Astronomers have discovered a new, two-planet system where the planets are closer to each other than any other system yet found. The newfound system of Kepler-36 contains two planets circling a subgiant star similar to the Sun except several billion years older. The inner world, Kepler-36b, is a rocky planet 1.5 times the size of Earth and weighing 4.5 times as much. The outer world, Kepler-36c, is a “hot Neptune” gaseous planet 3.7 times the size of Earth and weighing 8 times as much.

The planets were spotted using data from NASA’s Kepler spacecraft, and the findings were published in the June 21st edition of Science Express.

The discovery is providing new data about the diversity of worlds that exist around distant stars. Understanding the variety of extrasolar planets can help astrobiologists understand the best locations in which search for habitable worlds beyond our own solar system.