PASADENA - From the ashes of a dying star, new planets may be springing to life.

An international team of astronomers and planetary scientists has captured the first images of a disk of dust around one star, Mira B, that is being supplied by the last gasps of its sister star, Mira A.

Such disks are breeding grounds for new planets as the dust collides and collects.

"The reason this is exciting is because the big dusty disks have only so far been found around young stars," said Michael Ireland, a Caltech planetary scientist and the project's lead researcher. "It's basically a new potential way that you could form planets in a place that we didn't expect it."

Planets usually form at about the same time as the star they circle, when the collapsing clouds of dust and gas form a spinning disk of debris. In this case, however, Mira B is collecting gas and dust that's being expelled from the dying Mira A.

"It's surprising in the sense in which it sort of expands the range of conditions in which solar systems could appear," said Joel Kastner, an astronomer at Rochester Institute of Technology in Rochester, N.Y.

Mira A has been an object of astronomical curiosity since the 16th century

because it alternately dims and glows as it ejects its outer atmosphere. For one month out of every 11, it is bright enough to see from Earth.

No longer a normal star, it is now part of a class of stars called red giants, and has swelled to the size of the Earth's orbit around the sun. Once it burns itself out, it will be a white dwarf - a dead star.

The next step in his research, Ireland said, is to find star pairs in which one star has already become a white dwarf, and see what can be found around the other star.

That could pose quite a challenge, though - stars can easily overpower the faint glow of warm dust that astronomers use to detect planet-forming disks.

Even finding such a glow around Mira B, which is relatively close to Earth, was an achievement, said UCLA astronomer Mike Jura.

"I think it is quite surprising that given how powerful Mira A is, that they were able to pick up Mira B," Jura said.

elise.kleeman@sgvn.com

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