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Friday, October 16, 1998 Published at 16:39 GMT 17:39 UK


Watching a star die

The Dumbbell nebula - a gas cocoon around a dying star

By our science editor David Whitehouse

When they are completed, the four large telescopes at the Paranal Observatory in northern Chile will be the most powerful in the world. Already, with just one telescope working, the observatory is producing some of the most spectacular astronomical pictures.

One shows a gas cloud called the Dumbbell nebula. This is one of the clearest pictures of a dramatic event near the end of a star's life.

When a star like our sun runs out of the nuclear fuel it needs to generate sunlight, it will swell to become a red giant star.

When this happens it will probably swallow the Earth and most of the other closer planets.

[ image: The Paranal observatory]
The Paranal observatory
After this brief phase it will shrink to become a white dwarf - a star with about the mass of our sun but the size of Earth.

Before it becomes a white dwarf it will have ejected into the space around it a cocoon of gas. Later the white dwarf will heat this gas with its intense radiation.

Astronomers call these objects 'planetary nebulae' - but this is a misnomer. They were given this name because some of them looked like tiny planetary disks on the sky. In reality they are nothing to do with planets.

The working telescope at the Paranal observatory is undergoing its commissioning phase and has turned its attention to the most famous planetary nebula in the sky, the so-called Dumbbell nebula.

First identified in 1764 by French astronomer Charles Messier, the gas cocoon displays intricate structure that will tell astronomers a lot about a star's final millions of years.

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