New Neighbor (New Star)
Newly Discovered Star May Be Third-Closest
The local celestial neighborhood just got more
crowded with a discovery of a new star that may be the third
closest to the Sun. The new star, "SO25300.5+165258," is a faint
red dwarf star estimated to be about 7.8 light-years from Earth
in the direction of the constellation Aries.
"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,
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.
One light-year is almost six trillion miles, or
nearly 9.5 trillion kilometers.
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.