英语听力：自然百科 穿越银河系的旅行 Through Milky Way—11

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We collect that light and we analyze¹ it in great detail in order to determine what’s going on, what’s the chemical makeup² of the star, what’s the pressure inside, what’s the temperature, what kind of nuclear reactions are going on, how does the star explore. All these things we figured out through the analysis of light.

 

In doing so, astronomers³ have discovered that it’s only star with a huge mass that go out with a bang.

 

A massive star has a very interesting and vigorous life. Initially⁴ it fuses hydrogen to form helium and that produces energy that makes the star shine, then the ashes of that reaction the helium fuse together to form carbon and oxygen, releasing yet more energy. Then the carbon and oxygen can fuse into still heavier elements, magnesium⁵, sodium⁶, and neon, and things like that and then silicon⁷ and sulfur⁸, and finally iron.

 

When it starts to make iron, the giant star is doomed⁹. In the core, there is a fierce battle. Energy is pushing outwards¹⁰, holding it up, while gravity wants to crash it inwards. The battle continues as the star makes heavier and heavier elements, producing energy, fending¹¹ off total collapse¹². But once it stops to form iron, the battle is lost.

 

Fusion¹³ of iron, nuclear iron to heavier things, does not release energy; it absorbs energy. So an iron core builds up, but finally it becomes so massive, the gravity wins, the iron core collapses¹⁴, in last second, the out layer collapse inward then rebound¹⁵ and get blown to smithereens.

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