A team of astronomers led by Tomoharu Oka, a professor at Keio University in Japan, has found an enigmatic gas cloud, called CO-0.40-0.22, only 200 light years away from the center of the Milky Way. What makes CO-0.40-0.22 unusual is its surprisingly wide velocity dispersion: the cloud contains gas with a very wide range of speeds. The team found this mysterious feature with two radio telescopes, the Nobeyama 45-m Telescope inJapan and the ASTE Telescope in Chile, both operated by the National Astronomical Observatory of Japan. To investigate the detailed structure, the team observed CO-0.40-0.22 with the Nobeyama 45-m Telescope again to obtain 21 emission linesfrom 18 molecules. The results show that the cloud has an elliptical shape and consists of two components: a compact but low density component with a very wide velocity dispersion of 100 km/s, and a dense component extending 10 light years with a narrow velocity dispersion.
What makes this velocity dispersion so wide? There are no holes inside of the cloud.Also, X-ray and infrared observations did not find any compact objects. These features indicate that the velocity dispersion is not caused by a local energy input, such as supernova explosions.
The team performed a simple simulation of gas clouds flung by a strong gravity source.In the simulation, the gas clouds are first attracted by the source and theirspeeds increase as they approach it, reaching maximum at the closest point tothe object. After that the clouds continue past the object and their speedsdecrease. The team found that a model using a gravity source with 100 thousandtimes the mass of the Sun inside an area with a radius of 0.3 light years provided the best fit to the observed data. "Considering the fact that no compact objects are seen in X-ray or infrared observations," Oka, the lead author of the paper that appeared in the Astrophysical Journal Letters,explains "as far as we know, the best candidate for the compact massive object is a black hole."
If that is the case, this is the first detection of an intermediate mass black hole.Astronomers already know about two sizes of black holes: stellar-mass black holes, formed after the gigantic explosions of very massive stars; and supermassive black holes (SMBH) often found at the centers of galaxies. Themass of SMBH ranges from several million to billions of times the mass of the Sun. A number of SMBHs have been found, but no one knows how the SMBHs are formed. One idea is that they are formed from mergers of many intermediate mass black holes. But this raises a problem because so far no firm observational evidence for intermediate mass black holes has been found. If the cloud CO-0.40-0.22, located only 200 light years away from Sgr A* (the 400 millionsolar mass SMBH at the center of the Milky Way), contains an intermediate mass black hole, it might support the intermediate mass black hole merger scenario of SMBH evolution.
These results open a new way to search for black holes with radio telescopes. Recent observations have revealed that there are a number of wide-velocity-dispersion compact clouds similar to CO-0.40-0.22. The team proposes that some of those clouds might contain black holes. A study suggested that there are 100 million black holes in the Milky Way Galaxy, but X-ray observations have only found dozens so far. Most of the black holes may be "dark" and verydifficult to see directly at any wavelength. "Investigations of gas motion with radio telescopes may provide a complementary way to search for dark blackholes" said Oka. "The on-going wide area survey observations of the Milky Way with the Nobeyama 45-m Telescope and high-resolution observations of nearby galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA) have the potential to increase the number of black hole candidates dramatically."
1 astronomers
n.天文学者，天文学家(astronomer的名词复数 )
参考例句：
• Astronomers can accurately foretell thedate,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturnhas rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。来自《简明英汉词典》
2 milky
adj.牛奶的，多奶的；乳白色的
参考例句：
• Alexander always has milky coffee atlunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。
3 velocity
n.速度，速率
参考例句：
• Einstein's theory links energy with massand velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
• The velocity of light is about 300000kilometres per second.光速约为每秒300000公里。
4 astronomical
adj.天文学的，（数字）极大的
参考例句：
• He was an expert on ancient Chineseastronomical literature.他是研究中国古代天文学文献的专家。
• Houses in the village are selling forastronomical prices.乡村的房价正在飙升。
5 observatory
n.天文台，气象台，瞭望台，观测台
参考例句：
• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory havethe clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
6 detailed
adj.详细的，详尽的，极注意细节的，完全的
参考例句：
• He had made a detailed study of theterrain.他对地形作了缜密的研究。
• A detailed list of our publications isavailable on request.我们的出版物有一份详细的目录备索。
7 emission
n.发出物，散发物；发出，散发
参考例句：
• Rigorous measures will be taken to reducethe total pollutant emission.采取严格有力措施，降低污染物排放总量。
• Finally,the way to effectively controlparticulate emission is pointed out.最后，指出有效降低颗粒排放的方向。
8 molecules
分子( molecule的名词复数 )
参考例句：
• The structure of molecules can be seenunder an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large moleculesare cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。
9 component
n.组成部分，成分，元件；adj.组成的，合成的
参考例句：
• Each component is carefully checkedbefore assembly.每个零件在装配前都经过仔细检查。
• Blade and handle are the component partsof a knife.刀身和刀柄是一把刀的组成部分。
10 components
（机器、设备等的）构成要素，零件，成分； 成分( component的名词复数 )； [物理化学]组分； [数学]分量； （混合物的）组成部分
参考例句：
• the components of a machine 机器部件
• Our chemistry teacher often reduces acompound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。
11 density
n.密集，密度，浓度
参考例句：
• The population density of that country is685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high populationdensity.该地区的人口密度很高。
12 dense
a.密集的，稠密的，浓密的；密度大的
参考例句：
• The general ambushed his troops in thedense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by thedense foliage. 小路被树叶厚厚地盖了一层。
13 infrared
adj./n.红外线(的)
参考例句：
• Infrared is widely used in industry andmedical science.红外线广泛应用于工业和医学科学。
• Infrared radiation has wavelengths longerthan those of visible light.红外辐射的波长比可见光的波长长。
14 input
n.输入(物)；投入；vt.把(数据等)输入计算机
参考例句：
• I will forever be grateful for hisconsiderable input.我将永远感激他的大量投入。
• All this information had to be input ontothe computer.所有这些信息都必须输入计算机。
15radius
n.半径，半径范围；有效航程，范围，界限
参考例句：
• He has visited every shop within a radiusof two miles.周围两英里以内的店铺他都去过。
• We are measuring the radius of thecircle.我们正在测量圆的半径。
16 galaxies
星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）
参考例句：
• Quasars are the highly energetic cores ofdistant galaxies. 类星体是遥远星系的极为活跃的核心体。
• We still don't know how many galaxiesthere are in the universe. 我们还不知道宇宙中有多少个星系。
17 merger
n.企业合并，并吞
参考例句：
• Acceptance of the offer is the first stepto a merger.对这项提议的赞同是合并的第一步。
• Shareholders will be voting on the mergerof the companies.股东们将投票表决公司合并问题。
18 mergers
n.（两个公司的）合并(merger的名词复数 )
参考例句：
• Mergers fall into three categories:horizontal, vertical, and conglomerate. 合并分为以下三种：横向合并，纵向合并和混合合并。 来自辞典例句
• Many recent mergers are concentratedwithin specific industries, particularly in retailing, airlines andcommunications. 现代许多合并企业集中进行某些特定业务，在零售业、民航和通讯业中更是如此。来自英汉非文学 - 政府文件
19 scenario
n.剧本，脚本；概要
参考例句：
• But the birth scenario is not completelyaccurate.然而分娩脚本并非完全准确的。
• This is a totally different scenario.这是完全不同的剧本。
20 galaxy
n.星系；银河系；一群(杰出或著名的人物)
参考例句：
• The earth is one of the planets in theGalaxy.地球是银河系中的星球之一。
• The company has a galaxy of talent.该公司拥有一批优秀的人才。
21 wavelength
n.波长
参考例句：
• The authorities were unable to jam thiswavelength.当局无法干扰这一波长。
• Radio One has broadcast on thiswavelength for years.广播1台已经用这个波长广播多年了。
22 investigations
（正式的）调查(investigation的名词复数 )；侦查； 科学研究； 学术研究
参考例句：
• His investigations were intensive andthorough but revealed nothing. 他进行了深入彻底的调查，但没有发现什么。
• He often sent them out to makeinvestigations. 他常常派他们出去作调查。
免责声明：以上内容源自网络，版权归原作者所有，如有侵犯您的原创版权请告知，我们将尽快删除相关内容。
