Astronomers Find Black Holes Do Not Absorb Dark Matter
Written by Nancy Atkinson
Artist’s schematic impression of the distortion of spacetime by a supermassive black hole at the centre of a galaxy. The black hole will swallow dark matter at a rate which depends on its mass and on the amount of dark matter around it. Image: Felipe Esquivel Reed藝術家的概要印象，在銀河系的中心時空被一超大規模的黑洞扭曲。黑洞會吞噬暗物質以一速率，取決於它周圍暗物質的的質量和數量。 圖：費利佩埃斯基韋爾里德
There's the common notion that black holes suck in everything in the nearby vicinity by exerting a strong gravitational influence on the matter, energy, and space surrounding them. But astronomers have found that the dark matter around black holes might be a different story. Somehow dark matter resists 'assimilation' into a black hole.
有共同的概念黑洞會吸啜在附近一帶的一切東西，以施加強大的引力影響它周圍們的物質、能量和空間。但是天文學家已發現，黑洞周圍的暗物質可能是一個不同的故事，不知怎的暗物質抵抗進入黑洞 '同化'。
About 23% of the Universe is made up of mysterious dark matter, invisible material only detected through its gravitational influence on its surroundings. In the early Universe clumps of dark matter are thought to have attracted gas, which then coalesced into stars that eventually assembled the galaxies we see today. In their efforts to understand galaxy formation and evolution, astronomers have spent a good deal of time attempting to simulate the build up of dark matter in these objects.
約 23％的宇宙是由神秘的暗物質造成，隱形的物質只有透過它的引力影響周圍環境而探測到。在早期宇宙中，暗物質的團塊被認為會吸引氣體，然後聯合起來成為恆星，而最終聚集成我們今天看到的星系。在他們的努力去了解星系形成和演化，天文學家已花去很多時間，試圖在這些物體中模擬建立暗物質。
Dr. Xavier Hernandez and Dr. William Lee from the National Autonomous University of Mexico (UNAM) calculated the way in which the black holes found at the center of galaxies absorb dark matter. These black holes have anything between millions and billions of times the mass of the Sun and draw in material at a high rate.
The researchers modeled the way in which the dark matter is absorbed by black holes and found that the rate at which this happens is very sensitive to the amount of dark matter found in the black holes’ vicinity. If this concentration were larger than a critical density of 7 Suns of matter spread over each cubic light year of space, the black hole mass would increase so rapidly, hence engulfing such large amounts of dark matter, that soon the entire galaxy would be altered beyond recognition.
“Over the billions of years since galaxies formed, such runaway absorption of dark matter in black holes would have altered the population of galaxies away from what we actually observe,” said Hernandez
Their work therefore suggests that the density of dark matter in the centers of galaxies tends to be a constant value. By comparing their observations to what current models of the evolution of the Universe predict, Hernandez and Lee conclude that it is probably necessary to change some of the assumptions that underpin these models – dark matter may not behave in the way scientists thought it did.
There work appears in the journal Monthly Notices of the Royal Astronomical Society
http://www.universetoday.com/2010/03/22/astronomers-find-black-holes-do-not-absorb-dark-matter/
超大型黑洞掙紥吞下銀河系
暗物質'的踪跡'被發現在地下二千呎
世界最深實驗室 地下2400米 啟程探尋暗物質
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