| |
次の英文を読んで最も適切なものを(A)〜(D)の中から一つ選びなさい。
BLACK HOLES
Astronomers have detected two new kinds of black holes: quiet, supermassive ones and medium-size ones that take up about as much space as the Earth's moon. A black hole is a high-gravity region of space that sucks in every bit of matter it can, not even letting light escape. No one has ever seen a black hole, but astronomers have long believed in their existence based on cosmic activity around them. Until now, scientists thought black holes came in two sizes: (1) stellar black holes that were the remnants* of dead sun-like stars, and (2) supermassive black holes thought to have formed in the earliest days of the universe. Stellar black holes had the mass of several suns, while supermassive ones carried the mass of perhaps a billion suns, covering an area about the size of our solar system.
Now NASA scientists have observed signs of a new type of black hole, with about 10 to 100 times the sun's mass but compressed into a comparatively tiny moon-size slice of space. They detected the new class of black holes by monitoring X-rays produced at the center of 39 nearby galaxies. X-rays often indicate the existence of a black hole, since they are produced when hot cosmic gases swirl around the black hole's“mouth,”like water spiraling down a drain. Astronomers spotted luminous X-rays at the heart of these galaxies, suggesting the existence of medium-size black holes. At this point, it is not certain what created these mid-size phenomena. A likely theory is that there are a lot of stellar-size black holes that have merged to form intermediate-range black holes. There might be from one to three such medium-size black holes in most galaxies, according to astronomers.
Scientists say they have found such a mid-size black hole about 3.6 million light years away from Earth in galaxy M82. Such huge matter-sucking phenomena might be expected to produce hugely luminous X-ray glows, but astronomers say they have found that most of these big black holes are quiet, producing no detectable X-rays. These black holes are believed to date from the universe's earliest moments, when there was plenty of gas for them to feed on. But as the galaxies matured, the gas left to form stars, leaving little for the black holes to eat. Without a big stream of matter circling into them, the supermassive black holes' X-ray luminosity is bound to be less, or at least different, from that of black holes that feed on plentiful matter, scientists say.
*remnant＝残物
(89) How big are the medium-size black holes?
(A) smaller than the Earth's moon
(B) larger than the sun
(C) as big as the Earth's moon
(D) bigger than a supermassive black hole
(90) The word“compressed” in paragraph 2, line 2, is closest in meaning to which of the following words?
(A) contained (B) squeezed (C) composed (D) sustained
(91) How were the new types of black hole discovered?
(A) with a special software program that can search for stars
(B) accidently by a scientist
(C) with a large telescope
(D) by observing X-rays
(92) Astronomers believe most galaxies have how many medium-size black holes?
(A) one to three (B) two to four (C) four to five (D) five or more
(93) According to scientists, what is one main characteristic of mid-size black holes?
(A) They are older than the universe.
(B) They are full of detectable X-rays.
(C) They are more than 4 million light years away from Earth.
(D) Most of them are quiet.
(94) In what situation is it possible for the X-ray luminosity of a black hole to decrease?
(A) When a black hole collides with a star.
(B) When a black hole has little gaseous matter to eat.
(C) When black holes feed upon each other.
(D) When a new black hole is formed.
――会津大学――2000年
|
|
- 06/6/5(月) -
