Telescope takes close-ups of distant star

New images from an array of radio telescopes are providing the first detailed view of activity near a star other than our sun.

Bright spots in these radio-wavelength images (above, and below) show gas expelled from a dying star. Circle indicates star’s surface. VLBA/Kemball, Diamond

Although the elderly star, TX Camelopardalis, lies 1,000 light-years away, researchers were able to examine radio-emitting gas flung just a few hundred million kilometers—equivalent to about twice Earth’s distance from the sun. Astronomers obtained the images by using the Very Large Baseline Array, a network of 10 radio telescopes stretching from the U.S. Virgin Islands to Hawaii.

Silicon monoxide gas spewing from the star generates intense radio emissions that the telescope array recorded. Visible-light telescopes can’t detect these gaseous expulsions because material surrounding the star absorbs and scatters visible light.

At least 3 billion years old, TX Camelopardalis is classified as a Mira variable, an old, pulsating star that periodically brightens and dims. When it contracts, the star draws in nearby gas, and when it expands, it blows out an even larger amount. At this age, the star expels about an Earth’s mass of gas each year.

The pictures, recorded over 80 weeks, reveal for the first time how the gas flows out from a star during this late stage, which lasts only about 10,000 years, notes Athol J. Kemball of the National Radio Astronomy Observatory in Socorro, N.M. Exactly how such stars lose mass remains a mystery, but “this monitoring campaign has allowed a movie of the gas motions to be produced, which provides new insights into how this might occur,” he notes. Instead of ejecting the gas equally in all directions, the star expels the material asymmetrically, just as the sun does during localized storms.

Kemball’s collaborator, Philip Diamond of the University of Manchester in England, unveiled the images Aug. 15 at a meeting of the International Astronomical Union in Manchester.

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