Gliese 777, often abbreviated as Gl 777 or GJ 777, is a

yellow subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

approximately 52

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Cygnus. The system is also a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

system made up of two

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s and possibly a third. As of 2005, two extrasolar planets are known to orbit the primary star.

Stellar components

The primary star of the system (catalogued as Gliese 777A) is a

, 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 ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

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.

Planetary system

In 2002, a discovery of a long-period, wide-orbiting, planet (

Gliese 777b Gliese 777 b, also known as Gliese 777 Ab or HD 190360 b, is an extrasolar planet approximately 52 light-years away in the constellation of Cygnus. The planet was discovered orbiting the primary star of the Gliese 777 system in June 2002 (by the ...

) was announced by the

Geneva extrasolar planet search team The Geneva Extrasolar Planet Search is a variety of observational programs run by the Geneva Observatory at Versoix, a small town near Geneva, Switzerland. The programs are executed by M. Mayor, D. Naef, F. Pepe, D. Queloz, N.C. Santos, and S. ...

. The planet was estimated to orbit in a circular path with low

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

, but that estimate was increased with later measurements (e=0.36). 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 via

astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. His ...

. In 2005, further observation of the star showed another amplitude with a period of 17.1 days. The mass of this second planet (

Gliese 777c Gliese 777 c, often catalogued as Gliese 777 Ac or simply HD 190360 c, is an extrasolar planet approximately 52 light-years away in the constellation of Cygnus. The planet was discovered orbiting the primary star of the Gliese 777 system in 2005 ...

) was only 18 times more than Earth, or about the same as

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

, indicating it was one of the smallest planets discovered at the time. It too was initially thought to be on a circular orbital path that with later measurements turned out to be not the case. 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 Cosmic commonly refers to: * The cosmos, a concept of the universe Cosmic may also refer to: Media * ''Cosmic'' (album), an album by Bazzi * Afro/Cosmic music * "Cosmic", a song by Kylie Minogue from the album '' X'' * CosM.i.C, a member of ...

; it was sent on July 1, 1999, and it will arrive at Gliese 777 in April 2051.

References

External links

Extrasolar Planet Interactions
by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona {{Stars of Cygnus Binary stars Cygnus (constellation) 190360 098767 7670 0777 M-type main-sequence stars G-type subgiants Planetary systems with two confirmed planets Durchmusterung objects TIC objects

Stellar components

Planetary system

See also

References

External links