{{Short description|Jovian planet orbiting HR 8799}} {{Infobox planet | name = HR 8799 b | image = Exoplanet Comparison HR 8799 b.png | caption = Size comparison of HR 8799 b (gray) with Jupiter. <!-- DISCOVERY --> | discoverer = Marois ''et al.'' | discovery_site = Keck and Gemini<br/>observatories in Hawaii | discovered = November 13, 2008 | discovery_method = Direct imaging <!-- ORBITAL --> | apsis = astron | semimajor = {{Val|71.3|0.2}}<ref name=Zurlo2022/>{{rp|6}} AU | period = 419<ref name=Gozdzwsk2020/>{{rp|3}} years | inclination = {{Val|26.5|0.5}}<ref name=Zurlo2022/>{{rp|6}} | eccentricity = {{Val|0.017|0.002}}<ref name=Zurlo2022/>{{rp|6}} | star = HR 8799 <!-- PHYS CHARS --> | mean_radius = {{val|1.10|0.03}}<ref name="Nasedkin2024"/>{{rp|20}} {{Jupiter radius|link=y}} | mass = {{val|6.0|0.4|0.3}}<ref name="Nasedkin2024"/>{{rp|20}} {{Jupiter mass|link=y}} | density = {{val|5.041|u=g/cm3}}<ref>{{cite web |url=https://www.stellarcatalog.com/exoplanet.php?planetID=100840 |title=Exoplanet HR 8799 b |access-date=29 July 2024}}</ref> | surface_grav = 10<sup>{{val|4.10|0.03|0.04}}</sup><ref name="Nasedkin2024"/>{{rp|20}} cgs | single_temperature = {{val|942|12|16}}<ref name="Nasedkin2024"/>{{rp|20}} K <!-- ATMOSPHERE --> | atmosphere_composition = hydrogen, water vapor, ammonia and/or acetylene, carbon dioxide, carbon monoxide, possibly with methane<ref name="clouds" /><ref name="Barman2015" /><ref name="Roche2018" /><ref name="Gilliland" /> <!-- NOTES --> | note = below }} '''HR 8799 b''' is an extrasolar planet located approximately 129 light-years away in the constellation of Pegasus, orbiting the 6th magnitude Lambda Boötis star HR 8799. It has a mass of six Jupiter masses and a radius 10% larger than Jupiter's.<ref name="Nasedkin2024">{{Cite journal |last1=Nasedkin |first1=E. |last2=Mollière |first2=P. |last3=Lacour |first3=S. |last4=Nowak |first4=M. |last5=Kreidberg |first5=L. |last6=Stolker |first6=T. |last7=Wang |first7=J. J. |last8=Balmer |first8=W. O. |last9=Kammerer |first9=J. |last10=Shangguan |first10=J. |last11=Abuter |first11=R. |last12=Amorim |first12=A. |last13=Asensio-Torres |first13=R. |last14=Benisty |first14=M. |last15=Berger |first15=J.-P. |date=July 2024 |title=Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY |journal=Astronomy & Astrophysics |volume=687 |pages=A298 |arxiv=2404.03776 |bibcode=2024A&A...687A.298N |doi=10.1051/0004-6361/202449328 |issn=0004-6361}}</ref> It orbits at 71.3 AU from HR 8799 with a low ecccentricity<ref name=Zurlo2022>{{Cite journal |last=Zurlo |first=A. |last2=Goździewski |first2=K. |last3=Lazzoni |first3=C. |last4=Mesa |first4=D. |last5=Nogueira |first5=P. |last6=Desidera |first6=S. |last7=Gratton |first7=R. |last8=Marzari |first8=F. |last9=Langlois |first9=M. |last10=Pinna |first10=E. |last11=Chauvin |first11=G. |last12=Delorme |first12=P. |last13=Girard |first13=J. H. |last14=Hagelberg |first14=J. |last15=Henning |first15=Th |date=2022-10-19 |title=Orbital and dynamical analysis of the system around HR 8799. New astrometric epochs from VLT/SPHERE and LBT/LUCI |journal=Astronomy and Astrophysics |language=en |volume=666 |pages=A133 |doi=10.1051/0004-6361/202243862 |bibcode=2022A&A...666A.133Z |issn=0004-6361|arxiv=2207.10684 }}</ref>{{rp|6}} and a period of around 419 years, being the outermost known planet in the HR 8799 system.<ref name=Gozdzwsk2020>{{cite journal |last1=Gozdziewski |first1=Krzysztof |last2=Migaszewski |first2=Cezary |year=2020 |title=An exact, generalised Laplace resonance in the HR 8799 planetary system |journal=The Astrophysical Journal |volume=902 |issue=2 |page=L40 |doi=10.3847/2041-8213/abb881 |s2cid=221702978 |arxiv=2009.07006 |bibcode=2020ApJ...902L..40G |doi-access=free }}</ref>
== Discovery == Along with two other planets orbiting HR 8799, the planet was discovered on 13 November 2008 by Marois ''et al.'', using the Keck and Gemini observatories in Hawaii. These planets were discovered using the direct imaging technique.<ref name="Marois2008">{{cite journal |last1=Marois |first1=Christian |date=November 2008 |title=Direct Imaging of Multiple Planets Orbiting the Star HR 8799 |journal=Science |volume=322 |issue=5906 |pages=1348–1352 |doi=10.1126/science.1166585 |arxiv=0811.2606 |pmid=19008415 |bibcode = 2008Sci...322.1348M |last2=Macintosh|first2=Bruce|last3=Barman |first3=Travis |last4=Zuckerman |first4=B. |last5=Song |first5=Inseok |last6=Patience |first6=Jennifer |last7=Lafrenière |first7=David |last8=Doyon |first8=René |s2cid=206516630 }}</ref><ref>{{cite press release|url=http://www.keckobservatory.org/article.php?id=231|title=Astronomers capture first images of newly-discovered solar system|publisher=W. M. Keck Observatory|date=2008-11-13|accessdate=2008-12-02|url-status=dead|archive-url=https://web.archive.org/web/20131126160805/http://www.keckobservatory.org/article.php?id=231|archive-date=2013-11-26}}</ref><ref>{{cite press release|url=http://www.gemini.edu/node/11151|title=Gemini Releases Historic Discovery Image of Planetary First Family|publisher=Gemini Observatory|date=2008-11-13|accessdate=2008-12-02}}</ref><ref>{{cite news|title=Scientists Publish First Direct Images of Extrasolar Planets|first=Joel|last=Achenbach|newspaper=The Washington Post|date=2008-11-13|accessdate=2008-12-02|url=https://www.washingtonpost.com/wp-dyn/content/article/2008/11/13/AR2008111302267.html}}</ref><ref>{{cite journal |title=Stability of the directly imaged multiplanet system HR 8799: resonance and masses |year=2010|pages=1408–1421 |issue=2 |volume=710 |author2=Murray-Clay |doi=10.1088/0004-637X/710/2/1408 |journal=Astrophys. J. |arxiv=0812.0011|bibcode = 2010ApJ...710.1408F |author=Fabrycky |s2cid=11760422|display-authors=1 }}</ref>
In 2009 it was discovered that the Hubble Space Telescope had in fact directly imaged HR 8799 b eleven years earlier, in 1998, suggesting that more exoplanets might be revealed through analysis of HST photographic archives.<ref>{{cite journal |title=HST/NICMOS detection of HR 8799 b in 1998 |date=18 February 2009|doi=10.1088/0004-637X/694/2/L148 |last2=Marois |first2=Christian |last3=Doyon |first3=René |last4=Barman |first4=Travis |journal= The Astrophysical Journal|volume=694 |issue=2 |pages=L148–L152 |arxiv=0902.3247|bibcode = 2009ApJ...694L.148L |author= Lafrenière |s2cid=7332750|display-authors= 1 }}</ref> Additional precovery images were also obtained by reanalyzing data taken in 2002 at the Subaru Telescope and in 2005 and 2007 at the W. M. Keck Observatory.<ref name="Fukagawa2009">{{cite journal |last1=Fukagawa |first1=Misato |date=July 2012 |title=H-Band Image of a Planetary Companion Around HR 8799 in 2002 |journal= The Astrophysical Journal|volume=696|issue=1 |pages=L1–L5 |arxiv=1206.0483 |bibcode = 2009ApJ...696L...1F|doi = 10.1088/0004-637X/696/1/L1 |last2=Tamura |first2=Motohide |last3=Oasa |first3=Yumiko |last4=Hayashi |first4=Saeko S.|author4-link=Saeko Hayashi |last5=Fujita |first5=Yutaka |last6=Shibai |first6=Hiroshi |last7=Hayashi |first7=Masahiko |s2cid=18266866 }}</ref><ref name="Metchev2009">{{cite journal |last1=Metchev |first1=Stanimir |date=November 2009 |title=Pre-Discovery 2007 Image of the HR 8799 Planetary System |journal= The Astrophysical Journal|volume=696|issue=2 |pages=L204–L207 |arxiv=0910.0915|bibcode = 2009ApJ...705L.204M|doi = 10.1088/0004-637X/705/2/L204 |last2=Zuckerman |first2=B. |s2cid=42181708 }}</ref><ref name="Currie2012">{{cite journal |last1=Currie |first1=Thayne |date=July 2012 |title=Direct Detection and Orbital Analysis of the Exoplanets HR 8799 bcd from Archival 2005 Keck/NIRC2 Data |journal= The Astrophysical Journal|volume=755 |issue=2 |pages=34 |arxiv=1206.0483 |bibcode = 2012ApJ...755L..34C |doi=10.1088/2041-8205/755/2/l34|last2=Thalmann |first2=Christian |last3=Matsumura |first3=Soko |last4=Plavchan |first4=Peter |s2cid=32538115 }}</ref>
== Atmosphere == thumb|Artistic illustration of HR 8799b. Broadband photometry of HR 8799 b shows that it has thicker clouds in its atmosphere than do older, higher surface gravity substellar objects of the same effective temperature.<ref name="Currie2011">{{cite journal |last1=Currie |first1=Thayne |date=March 2011 |title=A Combined Subaru/VLT/MMT 1--5 Micron Study of Planets Orbiting HR 8799: Implications for Atmospheric Properties, Masses, and Formation |journal= The Astrophysical Journal|volume=729 |issue=2|pages=128 |arxiv=1101.1973 |bibcode = 2011ApJ...729..128C |doi=10.1088/0004-637x/729/2/128|last2=Itoh |first2=Yoichi |last3=Matsumura |first3=Soko |last4=Fukagawa |first4=Misato |last5=Apai |first5=Daniel |last6=Madhusudhan |first6=Nikku |last7=Hinz |first7=Philip M. |last8=Rodigas |first8=T. J. |last9=Kasper |first9=Markus |last10=Pyo |first10=T.-S. |last11=Ogino |first11=Satoshi |s2cid=119221800 }}</ref> Near infrared H band and K band spectroscopy of HR 8799 b published in May 2011 indicate a hydrogen rich, dusty atmosphere with disequilibrium CO / CH<sub>4</sub> chemistry.<ref name="clouds">{{Cite journal|arxiv=1103.3895|title=Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b|journal=The Astrophysical Journal|volume=733|issue=1|pages=65|date=2011-03-20|last1= Barman|first1=Travis S.|last2=Macintosh|first2=Bruce|last3= Konopacky|first3=Quinn M.|last4=Marois|first4=Christian|doi=10.1088/0004-637X/733/1/65|bibcode=2011ApJ...733...65B|s2cid=119221025}}</ref>
=== Composition === Near infrared spectroscopy made with the Palomar Observatory show evidence of ammonia and/or acetylene as well as carbon dioxide, and some methane.<ref name="Gilliland">{{Cite journal|first = B. R.|last= Oppenheimer|title= Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy|journal= The Astrophysical Journal|volume= 768|issue= 1|pages= 24|publisher=Cornell University|arxiv= 1303.2627|bibcode = 2013ApJ...768...24O |doi = 10.1088/0004-637X/768/1/24 |year= 2013|s2cid= 7173368}}</ref> In 2015, the signals of water vapor, carbon monoxide and methane were reported in infrared spectra taken at the Keck telescope.<ref name="Barman2015">{{cite journal|first1=Travis S.|last1=Barman|first2=Quinn M.|last2=Konopacky|first3=Bruce|last3=Macintosh|first4=Christian|last4=Marois|title=Simultaneous detection of water, methane, and carbon monoxide in the atmosphere of exoplanet HR 8799 b|doi=10.1088/0004-637X/804/1/61|journal=The Astrophysical Journal|volume=804|issue=1|pages=61|date=4 May 2015|arxiv=1503.03539|bibcode=2015ApJ...804...61B|s2cid=118693314}}</ref> However, a reanalysis of the same data in 2018 shows that water and carbon monoxide are present, but that the methane detection may have been spurious. Observations by the James Webb Space Telescope (JWST) will likely be capable of confirming or disproving the presence of methane in HR 8799 b's atmosphere.<ref name="Roche2018">{{cite journal|first1=D. J. M.|last1= Petit dit de la Roche|first2= H. J.|last2= Hoeijmakers|first3=I. A. G.|last3=Snellen|title=Molecule mapping of HR8799b using OSIRIS on Keck: Strong detection of water and carbon monoxide, but no methane|journal=Astronomy and Astrophysics|volume=616|pages=A146|doi=10.1051/0004-6361/201833384|arxiv=1808.10790|date=31 August 2018|bibcode=2018A&A...616A.146P|s2cid= 119529869}}</ref> In 2025, JWST confirmed the presence of carbon dioxide in the planet's atmosphere.<ref>{{Cite web |last=Cowing |first=Keith |date=2025-03-17 |title=Webb Telescope Images Young and Giant Exoplanets, Detects Carbon Dioxide |url=https://astrobiology.com/2025/03/webb-telescope-images-young-and-giant-exoplanets-detects-carbon-dioxide.html |access-date=2026-03-06 |website=Astrobiology |language=en-US}}</ref>
==References== {{reflist}}
==External links== {{Commons category-inline}} * {{cite web | url=http://media4.obspm.fr/exoplanets/base/planete.php?etoile=HR+8799&planete=b | title=HR 8799 b | work=Exoplanets | access-date=2008-12-02 | archive-url=https://web.archive.org/web/20120304131129/http://media4.obspm.fr/exoplanets/base/planete.php?etoile=HR+8799&planete=b | archive-date=2012-03-04 | url-status=dead }}
{{HR 8799}} {{Sky|23|07|28.7150|+|21|08|03.302|129}}
{{DEFAULTSORT:Hr 8799 B}} Category:HR 8799 Category:Exoplanets discovered in 2008 Category:Giant planets Category:Pegasus (constellation) Category:Exoplanets detected by direct imaging