Dying star provides nursery for new suns

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THE DEATH of our Sun is probably going to look like this, five billion years or so from now: the moment when the hydrogen and helium from its core are thrown off into interstellar space, where they can create a new generation of stars.

This picture, captured by the Hubble space telescope, is actually of a star called NGC7027, which is 3,000 light-years away in the direction of the constellation Cygnus. It is in the stage known as a "planetary nebula" - because viewed by small telescopes, such cosmic explosions looked like the disc of a planet.

When a star starts to die, the nuclear fuel at its heart runs out and a very dense, cool shell of hydrogen molecules is deposited around the star, far into space. The human eye cannot see this shell, but Hubble's infrared camera can. In the picture, the actual star is the intense white dot, while the shell of hydrogen atoms appears as the red wisps surrounding it; the white wisps are stellar dust. The actual distance between the star's surface and the shell is roughly 1.2 billion miles.

In a period lasting about 1,000 years, the molecular shell is atomized, and the resulting atoms are flung into space by a "solar wind" from the star, Meanwhile the matter thrown off will form the most primitive building blocks for other stars, planets - and any life that may form on them.