2010/09/29 by Steven S. Vogt, R. Paul Butler, Eugenio J. Rivera +3 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph.EP
paper · pdf · doi:10.1088/0004-637x/723/1/954
Accepted for publication in ApJ; 44 pages, 6 figures, 3 tables
arxiv created 2010/09/29 · openalex publication_date 2010/10/15 · arxiv updated 2015/05/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present 11 years of HIRES precision radial velocities (RVs) of the nearby M3V star Gliese 581, combining our data set of 122 precision RVs with an existing published 4.3-year set of 119 HARPS precision RVs. The velocity set now indicates six companions in Keplerian motion around this star. Differential photometry indicates a likely stellar rotation period of ∼94 days and reveals no significant periodic variability at any of the Keplerian periods, supporting planetary orbital motion as the cause of all the RV variations. The combined data set strongly confirms the 5.37-day, 12.9-day, 3.15-day, and 67-day planets previously announced by Bonfils et al., Udry et al., and Mayor et al.. The observations also indicate a fifth planet in the system, GJ 581f, a minimum-mass 7.0 M ⊕ planet orbiting in a 0.758 AU orbit of period 433 days, and a sixth planet, GJ 581g, a minimum-mass 3.1 M ⊕ planet orbiting at 0.146 AU with a period of 36.6 days. The estimated equilibrium temperature of GJ 581g is 228 K, placing it squarely in the middle of the habitable zone of the star and offering a very compelling case for a potentially habitable planet around a very nearby star. That a system harboring a potentially habitable planet has been found this nearby, and this soon in the relatively early history of precision RV surveys, indicates that η ⊕ , the fraction of stars with potentially habitable planets, is likely to be substantial. This detection, coupled with statistics of the incompleteness of present-day precision RV surveys for volume-limited samples of stars in the immediate solar neighborhood, suggests that η ⊕ could well be on the order of a few tens of percent. If the local stellar neighborhood is a representative sample of the galaxy as a whole, our Milky Way could be teeming with potentially habitable planets.