Gliese 777, also known asHD 190360, is abinary star system approximately 52light-years away in theconstellation ofCygnus. The system is made up of twostars and possibly a third. Threeexoplanets are known to orbit the primary star.
The primary star of the system (catalogued as Gliese 777 A) is ayellow subgiant, aSun-like star that is ceasingfusinghydrogen 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 rathermetal-rich, having about 70% more "metals" (elements heavier thanhelium) than the Sun, which is typical for stars with extrasolar planets.
The secondary star (Gliese 777 B) is a distant, dimred dwarf star orbiting the primary at a distance of 3,000astronomical units (0.047 light years). A faint companion has been reported, but not confirmed.[15]
In 2002, a discovery of a long-period, wide-orbiting, planet (Gliese 777 Ab) was announced by theGeneva extrasolar planet search team.[16] The planet was estimated to orbit in a circular path with loworbital eccentricity, but that estimate was increased with later measurements (e=0.36).[17] Initially therefore, the planet was believed to be a true "Jupiter-twin" but was later redefined as being more like an "eccentric Jupiter", with a mass of at least 1.5 times Jupiter and about the same size. In 2021, the true mass of Gliese 777 Ab was measured viaastrometry.[18]
In 2005, further observation of the star showed another amplitude with a period of 17.1 days.[17] The mass of this second planet (Gliese 777 Ac) was only 18 times more thanEarth, or about the same asNeptune, indicating it was one of the smallest planets discovered at the time. Initially thought to be on a circular orbital path (e = 0.01),[17] Gliese 777 c was revealed to have a more eccentric orbit with later measurements.[9]
Evidence for a third candidate planet with an orbital period around 89 days was presented in 2025.[9] It was confirmed in the same year.[19]
There was aMETI message sent to Gliese 777. It was transmitted fromEurasia's largestradar, 70-meterEupatoria Planetary Radar. The message was namedCosmic Call 1; it was sent on July 1, 1999, and it will arrive at Gliese 777 in April 2051.[20]
^abcMann, Andrew W.; Feiden, Gregory A.; Gaidos, Eric; Boyajian, Tabetha; von Braun, Kaspar (2015). "How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius".The Astrophysical Journal.804 (1): 64.arXiv:1501.01635.Bibcode:2015ApJ...804...64M.doi:10.1088/0004-637X/804/1/64.
^Alonso-Floriano, F. J.; Morales, J. C.; Caballero, J. A.; Montes, D.; Klutsch, A.; Mundt, R.; Cortés-Contreras, M.; Ribas, I.; Reiners, A.; Amado, P. J.; Quirrenbach, A.; Jeffers, S. V. (2015). "CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS".Astronomy and Astrophysics.577: A128.arXiv:1502.07580.Bibcode:2015A&A...577A.128A.doi:10.1051/0004-6361/201525803.
^abcdeGiovinazzi, Mark R.; Blake, Cullen H.; Robertson, Paul; Lin, Andrea S. J.; Gupta, Arvind F.; Mahadevan, Suvrath; Fernandes, Rachel B.; Wright, Jason T.; Daniella Bardalez Gagliuffi; Dong, Jiayin; Fitzmaurice, Evan; Halverson, Samuel; Kanodia, Shubham; Logsdon, Sarah E.; Luhn, Jacob K.; McElwain, Michael W.; Monson, Andy; Ninan, Joe P.; Rajagopal, Jayadev; Roy, Arpita; Schwab, Christian; Stefánsson, Gudmundur; Terrien, Ryan; Eastman, Jason D.; Horner, Jonathan; Plavchan, Peter; Wang, Sharon X.; Wilson, Maurice L.; Wittenmyer, Robert A. (2025)."The NEID Earth Twin Survey. II. Dynamical Masses in Seven High-acceleration Star Systems".The Astronomical Journal.170 (1): 52.arXiv:2505.12563.Bibcode:2025AJ....170...52G.doi:10.3847/1538-3881/add922.
^abcSebastian, D.; Gillon, M.; Ducrot, E.; Pozuelos, F. J.; Garcia, L. J.; Günther, M. N.; Delrez, L.; Queloz, D.; Demory, B. O.; Triaud, A. H. M. J.; Burgasser, A.; De Wit, J.; Burdanov, A.; Dransfield, G.; Jehin, E.; McCormac, J.; Murray, C. A.; Niraula, P.; Pedersen, P. P.; Rackham, B. V.; Sohy, S.; Thompson, S.; Van Grootel, V. (2021). "SPECULOOS: Ultracool dwarf transit survey. Target list and strategy".Astronomy and Astrophysics.645.arXiv:2011.02069.Bibcode:2021A&A...645A.100S.doi:10.1051/0004-6361/202038827.
