GRE閱讀練習之Black Holes。同學們如何應對GRE備考呢?下面是小編為同學們搜索整理的有關GRE閱讀練習之Black Holes的介紹。希望對同學們的gre 考試有所幫助，下面和小編一起來看看吧：
　　Astronomers think the object shown in this Chandra X-ray Observatory image (in box) may be an elusive intermediate-mass black hole. Located about 32 million light-years from Earth in the Messier 74 galaxy (M74), this object emits periodic bursts of x-rays at a rate that suggests it is much larger than a stellar-mass black hole but significantly smaller than the supermassive black holes found at the centers of galaxies. Few such middling black holes have been discovered, and scientists aren't sure how they form.
　　Black holes are the cold remnants of former stars, so dense that no matter—not even light—is able to escape their powerful gravitational pull.
　　While most stars end up as white dwarfs or neutron stars, black holes are the last evolutionary stage in the lifetimes of enormous stars that had been at least 10 or 15 times as massive as our own sun.
　　When giant stars reach the final stages of their lives they often detonate in cataclysms known as supernovae. Such an explosion scatters most of a star into the void of space but leaves behind a large "cold" remnant on which fusion no longer takes place.