Scientists using the European Southern Observatory telescope didn't find any planets quite the size of Earth or any that seemed habitable or even unusual. But their announcement increased the number of planets discovered outside the solar system to more than 400.
Six of the newly found planets are several times bigger than Earth, increasing the population of so-called super-Earths by more than 30 percent. Most planets discovered so far are far bigger, Jupiter-sized or even larger.
Two of the newly discovered planets were as small as five times the size of Earth and one was up to five times larger than Jupiter.
Astronomer Stephane Udry of the University of Geneva said the results support the theory that planet formation is common, especially around the most common types of stars.
"I'm pretty confident that there are Earth-like planets everywhere," Udry said in a Web-based news briefing from a conference in Portugal. "Nature doesn't like a vacuum. If there is space to put a planet there, there will be a planet there."
What astronomers said is especially exciting is that about 40 percent of sun-like stars have planets that are closer to being Earth-sized than the size of Jupiter. Jupiter's mass is more than 300 times that of Earth's.
Depending on definitions of the size of super-Earths, the discovery suggests that planets that have a mass similar to Earth's are "extraordinarily commonplace," said Alan Boss, an astronomer at the Carnegie Institution of Washington. He was not part of the European team. "The universe must indeed be crowded with habitable worlds."
Boss said finding 32 planets at once is a record "and it really shows that the Europeans have taken the lead" in finding planets outside the solar system.
The discoveries were made by the High Accuracy Radial Velocity Planet Searcher, which is an attachment to the European observatory telescope in Chile that looks for slight wobbles in a star's movements. Those changes would be made by the tug of a planet's gravity on the star. There are no photos of these planets.