Many stars close to the Sun have familiar names, like the Centauri triple-star system, Barnard’s Star, Epsilon Eridani and Tau Ceti. But the catalog of nearby stars is by no means complete, as we are reminded periodically by the discovery of stars showing large proper motion as observed from Earth. That motion flags the object as close, but the fact that so many of the galaxy’s stars are M-class red dwarfs (up to 70 percent in some estimates) makes detecting them tricky. These are small, dim stars; some may have been in our catalogs for years before astronomers realized how close they were.
Some scientists, in fact, measure the number of missing stellar systems at 25 percent or more, even so close as 10 parsecs from the Sun. Now an international team of researchers has found three of the missing stars. Using data from the Two-Micron All Sky Survey (2MASS), the Deep Near Infrared Survey (DENIS) and the SuperCOSMOS Sky Survey (SSS), the team uncovered the three close neighbors by noting their high proper motion in SSS data from four different sets of observations, and cross-checking against data in the other databases. Further observations were made at the European Southern Observatory facility at La Silla (Chile).
The three stars, known as L 449-1, L 43-72, and LP 949-15, are all thought to be within 10 parsecs. The findings are summarized in Scholz, R.-D., Lo Curto, Mendez et al., “Three active M dwarfs within 8 pc: L 449-1, L 43-72, & LP 949-15,” now available in preprint form at the arXiv site and accepted for publication by Astronomy & Astrophysics. From the paper:
Although all three stars are known X-ray sources and were earlier classified as proper motion stars, we are not aware of any publication treating them as nearby stars. Our cross identification with the 2MASS providing accurate photometry and the follow-up low-resolution spectroscopy allowed us to uncover them as close neighbours to the Sun. As such, they are certainly worth investigating further, with more accurate distances to be obtained in a trigonometric parallax program.
Centauri Dreams note: We need to complete the catalog of nearby star systems for several reasons. Not only should they be excellent candidates for identifying extrasolar planets, but their proximity gives us the chance to study stars of this stellar type in detail. They will likely be added to the target list for upcoming planet-identification missions like the Space Interferometry Mission and Terrestrial Planet Finder.
Be aware, too, of the Wide-field Infrared Survey Explorer, a mission that will scan the sky in infrared looking for such objects. An earlier post here quoted WISE Principal Investigator Dr. Edward Wright of the University of California, Los Angeles: “Approximately two-thirds of nearby stars are too cool to be detected with visible light. The Wide-field Infrared Survey Explorer will see most of them.”