View source for HIP 99770 b

{{Short description|Astronomical object orbiting 29 Cygni}}
{{Use mdy dates|date=April 2022}}
{{Infobox planet
| name                     = HIP 99770 b
| image                    = HIP_99770_b.png
| caption                  = Subaru Telescope detection of HIP 99770 b.
<!-- DISCOVERY           -->
| discoverer               = Currie et al.<ref name="Currie2022"/>
| discovery_site           = [[Subaru Telescope]]
| discovered               = November 30, 2022
| discovery_method         = [[Direct imaging]]
<!-- DESIGNATIONS        -->
<!-- ORBITAL             -->
| apsis                    = astron
| semimajor                = 16.9{{±|3.4|1.9}}[[astronomical unit|AU]]
| eccentricity             = 0.25{{±|0.14|0.16}}
| inclination              = {{val|148|13|11}}
<!-- PHYS CHARS          -->
| mean_radius              =
| mass                     = 16.1{{±|5.4|5.0}}<ref name="Currie2022"/> {{Jupiter mass|link=y}}
| single_temperature       = {{val|1400|ul=K|fmt=commas}}<ref name="Currie2022"/>
| star                     = [[HIP 99770]]
<!-- ATMOSPHERE          -->
<!-- NOTES               -->
}}
'''HIP 99770 b'''  <ref name="Currie2022"/> is a directly imaged superjovian [[extrasolar planet]] orbiting the dusty A-type star HIP 99770 ([[29 Cygni]]), detected with [[Gaia_(spacecraft)|Gaia]]/[[Hipparcos]] precision astrometry and high-contrast imaging.<ref>{{cite web|website=[[Space.com]]|title=Giant exoplanet found, imaged directly thanks to star-mapping data (photos)|author=Andrew Jones|date=April 17, 2023|url=https://www.space.com/giant-exoplanet-discovered-gaia-star-mapping-data}}</ref>   HIP 99770 b is the first joint [[direct imaging]] + [[astrometry|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_(spacecraft)|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 [[Methods of detecting exoplanets#Radial velocity|radial velocity]] and [[Methods of detecting exoplanets#Transit photometry|transits]] and is similar to that of [[HR 8799 d]].
== See also ==
* [[List of exoplanets discovered in 2023]]
==References==
{{reflist|refs=
<ref name=Currie2022>{{citation|arxiv=2212.00034|year=2022|title=Direct Imaging and Astrometric Discovery of a Superjovian Planet Orbiting an Accelerating Star}}</ref>
}}
==Further reading==
*{{citation|work=[[Scientific American]]|title=New Planet-Hunting Technique Finds Worlds We Can See Directly|author=Nola Taylor Tillman |date= April 13, 2023|url=https://www.scientificamerican.com/article/new-planet-hunting-technique-finds-worlds-we-can-see-directly/}}
{{Cygnus (constellation)}}
{{2022 in space}}
[[Category:Exoplanets discovered in 2022]]
[[Category:Exoplanets detected by direct imaging]]
[[Category:Exoplanets detected by astrometry]]