This award will support an observational project to explore the nature of cool ("red") binary and multiple stars. The project adopts a two-pronged approach to uncover both close binaries and those with wide separation. The main goals of the project are to reveal important clues about star formation, improve knowledge of the luminosity and mass functions of individual and multiple red dwarfs, provide samples for studies of the longevity of wide multiples in the solar neighborhood, and evaluate whether multiplicity affects the formation of exoplanets around red dwarfs.
The project is expected to shed light on the process of star formation and how binary and multiple systems evolve with time. The research will also contribute to the education and training of students from a variety of backgrounds, and non-scientists will benefit from opportunities to participate in this project.
The REsearch Consortium On Nearby Stars (RECONS, www.recons.org) is a group of astronomers who are exploring the stars nearest to our Sun. The group focuses on the population of stars closer than 25 parsecs, or about 82 light years. They study the stars themselves and their surrounding environments, which may include stellar companions, brown dwarfs (sometimes called "failed stars"), or planets in orbit around the target stars. During the project supported by this funding, the astronomers discovered several hundred new nearby red dwarf stars. Red dwarfs are the smallest type of normal stars that convert hydrogen into helium to shine, and dominate the population of stars in our Milky Way Galaxy, accounting for at least 75% of all stars. The group's fundamental census of red dwarfs within 25 parsecs includes 1404 stars in the southern sky --- this is by far the most careful and comprehensive census ever done of these stars. They used a combination of archival images taken using glass plates between 1950 and 2000, combined with new observations taken using telescopes in Arizona and Chile to identify and characterize the stars. Of critical importance to our understanding of how stars are made, they found that there are many more of the smallest red dwarf stars with masses of 10% that of the Sun than those with masses 60% that of the Sun. In addition, they discovered that only about 30% of red dwarfs have companions that are other stars. Curiously, these companions are found at separations of a few to 100 Astronomical Units (the distance of the Sun to our Earth is 1 AU), indicating that most of the companions orbit their stars at Solar System scales. The remaining 70% of red dwarfs are single, traveling around the Milky Way alone, and could be ideal places to find planets.