Source: MSNBC July 11
By Alan Boyle
This week in space - 

Planets, Planets Everywhere 

Is there life on other planets? It will take decades to even begin to answer that question, but scientists are suddenly finding plenty of places to look — on faraway planets as well as the moons that might be circling them.

UNTIL A FEW years ago, astronomers assumed that: a) planetary systems were relatively rare in the universe, and b) if they did exist, they would probably be set up pretty much the way our own solar system is.

The quickly moving consensus, at least among a new breed of planet-hunters, is that both those assumptions are false.

The key to the quest is a method by which astronomers look for slight variations in the spectrum of stars — oscillations that hint at a gravitational wobble induced by a circling planet. So far more than a dozen such wobbles have been detected, and scientists are just starting on a list of hundreds of candidates.

Most of the planets detected so far appear to be much larger than Jupiter, in an orbit tighter than Mercury's path around our own sun. There also seems to be at least one distant celestial body that's been kicked out of its planetary cradle.

Just in the past week, astronomers spread the news about a dust disk around Epsilon Eridani that looks suspiciously like the beginnings of a planetary system. And, at least as significantly, scientists found another giant planet with an orbit wider than Earth's — passing through what might be a prime "habitable zone" for liquid water and sustainable life.

If these planets are huge gas giants like Jupiter or Saturn, they probably aren't good candidates to harbor life as we know it even if they're in the habitable zone. But Michael Shao of NASA's Jet Propulsion Laboratory points out that we shouldn't stop with just the planets.

"If we're looking for habitable planets, we should not be looking just for Earthlike planets, but we should be looking for moons around Jupiterlike planets," he said last week.

We still don't have any instruments to detect planets that are closer to Earth's size. But once such instruments are available in the next decade or so, we might be surprised at the diversity we find within distant planetary systems. We might be even more surprised by what we find on those planets in the decades to come.