天文学家发现一个新的中型黑洞

天文学家发现一个新的中型黑洞

Nearly all black holes come in one of two sizes: stellar mass black holes that weigh up to a few dozen times the mass of our sun or supermassive black holes ranging from a million to several billion times the sun's mass. Astronomers1 believe that medium-sized black holes between these two extremes exist, but evidence has been hard to come by, with roughly a half-dozen candidates described so far. A team led by astronomers at the University of Maryland and NASA's Goddard Space Flight Center has found evidence for a new intermediate-mass black hole about 5,000 times the mass of the sun. The discovery adds one more candidate to the list of potential medium-sized black holes, while strengthening the case that these objects do exist. The team reported its findings in the September 21, 2015 online edition of Astrophysical Journal Letters.

The result follows up on a similar finding by some of the same scientists, using the same technique, published in August 2014. While the previous study accurately2 measured a black hole weighing 400 times the mass of the sun using data from NASA's Rossi X-ray Timing3 Explorer (RXTE) satellite, the current study used data from the European Space Agency's XMM-Newton satellite.

"This result provides support to the idea that black holes exist on all size scales. When you describe something for the first time, there is always some doubt," said lead author Dheeraj Pasham, a postdoctoral associate at the Joint4 Space-Science Institute, a research partnership5 between UMD's Departments of Astronomy and Physics and NASA Goddard. "Identifying a second candidate with a different instrument puts weight behind both findings and gives us confidence in our technique."

The new intermediate-mass black hole candidate, known as NGC1313X-1, is classified as an ultraluminous X-ray source, and as such is among the brightest X-ray sources in the nearby universe. It has proven hard to explain exactly why ultraluminous X-ray sources are so bright, however. Some astronomers suspect that they are intermediate-mass black holes actively6 drawing in matter, producing massive amounts of friction7 and X-ray radiation in the process.

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 the date,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 Saturn has 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 accurately

adv.准确地，精确地

参考例句：

It is hard to hit the ball accurately.准确地击中球很难。

Now scientists can forecast the weather accurately.现在科学家们能准确地预报天气。

3 timing

n.时间安排，时间选择

参考例句：

The timing of the meeting is not convenient.会议的时间安排不合适。

The timing of our statement is very opportune.我们发表声明选择的时机很恰当。

4 joint

adj.联合的，共同的；n.关节，接合处；v.连接，贴合

参考例句：

I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤，肩膀脫臼了。

We wrote a letter in joint names.我们联名写了封信。

5 partnership

n.合作关系，伙伴关系

参考例句：

The company has gone into partnership with Swiss Bank Corporation.这家公司已经和瑞士银行公司建立合作关系。

Martin has taken him into general partnership in his company.马丁已让他成为公司的普通合伙人。

6 actively

adv.积极地，勤奋地

参考例句：

During this period all the students were actively participating.在这节课中所有的学生都积极参加。

We are actively intervening to settle a quarrel.我们正在积极调解争执。

7 friction

n.摩擦，摩擦力

参考例句：

When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。

Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。