On Wednesday, NASA’s Kepler missions announced that 715 new planets have been verified in orbit around 305 stars. The discovery includes multiple planet systems similar to the Solar System, and marks a significant increase in the number of small-sized planets known to orbit distant stars.

Four of the planets are less than 2.5 times the size of Earth and orbit within the ‘habitable zone’ of their host star. The habitable zone is the distance at which the surface temperature of a planet is suitable for liquid water.

The announcement brings the total number of confirmed exoplanets to nearly 1,700. Each planet provides new information about how planets form and evolve. This is useful for astrobiologists who are trying to determine how and where habitable planets might form in the Universe.