How does the Kepler space telescope detect water vapor on other planets?

Question

So how?

Source(s):
http://news.nationalgeographic.com/news/2014/09/140924-space-exoplanet-water-neptune-science-ngspace/
http://www.jpl.nasa.gov/m/news/news.php?release=2014-322#.VDFSEKMpDFo

Answer 1

It doesn't. Kepler was a planet hunter, it's dead in space now. It watched for planets transiting stars. If you'd read the articles they use Hubble and Spitzer to run a spectrum on the starlight passing through the planet's atmosphere.

Answer 2

George is sorta right... It relays some basic data - mostly about the intensity of the star's light that a transiting planet may dim a bit; one advantage of the data is that it's light - both intensity and color - are relayed to Earth (or was - Kepler lost it's gyroscopes a year ago...) and, that the color of the light can be broken apart into a spectrum - which *sometimes* tells us about the atmosphere of that planet.

A small drop in light from a star tells us there's a planet crossing it; if the drop is sharp, it's likely a planet with little to no atmosphere. If the drop is 'fuzzy' - not as sharp, then the gradual drop might be due to the star's light filtering through an atmosphere.

Answer 3

By studying the spectrum of its light.

Don't ask me how that's done, something to do with dark lines.