Terrestrial mass planet measured orbiting nearby red dwarf Answered
From Science Magazine:
A group of astronomers today announced the discovery of the least massive planet yet detected outside of our solar system. It is lightweight enough--between two and three times the mass of Earth--to almost certainly be rocky like Earth rather than a huge ball of gas. Although the planet orbits too close to its star to be habitable, a new analysis of one of its neighbors suggests a world with deep oceans.
The observation of Gliese 581e, made with the usual radial-velocity residuals fit, is of a terrestrial-mass planet orbiting insanely close to a red dwarf star. Nevertheless, it marks a substantial improvement (a factor of three in mass) in the precision of the radial-velocity technique.
Read the whole article (let me know if it's password protected) for details.
Another news article (including a very nice diagram of the habitable zone as a function of the mass of Gliese 581) is available from Science News.