{{Short description|Red dwarf star in the constellation Centaurus}} {{Starbox begin | name = HD 131399 Ab }} {{Starbox image | image = [[File:Eso1624d.jpg|250px]] | caption = HD 131399 Ab photographed alongside the HD 131399 star system | credit = ESO/K. Wagner et al. }} {{Starbox observe | epoch = J2000 | constell = [[Centaurus]] | ra = {{RA|14|54|25.3}} | dec = {{dec|-34|08|34}} | appmag_v = <!--Apparent magnitude (Johnson-Cousins V system)--> }} {{Starbox character | type = [[main sequence]] | class = [[K-type main-sequence star|K]]–[[Red dwarf|M]] }} {{Starbox astrometry | radial_v = <!--Radial velocity (in km/s)--> | total_v = <!--Total velocity (radial velocity combined with proper motion in km/s)--> | prop_mo_ra = {{val|-4.7|1.6}} | prop_mo_dec = {{val|-11.2|1.3}} | pm_footnote = <ref name="Nielsen"/> | parallax = ≲1 | p_error = <!--Parallax error (in milliarcsec)--> | parallax_footnote = <ref name=":0"/> | dist_pc = ≳1,000<ref name=":0"/> <!-- | dist_ly = | absmag_v = | absmag_bol = --> }} <!--{{Starbox detail | source = | mass = | mass_mj = | radius = | luminosity = | luminosity_bolometric = | luminosity_visual = | gravity = | temperature = | metal_fe = | rotation = | rotational_velocity = | age_gyr = }}--> {{Starbox catalog | names = WGK 1Aa, WDS J14544-3409Ab, Scorpion-1b }} {{Starbox reference | component = <!--Component name--> | Simbad = NAME+HD+131399Ab | NSTED = <!--Exoplanet Archive name--> | ARICNS = <!--Code--> | EPE = HD 131399 A b | KIC = <!--KIC identifier--> }} {{Starbox end}} '''HD 131399 Ab''' (nicknamed '''Scorpion-1b''')<ref name="Scorpion-1b">{{cite web|title=UC mountaineer, galactic explorer|url=https://magazine.uc.edu/editors_picks/recent_features/scorpion.html|website=[[University of Cincinnati|UC Magazine]]|date=12 April 2017|access-date=4 May 2026|last=Miller|first=Michael}}</ref> is a [[K-type main-sequence star|K-type]] or [[Red dwarf|M-type]] [[main-sequence star]] located in the constellation of [[Centaurus]] which was mistaken for an [[exoplanet]] orbiting the quadruple-star system [[HD 131399]].
==Characteristics== The planet was thought to be about 16 million years old, with a mass of 4 (± 1) {{Jupiter mass}} ([[Jupiter mass]]es), and a temperature of {{cvt|850|K}} (± 50 K), which would make it one of the coldest and least massive directly imaged exoplanets.<ref name="SciNews">{{Cite web|url=https://www.sci.news/astronomy/hd-131399ab-super-jupiter-triple-star-system-04008.html|title=HD 131399Ab: Astronomers Find Super-Jupiter in Triple-Star System|language=en-US|access-date=4 May 2026|website=Sci-News.com|date=7 July 2016|last=de Lazaro|first=Enrico}}</ref> Its atmosphere was shown to contain both water and methane through the use of [[near-infrared spectroscopy]] (1.4–1.6 μm).<ref name="scimag">{{cite journal|title=Direct imaging discovery of a Jovian exoplanet within a triple-star system|journal=Science|date=7 July 2016|doi=10.1126/science.aaf9671|pmid=27386921|volume=353|issue=6300|pages=673–8|bibcode=2016Sci...353..673W|arxiv = 1607.02525 |s2cid=206650422|last=Wagner|first=Kevin}}{{Retracted|doi=10.1126/science.abq1709|pmid=35420970|https://retractionwatch.com/2022/04/14/triple-sunrise-triple-sunset-science-paper-retracted-when-it-turns-out-a-planet-is-a-star/ ''Retraction Watch''}}</ref><ref>{{cite news |date=7 July 2016 |title=Astronomers spot giant planet with 3 suns |url=https://www.cbc.ca/news/science/planet-3-suns-1.3668976 |work=[[CBC News]] |agency=The Associated Press |access-date=10 May 2026}}</ref> Scientists believed it was unlikely that the planet harbored life due to it being gaseous. The planet was said to have "no liquid water, extremely powerful winds, and no surface; just below the uppermost layer of the atmosphere it rains liquid iron droplets."
The central star HD 131399A is orbited by the less massive stars (HD 131399B and HD 131399C) at about 300 [[astronomical unit]]s (AU). HD 131399B and HD 131399C orbit each other at about 10 AU, while HD 131399 Ab was thought to orbit HD 131399A at about 80 AU.<ref name="SciNews"/>
One orbit of HD 131399 Ab was thought to take 550 years.<ref name="scimag"/> During about a quarter of the orbit, 100 to 140 years, all three suns would have been visible during a single day: during this period, any spot on the planet would be in perpetual sunlight—as the single sun sets, the binary pair rises.<ref name="cbsnews">{{cite web |title=This strange new planet has three suns |url=https://www.cbsnews.com/news/planet-with-three-suns-triple-sunrises-sunsets/ |work=[[CBS News]] |date=7 July 2016 |access-date=7 July 2016|agency=AP}}</ref>
==Discovery== HD 131399 Ab was discovered using the [[SPHERE]] imager of the [[Very Large Telescope]] at the [[European Southern Observatory]], located in the [[Atacama Desert]] of [[Chile]], and announced in a July 2016 paper in the journal ''[[Science (journal)|Science]]''.<ref name="scimag"/><ref name="cbsnews"/> This would hae been the first exoplanet to be discovered by SPHERE and one of very few [[list of directly imaged exoplanets|directly imaged exoplanets]]. The image was created from two separate SPHERE observations: one to image the three stars and one to detect the faint planet.<ref name="ESO">{{cite web|url=https://www.eso.org/public/news/eso1624/|title=A Surprising Planet with Three Suns|work=[[ESO]]|access-date=7 July 2016|date=7 July 2016}}</ref> After its discovery, the team unofficially named the system "Scorpion-1" and the planet "Scorpion-1b", after the survey that prompted its discovery, the Scorpion Planet Survey (principal investigator: [[Daniel Apai]]).<ref name="Scorpion-1b"/>
In May 2017, observations collected with the [[Gemini Planet Imager]], and including a reanalysis of the SPHERE data, suggested that this target is in fact a [[Fixed stars|background star]].<ref name="Nielsen">{{cite journal|last1=Nielsen|first1=Eric L.|last2=De Rosa|first2=Robert J.|last3=Rameau|first3=Julien|last4=Wang|first4=Jason J.|last5=Esposito|first5=Thomas M.|last6=Millar-Blanchaer|first6=Maxwell A.|last7=Marois|first7=Christian|last8=Vigan|first8=Arthur|last9=Ammons|first9=S. Mark|display-authors=etal|date=1 May 2017|title=Evidence that the Directly-Imaged Planet HD 131399 Ab is a Background Star|journal=The Astronomical Journal|volume=154|issue=6|pages=218|arxiv=1705.06851|doi=10.3847/1538-3881/aa8a69|doi-access=free |bibcode=2017AJ....154..218N|s2cid=55138870}}</ref> Further observations in 2022 confirmed this.<ref name=":0">{{Cite journal |last1=Wagner |first1=Kevin |last2=Apai |first2=Dániel |last3=Kasper |first3=Markus |last4=McClure |first4=Melissa |last5=Robberto |first5=Massimo |date=2022-02-01 |title=The Scorpion Planet Survey: Wide-orbit Giant Planets Around Young A-type Stars |journal=The Astronomical Journal |volume=163 |issue=2 |pages=80 |doi=10.3847/1538-3881/ac409d |doi-access=free |arxiv=2112.02168 |bibcode=2022AJ....163...80W |issn=0004-6256|author-link2=Daniel Apai}}</ref><ref>{{Cite journal |last1=Wagner |first1=Kevin |last2=Apai |first2=Dániel |last3=Kasper |first3=Markus |last4=Kratter |first4=Kaitlin |author4-link=Kaitlin Kratter|last5=McClure |first5=Melissa |last6=Robberto |first6=Massimo |last7=Beuzit |first7=Jean-Luc |date=2022-04-15 |title=Retraction |url=https://www.science.org/doi/10.1126/science.abq1709 |journal=Science |language=en |volume=376 |issue=6590 |pages=255 |doi=10.1126/science.abq1709 |pmid=35420970 |bibcode=2022Sci...376..255W |issn=0036-8075|url-access=subscription |author-link2=Daniel Apai}}</ref>
==Gallery== <gallery align="center" width="250"> Artist’s impression of planet orbiting in the HD 131399 system.webm|This artist's impression shows the orbit of the planet in the triple-star system. Artist’s impression of planet in the HD 131399 system.jpg|Artist's impression of the system as seen from the supposed planet. HD 131399 A is at the center. The other two stars can be seen in the distance. </gallery>
==See also== *[[HD 188753 Ab]] *[[YSES 2b]], a red dwarf similarly mistaken to be a gaseous exoplanet
==References== {{Reflist}}
{{2016 in space}}{{Centaurus}} [[Category:Centaurus]] [[Category:K-type main-sequence stars]] [[Category:M-type main-sequence stars]] [[Category:Astronomical objects discovered in 2016]] [[Category:Disproven exoplanets]]