is just right for life. 

 

The location of this habitable green zone depends on the star. With hot blue stars, the green zone is further out. With cooler red stars, it's closer in. Every star in the Milky Way must have a habitable zone. The question is do they also have planets within them. 

 

In 1995, something happened that was extraordinary, I’d got a call from my collaborator Paul Butler and all he said was ，Jeff ，come over here, and it was a moment that I would never forget. I was silent, Paul was silent and we were just stunned. They are on the computer screen I saw the unmistakable signature of a planet. 

 

Jeff / discovered the first planet around another star. But he couldn't actually see it because the planet itself was too small and dim. 

 

Any planet orbiting a star is lost in the glare of that host star that outshines by a factor of a billion. And so instead, to detect planets, we watch the stars. And in fact, the star will wobble in space because it's yanked on gravitationally by the planet or planets orbiting that star and by watching the star alone, we can determine whether the star has planets and how far out those planets are from the host star.