HR 8799 b

HR 8799 b
Size comparison of HR 8799 b (gray) with Jupiter.
Discovery
Discovered byMarois et al.
Discovery siteKeck and Gemini
observatories in Hawaii
Discovery dateNovember 13, 2008
Direct imaging
Orbital characteristics
71.3±0.2[1]: 6  AU
Eccentricity0.017±0.002[1]: 6 
419[2]: 3  years
Inclination26.5±0.5[1]: 6 
StarHR 8799
Physical characteristics
1.10±0.03[3]: 20  RJ
Mass6.0+0.4
−0.3[3]: 20  MJ
Mean density
5.041 g/cm3[4]
104.10+0.03
−0.04[3]: 20  cgs
Temperature942+12
−16[3]: 20  K
Atmosphere
Composition by volumehydrogen, water vapor, ammonia and/or acetylene, carbon dioxide, carbon monoxide, possibly with methane[5][6][7][8]

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.[3] It orbits at 71.3 AU from HR 8799 with a low ecccentricity[1]: 6  and a period of around 419 years, being the outermost known planet in the HR 8799 system.[2]

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.[9][10][11][12][13]

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.[14] 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.[15][16][17]

Atmosphere

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.[18] 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 / CH4 chemistry.[5]

Composition

Near infrared spectroscopy made with the Palomar Observatory show evidence of ammonia and/or acetylene as well as carbon dioxide, and some methane.[8] In 2015, the signals of water vapor, carbon monoxide and methane were reported in infrared spectra taken at the Keck telescope.[6] 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.[7] In 2025, JWST confirmed the presence of carbon dioxide in the planet's atmosphere.[19]

References

  1. ^ a b c d Zurlo, A.; Goździewski, K.; Lazzoni, C.; Mesa, D.; Nogueira, P.; Desidera, S.; Gratton, R.; Marzari, F.; Langlois, M.; Pinna, E.; Chauvin, G.; Delorme, P.; Girard, J. H.; Hagelberg, J.; Henning, Th (2022-10-19). "Orbital and dynamical analysis of the system around HR 8799. New astrometric epochs from VLT/SPHERE and LBT/LUCI". Astronomy and Astrophysics. 666: A133. arXiv:2207.10684. Bibcode:2022A&A...666A.133Z. doi:10.1051/0004-6361/202243862. ISSN 0004-6361.
  2. ^ a b Gozdziewski, Krzysztof; Migaszewski, Cezary (2020). "An exact, generalised Laplace resonance in the HR 8799 planetary system". The Astrophysical Journal. 902 (2): L40. arXiv:2009.07006. Bibcode:2020ApJ...902L..40G. doi:10.3847/2041-8213/abb881. S2CID 221702978.
  3. ^ a b c d e Nasedkin, E.; Mollière, P.; Lacour, S.; Nowak, M.; Kreidberg, L.; Stolker, T.; Wang, J. J.; Balmer, W. O.; Kammerer, J.; Shangguan, J.; Abuter, R.; Amorim, A.; Asensio-Torres, R.; Benisty, M.; Berger, J.-P. (July 2024). "Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY". Astronomy & Astrophysics. 687: A298. arXiv:2404.03776. Bibcode:2024A&A...687A.298N. doi:10.1051/0004-6361/202449328. ISSN 0004-6361.
  4. ^ "Exoplanet HR 8799 b". Retrieved 29 July 2024.
  5. ^ a b Barman, Travis S.; Macintosh, Bruce; Konopacky, Quinn M.; Marois, Christian (2011-03-20). "Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b". The Astrophysical Journal. 733 (1): 65. arXiv:1103.3895. Bibcode:2011ApJ...733...65B. doi:10.1088/0004-637X/733/1/65. S2CID 119221025.
  6. ^ a b Barman, Travis S.; Konopacky, Quinn M.; Macintosh, Bruce; Marois, Christian (4 May 2015). "Simultaneous detection of water, methane, and carbon monoxide in the atmosphere of exoplanet HR 8799 b". The Astrophysical Journal. 804 (1): 61. arXiv:1503.03539. Bibcode:2015ApJ...804...61B. doi:10.1088/0004-637X/804/1/61. S2CID 118693314.
  7. ^ a b Petit dit de la Roche, D. J. M.; Hoeijmakers, H. J.; Snellen, I. A. G. (31 August 2018). "Molecule mapping of HR8799b using OSIRIS on Keck: Strong detection of water and carbon monoxide, but no methane". Astronomy and Astrophysics. 616: A146. arXiv:1808.10790. Bibcode:2018A&A...616A.146P. doi:10.1051/0004-6361/201833384. S2CID 119529869.
  8. ^ a b Oppenheimer, B. R. (2013). "Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy". The Astrophysical Journal. 768 (1). Cornell University: 24. arXiv:1303.2627. Bibcode:2013ApJ...768...24O. doi:10.1088/0004-637X/768/1/24. S2CID 7173368.
  9. ^ Marois, Christian; Macintosh, Bruce; Barman, Travis; Zuckerman, B.; Song, Inseok; Patience, Jennifer; Lafrenière, David; Doyon, René (November 2008). "Direct Imaging of Multiple Planets Orbiting the Star HR 8799". Science. 322 (5906): 1348–1352. arXiv:0811.2606. Bibcode:2008Sci...322.1348M. doi:10.1126/science.1166585. PMID 19008415. S2CID 206516630.
  10. ^ "Astronomers capture first images of newly-discovered solar system" (Press release). W. M. Keck Observatory. 2008-11-13. Archived from the original on 2013-11-26. Retrieved 2008-12-02.
  11. ^ "Gemini Releases Historic Discovery Image of Planetary First Family" (Press release). Gemini Observatory. 2008-11-13. Retrieved 2008-12-02.
  12. ^ Achenbach, Joel (2008-11-13). "Scientists Publish First Direct Images of Extrasolar Planets". The Washington Post. Retrieved 2008-12-02.
  13. ^ Fabrycky; et al. (2010). "Stability of the directly imaged multiplanet system HR 8799: resonance and masses". Astrophys. J. 710 (2): 1408–1421. arXiv:0812.0011. Bibcode:2010ApJ...710.1408F. doi:10.1088/0004-637X/710/2/1408. S2CID 11760422.
  14. ^ Lafrenière; et al. (18 February 2009). "HST/NICMOS detection of HR 8799 b in 1998". The Astrophysical Journal. 694 (2): L148–L152. arXiv:0902.3247. Bibcode:2009ApJ...694L.148L. doi:10.1088/0004-637X/694/2/L148. S2CID 7332750.
  15. ^ Fukagawa, Misato; Tamura, Motohide; Oasa, Yumiko; Hayashi, Saeko S.; Fujita, Yutaka; Shibai, Hiroshi; Hayashi, Masahiko (July 2012). "H-Band Image of a Planetary Companion Around HR 8799 in 2002". The Astrophysical Journal. 696 (1): L1–L5. arXiv:1206.0483. Bibcode:2009ApJ...696L...1F. doi:10.1088/0004-637X/696/1/L1. S2CID 18266866.
  16. ^ Metchev, Stanimir; Zuckerman, B. (November 2009). "Pre-Discovery 2007 Image of the HR 8799 Planetary System". The Astrophysical Journal. 696 (2): L204–L207. arXiv:0910.0915. Bibcode:2009ApJ...705L.204M. doi:10.1088/0004-637X/705/2/L204. S2CID 42181708.
  17. ^ Currie, Thayne; Thalmann, Christian; Matsumura, Soko; Plavchan, Peter (July 2012). "Direct Detection and Orbital Analysis of the Exoplanets HR 8799 bcd from Archival 2005 Keck/NIRC2 Data". The Astrophysical Journal. 755 (2): 34. arXiv:1206.0483. Bibcode:2012ApJ...755L..34C. doi:10.1088/2041-8205/755/2/l34. S2CID 32538115.
  18. ^ Currie, Thayne; Itoh, Yoichi; Matsumura, Soko; Fukagawa, Misato; Apai, Daniel; Madhusudhan, Nikku; Hinz, Philip M.; Rodigas, T. J.; Kasper, Markus; Pyo, T.-S.; Ogino, Satoshi (March 2011). "A Combined Subaru/VLT/MMT 1--5 Micron Study of Planets Orbiting HR 8799: Implications for Atmospheric Properties, Masses, and Formation". The Astrophysical Journal. 729 (2): 128. arXiv:1101.1973. Bibcode:2011ApJ...729..128C. doi:10.1088/0004-637x/729/2/128. S2CID 119221800.
  19. ^ Cowing, Keith (2025-03-17). "Webb Telescope Images Young and Giant Exoplanets, Detects Carbon Dioxide". Astrobiology. Retrieved 2026-03-06.

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