HIP 99770 b

Astronomical object orbiting 29 Cygni

HIP 99770 b ^[1] is a directly imaged superjovian extrasolar planet orbiting the dusty A-type star HIP 99770 (29 Cygni), detected with Gaia/Hipparcos precision astrometry and high-contrast imaging.^[2] HIP 99770 b is the first joint direct imaging + astrometric discovery of an extrasolar planet and the first planet discovered using precision astrometry from the Gaia mission.

Discovery

HIP 99770 b was discovered by a team led by Thayne Currie, Mirek Brandt, and Tim Brandt using the Subaru Telescope on Mauna Kea. The Subaru data utilized the observatory's extreme adaptive optics system, SCExAO, to correct for atmospheric turbulence and the CHARIS integral field spectrograph to detect HIP 99770 b at 22 different near-infrared wavelength passbands from 1.1 microns to 2.4 microns. It was also detected at longer wavelengths using the NIRC2 camera on the Keck Observatory.

Atmosphere

With a spectral type of L7.5--L9, HIP 99770 b lies at the L/T transition for substellar objects, transition from cloudy atmospheres without methane absorption to clear atmospheres with methane absorption. Atmospheric modeling favors an effective temperature of 1400 K and a Jupiter-like radius. The planet is likely intermediate in cloudiness between older, more massive field brown dwarfs and young L/T transition exoplanets like HR 8799 d.

Orbit and mass

Jointly modeling relative astrometry of HIP 99770 b with absolute astrometry of the primary as measured by Gaia and Hipparcos yields precise estimates for the companion's orbit and mass. HIP 99770 b lies at about 16.9 au from its host star. The host star is significantly more luminous than the Sun: HIP 99770 b receives roughly as much light as Jupiter receives from the Sun. HIP 99770 b is a super-jovian planet with a mass of roughly 16.1 times that of Jupiter. Its mass ratio -- mass divided by the mass of the host star -- is comparable to that of many planets detected through methods such as radial velocity and transits and is similar to that of HR 8799 d.

References

^ ^a ^b ^c ^d Direct Imaging and Astrometric Discovery of a Superjovian Planet Orbiting an Accelerating Star, 2022, arXiv:2212.00034
^ Andrew Jones (April 17, 2023). "Giant exoplanet found, imaged directly thanks to star-mapping data (photos)". Space.com.

2021 LL37 (TNO) 2021 RR205 (TNO) Alcyoneus (galaxy) CEERS-93316 Gaia BH1 GLASS-z12 GNz7q GRB 221009A HD1 (galaxy) J1144–4308 JADES-GS-z13-0 OGLE-2011-BLG-0462 PKS 2131-021 PSR J0901–4046 PSR J0952–0607 Sagittarius A* imaged S4716 SN 2022jli VFTS 243 Webb's First Deep Field (SMACS J0723.3–7327) WD 1054–226 WHL0137-LS ZTF J1813+4251 12 moons of Jupiter
Exoplanets	AB Aurigae b CO₂ on WASP-39b Gliese 514 b Gliese 3929 b c Gliese 896 Ab HD 83443 c HD 260655 b c K2-2016-BLG-0005Lb Kepler-451 c d Kepler-1708b and possible exomoon Kepler-1708b I LP 890-9 b c Mu2 Scorpii b c OGLE-2018-BLG-1119Lb Pi Mensae d Proxima Centauri d TOI-1227 b TOI-1452 b TOI-2180 b