太空中的粒子加速器（图）   

钱德拉X射线望远镜所观测到的具有极高能量的银河中心

The Giant Particle Accelerator in the Sky

The black hole at the centre of the Milky Way is a giant particle accelerator, say astrophysicists.	天体物理学家们说，银河中心的黑洞是一个巨大的粒子加速器。
Australian researcher Dr Roland Crocker of the University of Adelaide and international colleagues say magnetic fields at the edge of the black hole could accelerate protons into space.And these protons could combine with hydrogen gas to produce high-energy gamma rays.	澳大利亚阿德雷德大学的研究人员罗兰德·克罗克博士及其跨国的同事们指出，黑洞边缘的磁场可以使质子加速飞入太空。这些质子可以同氢气结合，产生高能伽马射线。
The researchers report their findings in the 1 March issue of Astrophysical Journal Letters, published by the American Astronomical Society.	研究人员将他们的发现报道在美国天文学会3月1日出版的《天体物理杂志通讯》上。
Previous astronomical observations have detected high-energy gamma rays coming from the centre of our galaxy, and scientists have wondered where they came from.	以前的天文观察探测到来自银河系中心的高能伽马射线，但科学家们却搞不清这些射线具体来自何处。
"There has to be some sort of energetic particles buzzing around in the region in order to generate those very, very high energy light particles [gamma rays] that we detect from the region," says Crocker.	克罗克说：“一定有某种高能量的粒子在该区域做无序的高速运动，结果产生了我们探测到的超高能发光粒子（伽马射线）。”
The black hole at the galaxy's centre is an obvious suspect. But how can it produce these high energy emissions?	银河系中心的黑洞显然是个怀疑对象。然而，这个黑洞又如何释放出如此高的能量呢？
Crocker and colleagues took their cue from what happens in particle accelerators, such as those at CERN, the European Organization for Nuclear Research facilities in Switzerland.Experiments here show that high-energy gamma rays are produced by colliding high-energy protons (hydrogen nuclei), accelerated to almost the speed of light.This produces particles called pions, the 'glue' that holds a nucleus together, and some of these tiny particles degrade into gamma rays.	克罗克及同事通过粒子加速器里发生的现象得到了线索。粒子加速器就如同位于瑞士的欧洲原子核研究组织（CERN）的那些设备。他们的实验表明，高能伽马射线是碰撞中的高能质子（氢核）加速到接近光速时产生的。这一过程产生的粒子叫做介子，介子象胶质封固在原子核的周围，其中有些发生衰变，成为伽马射线。
Crocker and team reasoned that strong and chaotic magnetic fields, suspected to be at the rim of the black hole, could also accelerate protons.They modelled this idea on computer and found that the accelerated protons bounce around and eventually escape into space.About three light-years out from the black hole the high-energy protons smash into a cloud of hydrogen gas to produce gamma rays.	克罗克研究小组推测：被认为处于黑洞边缘的强烈无序的磁场也可能使质子加速。他们将这个推测在计算机上进行模拟，发现加速的质子剧烈运动，最终逃往太空。大约在黑洞外3光年处，高能质子冲进氢气云，产生了伽马射线。
"We've basically explained what that gamma ray source is," says Crocker.	克罗克说；“我们基本上解释了伽马射线的来源。”
Uncertainties	疑点
Astrophysicist Dr Zdenka Kuncic of the University of Sydney says it's a "fairly solid argument". But she emphasises a few problems, which the authors themselves acknowledge in their paper.	悉尼大学的天体物理学家登卡·坤塞克博士指出：“这是相当可靠的观点。”但是，她强调了几个仍然存在的问题，对这些问题研究人员自己在论文中也予以承认。
"They [Crocker and colleagues] are actually just testing one specific model, or one specific interpretation and others have been proposed," she says.	坤塞克说：“他们（克罗克及其同事）实际上只进行了一种特效模拟试验，只给出了一种特定的解释。”
And Kuncic says telescopes can only locate the source of the gamma rays to an area with a five-light-year radius. Since the black hole is a million times smaller than this, she says the gamma rays might not be coming from the black hole at all.	坤塞克指出，望远镜只能将伽马射线源确定在半径为5光年的范围内，黑洞要比这个范围小上百万倍，因此伽马射线可能根本不是来自黑洞。
Another problem is the number of protons that are needed to produce the observed gamma rays is much higher than the number of protons that can be produced by known mechanisms for accelerating particles to high energies, says Kuncic.	坤塞克说另外的一个问题是：产生可以观测到的伽马射线所需要的质子数量，要比任何已知的粒子加速装置所产生的质子数量多得多。
Another particle accelerator?	其他的粒子加速器
This means that if Crocker and colleagues are right, then there must be a more efficient, yet-to-be-discovered mechanism that accelerates particles in space. The protons produced at the centre of the Milky Way are accelerated to 100 trillion electronvolts (a measure of energy), much higher than what is possible on Earth. For example, it is 18 times more energetic than the particles that will be produced by the proposed Large Hadron Collider in Switzerland.	如果克罗克及其同事是正确的，这就意味着太空中一定存在着更为高效的、有待发现的粒子加速机制。银河中心产生的质子被加速，能量达到100万亿电子伏特（能量的计量单位），比地球上可能产生的能量高得多。举个例子来说，这个能量比提议制造的瑞士大型强子对撞机将会产生的能量高出18倍。
The researchers suggest other black holes in the universe, which are much larger than the one in the Milky Way, may also act as particle accelerators, accelerating protons to much higher energies.	研究人员提出，宇宙中的其他黑洞比银河中的黑洞大得多，也可能起着粒子加速器的作用，将质子加速到更高的能量。