The Kepler orbiting telescope has been a huge boon to planetary scientists. All by itself it's discovered more than 1,200 possible extrasolar planets, with 15 confirmed so far. But it turns out Kepler's also providing valuable data to astronomers interested in stars. The telescope's huge field of view lets it gather data from thousands of stars at once, tracking how their light brightens and dims. For some stars, this reveals the passage of planets in front of the star's disk, but for others it reveals changes in the star's energy output.
In particular, Kepler has allowed astrophysicists to track the pulsations of red giant stars as they shift from burning the last remnants of hydrogen fuel to burning helium. This is the real benefit to pure-science research. Not only do you find out what you were trying to learn, but you find out other things you hadn't expected.