Group XVII's Journal: An Estimated 15% of Stars in the Milky Way Have Planetary Systems Like Our Own

Centauri Dreams is among those reporting from the American Astronomical Society meeting in Washington. They say:

Right now Scott Gaudi's talk on Tuesday is generating the biggest buzz. Gaudi (Ohio State) reported on a gravitational microlensing effort called MicroFUN (Microlensing Follow-Up Network), one we've previously discussed in these pages. The method is well understood: One star occults another as seen from Earth. The light of the more distant star is magnified by the nearer one, and any planets around the lensing star momentarily boost the magnification as well. You find planets this way, though they're not planets likely to be observed again because of the nature of the method.

I love this Gaudi quote from the talk: "Planetary microlensing basically is looking for planets you can't see around stars you can't see."

Gaudi's team has concluded that about fifteen percent of the stars in the galaxy are orbited by planetary systems like our own, meaning they have several gas giants in the outer part of the solar system. That fifteen percent is telling. "Solar systems like our own are not rare," says Gaudi, "but we're not in a majority, either." Microlensing is useful for this kind of study because the method does a good job at picking up giant planets far from their primary star, a more difficult task with Doppler methods.

The full discussion is here. Also reporting are Space.Com and Science Daily and Universe Today.