Astronomers from the Giant Outer Transiting Exoplanet Mass (GOT ’EM) Survey have discovered a long-period giant planet circling the 7.4-billion-year-old star Kepler-1704.
“Giant planet migration is typically invoked to explain the present day architecture of exoplanetary systems,” University of California, Riverside astronomer Paul Dalba and colleagues wrote in their paper.
“Theories of planetary migration abound but can broadly be categorized as disk-driven migration, caused by torques from the protoplanetary disk, or high-eccentricity migration, whereby a giant planet exchanges orbital energy and angular momentum with one or more other objects in its system and subsequently experiences tidal circularization during close periastron passages.”
“The characterization of giant planets and their orbits offers a window into which mechanisms might have been at play.”
The newfound giant planet, labeled Kepler-1704b, has a mass of 4.15 times that of Jupiter.
The alien world orbits its host star once every 989 days in an extremely eccentric orbit (e=0.92).
“Kepler-1704b is a failed hot Jupiter that was likely excited to high eccentricity by scattering events that possibly began during its gas accretion phase,” the astronomers said.
“Its final periastron distance was too large to allow for tidal circularization, so now it orbits it host from distances spanning 0.16-3.9 AU.”
“The maximum difference in planetary equilibrium temperature resulting from this elongated orbit is over 700 K (varies from 180 to 900 K).”
The host star, Kepler-1704, is slightly larger, more massive, and more luminous than our Sun.
Also known as KOI-375, TIC 350738167, and KIC 12356617, it lies approximately 2,691 light-years away in the constellation of Cygnus.
Dr. Dalba and co-authors collected and analyzed 14 radial velocity measurements of Kepler-1704 from the High Resolution Echelle Spectrometer (HIRES) on the Keck I telescope at the W.M. Keck Observatory spanning 9.6 years.
“Kepler-1704b is an extraordinary system owing to its high eccentricity and transiting geometry,” they wrote.
“Much like HD 80606b, it provides a laboratory for testing the extremes of planetary migration scenarios.”
“Continued characterization of the system promises to refine theories explaining the formation of hot Jupiters and cool giant planets like those in the Solar System.”
Paul A. Dalba et al. 2021. Giant Outer Transiting Exoplanet Mass (GOT ’EM) Survey. II. Discovery of a Failed Hot Jupiter on a 2.7 Year, Highly Eccentric Orbit. AJ, in press; arXiv: 2107.06901