英语听力：自然百科 Planetary Life After Death 浴火重生的行星
时间：2014-04-18 07:30:53
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（单词翻译）
Like a phoenix1 rising from the ashes, astronomers2 have found a whole new solar system may be forming in the wake of a star's violent death.
This is the Hidden Universe of the Spitzer Space Telescope, exploring the mysteries of
infrared3 astronomy with your host Dr. Robert Hurt.
When a massive star reaches the end of the line, it ''does not go gentle into that good night''. It becomes a supernova, an explosion so bright that it
briefly4 outshines everything else in the
galaxy5. Most of the heavy elements that make up planets, and even people, are forged in the nuclear furnaces of such explosions. Here we see heavy elements in the Cassiopeia A supernova remnant blowing back into the galaxy and
mingling6 with interstellar gases. The next generation of baby stars forms from this material now enriched with building blocks for growing new solar systems and planets.
But what of the star that went supernova? Its core still
remains7 in the form of a pulsar. This stellar
corpse8 is tiny and
dense9, squeezing about 1.5 times the mass of the Sun into an object a
mere10 10 miles across.
A team led by Dr. Deepto Chakrabarty at the Massachusetts Institute of Technology has found that even a dead pulsar might play host to a whole new generation of planet formation. They studied a once-massive star that went supernova about 100,000 years ago. In the process it likely wiped out any existing planets. While most of the star-stuff blew off into space, a little bit fell back under the pull of gravity. Dr. Chakrabarty explains. "If the original massive star was spinning fast enough then that material won't fall directly back onto the
neutron11 star, but may instead form a disk, and so what we think we've found is a disk of this
debris12 material that's left over from the explosion that formed the neutron star.
This disk has about 10 times the Earth's mass and looks very much like ones that produce planets around young stars. Moreover, it may help solve a recent planet-making mystery. In 1992, astronomers found the first planets outside our solar system, which were orbiting an older pulsar. But where did they come from? Could they have formed after their star went supernova? The discovery of a planet forming disk around a younger pulsar makes this likely. It seems new planets can arise from the ashes of their own star's death.
However pulsar planets are pretty hostile real estate for life. Pulsars provide little light or heat and would bathe these worlds in intense radiation. A nuclear waste dump at the South Pole might actually be a little more pleasant.
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