Stars and Brown Dwarfs: RECONS Studies of the Solar Neighborhood

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The RECONS (REsearch Consortium On Nearby Stars) project is making a reconnaissance of the nearest stars to the Sun, focusing on our neighbors out to a horizon of about 80 light years. In the current effort, the team is focusing on the smallest stars, known as red dwarfs, and their slightly less massive cousins, the brown dwarfs. The main difference between the two types of objects is whether or not they can shine via nuclear reactions. Red dwarfs are true stars that fuse hydrogen into helium in their cores, like our Sun, and shine for many billions of years. Although they are the smallest true stars in the Universe, the red dwarfs are by far the most common type of star, accounting for at least three-quarters of all stars, but we're not quite sure how many there are. On the other hand, brown dwarfs are cooling bodies like Jupiter that do not fuse hydrogen, and behave more like superplanets. The RECONS team is taking a census of red and brown dwarfs and revealing how often they are orbited by stellar, brown dwarf, or planetary companions. We will then ultimately know just what fraction of the Sun's neighbors are stars and where some of the nearest planets are found. Through this program, specialized training in astrometry - the precise measurement of positions and motions on the sky - will be provided to Georgia State University students. As a large minority-serving institution, Georgia State well placed to provide research opportunities to students from underrepresented groups. The program will also involve graduate and undergraduate students in all aspects of the research, and they will share their results with the general public through their website (www.recons.org) and through public outreach activities.RECONS is a long-term, NSF-supported program to characterize the astronomical objects closest to the Sun. Most of these are M dwarfs and Brown Dwarfs. Among the many studies enabled by this program is a detailed description of how the mass and luminosity functions transition between fusion-powered stars and the non-stellar dwarfs. The RECONS catalog, publicly-available at their website, also provides the best estimate available for the relative populations of late-type stars and brown dwarfs. In this proposal, they will extend the volume of space completely sampled, extend their 20-year timeline of astrometric measurements, and map orbits of low-mass binaries (including those with planetary companions).