又想选C了,虽然B也是反驳star cluster,支持黑洞;但是C是文中第2段提到过的为什么反驳star cluster,就是NGC和M87一样,但是它里面如果是cluster的话,间距太小就会碰撞,所以就不是cluster,如果“C. The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.”有更多的galaxies都有比M87密度大的这种情况,那么是star cluster的这个解释就会被削弱了 but the notion of such a cluster’s existing in NGC 4258 was severely undermined when astronomers mea- sured the speed of a ring of dust and gas rotating close to the galaxy’s (30)center. From its speed, they calcu- lated that the core’s density is more than 40 times the density estimated for any other galaxy. |