英语听力：自然百科 穿越银河系的旅行 Through Milky Way—12（在线收听） |
We are at a foundry here, and they are pouring molten iron from all machinery. And they are going to make parts for new machines out of that iron, so they are recycling yet, but all that iron was created and ejected into the cosmos by gigantic stars that exploded as supernovae. Those explosions created the iron and ejected into the cosmos, and then they got incorporated into planetary systems like ours, but ultimately the atoms of iron were created by exploding stars. Supernovae are the industrial zones of our star city, cosmic foundries in which the chemistry of the heavens forges new elements. It is fascinating to realize that the heavy elements in our bodies, the carbon in our cells, the calcium in our bones, the oxygen that we breathe, the iron in our red blood cells. All of those heavy elements were synthesized, created through nuclear reactions in star, and ejected into the cosmos by supernovae.
Only some stars are massive enough to die as supernovae. Most, like our sun, suffer a more gentle death. Most stars don’t die in the cataclysmic explosion. Our own sun, for example, a typical star, will die with a whimper not a bang.
The death of most stars occurs when the battle, between gravity pulling in and nuclear energy pushing out, is won, not by gravity but by the nuclear energy. |
| 原文地址：http://www.tingroom.com/lesson/zrbaike/2011/260158.html |