Astronomers have witnessed the biggest bang since the Big Bang — the moment about 15 billion years ago when the universe was created in a massive explosion.The huge burst of energy from the edge of the universe is estimated to be second only to the moment of creation in its explosive force,releasing more energy in two seconds than the sun will give out in its lifetime. Scientists hope the explosion — known as a gamma-ray burst because it emits energy in the form of gamma radiation — will shed light on the earliest stages in the evolution of the stars and galaxies. Gamma-ray bursts cannot be seen by the human eye but if they could the sky would light up like a camera flash each time they occurred.They are by far the most energetic events in the universe and,until now,have remained largely a mystery.
The latest gamma-ray burst to be detected accurately occurred last December.Using a network of telescopes and satellites,the astronomers were able to calculate its distance from earth at about 15 billion light years.This means it must have happened soon after the Big Bang itself,while the intensity of the radiation revealed it to be the biggest bang recorded by man. Scientists from the American National Aeronautics and Space Administration and the California Institute of Technology are to announce details of their analysis this week. The huge distance between the source of the explosion and the Earth suggests gamma-ray bursts are up to 10 times larger than previously thought,said Jonathan Katz,professor of physics at Washington University in St Louis.
“Gamma-ray bursts may be the most distant things we will ever see and as such will act as beacons to probe into the very distant regions of the universe when stars and galaxies were first formed.”
American spy satellites looking for the radiation released from Soviet nuclear tests first detected gamma-ray bursts in 1967 but the details were kept classified until 1973. For nearly 25 years scientists were hampered in their efforts to find an explanation for the huge explosions because they lasted no longer than a few seconds. The inability to explain them led to speculation that gamma-ray bursts were the remnants of nuclear battles between alien civilizations,or even the exhaust energy of extraterrestrial spaceships going into warp drive.Two satellites,the American Compton gamma-ray observatory and the Italian-Dutch Bepposax satellite,have now been able to locate the precise direction of gamma-ray bursts within seconds of them occurring.John Quenby,professor of physics at Imperial College of Science,Technology and Medicine in London,said the most likely explanation for gamma-ray bursts is that they result from the enormous energy released when two very dense objects—called neutron stars—collide.
宇宙大爆炸
天文学家目击了最大的宇宙大爆炸——这次大爆炸是发生在150亿年前宇宙在一次大爆炸形成的时候。从宇宙边缘所爆发的能量在爆炸力方面估计仅次于宇宙创世大爆炸，两秒钟爆炸所释放的能量比太阳一生释放的能量还要多。科学家希望这次爆炸 —— 就是众所周知的伽马射线爆炸，因为它以伽马放射的方式散发能量 —— 在星球进化的早期能够显现出来。伽马星系的放射人类用肉眼是看不见的，除非每次爆炸发生时天空都能像照相机闪光灯那么亮。到现在为止，包括现在宇宙中发生的事件仍然是个很大的迷。
去年十二月份，用网络望远镜和卫星精确地侦察到了最新一次伽马射线的爆炸。天文学家估计它与我们地球大概有15光年。意思就是它在大爆炸发生不久就发生了。极大的爆炸强度使人们把它记载为史上最大的爆炸。这星期，美国国家航天航空中心和加里弗尼亚技术研究所宣布了他们对爆炸研究分析的细节。圣劳伦斯华盛顿大学的物理教授Jonathan Katz认为：从地球到爆炸源如此远的距离可以知道，伽马射线的爆炸要比我们所看到的要大十倍。
伽马射线爆炸是我们所见的最远距离的东西，当在这宇宙星星和星系最初形成时它就像信号灯一样，促使我们去探究宇宙更远的地方。
寻找苏联核试验所释放的射线的美国间谍卫星1967年探测到了伽马射线爆炸，但爆炸的细节却一直保密到1973年。在其后大约25年的时间里，科学家试图为大爆炸找到一个解释，但由于大爆炸的持续时间只有几秒钟，他们显然对此束手无策。由于无法解释这种现象，因此人们推测这些伽马射线爆炸是外星人之间核战争的遗迹，甚至后来有人认为是外星人飞船偏离轨道后释放的最后能量。美国康普顿伽马卫星天文台的两颗卫星和意大利比珀撒克斯公爵的卫星将在第二次伽马射线发生爆炸的方向准确地登陆。伦敦的国家科学技术和医学学院的物理教授John Quenby说道：对伽马射线爆炸的最好解释就是，他们是由于两个被称为中子星的高密度物体的碰撞，而释放出来的巨大能量。