Lots of Earth-Like Planets

I'm at least as fascinated by how they find earth-like planets around other stars as by the fact that they have.

I read an article once in Discover Magazine—a magazine I highly recommend as interesting, reliable, and readable—explaining some techniques for finding planets.

Think about how hard that would be. You look in a telescope at some distant sun, shining as brightly or more brightly than ours, that is between 4 and 50,000 light years away. Next to it is an unlighted object between 5 and 60 light minutes away from its sun and a million times smaller.

If I used my scientific calculator—an app on my android phone—correctly, which I doubt, then the angle difference between a sun that is 100 light years away and a planet orbiting it at the same distance as earth is less than 2 tenths of one millionth of a degree.

Keeping in mind that an earth-sized planet orbiting an sun-sized star is going to be only one millionth of the size of that sun.

At those distances, it seems like it would be impossible to see the planet.

Nonetheless, scientists at the earth-bound Keck observatory in Hawaii were able to survey 166 sun-sized stars and find 38 earth-sized planets around them.

Amazing.

NASA has an article on 4 ways to to find such exoplanets.