the analysis came from data collected by the kepler spacecraft geoff marcie is one of the lead researchers joins me from mountain view, california. welcome back. we've had you on this program in the past talking about the discovery of planets so i was struck when you said about this new finding this is the most important work i've ever done. tell us why? what's the significance? >> well, you know, we've wondered for a long time even going back to the time of the greeks whether there were planet around the twinging lights you see in the night sky. but the real question is always been what about habitable planets? earth like planets that could support primitive life and maybe even intelligent life? now for the first time we have a census of stars showing that about one in five of the sunlight stars out there really do have planet it is size of the earth, the temperature of the earth and perhaps conditions conducive to life as we know it. >> brown: that's what we mean by a habitable planet or potentially habitable? and this idea of a goldilocks zone? >> that's right. of course the properties