This artist's conception shows the inner four planets of the Gliese 581 system and their host star, a red dwarf star only 20 light years away from Earth. The large planet in the foreground is the newly discovered GJ 581g, which has a 37-day orbit right in the middle of the star's habitable zone and is only three to four times the mass of Earth, with a diameter 1.2 to 1.4 times that of Earth. The other three planets are visible along a diagonal from the upper left to GJ 581g.

Credit: Artwork by Lynette Cook

Steven Vogt of UC Santa Cruz and UC Observatories and Paul Butler of the Carnegie Institution of Washington join NSF's Lisa-Joy Zgorski to announce the discovery of the first exoplanet that has the potential to support life.

Credit: National Science Foundation

The orbits of planets in the Gliese 581 system are compared to those of our own solar system. The Gliese 581 star has about 30 percent the mass of our Sun, and the outermost planet is closer to its star than the Earth is to the Sun. The 4th planet, G, is a planet that could sustain life.

Credit: Zina Deretsky, National Science Foundation

The new findings are based on 11 years of observations of Gliese 581 using the HIRES spectrometer on the Keck I Telescope at the W. M. Keck Observatory in Hawaii. The spectrometer allows precise measurements of a star's radial velocity (its motion along the line of sight from Earth), which can reveal the presence of planets. HIRES (the High Resolution Echelle Spectrometer), designed by Vogt, is the largest and most mechanically complex of the Kecks main instruments. HIRES breaks up incoming starlight into its component colors to measure the precise intensity of each of thousands of color channels. Its spectral capabilities have resulted in many breakthrough discoveries, such as the detection of planets outside our solar system and direct evidence for a model of the Big Bang theory.

Credit: NASA