Gamma¹ Leonis b

Gamma¹ Leonis b
Discovery
Discovered by	Inwoo Han et al.
Discovery site	South Korea
Discovery date	November 6, 2009
Detection method	Radial velocity
Orbital characteristics
Apastron	1.36 AU (203,000,000 km)
Periastron	1.02 AU (153,000,000 km)
Semi-major axis	1.19 AU (178,000,000 km)
Eccentricity	0.14
Orbital period (sidereal)	429 d; 1.17 y
Average orbital speed	30.3
Star	Gamma1 Leonis (Algieba A)
Physical characteristics
Mass	>10.7 MJ

Gamma¹ Leonis b is an extrasolar planet located 125.5 light years away in the constellation Leo, orbiting the giant star Gamma¹ Leonis.^[1]

Discovery

On November 6, 2009, a planetary companion around primary star Gamma¹ Leonis has been announced.^[1] Moreover, radial velocity variations would also hint two strong signals at 8.5 and 1340 days. The former periodicity is likely due to stellar pulsation, whereas the latter could be indicative of the presence of an additional planetary companion with 2.14 Jupiter masses, moderate eccentricity (e=0.13) and located at 2.6 Astronomical Units away from the giant star. Nevertheless, the nature of such a signal is still unclear and further investigations are needed to confirm or rule out an additional substellar companion.

Characteristics

The planet has a minimum mass of 10.7 Jupiter masses. The true mass, as with the majority of other extrasolar planets discovered by the radial velocity method, is unknown.^[3] Depending on the planet's inclination relative to Earth, it may be sufficently massive to be classified as a brown dwarf.^[2]

Host star

Gamma Leonis A is the main star of a binary star system in the constellation Leo (the lion). It is a K-type red giant of apparent magnitude 2.37, with around 26 times the size of the Sun and 250 times its luminosity. The secondary component is a fainter G-type giant of apparent magnitude 3.64, eleven times bigger than the Sun with 63 times its luminosity.^[2] Together, they shine with apparent magnitude 2.04, making it the second-brightest star in Leo after Regulus. This system shares the traditional name Algieba.

The Algieba system can be easily splitted by a telescope. Due to the large orbital separation between the stars, only a small fraction of the orbit has been observed since discovery, and the orbital parameters are still poorly known.^[2]

References

^ ^a ^b ^c ^d ^e ^f Han, Inwoo; Lee, B. C.; Kim, K. M.; Mkrtichian, D. E.; Hatzes, A. P.; Valyavin, G. (2010). "Detection of a Planetary Companion around the giant star γ¹ Leonis". Astronomy and Astrophysics. 509: A24. arXiv:0911.0968. Bibcode:2010A&A...509A..24H. doi:10.1051/0004-6361/200912536. S2CID 118962986.
^ ^a ^b ^c ^d Takeda, Yoichi (July 2023). "Spectroscopic comparative study of the red giant binary system gamma Leonis A and B". Astrophysics and Space Science. 368 (7): 56. arXiv:2306.16723. Bibcode:2023Ap&SS.368...56T. doi:10.1007/s10509-023-04214-1. ISSN 0004-640X.
^ "The Extrasolar Planet Encyclopaedia — Gamma1 Leonis b". Extrasolar Planets Encyclopaedia. Retrieved 10 September 2023.

[Inwoo_Han-1] ^ ^a ^b ^c ^d ^e ^f Han, Inwoo; Lee, B. C.; Kim, K. M.; Mkrtichian, D. E.; Hatzes, A. P.; Valyavin, G. (2010). "Detection of a Planetary Companion around the giant star γ¹ Leonis". Astronomy and Astrophysics. 509: A24. arXiv:0911.0968. Bibcode:2010A&A...509A..24H. doi:10.1051/0004-6361/200912536. S2CID 118962986.

[takeda-2] Takeda, Yoichi (July 2023). "Spectroscopic comparative study of the red giant binary system gamma Leonis A and B". Astrophysics and Space Science. 368 (7): 56. arXiv:2306.16723. Bibcode:2023Ap&SS.368...56T. doi:10.1007/s10509-023-04214-1. ISSN 0004-640X.

[3] "The Extrasolar Planet Encyclopaedia — Gamma1 Leonis b". Extrasolar Planets Encyclopaedia. Retrieved 10 September 2023.

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