A Newly Found Giant Planet Will Stop Crossing Its Star in 2033
A team led from the University of Tokyo has found a giant planet that circles a hot star every 2.17 days on an orbit still stretched into an oval rather than round. Noriharu Watanabe and colleagues report the planet, TOI-1355 b, in Publications of the Astronomical Society of Japan as one of the rare eccentric hot Jupiters (giant planets on very short orbits) found around hot stars. It carries about 5.8 times Jupiter's mass, and its orbit has an eccentricity near 0.22.
The shape matters because of how such planets are thought to have arrived. Hot Jupiters around hot stars are believed to have reached their tight orbits through high-eccentricity migration, a route that begins with a long, stretched orbit. The paper says the ones found so far are on circular orbits. TOI-1355 b's is not, and the authors write that the system could be undergoing that migration now.
The transits also have an end date. The planet's path across the star's face has been shifting, a nodal precession, or slow tilt of the orbit's plane. The authors put the end of the transits at the middle of 2033.
TESS identified the planet from its transits. The star's properties come from the high-resolution spectrograph Seimei/GAOES-RV, and the planet's from TESS photometry and ground-based telescopes, which put its radius at about 1.4 times Jupiter's. The team also reports a hint that the planet's atmosphere varies and expects it to be a worthwhile target for atmospheric observations.
