View source for HD 89345 b

{{Short description|Neptune-like exoplanet}}
{{Cleanup|reason=Article is a mess and needs to be rewritten, see talk page|talk=Needs cleanup|date=July 2024}}
{{Infobox planet|period=11.8143 day|mean_radius=0.616 {{Jupiter radius}}|name=HD 89345 b|image=File:HD_89345_b_infrared_spectographic,_2018.png|caption=Image from [[2MASS]] Two Micron All-Sky Survey|mass=0.103 {{Jupiter mass}}|semimajor=0.1086 AU|eccentricity=0.25°|inclination=87.7°|single_temperature=1059 K|extrasolarplanet=yes}}

'''HD 89345 b''' is a Neptune-like exoplanet that orbits a [[G-type star]]. It is also called K2-234b. Its mass is equivalent to 35.7 Earths, it takes 11.8 days to complete one orbit of its star, and is 0.105 AU away from its star. It was discovered by a team of 43 astrophysicists, one of which was [[Vincent Van Eylen|V. Van Eylen]], and was announced in 2018.<ref>{{Cite web|url=https://exoplanets.nasa.gov/newworldsatlas/6306/hd-89345-b/|title=HD 89345 b {{!}} New World Atlas - Exoplanet Exploration: Planets Beyond our Solar System|website=Exoplanet Exploration: Planets Beyond our Solar System|access-date=2018-07-03}}{{dead link|date=June 2021|bot=medic}}{{cbignore|bot=medic}}</ref>

== Overview ==
The exoplanet HD 89345 b, which has a [[mass]] of 0.1 {{Jupiter mass|link=y}} and a [[radius]] of 0.61 {{Jupiter radius}}, was assigned to the class of ocean [[planet]]s. The parent [[star]] of the planet, which is about 5.3 billion [[year]]s old, belongs to the [[Stellar classification|spectral class]] of [[Class G stars|G5V-G6V]]. It is 66 percent larger and 22 percent more massive than the [[Sun]], and is located 413 [[light-year]]s away. The effective temperature of the star is 5609 [[Kelvin|K]]. Considering that HD 89345 b makes one revolution around the [[star]] in 11.8 days at a [[distance]] of 0.11 [[astronomical unit|AU]], this planet was described by researchers as a warm subterranean with an [[equilibrium temperature]] of 1059 [[Kelvin|K]].<ref>{{Cite news|url=https://upcosmos.com/exoplanets-sub-jupiter-type/|title=HD 89345b and HD 286123b, two exoplanets of the sub-Jupiter type are discovered in orbits around bright stars - Upcosmos.com|date=2018-03-20|work=Upcosmos.com|access-date=2018-07-03|language=en-US|archive-date=2018-07-03|archive-url=https://web.archive.org/web/20180703220344/https://upcosmos.com/exoplanets-sub-jupiter-type/|url-status=dead}}</ref>

== Discovery ==
HD 89345 b, a Saturn-sized [[exoplanet]] orbiting a slightly evolved [[star]] HD 89345, was discovered in 2018 using the [[Transit-method|transit]] [[Photometry (astronomy)|photometry]] method, the process that detects distant [[planet]]s by measuring the minute dimming of a [[star]] as an orbiting [[planet]] passes between it and the [[Earth]]. It is the only [[planet]] orbiting around HD 89345, a [[Class G stars|G5 class star]], situated in the [[constellation]] of [[Leo (constellation)|Leo]] in 413 [[light-year]]s from the [[Sun]]. This [[star]] is aged 9.4 billion years. HD 89345 b [[orbit]]s its [[star]] in about 12 terrestrial days in an [[Elliptic orbit|elliptical orbit]]. The [[orbit]] is closer to the [[star]] than the inner limit of the habitable zone. It has a low [[density]] and can be composed of gas.

Its parent [[star]], HD 89345, is a bright [[star]] ([[apparent magnitude]] 9.3) observed by the K2 mission with one-minute time sampling. It exhibits solar-like [[oscillation]]s. The data is collected by [[asteroseismology]], which enables to determine the parameters of the star and find its [[mass]] and [[radius]]. Its [[mass]] is 1.12{{±|0.04|0.01}} {{Solar mass|link=y}} and its [[Radius|mean radius]] is 1.657{{±|0.020|0.004}} {{Solar radius|link=y}}. The [[star]] appears to have recently left the main sequence, based on the inferred age, 9.4{{±|0.4|1.3}} [[Gya (unit)|Gyr]], and the non-detection of mixed modes. The [[star]] hosts a "warm Saturn" with an orbital period of approximately 11.8 days and a radius of {{val|6.86|0.14|ul=Earth radius}}. [[Radial velocity method|Radial-velocity]] follow-up observations performed with the FIES, [[High Accuracy Radial Velocity Planet Searcher|HARPS]], and [[HARPS-N]] [[spectrograph]]s show that the [[planet]] has a mass of {{val|35.7|3.3|ul=Earth mass}}. The data also show that the planet's orbit is [[Eccentricity (astronomy)|eccentric]] (<math>e \thickapprox 0.2
</math>).<ref>{{Cite journal|last1=Van Eylen|first1=V.|last2=Dai|first2=F.|last3=Mathur|first3=S.|last4=Gandolfi|first4=D.|last5=Albrecht|first5=S.|last6=Fridlund|first6=M.|last7=García|first7=R. A.|last8=Guenther|first8=E.|last9=Hjorth|first9=M.|date=2018-08-21|title=HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2|arxiv=1805.01860|journal=Monthly Notices of the Royal Astronomical Society|volume=478|issue=4|pages=4866–4880|doi=10.1093/mnras/sty1390|doi-access=free |issn=0035-8711|bibcode=2018MNRAS.478.4866V}}</ref><ref>{{Cite web|url=https://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=HD+89345+b&type=CONFIRMED_PLANET|title=HD 89345 b|website=exoplanetarchive.ipac.caltech.edu|language=en|access-date=2018-07-03}}</ref>

== See also ==

* [[List of potentially habitable exoplanets]]
* [[List of exoplanet firsts]]
* [[List of exoplanetary host stars]]
* [[List of exoplanets discovered using the Kepler spacecraft]]
* [[List of planets observed during Kepler's K2 mission]]
* [[List of nearest terrestrial exoplanet candidates]]

== References ==
{{Reflist}}

{{Exoplanet search projects}}
{{2018 in space}}

[[Category:Transiting exoplanets]]
[[Category:Exoplanets discovered in 2018]]
[[Category:Leo (constellation)]]