The other sort of planet we have found is also bizarre. We’ve found planets that orbit in elongated orbits, elliptical, stretched-out orbits, but then the planets go very far from the star where they would be quite cold. And so the planets that we have found so far are a little too weird for us to imagine that life would have a good chance of surviving.   

 

 

 

 

 

But all that may be about to change. Recently, NASA launched a powerful new telescope called Kepler on the hunt for earth size planets which may orbit inhabitable zones around nearby stars.

 

 

 

Kepler works in the most simple way. All Kepler does is monitor the brightness of 100,000 stars with such exquisite position that it would detect a planet as small as an earth-like one, as it blocks the star light. 

 

 

 

We see the same thing from earth when Venus and Mercury are silhouetted against the Sun, but Kepler’s task is far more difficult. It is a little bit like having a searchlight in which you are trying to detect any dust on that searchlight by noticing a dimming of the searchlight when one dust particle falls on this massive searchlight. 

 

 

 

From this tiny dimming, the size of a planet can be measured. And more importantly, together with the way it causes its host star to be wobbled, Jeff can work out its density.  

 

 

 

And of course, this is glorious because by these measurements, we will be able to distinguish gaseous planets probably not suitable for life, from the rocky planets that may have a surface covered by liquid water. 

 

 

 

Astronomers like Seth shostak aren’t sure how many planets Kepler will find, but with 200 billion stars in the Milky Way, surely the galaxy is teeming with them.