Movie captures dying star

Gas hurtles out from the surface of TX Cam

By BBC News Online science editor Dr David Whitehouse

Astronomers have, for the first time, made a time-lapse movie of gas being ejected from the surface of a star other than our own.

The images are the most detailed ever taken of activity around another star.

The dying star, called TX Cam, is an example of what is known as a Mira variable. This group of stellar objects are named after the famous star Mira, which changes in brightness every year.

The movie will give astronomers clues as to the eventual fate of our Sun and the planets in orbit around it.

Sun's fate

In a few billion years, when our own Sun approaches the end of its life, it will eject gas like TX Cam, swallowing the Earth and the other inner planets.

Eventually, much of the Sun's mass will be thrown into the depths of interstellar space.

Then, it will shrink to a shadow of its former self, becoming what astronomers call a white dwarf.

This is happening now for the many thousands of Mira variable stars throughout our galaxy.

By looking at them, astronomers can study this mass-loss process and learn about the fate of the Sun.

Distant star

TX Cam is in the constellation of the Camel, lying almost 1,000 light years from our planet. Its brightness changes regularly over a period of 80 weeks.

To look at the outflow on TX Cam, the radio astronomers tuned in on gaseous bright spots using several radio telescopes observing in unison.

The bright spots are caught up in the outflow of material from the star's surface.

The movie, made by adding all the observations in sequence, shows the gas moving outward from the star.

Complex gas motions can be seen, said Dr Philip Diamond of the Jodrell Bank radio observatory near Manchester, UK.

These are "immensely complex motions which cannot be explained by current theory".

Shock waves

The movie covers a period of 88 weeks, with observations being made every two weeks.

"The structures that we observe in the outflow suggest that we might be seeing the effects of shock waves passing through the gas," said Dr Athol Kemball, of the Very Large Array radio observatory in New Mexico.

"However, it is difficult to explain why most of the gas is moving away from the star whilst, at the same time, some is falling towards it," Dr Kemball added.

The astronomers have another 80 weeks of observations of TX Cam that they have yet to process into a movie.

They hope they can use that data to understand the dying star and what fate may await our own Sun.

The results were presented at a symposium during the International Astronomical Union General Assembly in Manchester.