A suite of some 30 newly discovered planets in other solar systems, unveiled today, brings the catalogue of such extrasolar planets, or exoplanets, to more than 400.

The newfound bodies were turned up by the High Accuracy Radial Velocity Planetary Search (HARPS), a program designed to detect the presence of orbiting planets by tracking the motion of their host stars. As a star wobbles under the gravitational influence of a planet, it periodically moves closer to our solar system before drawing away again, imbuing its emitted light with telltale Doppler shifts.

The research team announced its findings today at an exoplanet conference in Porto, Portugal, hosted by the European Southern Observatory and the Center for Astrophysics at the University of Porto.

With the new influx from HARPS, the known population of exoplanets is now 403, according to the online Extrasolar Planets Encyclopaedia. (HARPS announced 32 new finds today, but the encyclopedia catalogued just 30 of them, characterizing the other two as brown dwarfs, failed stars too small to sustain fusion.)

The swelling planetary catalogue is still bereft of the ultimate goal of planet hunters, however: small, rocky planets at the right distance from their stars to potentially host life as we know it. Those planets may indeed be common throughout the galaxy, but most current detection methods tend to favor massive planets or planets in tight orbits around their host stars. (The smallest planet in the new group found by HARPS, for instance, is roughly 5.5 times the mass of Earth and is so close to its star that it completes an orbit in about four days.)

Ground-based telescopes such as that used by HARPS as well as space-based observatories are turning up ever smaller extrasolar planets, but the real payoff—an Earth-like planet orbiting a distant star—may have to wait until 2012 or 2013. That is when NASA's Kepler spacecraft will have logged enough time in its dedicated search for planetary transits, or periodic dips in a star's brightness as an orbiting planet partially obscures it, to have solid evidence for an Earth-like planet.

Artist's impression of GJ 667C b, a newfound exoplanet that orbits a star 23 light-years from the sun in a triple-star system (the two companion stars to the exoplanet's host star are depicted in the background): ESO