View source for HD 106906 b

{{Short description|Candidate exoplanet in the constellation Crux}}
{{Use mdy dates|date=March 2019}}

{{Infobox planet
| extrasolarplanet = yes
| name = [[Henry Draper Catalogue|HD]] 106906 b
| image = HD 106906 b image.jpg
| image_scale = 
| caption = The star {{nowrap|HD 106906}} and the planet {{nowrap|HD 106906 b}}, with [[Neptune]]'s orbit for comparison
| apsis = astron
| discoverer = Vanessa Bailey, ''et al.''<ref name="LATimes">{{cite web |last=Morin |first=Monte |url=http://www.latimes.com/science/sciencenow/la-sci-sn-gigantic-alien-planet-discovered-where-it-shouldnt-be-20131205,0,5223068.story |title=Giant alien world discovered where it should not exist |date=December 5, 2013 |work=[[Los Angeles Times]] |access-date=December 8, 2013}}</ref>
| discovery_site = [[Magellan Telescopes]] at the [[Las Campanas Observatory]] in [[Chile]]<ref name = "LATimes"/>
| discovered = December 4, 2013 (published)<ref name="Bailey2014"/>
| discovery_method = [[Direct imaging]]<ref name="ExoPlanet">{{cite encyclopedia |url=http://exoplanet.eu/catalog/hd_106906_b/ |title=Planet HD 106906 b |access-date=December 8, 2013 |archive-date=October 31, 2019 |archive-url=https://web.archive.org/web/20191031203552/http://exoplanet.eu/catalog/hd_106906_b/ |encyclopedia=[[Extrasolar Planets Encyclopaedia]] |url-status=dead }}</ref>
| mean_orbit_radius = {{convert|738|AU|e9km|0|abbr=unit|lk=on}}<ref name="DeRosa2019" />
| eccentricity = 
| period = 8,910.501 years<ref name="Rodet2017" />
| inclination = 
| semi-amplitude = 
| star = [[HD 106906]]
| mean_radius = {{val|1.54|0.04|0.05|ul=Jupiter radius}}<ref name=Bryan>{{Cite journal |last1=Bryan |first1=Marta L. |last2=Ginzburg |first2=Sivan |last3=Chiang |first3=Eugene |last4=Morley |first4=Caroline |last5=Bowler |first5=Brendan P. |last6=Xuan |first6=Jerry W. |last7=Knutson |first7=Heather A. |date=2020-12-01 |title=As the Worlds Turn: Constraining Spin Evolution in the Planetary-mass Regime |bibcode=2020ApJ...905...37B |journal=The Astrophysical Journal |volume=905 |issue=1 |pages=37 |doi=10.3847/1538-4357/abc0ef |doi-access=free |arxiv=2010.07315 |issn=0004-637X}}</ref>
| surface_area = 
| volume = 
| density = 
| mass = {{val|11|2|u={{Jupiter mass|link=y|jup=y}}}}<ref name="Bailey2014">{{cite journal |title=HD 106906 b: A planetary-mass companion outside a massive debris disk |journal=[[The Astrophysical Journal Letters]] |first1=Vanessa |last1=Bailey |first2=Tiffany |last2=Meshkat |first3=Megan |last3=Reiter |first4=Katie |last4=Morzinski |first5=Jared |last5=Males |first6=Kate Y. L. |last6=Su |first7=Philip M. |last7=Hinz |first8=Matthew |last8=Kenworthy |first9=Daniel |last9=Stark |first10=Eric |last10=Mamajek |first11=Runa |last11=Briguglio |first12=Laird M. |last12=Close |first13=Katherine B. |last13=Follette |first14=Alfio |last14=Puglisi |first15=Timothy |last15=Rodigas |first16=Alycia J. |last16=Weinberger |first17=Marco |last17=Xompero |display-authors=1 |volume=780 |issue=1 |page=L4 |date=January 2014 |arxiv=1312.1265 |doi=10.1088/2041-8205/780/1/L4 |bibcode=2014ApJ...780L...4B|s2cid=119113709 }}</ref>
| surface_grav = 
| albedo = 
| single_temperature = ≈{{convert|1800|K|C F|sigfig=2}}<ref name="Bailey2014" />
}}
'''HD 106906 b''' is a directly imaged planetary-mass companion<ref name="Bailey2014" /> and [[exoplanet]] orbiting the star {{nowrap|[[HD 106906]]}}, in the constellation [[Crux]] at about {{convert|103|±|4|pc|ly|order=flip|lk=on}} from [[Earth]].<ref name="Rodet2017">{{cite journal |title=Origin of the wide-orbit circumbinary giant planet HD 106906. A dynamical scenario and its impact on the disk |journal=[[Astronomy & Astrophysics]] |first1=L. |last1=Rodet |first2=H. |last2=Beust |first3=M. |last3=Bonnefoy |first4=A.-M. |last4=Lagrange |first5=P. A. B. |last5=Galli |first6=C. |last6=Ducourant |first7=R. |last7=Teixeira |display-authors=1 |volume=602 |at=A12 |date=June 2017 |doi=10.1051/0004-6361/201630269 |bibcode=2017A&A...602A..12R |arxiv=1703.01857|s2cid=119424481 }}</ref> It is estimated to be about eleven times the [[Jupiter mass|mass]] of [[Jupiter]] and is located about 738&nbsp;[[astronomical unit|AU]] away from its host star.<ref name="DeRosa2019">{{cite journal |title=A Near-coplanar Stellar Flyby of the Planet Host Star HD 106906 |journal=[[The Astronomical Journal]] |first1=Robert J. |last1=De Rosa |first2=Paul |last2=Kalas |volume=157 |issue=3 |at=125 |date=February 2019 |doi=10.3847/1538-3881/ab0109 |bibcode=2019AJ....157..125D |arxiv=1902.10220|s2cid=119191779 |doi-access=free }}</ref> {{nowrap|HD 106906 b}} is an oddity; while its mass estimate is nominally consistent with identifying it as an exoplanet, it appears at a much wider separation from its parent star than thought possible for [[in-situ]] formation from a [[protoplanetary disk]].<ref name="IBT">{{cite news |url=http://www.ibtimes.co.uk/articles/528146/20131206/mystery-planet-exist-location-young-star-formation.htm |title=Mystery Planet 'That Shouldn't Exist' Baffles Astronomers |work=[[International Business Times]] |last=Osborne |first=Hannah |date=December 6, 2013 |access-date=December 8, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131213065309/http://www.ibtimes.co.uk/articles/528146/20131206/mystery-planet-exist-location-young-star-formation.htm |archive-date=December 13, 2013}}</ref>

==Description==
{{nowrap|HD 106906 b}} is the only known companion orbiting {{nowrap|[[HD 106906]]}}, a [[spectroscopic binary]] star composed of two [[F-type main-sequence star|F5V]] [[main-sequence star]]s with a combined mass of {{Solar mass|2.71|link=y}}.<ref name="Rodet2017" /> Based on the star's luminosity and temperature, the system is estimated to be about {{val|13|2|u=million years old}}. The system is a likely member of the [[Scorpius–Centaurus association]]. The star is surrounded by a [[debris disk]] oriented 21 degrees away from {{nowrap|HD 106906 b}};<ref name="Kalas2015">{{cite journal |title=Direct Imaging of an Asymmetric Debris Disk in the HD 106906 Planetary System |journal=[[The Astrophysical Journal]] |first1=Paul |last1=Kalas |display-authors=et al |volume=814 |issue=1 |page=32 |date=November 2015 |arxiv=1510.02747 |doi=10.1088/0004-637X/814/1/32 |bibcode=2015ApJ...814...32K|s2cid=59575201 }}</ref><ref name="Lagrange2015">{{cite journal |title=A narrow, edge-on disk resolved around HD 106906 with SPHERE |journal=[[Astronomy & Astrophysics]] |first1=A.-M. |last1=Lagrange |display-authors=et al |volume=586 |page=L8 |date=February 2016 |arxiv=1510.02511 |doi=10.1051/0004-6361/201527264 |bibcode=2016A&A...586L...8L|s2cid=4812512 }}</ref> this disk is about {{convert|65|AU|e9km e9mi|0|abbr=unit|lk=in}} from the binary on its interior and ranges asymmetrically from approximately {{convert|120|to|550|AU|e9km e9mi|0|abbr=unit|lk=in}} from the binary at its outer edge.<ref name="Rodet2017" /> Based on its [[near-infrared spectroscopy|near-infrared spectral-energy distribution]], its age, and relevant evolutionary models, {{nowrap|HD 106906 b}} is estimated to be {{val|11|2|u={{Jupiter mass|link=y|jup=y}}}}, with a surface temperature of {{convert|1800|K|C F|sigfig=2}}. A spectrum with Magellan does show a spectral type of [[L dwarf|L2.5]] ±1 and intermediate [[Surface gravity|gravity]].<ref name="Bailey2014"/> A high-signal-to-noise spectrum was taken with [[Very Large Telescope|VLT]]/SINFONI, which resulted in a spectral type of L1.5 ± 1.0 and a temperature of 1820 ± 240 K. Depending on its formation it has a mass of {{Val|11.9|1.7|0.8}} {{Jupiter mass}} (hot start) or {{Val|14.0|0.2|0.5}} {{Jupiter mass}} (cold start).<ref name="Daemgen2017">{{Cite journal |last1=Daemgen |first1=Sebastian |last2=Todorov |first2=Kamen |last3=Quanz |first3=Sascha P. |last4=Meyer |first4=Michael R. |last5=Mordasini |first5=Christoph |last6=Marleau |first6=Gabriel-Dominique |last7=Fortney |first7=Jonathan J. |date=2017-12-01 |title=High signal-to-noise spectral characterization of the planetary-mass object HD 106906 b |url=https://ui.adsabs.harvard.edu/abs/2017A&A...608A..71D/abstract |journal=Astronomy and Astrophysics |volume=608 |pages=A71 |arxiv=1708.05747 |bibcode=2017A&A...608A..71D |doi=10.1051/0004-6361/201731527 |issn=0004-6361}}</ref> The high surface temperature, a relic of its recent formation, gives it a luminosity of about 0.02% of the Sun's.<ref name="Bailey2014"/> While its mass and temperature are similar to other planetary-mass companions/exoplanets like {{nowrap|[[beta Pictoris]] b}} or {{nowrap|[[1RXS J160929.1−210524]] b}}, its [[projected separation]] from the star is much larger, about {{convert|738|AU|e9km e9mi|0|abbr=unit|lk=in}},<ref name="Bailey2014" />{{efn|This distance is about 24.5 times the separation of [[Neptune]] from the Sun, or about 3/4 that of [[90377 Sedna|Sedna]] at [[aphelion]].}} giving it one of the widest orbits of any currently known planetary-mass companions.<ref name="Bailey2014"/>

The measurements obtained thus far are not adequate to evaluate its orbital properties. If its [[Orbital eccentricity|eccentricity]] is large enough, it might approach the outer edge of the primary's debris disk closely enough to interact with it at [[periastron]]. In such a case, the outer extent of the debris disk would be truncated at the inner edge of {{nowrap|HD 106906 b's}} [[Hill sphere]] at periastron.<ref name="Bailey2014"/>

The discovery team evaluated the possibility that {{nowrap|HD 106906 b}} is not gravitationally bound to {{nowrap|HD 106906}}, but is seen close to it along our line of sight and moving in the same direction by chance. The odds of such a coincidence were found to be less than 0.01%.<ref name="Bailey2014"/>

==Discovery==
Observation of star {{nowrap|HD 106906}} began in 2005, utilizing the [[Magellan Telescopes]] at the [[Las Campanas Observatory]] in the [[Atacama Desert]] of [[Chile]], some eight years before the companion was discovered. The initial interest in {{nowrap|HD 106906 A}} was directed largely to the debris disk surrounding the star, a pre-main-sequence member of Lower Centaurus–Crux. On December 4, 2013, [[University of Arizona]] graduate student Vanessa Bailey, leader of an international team of astronomers, detailed the discovery of {{nowrap|HD 106906 b}} with a paper first published as a [[preprint]] on the ''[[arXiv]]'' and later as a refereed article in ''[[The Astrophysical Journal Letters]]''.<ref name="Bailey2014"/>

==Possible formation mechanism==
The discovery team and astronomers worldwide were puzzled by {{nowrap|HD 106906 b's}} extreme separation from its host star, because it is not considered possible that a star's [[protoplanetary disk]] could be extensive enough to permit formation of gas giants at such a distance. To account for the separation, it is theorized that the companion formed independently from its star as part of a [[binary system]]. This proposal is somewhat problematic in that the mass ratio of ~140:1 is not in the range expected from this process; [[binary star]]s typically do not exceed a ratio of 10:1.<ref name="IBT"/><ref name="space20131206">{{cite news |url=http://www.space.com/23858-most-distant-alien-planet-discovery-hd106906b.html |title=Giant Alien Planet Discovered in Most Distant Orbit Ever Seen |work=[[Space.com]] |last=Chow |first=Denise |date=December 6, 2013 |access-date=December 8, 2013}}</ref> This is still considered preferable, however, to the alternate theory that the companion formed closer to its primary and then was [[Planetary migration#Gravitational scattering|scattered]] to its present distance by gravitational interaction with another orbital object. This second companion would need to have a mass greater than that of {{nowrap|HD 106906 b}}, and the discovery team found no such object beyond 35&nbsp;AU from the primary. Additionally, the scattering process would have likely disrupted the protoplanetary disk.<ref name="Bailey2014"/>

Subsequently, astronomer [[Paul Kalas]] and colleagues discovered that [[Hubble Space Telescope]] images show a highly asymmetric shape to the debris disk beyond a radius of 200&nbsp;AU, supporting the hypothesis of a dynamical upheaval that involved the planet and another perturber, such as a second planet in the system or a close encounter with a passing star.<ref name="Kalas2015"/>  One theory modeled the planet as originating in a disk close to the central binary, migrating inward to an unstable resonance with the binary, and then evolving rapidly to a highly eccentric orbit.<ref name="Rodet2017" /> The planet would be ejected unless its [[periastron]] distance was increased away from the binary, such as by a gravitational encounter with a passing star during [[apastron]]. An analysis of the motions of 461 nearby stars using ''[[Gaia (spacecraft)|Gaia]]'' observations revealed two (HIP&nbsp;59716 and HIP&nbsp;59721, a possible loosely bound binary system) that passed within {{convert|1|pc|ly|abbr=on}} of {{nowrap|HD 106906}} between 2 and 3 million years ago.<ref name="DeRosa2019" />

Using archival spectral data a team found a C/O={{Val|0.53|0.15|0.25}} for {{nowrap|HD 106906 b}}, consistent with the stellar association its host star formed in. This is consistent with stellar-like formation for the companion. This makes it unlikely that it formed like a planet in a disk around the binary.<ref name="Adams2023">{{Cite journal |last1=Adams |first1=Arthur D. |last2=Meyer |first2=Michael R. |last3=Howe |first3=Alex R. |last4=Burningham |first4=Ben |last5=Daemgen |first5=Sebastian |last6=Fortney |first6=Jonathan |last7=Line |first7=Mike |last8=Marley |first8=Mark |last9=Quanz |first9=Sascha P. |last10=Todorov |first10=Kamen |date=2023-11-01 |title=Atmospheric Retrieval of L Dwarfs: Benchmarking Results and Characterizing the Young Planetary Mass Companion HD 106906 b in the Near-infrared |journal=The Astronomical Journal |volume=166 |issue=5 |pages=192 |arxiv=2309.10188 |bibcode=2023AJ....166..192A |doi=10.3847/1538-3881/acfb87 |doi-access=free |issn=0004-6256}}</ref>

==Public reaction==
In 2009, IAU stated that it had no plans to assign names to extrasolar planets, considering it impractical.<ref>{{cite web |url=http://www.iau.org/public_press/themes/extrasolar_planets/ |title=Planets around other stars |publisher=[[International Astronomical Union]] |access-date=December 6, 2009 |archive-url=https://web.archive.org/web/20100101175440/http://www.iau.org/public_press/themes/extrasolar_planets/ |archive-date=January 1, 2010}}</ref> However, in August 2013 the IAU changed its stance, inviting members of the public to suggest names for exoplanets.<ref>{{cite web |url=http://www.iau.org/enwiki/static/public/naming/planets_and_satellites.pdf |title=Public Naming of Planets and Planetary Satellites: Reaching Out for Worldwide Recognition with the Help of the IAU |publisher=[[International Astronomical Union]] |date=August 13, 2013 |access-date=August 19, 2013}}</ref>

A petition had been launched asking the [[International Astronomical Union]] (IAU) to name the companion Gallifrey, after [[Gallifrey|the homeworld]] of [[The Doctor (Doctor Who)|The Doctor]] on the British science fiction series ''[[Doctor Who]]''. The petition gathered over 139,000 signatures. In January 2014, however, it was agreed by the IAU not to accept the petition's goal to name it Gallifrey, as the petition did not follow the public policy of the IAU that a discussion between the public and IAU should be started before naming any spatial entity, and that this policy was not respected.<ref>{{cite web |url=http://www.themightychallenge.com/gallifreypetition.html |title=Gallifrey Petition |work=The Mighty Challenge |access-date=February 20, 2014}}</ref><ref name="smh20131211">{{cite news |url=http://www.smh.com.au/entertainment/tv-and-radio/doctor-who-fan-in-online-petition-to-name-newly-found-planet-20131210-2z421.html |title=Doctor Who fan in online petition to name newly found planet |work=[[The Sydney Morning Herald]] |first=Karl |last=Quinn |date=December 11, 2013 |access-date=December 10, 2013}}</ref>

Recent observations made by the [[Hubble Space Telescope]] strengthened the case for the planet having an unusual orbit that perturbed it from its host star's debris disk.  NASA and several news outlets compared it to the hypothetical [[Planet Nine]].<ref>{{Cite web|url=http://www.nasa.gov/feature/goddard/2020/hubble-pins-down-weird-exoplanet-with-far-flung-orbit|title=Hubble Pins Down Weird Exoplanet with Far-Flung Orbit|first=Lynn|last=Jenner|date=December 9, 2020|website=NASA}}</ref><ref>{{Cite web|url=https://scitechdaily.com/hubble-discovers-a-strange-exoplanet-that-resembles-the-long-sought-planet-nine/|title=Hubble Discovers a Strange Exoplanet That Resembles the Long-Sought "Planet Nine"|date=December 11, 2020}}</ref>

==See also==
* [[DT Virginis]], a planetary mass object which orbits a binary star, it has the farthest known orbit of a known  circumbinary object 
* [[GU Piscium b]], an exoplanet orbiting [[GU Piscium]] at a distance of 2000 AU and period of 80,000 years in the [[AB Doradus moving group]]
* [[Gliese 900 b]], a planetary mass object with the widest discovered orbit
* [[Planet Nine]], a hypothetical ninth planet in the outer region of the [[Solar System]] with similar wide semi-major axis of 460{{±|160|100}} AU

==Notes==
{{notelist}}

==References==
{{reflist}}

{{Exoplanet}}
{{2013 in space}}
{{Crux}}

{{DEFAULTSORT:HD 106906 b}}
[[Category:Crux]]
[[Category:Exoplanets detected by direct imaging]]
[[Category:Exoplanets discovered in 2013]]
[[Category:Lower Centaurus Crux]]
[[Category:Giant planets]]
[[Category:Circumbinary planets]]