The Milky Way is awash in planets by the billions, and astronomers are finding more every day.

There's a tiny solar system way out there with three planets smaller than Earth, and at least three other new-found ones with a single planet flying around two suns at once.

And now an international team of astronomers calculates that there must be more than 10 billion rocky planets the size of Earth within the Milky Way, perhaps even more, if planets of all kinds were counted - small ones, big ones and "gas giants" bigger than Jupiter.

Scientists this week reported fresh results from NASA's planet-hunting Kepler spacecraft at a meeting of the American Astronomical Society in Austin, Texas, and two other groups are reporting online in the journal Nature that their calculations show there must be far more Earth-size planets than bloated Jupiter-size ones.

But no one is yet willing to predict how many of those might lie in friendly orbits around their suns where temperatures are just right for liquid water to stay liquid - not too hot and not too cold - that astronomers call the Goldilocks Zone, and more officially call it the habitable zone. That's the planetary region where life itself might exist.

At the meeting in Austin, a Kepler team led by California Institute of Technology astronomers reported the discovery of the three smallest "exoplanets" ever detected. They appear to be rocky with a solid surface, the scientists said, and the star is only a dim, small one called a red dwarf. The planets are so close to it that their temperatures would be far too hot to be habitable, they said.

"But red dwarfs make up 8 out of 10 stars in the galaxy," said John Johnson of Caltech, "and if these planets are as common as they appear, and because red dwarfs themselves are so common - then the whole galaxy must be just swarming with little habitable planets around faint red dwarfs."

While the astronomers at Austin were exchanging ideas about the new Kepler planets, William F. Welsh and more than a dozen colleagues reported in Nature that they have detected two new "gas giant" planets - each one flying in orbit around two stars at the same time rather than the usual one.

Laurance R. Doyle of the SETI Institute in Mountain View reported discovery of the first such "circumbinary" planet in September, and astronomers were amazed; it was like finding that Tatooine of "Star Wars" was real. But in Nature this week, Welsh of San Diego State University and his Kepler team colleagues, including Doyle, report discovering two more planets around double stars and estimate that the Milky Way must contain "at least several million."

Most of the newfound planets have been detected in data gleaned from the Kepler spacecraft that is surveying more than 150,000 stars far out in the Milky Way and finds planets by seeing how their infinitely small shadows dim the light of the stars as they pass in front of them.

But there are other and much more difficult ways to detect a distant planet around a distant star, and an international team using ground-based telescopes in South Africa, South America and Australia has calculated after a six-year study that, on average, every star in the Milky Way would have at least 1.6 planets around it - which means that there could even be as many as 100 billion planets in our galaxy.

"Planets around stars in our galaxy thus seem to be the rule rather than the exception," said Arnaud Cassan of the Paris Astrophysical Institute, the leader of the group that reports its findings in Nature.