Gliese 777 b, also known as Gliese 777 Ab or HD 190360 b, is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

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 planet was discovered orbiting the primary star of the

Gliese 777 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 ...

system in June 2002 (by the Geneva Extrasolar Planet Search Team) using the

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

method. The planet is at least one half more massive than

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

but roughly the same size as Jupiter. In 2021, the

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

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 ...

, allowing the

true mass In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial veloci ...

of 1.8 to be determined. The planet has one of the longest orbits currently known for an extrasolar planet. The planet's mean distance from the star is close to the distance between Jupiter and the Sun. However, unlike Jupiter it has an

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

orbit. At

periastron An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

the distance between the planet and the star is only 2.57 AU and at

apastron An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

the distance is as much as 5.23 AU (compared to the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

, distance from the Sun to the inner

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

and from Sun to just beyond the orbit of Jupiter). The signal produced by the planet is very weak and the eccentricity was originally supposed to be very circular which led to speculations of a very Jupiter-like planet, with a system of several large moons like Jupiter itself. The inner system should be stable for

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

-like planets despite a known, smaller inner

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 ...

-like planet which is known to orbit the star at distance of 0.12 AU every 17 Earth days.

References

External links

* {{Sky, 20, 03, 37.41, +, 29, 53, 48.50, 51.81 Cygnus (constellation) Exoplanets discovered in 2002 Giant planets Exoplanets detected by radial velocity Exoplanets detected by astrometry 7 de:Gliese 777#Gliese 777 Ab