英语四级听力练习

来源:步知资讯 时间:04-11 阅读:

 

Astronomers say the center of our galaxy has plenty of strange, super gravity objects.

  For years, scientists believed that circling the center of galaxies, including our own Milky Way galaxy, were not only stars, but lots of stellar black holes. These are stars that have collapsed, creating gravity so strong even light does not get out.

  But scientists had yet to find evidence of black holes at the center of the Milky Way until now.

  Twelve black hole low-mass binaries orbiting Sgr A* at the center of the Milky Way galaxy, appear in this illustration provided by Columbia University, April 5, 2018.

  Astronomers studying old x-ray observations have found signs of at least 12 black holes in the inner circle of the Milky Way. And since most black holes cannot be found that way, they believe that there are likely thousands of them there.

  In fact, a study suggests there may be more than 10,000 black holes in the center of our galaxy. The findings appear in the journal Nature.

  Chuck Hailey is an astrophysicist at Columbia University in New York. He was the lead writer of the report. He told the Associated Press, "There's lots of action going on there. ... The galactic center is a strange place. That's why people like to study it."

  Scientists already know about a supermassive black hole at the center of the Milky Way. They call it Sagittarius A.

  Supermassive black holes are the largest kind of black hole, being between a million and billion times bigger than others. This latest research shows that the newly discovered stellar black holes are in addition to Sagittarius A and they do, in fact, circle it.

  The newly discovered black holes are within about 31 trillion kilometers from the supermassive black hole at the center of the Milky Way. So there is still a lot of empty space and gas among all those black holes. But Hailey noted that if you looked at the amount of space around Earth, there would be zero black holes, not thousands.

  Our planet is part of a spiral arm circling the Milky Way. It is about 9.5 trillion kilometers, or 3,000 light years, from its center. In the rest of our galaxy, scientists have only identified about 60 black holes to date, Hailey added.

  Harvard astrophysicist Avi Loeb was not part of the latest study. He called the findings exciting, but noted that they confirmed what scientists had long expected.

  The newly confirmed black holes are about 10 times the mass of our sun. In comparison, Sagittarius A has the mass of 4 million suns.

  The recently discovered black holes are also only the kind that are binary, meaning they are partnered with another star. Black holes partnered with other stars produce large amounts of x-rays as the black holes pull in the star's outer layer. Those x-rays are what astronomers observe.

  When astronomers look at closer binary black hole systems, they could then compare what is seen with what is too weak to be observed from far away. Using that information, Hailey believes that there must be 300 to 500 binary black hole systems.

  Binary black hole systems are likely only five percent of all black holes, he added. So that means there are really thousands of them.

  Hailey said there are good reasons the Milky Way's black holes are usually in the center of the galaxy. First, their mass most often pulls them to the center. But mostly the middle of all those stars is the perfect place for black hole formation, with lots of dust and gas.

  He said it is "sort of like a little farm where you have all the right conditions to produce and hold on to a large number of black holes."

  I'm ­Dorothy Gundy.

责任编辑:wyq

相关推荐
① "步知网"上的内容(含文章、资料、资讯等), 本网注明"来源:步知网"的,版权均为"步知网"或步知公考所有,任何公司、媒体、网站或个人未经授权不得转载、链接、转贴或以其他方式使用。已授权许可的媒体、网站,在使用时必须注明"稿件来源:步知网",违者本网站将依法追究责任。
② 未注明来源:步知网"的文章、资料、资讯等,均为网络转载稿,本网站转载出于传递更多信息之目的,并不意味着赞同其观点或证实其内容的真实和准确性。如其他媒体、网站或个人从本网站转载使用,必须保留本网站注明的"稿件来源",并自负版权等法律责任。如擅自篡改为"来源:步知网",本站将依法追究其法律责任。
③ 如本网转载稿涉及版权等问题,请原作者见稿后在两周内与步知网联系。