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Astronomers Detect Shock Waves Revealing Dozens Of Milky Way's 'Runaway' Stars

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Astronomers say they've detected dozens of runaway stars in the Milky Way by capturing images of their bow waves, created as they shove an immense cloud of superheated gas ahead of them while charging through space.

That shock wave creates a brilliantly lighted arc that astronomers have used to identify dozens of the fugitive stars.

Flung out of their own cosmic neighborhood by stellar explosions or by gravity, they can travel at speeds higher than 18 miles per second in relation to their surrounding, astronomers say.

"Some stars get the boot when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters," says doctoral student William Chick from the University of Wyoming in Laramie.

"The gravitational boost increases a star's speed relative to other stars," he explained in presenting a new study at an American Astronomical Society meeting in Florida.

The size and shape of the bow shock depends on both the speed and mass of a runway star, the researchers say.

As an example they cite the massive star Zeta Ophiuchi, possessing a stunning bow shock as it travels through the galaxy at 54,000 mph.

The study team analyzed images captured by two NASA infrared space telescopes, the Wide-field Infrared Survey Explorer, or WISE, and Spitzer Space Telescope.

Surveying the images for the telltale curved red clouds seen in the infrared wavelengths, they say they identified more than 200 candidate bow waves.

Eighty such waves were selected for closer examination by a ground-based infrared telescope in Wyoming to look for stars in the center of each image, Chick says.

"We were surprised to discover that over 95 percent of these stars were, in fact, hot massive stars, as we'd predicted," he says.

While some of the stars were already known from previous studies to be runaways — Zeta Ophiuchi was discovered in the 1970s, and the first bow shocks were identified in the 1980s — many were not, the researchers say.

"We are using the bow shocks to find massive and/or runaway stars," says astronomer Henry Kobulnicky, also from the University of Wyoming. "The bow shocks are new laboratories for studying massive stars and answering questions about the fate and evolution of these stars."

There is a lot still unknown about these mysterious stars, Chick says, questions that may be answered with further observations.

"It may be that our Milky Way is, in fact, swarming with these hot, runaway stars," he suggests.

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