个黑洞都是超大质量的,其中一个甚至达到180亿倍太阳质量,另一个“仅为”1亿太阳质量。相对小质量的黑洞据信以一个非常偏心的轨道绕相对大质量的黑洞旋转,并周期性的靠近系统的中心点(过近拱点)——此处是大质量黑洞的气体吸积盘所在。当“小质量”黑洞通过吸积盘时,就会产生系统的能量大爆发,爆发辐射覆盖从射电波到X线的整个电磁波段。能量爆发大约每12年一次,并呈现为双峰。OJ287目前正在接近(下一个)爆发时段,在这一激动人心的时期,全球天文观测者正密切关注。
PS:general precession在物理学称为进动,在天文学称为岁差,具体内容解释请自己查找相关资料。1亿倍太阳质量的黑洞也非常大了,我们银河系中心的黑洞质量不过400万倍太阳质量左右。星系中存在2个超级黑洞,一般的观点是这个星系不久前刚刚吞并了一个星系。
原文prediodically也写为perdiodically。那个相对较小的黑洞轨道,大家可以参考短周期彗星。本文显然不是今年的内容。
——gohomeman1译注 |