StarDate 8/7/2014: Getting To Know The Neighbors
FROM THE UNIVERSITY OF TEXAS McDONALD OBSERVATORY, AS HEARD ON KCBS RADIO WEEKDAYS @ 9:52 A.M., 7:35 P.M. & 2:52 A.M.
STARDATE 8/7/2014: A few of our stellar neighbors are hard to miss. Vega, which passes high overhead on August evenings, is just 25 light-years away. And Sirius, the brightest star in all the night sky, is nine light-years away. Yet many of our neighbors are so faint that you need a telescope to see them. That list includes the closest star of all, Proxima Centauri, at just four light-years.
Astronomers are still working on the census of stars and other objects in our stellar neighborhood. One of the leaders in that effort is called RECONS. It got started 20 years ago this month.
So far, it’s tallied about 270 systems within 10 parsecs of Earth — about 33 light-years. Those systems incorporate more than 400 individual objects — stars, planets, and brown dwarfs.
Roughly three-quarters of the stars in the neighborhood are much smaller and fainter than the Sun — the cool cosmic embers known as red dwarfs. The faintest of them are only about one ten-thousandth as bright as the Sun, so it takes some effort to find them and measure their distances.
The census has revealed fewer brown dwarfs than expected. These objects are more massive than planets, but not massive enough to shine as stars. Some astronomers thought we’d see as many brown dwarfs as true stars, but so far, only a few have been found nearby. Brown dwarfs are so faint, though, that a few could still await detection — adding to the census of our stellar neighborhood.