HR 8799 d

HR 8799 d

Exoplanet		List of exoplanets
Size comparison of HR 8799 d (gray) with Jupiter.
Parent star
Star		HR 8799
Constellation		Pegasus
Right ascension	(α)	23^h 07^m 28.7150^s[1]
Declination	(δ)	+21° 08′ 03.302″[1]
Apparent magnitude	(mV)	5.964[1]
Distance		129 ± 4[2][note 1] ly (39 ± 1[2][note 1] pc)
Spectral type		kA5 hF0 mA5 V; λ Boo[3][4]
Observed separation Observation epoch 2008-09-18
Angular separation	(ρ)	621[5][note 2] mas
Position angle	(θ)	200.36[5][note 2]°
Projected separation	(d)	24[5] AU
Orbital elements
Semi-major axis	(a)	~24[5][note 3] AU (~3600 Gm)
Eccentricity	(e)	>0.04[6][note 4]
Orbital period	(P)	~100[5][note 3] y
Physical characteristics
Mass	(m)	7+3 −2[7] MJ
Radius	(r)	1.2+0.1 −0[5] RJ
Density	(ρ)	4+1.75 −1.1 kg m^−3
Temperature	(T)	1090+10 −90[5]
Discovery information
Discovery date		November 13, 2008
Discoverer(s)		Marois et al.
Discovery method		Direct imaging
Discovery site		Keck and Gemini observatories in Hawaii
Discovery status		Published
Other designations
HD 218396 d[8]
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		data
Exoplanet Archive		data
Open Exoplanet Catalogue		data

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.^{[5][9][10][11]}

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.^[12]

See also

• Fomalhaut b

Notes

1. Computed from parallax: $\scriptstyle {\mathrm {distance\ in\ parsecs}}={\frac {1000}{{\mathrm {parallax\ in\ milliarcseconds}}}}$
2. Calculated from the separations in the East and North directions which are −0.216 and −0.582 arcseconds respectively.
3. Value given assuming the planet's orbit is circular and is being observed face-on.
4. 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.

References

1. V* V342 Peg -- Variable Star of gamma Dor type, entry, SIMBAD. Accessed on line November 14, 2008.
2. van Leeuwen, F. (2007). "HIP 114189". Hipparcos, the New Reduction. Retrieved 2008-10-13.
3. Gray, R.O.; Kaye, A.B. (1999). "HR 8799: A Link between γ Doradus Variables and λ Bootis Stars". The Astronomical Journal. 118 (6): 2993–2996. Bibcode:1999AJ....118.2993G. doi:10.1086/301134.
4. Kaye, A.B.; et al. (1999). "Gamma Doradus Stars: Defining a New Class of Pulsating Variables". PASP. 111 (761): 840–844. arXiv:astro-ph/9905042. Bibcode:1999PASP..111..840K. doi:10.1086/316399.
5. 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. Missing |last2= in Authors list (help)
6. Fabrycky; et al. (1 December 2008). "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.
7. Marois; Zuckerman; Konopacky; Macintosh; Barman (2010). "Images of a fourth planet orbiting HR 8799". Nature. 468 (7327): 1080. arXiv:1011.4918. doi:10.1038/nature09684.
8. HD 218396d -- Extra-solar Planet Candidate, entry, SIMBAD. Accessed on line December 6, 2008.
9. "Astronomers capture first images of newly-discovered solar system" (Press release). W. M. Keck Observatory. 2008-11-13. Retrieved 2008-12-02.
10. "Gemini Releases Historic Discovery Image of Planetary First Family" (Press release). Gemini Observatory. 2008-11-13. Retrieved 2008-12-02.
11. Achenbach, Joel (2008-11-13). "Scientists Publish First Direct Images of Extrasolar Planets". The Washington Post. The Washington Post Company. Retrieved 2008-12-02.
12. B. R. Oppenheimer (2013). "Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy". The Astrophysical Journal. 768: 24. arXiv:1303.2627. Bibcode:2013ApJ...768...24O. doi:10.1088/0004-637X/768/1/24.

External links

Media related to HR 8799 d at Wikimedia Commons

• "HR 8799 d". Exoplanets.

Coordinates: 23^h 07^m 28.7150^s, +21° 08′ 03.302″