UNIVERSITY PARK, Pa. — A signal originally detected by the Kepler spacecraft has been validated as an exoplanet using the Habitable-zone Planet Finder (HPF), an astronomical spectrograph built by a Penn State team and recently installed on the 10m Hobby-Eberly Telescope at McDonald Observatory in Texas. The HPF provides the highest precision measurements to date of infrared signals from nearby low-mass stars, and astronomers used it to validate the candidate planet by excluding all possibilities of contaminating signals to very high level of probability. The details of the findings appear in the Astronomical Journal.
The planet, called G 9-40b, is about twice the size of the Earth, but likely closer in size to Neptune, and orbits its low mass host star, an M dwarf star, only 100 light years from Earth. Kepler detected the planet by observing a dip in the host star’s light as the planet crossed in front of — or transited — the star during its orbit, a trip completed every six Earth days. This signal was then validated using precision spectroscopic observations from the HPF, ruling out the possibility of a close stellar or substellar binary companion. Observations from other telescopes, including the 3.5m telescope at Apache Point Observatory and the 3m Shane Telescope at Lick Observatory, helped to confirm the identification.
“G 9-40b is amongst the top 20 closest transiting planets known, which makes this discovery really exciting,” said Guðmundur Stefánsson, lead author of the paper, and a former doctoral student at Penn State who is currently a postdoctoral fellow at Princeton University. “Further, due to its large transit depth, G 9-40b is an excellent candidate exoplanet to study its atmospheric composition with future space telescopes.”