Epoch J2000.0 Equinox J2000.0
|Right ascension||20h 03m 37.41s|
|Declination||+29° 53′ 48.5″|
|Apparent magnitude (V)||+5.73 / +14.40|
|Spectral type||G6IV / M4.5V|
|B−V color index||0.749|
|Radial velocity (Rv)||-45.3 km/s|
|Proper motion (μ)|| RA: 683.94 ± 0.22 mas/yr |
Dec.: -524.70 ± 0.27 mas/yr
|Parallax (π)||63.06 ± 0.34 mas|
|Distance||51.7 ± 0.3 ly |
(15.86 ± 0.09 pc)
|Absolute magnitude (MV)||+4.70 / +13.39|
|Surface gravity (log g)||4.3±0.09 cgs|
|Metallicity [Fe/H]||0.2 dex|
|Age||6.7 Gyr|
Gliese 777, often abbreviated as Gl 777 or GJ 777, is a yellow subgiant approximately 52 light-years away in the constellation of Cygnus. The system is also a binary star system made up of two stars and possibly a third. As of 2005, two extrasolar planets are known to orbit the primary star.
The primary star of the system (catalogued as Gliese 777A) is a yellow subgiant, a Sun-like star that is ceasing fusing hydrogen in its core. The star is much older than the Sun, about 6.7 billion years old. It is 4% less massive than the Sun. It is also rather metal-rich, having about 70% more "metals" (elements heavier than helium) than the Sun, which is typical for stars with extrasolar planets.
The secondary star (Gliese 777B) is a distant, dim red dwarf star orbiting the primary at a distance of 3,000 astronomical units. One orbit takes at least tens of thousands of years to complete. The star itself may be a binary, the secondary being a very dim red dwarf. Not much information is available on the star system.
In 2002 a discovery of a long-period, wide-orbiting planet (Gliese 777b) was announced by the Geneva extrasolar planet search team. The planet orbited in circular path and the orbital eccentricity was increased in later measurements (e=0.36). The planet was "Jupiter-twin" and was turned to "eccentric Jupiter" with mass about 1.5 times Jupiter and about the same size. In 2005 further observation of the star show another amplitude with a period of 17.1 days. This indicates one of the smallest discovered planets at the time. The mass was only 18 times more than Earth or about same as Neptune with very low eccentricity. There was a METI message sent to Gliese 777. It was transmitted from Eurasia's largest radar, 70-meter Eupatoria Planetary Radar. The message was named Cosmic Call 1; it was sent on July 1, 1999, and it will arrive at Gliese 777 in April 2051.
(in order from star)
|c||≥0.0600 ± 0.0076 MJ||0.1304 ± 0.0075||17.1110 ± 0.0048||0.237 ± 0.082||—||—|
|b||≥1.56 ± 0.13 MJ||4.01 ± 0.23||2915 ± 29||0.313 ± 0.019||—||—|
- van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
- Ligi, R.; et al. (February 2016), "Radii, masses, and ages of 18 bright stars using interferometry and new estimations of exoplanetary parameters", Astronomy & Astrophysics, 586: 23, arXiv:1511.03197, Bibcode:2016A&A...586A..94L, doi:10.1051/0004-6361/201527054, A94.
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- (in Russian) http://www.cplire.ru/rus/ra&sr/VAK-2004.html
- Wright, J. T.; et al. (2009). "Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems". The Astrophysical Journal. 693 (2): 1084–1099. arXiv:0812.1582. Bibcode:2009ApJ...693.1084W. doi:10.1088/0004-637X/693/2/1084.
- Extrasolar Planet Interactions by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona