Odd Star Sheds Cometlike Tail

August 15, 2007

The star Mira sheds a cometlike tail of rich material as it streaks through space—something that has never been seen before—astronomers announced today.

Acting sort of like a cosmic Johnny Appleseed, the star is leaving behind carbon, nitrogen, oxygen, and other important "seed" elements needed for new stars, planets, and potential life to form.

The phenomenon is "completely new and unexpected," Chris Martin, an astronomer at the California Institute of Technology in Pasadena, told reporters today in a telephone briefing.

"We believe that the tail is made up of material that is being shed by the star, which is heating up and then spiraling back into this turbulent wake," he said.

The star's tail is 13 light-years long—three times the distance from our sun to its nearest star neighbor.

Martin and colleagues describe the star's cometlike tail in tomorrow's issue of the journal Nature.

Interstellar Wake

Scientists have studied Mira, which lies about 420 light-years away in the constellation Cetus, for more than 400 years.

Mira is one of the first discovered "variable" red giant stars—that is, it expands and contracts over a 332-day period, at times growing bright enough to be seen with the naked eye. The star will next be visible in mid-November.

The tail, however, is invisible to the naked eye and was discovered using NASA's Galaxy Evolution Explorer space telescope, which observes in ultraviolet light. (See a photo gallery of space telescope snapshots.)

Billions of years ago, scientists say, Mira was like the sun. Over time it swelled into a variable red giant and today sheds massive amounts of surface material.

This material forms a tail because Mira—like all stars—is moving through space.

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