View source for HIP 65426 b

{{Short description|Gas giant exoplanet orbiting HIP 65426}}
{{Infobox planet
| extrasolarplanet = yes
| name = HIP 65426 b / Najsakopajk
| image = File:The unusual exoplanet HIP 65426b — SPHERE's first.jpg
| caption = HIP 65426 b is on the lower left of the image, with the circle representing what Neptune's orbit would look like around the star HIP 65426, represented by a small cross.
| discovery_ref = <ref name="Chauvin2017"/>
| discovered = 6 July 2017
| discoverer = [[SPHERE consortium]]<ref>{{Cite web|url=https://sphere.osug.fr/spip.php?rubrique7|title=Odd planetary system around fast-spinning star doesn't quite fit existing models of planet formation|website=www.sphere.osug.fr|access-date=2017-07-06}}</ref>
| discovery_method = [[Methods of detecting exoplanets#Direct imaging|Direct imaging]]
| alt_names = Najsakopajk<ref name="NEW2022"/>
| semimajor = {{val|87|108|31|ul=AU}}<ref name="Carter et al" />
| inclination = {{val|100|15|6|ul=deg}}<ref name="Carter et al" />
| mean_radius = {{val|1.44|0.03|ul=Jupiter radius}}<ref name="Carter et al" />
| mass = {{val|7.1|1.2|ul=Jupiter mass}}<ref name="Carter et al" />
| surface_grav = {{val|3.93|0.07|0.09}} [[common logarithm|dex]]<ref name="Carter et al" />
| single_temperature = {{val|1283|25|31|ul=K|fmt=commas}}<ref name="Carter et al" />
}}

'''HIP 65426 b''', formally named '''Najsakopajk''',<ref name="NEW2022"/> is a [[super-Jupiter]] [[exoplanet]] orbiting the [[star]] HIP 65426. It was discovered on 6 July 2017 by the SPHERE consortium using the [[Spectro-Polarimetric High-Contrast Exoplanet Research]] (SPHERE) instrument belonging to the [[European Southern Observatory]] (ESO),<ref name="Independent"/><ref name="scinews"/> being the first planet discovered by the SPHERE instrument.<ref>{{Cite web|url=https://www.eso.org/public/announcements/ann17041/|title=ESO's SPHERE Unveils its First Exoplanet|last=|website=www.eso.org|language=en-au|access-date=2017-07-07}}</ref> It is 385 [[light-year]]s from Earth in the [[Centaurus]] constellation.<ref name="nasa"/> 

==Nomenclature==
HIP 65426 b is a designation inherited from the host star's name, HIP 65426, following the [[exoplanet naming convention]], where exoplanets receive lowercase letters. The designation HIP 65426 has its origin on the [[Hipparcos catalogue]].<ref>{{Cite web |title=Details on Acronym:   HIP |url=https://cds.unistra.fr/cgi-bin/Dic-Simbad?HIP |access-date=2025-01-08 |website=[[SIMBAD]]}}</ref>

In August 2022, this planet and its host star were included among 20 systems to be named by the third [[NameExoWorlds]] project.<ref>{{cite web |url=https://www.nameexoworlds.iau.org/2022exoworlds |title=List of ExoWorlds 2022 |date=8 August 2022 |website=nameexoworlds.iau.org |publisher=[[International Astronomical Union|IAU]] |access-date=27 August 2022}}</ref> The approved names, proposed by a team from [[Mexico]], were announced in June 2023. HIP 65426 b is named '''Najsakopajk''' and its host star is named '''Matza''', after [[Zoque people|Zoque]] words for "Mother Earth" and "star".<ref name="NEW2022"/>

== Overview ==
The exoplanet HIP 65426 b orbits its host star HIP 65426, an [[A-type main-sequence star]] with [[apparent magnitude]] 7.01, with a mass of {{val|1.96|0.04|ul=solar mass}}, a radius of {{val|1.77|0.05|ul=solar radius}} and an [[effective temperature]] of {{cvt|8840|K|C|lk=in|abbr=on}}.<ref>{{cite EPE|name=HIP 65426 b|id=6586}}</ref> This planetary system is located in the constellation [[Centaurus]]. The planet is around 14 million years old, much younger than the [[Solar System]] which is 4.5&nbsp;billion years old, but is not associated with a debris disk, despite its young age,<ref name="scinews" /><ref name="nasa" /> causing it to not fit [[Planet formation|current models for planetary formation]].<ref>{{Cite web|url=https://phys.org/news/2017-07-discovery-exoplanet-spherevlt.html|title=Odd planetary system around fast-spinning star doesn't quite fit existing models of planet formation|website=phys.org|language=en-us|access-date=2019-08-03}}</ref> It is around 92 [[Astronomical Unit|AU]] from its parent star, with a possible dusty [[atmosphere]].<ref>{{Cite web|url=https://astronomy.com/news/2017/07/fast-spinning-exoplanet-system-deeper|title=New exoplanet challenges formation models|first1=Mara|last1=Johnson-Groh|last2=July 12, 2017|website=Astronomy.com|date=12 July 2017 |access-date=2019-08-03}}</ref> It was discovered as part of the SHINE program, which aimed to find [[planetary system]]s around 600 new stars.<ref name="Chauvin2017"/>

In September 2022, HIP 65426 b became the first exoplanet directly observed by the [[James Webb Space Telescope]].<ref>{{cite web |first=Alise |last=Fisher |title=NASA's Webb Takes Its First-Ever Direct Image of Distant World |url=https://blogs.nasa.gov/webb/2022/09/01/nasas-webb-takes-its-first-ever-direct-image-of-distant-world/?linkId=179637235 |website=NASA Blogs |publisher=[[NASA]] |date=2022-09-01 |access-date=2022-09-01}}</ref>

==Planetary atmosphere==
The spectrum taken in 2020 has indicated that HIP 65426 b is carbon-poor and oxygen-rich compared to Solar System gas giants.<ref name=Petrus2020/>

Spectral analysis of data from the James Webb Space Telescope revealed strong evidence of silicate clouds containing [[enstatite]] with no evidence of a dusty atmosphere.<ref>{{Cite journal |last=Wang 王 |first=Ji 吉 |date=2023-11-01 |title=Spectral Retrieval with JWST Photometric data: a Case Study for HIP 65426 b |journal=The Astronomical Journal |volume=166 |issue=5 |pages=203 |doi=10.3847/1538-3881/acfca0 |issn=0004-6256|doi-access=free |arxiv=2310.00089 |bibcode=2023AJ....166..203W }}</ref>

== James Webb Space Telescope observations ==
In August 2022, a [[Preprint|pre-print]] of the [[James Webb Space Telescope]] (JWST) observations was published. The JWST direct imaging observations between 2-16 μm of HIP 65426 b tightly constrained its [[Luminosity|bolometric luminosity]] to <math>\log(L_{bol}/L_{sun})=-4.23\plusmn0.08</math>, which provides a robust mass constraint of {{val|7.1|1.2|ul=Jupiter mass}}. Evolutionary models suggest a radius 45% larger than that of Jupiter and an [[effective temperature]] of {{convert|1283|K|C|lk=in|abbr=on}}. Atmospheric models suggest lower radii down to {{Jupiter radius|0.9}} and higher temperatures, but these results are unreliable. The team also constrained the [[Semi-major and semi-minor axes|semi-major axis]] and the [[Orbital inclination|inclination]] of the planet, but the new JWST astrometry of the planet did not significantly improve the orbit of the planet, especially the [[Orbital eccentricity|eccentricity]] remains unconstrained.<ref name="Carter et al"/>

HIP 65426 b is the first exoplanet to be imaged by JWST and the first to be detected in wavelengths beyond 5&nbsp;μm. The observations demonstrate that the James Webb Space Telescope will exceed its nominal predicted performance by a factor of 10 and that it will be able to image 0.3 {{Jupiter mass|link=true}} planets at 100 [[Astronomical unit|au]] for [[Main sequence|main-sequence stars]], [[Neptune]] and [[Uranus]]-mass objects at 100-200 au for [[Red dwarf|M-dwarfs]] and [[Saturn]]-mass objects at 10 au for M-dwarfs. For [[Alpha Centauri|α Cen A]] JWST might be able to push the limit to a 5 {{Earth radius|link=true}} planet at 0.5 to 2.5 au.<ref name="Carter et al" />
{{clear}}
{{multiple images |header= |direction= horizontal | caption_align=center |align=center |wdith= |image1=HIP 65426-starmap.png |caption1=HIP 65426 star map |width1=400 |image2=NASA’s Webb Takes Its First-Ever Direct Image of Distant World.png |caption2=HIP 65426 b viewed by the [[James Webb Space Telescope]] (August 2022) |width2=528 |footer= }}

== See also ==
* [[Lists of exoplanets]]
* [[List of exoplanets discovered in 2017]]

== References ==
{{reflist|refs=

<ref name="Chauvin2017">{{Cite journal|title=Discovery of a warm, dusty giant planet around HIP 65426|journal = Astronomy and Astrophysics|volume = 605|pages = L9|bibcode = 2017A&A...605L...9C|last1 = Chauvin|first1 = G.|last2 = Desidera|first2 = S.|last3 = Lagrange|first3 = A. -M.|last4 = Vigan|first4 = A.|last5 = Gratton|first5 = R.|last6 = Langlois|first6 = M.|last7 = Bonnefoy|first7 = M.|last8 = Beuzit|first8 = J. -L.|last9 = Feldt|first9 = M.|last10 = Mouillet|first10 = D.|last11 = Meyer|first11 = M.|last12 = Cheetham|first12 = A.|last13 = Biller|first13 = B.|last14 = Boccaletti|first14 = A.|last15 = d'Orazi|first15 = V.|last16 = Galicher|first16 = R.|last17 = Hagelberg|first17 = J.|last18 = Maire|first18 = A. -L.|last19 = Mesa|first19 = D.|last20 = Olofsson|first20 = J.|last21 = Samland|first21 = M.|last22 = Schmidt|first22 = T. O. B.|last23 = Sissa|first23 = E.|last24 = Bonavita|first24 = M.|last25 = Charnay|first25 = B.|last26 = Cudel|first26 = M.|last27 = Daemgen|first27 = S.|last28 = Delorme|first28 = P.|last29 = Janin-Potiron|first29 = P.|last30 = Janson|first30 = M.|display-authors = 29|year = 2017|arxiv = 1707.01413|doi = 10.1051/0004-6361/201731152|s2cid = 102344893}}</ref>

<ref name="Independent">{{Cite web|url=http://www.independent.co.uk/news/science/planets-hip-65426b-scientists-stars-solar-systems-sun-a7830556.html|title=Scientists have found a planet that means everything they thought about planets isn't true|date=2017-07-08|website=The Independent|language=en|access-date=2019-08-02}}</ref>

<ref name="scinews">{{Cite web|url=http://www.sci-news.com/astronomy/super-jupiter-hip-65426-05023.html|title=Astronomers Directly Image Super-Jupiter around HIP 65426 {{!}} Astronomy {{!}} Sci-News.com|website=Breaking Science News {{!}} Sci-News.com|language=en-US|access-date=2019-08-02}}</ref>

<ref name="nasa">{{Cite web|url=https://exoplanets.nasa.gov/news/1477/holiday-special-eight-nights-of-exoplanet-light/|title=Holiday Special: Eight nights of Exoplanet Light|publisher=NASA|website=Exoplanet Exploration: Planets Beyond our Solar System|access-date=2019-08-03}}</ref>

<ref name=Petrus2020>{{citation|arxiv=2012.02798|title=Medium-resolution spectrum of the exoplanet HIP 65426 B|year=2021|doi=10.1051/0004-6361/202038914|last1=Petrus|first1=S.|last2=Bonnefoy|first2=M.|last3=Chauvin|first3=G.|last4=Charnay|first4=B.|last5=Marleau|first5=G.-D.|last6=Gratton|first6=R.|last7=Lagrange|first7=A.-M.|last8=Rameau|first8=J.|last9=Mordasini|first9=C.|last10=Nowak|first10=M.|last11=Delorme|first11=P.|last12=Boccaletti|first12=A.|last13=Carlotti|first13=A.|last14=Houllé|first14=M.|last15=Vigan|first15=A.|last16=Allard|first16=F.|last17=Desidera|first17=S.|last18=d'Orazi|first18=V.|last19=Hoeijmakers|first19=H. J.|last20=Wyttenbach|first20=A.|last21=Lavie|first21=B.|journal=Astronomy & Astrophysics|volume=648|pages=A59|bibcode=2021A&A...648A..59P|s2cid=227347064}}</ref>

<ref name="Carter et al">{{cite journal |last1=Carter |first1=Aarynn L. |last2=Hinkley |first2=Sasha |last3=Kammerer |first3=Jens |last4=Skemer |first4=Andrew |last5=Biller |first5=Beth A. |last6=Leisenring |first6=Jarron M. |last7=Millar-Blanchaer |first7=Maxwell A. |last8=Petrus |first8=Simon |last9=Stone |first9=Jordan M. |last10=Ward-Duong |first10=Kimberly |last11=Wang |first11=Jason J. |last12=Girard |first12=Julien H. |last13=Hines |first13=Dean C. |last14=Perrin |first14=Marshall D. |last15=Pueyo |first15=Laurent |title=The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems I: High Contrast Imaging of the Exoplanet HIP 65426 b from 2-16 μm |arxiv=2208.14990 | doi=10.3847/2041-8213/acd93e | journal=The Astrophysical Journal Letters | date=2023-07-06 | volume=951 | issue=1 | pages=L20 |doi-access=free | bibcode=2023ApJ...951L..20C}}</ref>

<ref name="NEW2022">{{cite web |url=https://www.nameexoworlds.iau.org/2022approved-names |title=2022 Approved Names |website=nameexoworlds.iau.org |publisher=[[International Astronomical Union|IAU]] |access-date=7 June 2023}}</ref>

}}

{{Centaurus}}
{{DEFAULTSORT:HIP 65426 b}}
[[Category:Exoplanets detected by direct imaging]]
[[Category:Exoplanets discovered in 2017]]
[[Category:Giant planets]]
[[Category:Centaurus]]
[[Category:Exoplanets with proper names]]