Data from the Kepler space telescope has been used to identify thousands of planets beyond our solar system with radii between that of Earth and Neptune. However, there is a gap in this population planets near 1.5 to 2.0 Earth radii. On the low side of the gap are the ‘super-Earths,’ and above 2.0 Earth radii are ‘sub-Neptunes.’ This division is informal, and the exact differences between the two classes of planets are hard to study. This is due in part to the fact that most Kepler planets orbit stars that are so far away that follow-up measurements with techniques like radial velocity or transit spectroscopy are not yet possible. This means that the bulk density and atmospheric measurements for such planets are out of reach of today’s instruments.

A new study presents the discovery and validation of a planet in proximity to the radius gap. The planet orbits nearby star Wolf 503. Due to the properties of the star, planet Wolf 503b could be a prime target for further study with radial velocity follow-up studies, transit spectroscopy measurements with the Hubble Space Telescope, and atmospheric characterization with the James Webb Space Telescope. The hope is that Wolf 503b could provide a wider understanding of the populations of super-Earths and sub-Neptunes.

The study, “A 2 R Planet Orbiting the Bright Nearby K Dwarf Wolf 503,” was published in The Astronomical Journal. The work was supported by the Nexus for Exoplanet System Science (NExSS). NExSS is a NASA research coordination network supported in part by the NASA Astrobiology Program. This program element is shared between NASA’s Planetary Science Division (PSD) and the Astrophysics Division.