Ultracool stars are some of the hottest things in astronomy today.

In a paper published today in Nature researchers announced that they had discovered not one, not two, but three temperate Earth-sized planets orbiting a star so cool and dim it can't even be seen from Earth with the naked eye. The findings give astronomers hope that they could soon detect habitable areas on the planets which orbit their Jupiter-sized sun very closely.

Exoplanets are detected when a planet transits between it's sun and our telescopes here on Earth. The small shadow or dip in brightness is the tell-tale sign that something large is orbiting a planet. The simple version is, by counting the number and intensity of the dips, astronomers can determine how large a planet is, and how close to its star it is orbiting. But figuring out a planet's atmosphere is trickier, simply because a planet's atmosphere is usually not that large, and stars are very, very bright.