Ripped apart Supermassive black holes lurking in the heart of distant galaxies could be to blame for the 'missing' hydrogen in the early universe.
The discovery by Dr Stephen Curran of the University of Sydney and Dr Matthew Whiting of the CSIRO, explains why there doesn't appear to be enough hydrogen in the ancient universe to make all the stars we see today.
Their finding appears in the latest edition of the Astrophysical Journal.
Curran and Whiting were studying radio signals caused by monster black holes feeding in some of the earliest galaxies, 11 billion light years away.
"These are some of the oldest objects in the universe, " says Curran.
Stars form from clouds of cold hydrogen at temperatures of just a few degrees above absolute zero (-273°C), collapsing through their own gravity.
"If you've got a galaxy then you've got hydrogen, " says Curran.
"By studying these hydrogen signatures, we can determine the size and rotation of galaxies."
But some of the galaxies Curran and Whiting looked at appeared to contain less hydrogen than expected.
"We looked at ten ancient galaxies and were surprised to find no signs of hydrogen in any, " says Curran.
"There should have been more cold hydrogen gas in these ancient distant galaxies than there is today."
A pattern emerges
As Curran and Whiting looked at other galaxy surveys, they found a critical level beyond which cold hydrogen could not be detected.
They found that in galaxies of certain luminosity, extreme levels of ultra-violet radiation given off by the supermassive black hole at its cores, generates enough energy to ionise all the hydrogen gas.
This ionised hydrogen can't be detected by radio telescopes.
"We didn't know all the gas in the galaxy was being ionised. We thought it was just around the black hole's accretion disk, " says Curran.
"But it's the lot; ripping all the hydrogen into protons and electrons, preventing us from detecting it."
According to Curran, the Square Kilometre Array (SKA) radio telescope to be built in Australia, New Zealand and South Africa will provide a boost for their research.
"Not even the SKA can detect the hot ionised hydrogen in these active galaxies, " says Curran.
"But it will let us look for other galaxies in the early universe which do have the cold hydrogen gas we're seeking."
消失的氢和黑洞有关
早期宇宙中那些消失的氢和深藏在遥远的星系中心的特大质量黑洞有关。悉尼大学的史蒂芬·克伦教授和澳大利亚联邦科工组织 的马修·怀廷教授的这个发现解释了早期宇宙没有足够的氢来产生我们今天看到的所有恒星的原因。他们的发现刊登在最新一期的天体物理学报上。
“这是些宇宙中最古老的物质。”克伦说。恒星是由温度只比绝对零度（-273°C）高一点点的冷氢云由于自身重力坍塌而形成的。
“有星系就有氢”克伦说，“通过研究这些氢的特性我们可以确定星系的大小和自转周期。”
不过克伦和怀挺研究的一些星系含有的氢比预期的要少。
“我们很吃惊地发现有10个我们研究的远古星系没有任何氢存在的迹象。”克伦说，“在那些遥远的远古星系中本该有比如今更多的冷氢气。”
一种新模式
在克伦和怀挺翻阅其他星系的研究时，他们发现相当一部分的星系中探测不到氢。他们发现在某种光度的星系中，特大质量黑洞核心所发出的高强度紫外线辐射足以电离氢气。这些被电离的氢就无法被射电望远镜观测到。
“我们不知道星系中的氢被电离了。我们以为它是在黑洞的吸积盘附近。“克伦说。”但这很不一样。氢被分解成质子和电子，我们就探测不到了。“
由于克伦的研究，在澳大利亚，新西兰和南非平方公里整列建造射电望远镜被证明是有必要的。“他能让我们在早期宇宙星系中找到我们想要的冷氢气。”
