As reported in Astronomy magazine, Teegarden’s group spotted the red dwarf while studying images taken with the Near Earth Asteroid Tracking (NEAT) program. Since 1995, NEAT telescopes have been looking for near-Earth asteroids, which move relative to the stars. These repeat exposures also allowed Teegarden’s group to look for other stars that change position over time. They found 63 objects that move more than 1 arcsecond per year. The fastest one was SO25300.5+165258, which travels more than 5 arcseconds per year. Parallax measurements with other telescopes pinned this proper motion down to a location 7.8 light years away.
There’s still a mystery about SO25300.5+165258, though. While stellar parallax measurements put it at 7.8 light years away, it exhibits a M6.5 spectral type, which according to theory and previous observations of similar stars should result in it’s being three times brighter at that distance than is presently observed. Thus SO25300.5+165258 apparently has something to teach us about stellar spectra that we haven’t seen before. Meanwhile, the NEAR photos are being scoured to find traces of even closer unseen stellar neighbors – perhaps even the fabled Nemesis.