Astronomers have glimpsed a rare and fleeting moment in the final stages of a star's life. Using the Hubble Space Telescope they have witnessed the illumination of the Stingray nebula. Our Science Correspondent David Whitehouse reports:

The Stingray nebula is so named because its shape resembles a stingray fish. It was formed after an old star swelled to become a red giant and ejected its outer layers into space.

As the expelled gas expands the central star gets hotter and suddenly, over a period of only years, heats the expelled matter until it glows.

Twenty years ago the Stingray nebula was dark but it has recently been lit up by its central star.

Hubble in Earth orbit

"Such a fast evolution actually came as a surprise," said Kailash Sahu of the Space Telescope Institute in Maryland, USA.

Astronomers consider it an extraordinary stroke of luck to catch the Stingray nebula switching on.

Images of such an object, misnamed a planetary nebula for historical reasons, will help astronomers understand the last gasps of ordinary stars like our sun.
 

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