HR 8799 d

HR 8799 d 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 between 5 and 10 Jupiter masses and a radius from 20 to 30% larger than Jupiter's. The planet orbits at 24 AU from HR 8799 with an eccentricity greater than 0.04 and a period of 100 years. Upon initial discovery, it was the innermost known planet in the HR 8799 system, but e, discovered later, is now known to be closer to their parent star. Along with two other planets orbiting HR 8799, this planet was discovered on November 13, 2008 by Marois et al., using the Keck and Gemini observatories in Hawaii. These planets were discovered using the direct imaging technique.^[2][6][7][8]

HR 8799 d

Size comparison of HR 8799 d (gray) with Jupiter.
Discovery
Discovered by	Marois et al.
Discovery site	Keck and Gemini observatories in Hawaii
Discovery date	November 13, 2008
Detection method	Direct imaging
Orbital characteristics
Semi-major axis	~24 AU
Eccentricity	>0.04[1][note 1]
Orbital period (sidereal)	~100[2][note 2] y
Star	HR 8799
Physical characteristics
Mean radius	1.2+0.1 −0[2] RJ
Mass	7+3 −2[3] MJ
Mean density	5.978 g/cm3[4]
Synodic rotation period	6.0+11.3 −2.5 h[5]
Equatorial rotation velocity	~10.1+2.8 −2.7 km/s[5]
Temperature	1090+10 −90[2]

Near infrared spectroscopy from 995 to 1769 nanometers made with the Palomar Observatory show evidence of acetylene, methane, and carbon dioxide, but ammonia is not definitively detected.^[9] In 2021, the further detection of water and carbon monoxide in the planetary atmosphere was made with the Keck Planet Imager and Characterizer (KPIC).^[5]

See also

• Fomalhaut b

Notes

1. The lower limit on the eccentricity is given for the case that the planet is in a 2:1 resonance with HR 8799 c, as suggested by stability constraints.
2. Value given assuming the planet's orbit is circular and is being observed face-on.

References

1. 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.
2. Marois, Christian; 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.
3. Marois; Zuckerman; Konopacky; Macintosh; Barman (2010). "Images of a fourth planet orbiting HR 8799". Nature. 468 (7327): 1080–3. arXiv:1011.4918. Bibcode:2010Natur.468.1080M. doi:10.1038/nature09684. PMID 21150902. S2CID 4425891.
4. "Exoplanet HR 8799 d". Retrieved 29 July 2024.
5. Wang, Jason J.; Ruffio, Jean-Baptiste; et al. (2021-07-14). "Detection and Bulk Properties of the HR 8799 Planets with High-resolution Spectroscopy". The Astronomical Journal. 162 (4): 148. arXiv:2107.06949. Bibcode:2021AJ....162..148W. doi:10.3847/1538-3881/ac1349. S2CID 235898867.
6. "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.
7. "Gemini Releases Historic Discovery Image of Planetary First Family" (Press release). Gemini Observatory. 2008-11-13. Retrieved 2008-12-02.
8. Achenbach, Joel (2008-11-13). "Scientists Publish First Direct Images of Extrasolar Planets". The Washington Post. Retrieved 2008-12-02.
9. B. R. Oppenheimer (2013). "Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy". The Astrophysical Journal. 768 (1): 24. arXiv:1303.2627. Bibcode:2013ApJ...768...24O. doi:10.1088/0004-637X/768/1/24. S2CID 7173368.

External links

Media related to HR 8799 d at Wikimedia Commons

• "HR 8799 d". Exoplanets. Archived from the original on 2012-03-04. Retrieved 2008-12-02.