HD 89345 b

Lore & Background

HD 89345 b was discovered in 2018 by a team of 43 astrophysicists, including V. Van Eylen, using the transit photometry method. The planet orbits a slightly evolved G5 class star that exhibits solar-like oscillations and has an apparent magnitude of 9.3. The star was observed by the K2 mission with one-minute time sampling, and asteroseismology was used to determine its parameters. The planet's orbit is elliptical and lies closer to the star than the inner limit of the habitable zone. Radial-velocity follow-up observations with the FIES, HARPS, and HARPS-N spectrographs measured the planet's mass and confirmed the eccentricity of its orbit.

Reader's Guide

HD 89345 b is significant as a warm Saturn-sized exoplanet whose host star has recently left the main sequence, providing a rare opportunity to study planetary evolution around aging stars. The precise asteroseismic data from the K2 mission allowed accurate determination of the star's mass and radius, which in turn enabled robust characterization of the planet. Its classification as a warm subterranean planet with an equilibrium temperature of 1059 K places it in a regime distinct from both hot Jupiters and cold Neptunes. The planet's low density suggests a gaseous composition, and its orbital period of about 11.8 days at 0.105 AU makes it a valuable target for understanding the transition between close-in and more distant giant planets. The discovery also highlights the effectiveness of combining transit photometry with radial-velocity follow-up to confirm and characterize exoplanets around evolved stars.

Did You Know?

• HD 89345 b has a mass equivalent to 35.7 Earths.
• It orbits its star every 11.8 days at a distance of 0.105 AU.
• The planet was discovered by a team of 43 astrophysicists.
• Its host star is 66 percent larger and 22 percent more massive than the Sun.