New Neighbor (New Star)

Newly Discovered Star May Be Third-Closest

"Our new stellar neighbor is a pleasant surprise, since we weren't looking for it," said Dr. Bonnard Teegarden, an astrophysicist at NASA's Goddard Space Flight Center, Greenbelt, Md. Teegarden is lead author of a paper announcing the discovery to be published by the Astrophysical Journal. This work has been done in close collaboration with Dr. Steven Pravdo of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

If its estimate of distance is confirmed, the newfound star will be the Sun's third-closest stellar neighbor, slightly farther than the Alpha Centauri system, actually a group of three stars a bit more than four light-years away, and Barnard's star, about six light-years away.

The new star has only about seven percent of the mass of the Sun, and it is 300,000 times fainter. The star's feeble glow is the reason why it has not been seen until now, despite being relatively close.

"We discovered this new star in September 2002 while searching for white dwarf stars in an unrelated program," said Teegarden. The team was looking for white dwarf stars that move rapidly across the sky. Celestial objects with apparent rapid motion are called High Proper Motion objects. An object of this type can be discovered in successive images of an area of sky because it noticeably shifts its position while its surroundings remain fixed. Since either a distant star moving quickly or a nearby star moving slower can exhibit the same High Proper Motion, astronomers must use other measurements to determine its distance from Earth.

During its star search, the team used the SkyMorph database for NASA’s Near Earth Asteroid Tracking program, to search for asteroids that might be on a collision course for Earth. Pravdo is project manager of the asteroid tracking program and is principal investigator for SkyMorph, which was separately supported by NASA's Applied Information Systems Research Program. Like High Proper Motion stars, asteroids reveal themselves when they shift their position against background stars in successive images. Automated telescopes scan the sky, accumulating thousands of images for the Near Earth Asteroid Tracking program, which have been incorporated into SkyMorph, a web-accessible database, for use in other types of astronomical research.

Once the star revealed itself in the Near Earth Asteroid Tracking images, the team found other images of the same patch of sky to establish a rough distance estimate by a technique called trigonometric parallax. This technique is used to calculate distances to relatively close stars. As Earth progresses in its orbit around the Sun, the position of a nearby star will appear to shift compared to background stars much farther away -- the larger the shift, the closer the star.