August 15, 2007

Contact Dr. Mark Seibert

(626) 304-0273 or mseibert@ociw.edu

For a copy of the paper, please contact Helen Jamison at Nature: h.jamison@nature.com

Graphics and additional information about the Galaxy Evolution Explorer are online at http://www.galex.caltech.edu and http://www.nasa.gov/galex

Pasadena, CA - NASA's Galaxy Evolution Explorer has spotted an amazingly long comet-like tail behind a star streaking through space at extraordinary speeds.

The star, named Mira after the Latin word for "wonderful," has been a favorite of astronomers for about 400 years. It is a fast-moving older star, called a red giant, which sheds massive amounts of surface material.

The space-based Galaxy Evolution Explorer scanned the popular star during its ongoing survey of the entire sky in ultraviolet light. That's when astronomers noticed what looked like a comet with a gargantuan tail. In fact, material blowing off Mira is forming a wake 13 light-years long, or thousands of times the length of our solar system. Nothing like this has ever been seen before around a star.

"This is an utterly new phenomenon to us, and we are still in the process of understanding the physics involved," said co-author Mark Seibert of the Carnegie Observatories in Pasadena. "We hope to be able to read Mira's tail like a ticker tape to learn about the star's life."

Astronomers say Mira's tail offers a unique opportunity to study how stars like our sun die and ultimately seed new solar systems. As Mira hurls along, its tail drops off carbon, oxygen and other important elements needed for new stars, planets and possibly even life to form. This tail material, visible now for the first time, has been shed over the past 30,000 years.

Billions of years ago, Mira was like our sun. Over time, it began to swell into what's called a variable red giant - a pulsating, puffed-up star that periodically grows bright enough to see with the naked eye. Mira will eventually eject all of its remaining gas into space, forming a colorful shell called a planetary nebula. The pretty nebula will fade with time, leaving only the burnt-out core of the original star, an object called a white dwarf.

Compared to other red giants, Mira is traveling unusually fast, possibly due to gravitational boosts from other passing stars. It now plows along at 130 kilometers per second, or 291,000 miles per hour. Racing along with Mira is a small, distant companion thought to be a white dwarf. The pair, also known as Mira A (the red giant) and Mira B, orbit slowly around each other as they travel together in the constellation Cetus, 350 light-years from Earth.

In addition to Mira's tail, the Galaxy Evolution Explorer also discovered a bow shock, a type of buildup of hot gas, in front of the star, and two sinuous streams of material coming out of the star's front and back. Astronomers think hot gas in the bow shock is heating up the gas blowing off the star, causing it to fluoresce with ultraviolet light. This glowing material then swirls around behind the star, creating a turbulent, tail-like wake. The process is similar to a speeding boat leaving a choppy wake, or a steam train producing a trail of smoke.

"GALEX is so exquisitely sensitive to ultraviolet light and it has such a wide field of view that it is uniquely poised to scan the sky for previously undiscovered ultraviolet activity," said co-author Barry F. Madore, Senior Research Astronomer at the Carnegie Observatories. The fact that Mira's tail only glows with ultraviolet light might explain why other telescopes have missed it.

"We never would have predicted a turbulent wake behind a star that glows only with ultraviolet light," said Seibert. "Survey missions like the Galaxy Evolution Explorer can provide many surprises."

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This release is adapted from one issued by NASA’s Jet Propulsion Laboratory. For information contact Whitney Clavin at (818) 354-0850 or whitney.clavin@jpl.nasa.gov

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, also in Pasadena, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in France collaborated on this mission.

Graphics and additional information about the Galaxy Evolution Explorer is online at http://www.nasa.gov/galex/ and http://www.galex.caltech.edu .

The Carnegie Institution of Washington (www.carnegieinstitution.org), a private nonprofit organization, has been a pioneering force in basic scientific research since 1902. It has six research departments: the Geophysical Laboratory and the Department of Terrestrial Magnetism, both located in Washington, D.C.; The Observatories, in Pasadena, California, and Chile; the Department of Plant Biology and the Department of Global Ecology, in Stanford, California; and the Department of Embryology, in Baltimore, Maryland.