777

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Double star
Gliese 777
(GJ 777)
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation swan
Apparent brightness  5.71 likes
Known exoplanets

2

Astrometry
Radial velocity (−45.3 ± 2.0) km / s
parallax (62.9 ± 0.6) mas
distance  (51.8 ± 0.5) ly
((15.9 ± 0.2) pc )
Individual data
Names A ; B.
Observation data:
Right ascension A. 20 h 03 m 37.4 s
B. 20 h 03 m 26.5 s
declination A. 2295348.5+ 29 ° 53 ′ 48.5 ″
B. 2295200+ 29 ° 52 ′ 00.0 ″
Apparent brightness A. 5.73 likes
B. 14.4 mag
Typing:
Spectral class A. G6 IV
B. M4.5 V
B − V color index A. +0.73
Physical Properties:
Absolute vis.
Brightness M vis 		A. +4.72 mag
B. +13.39 mag
Dimensions A. 0.9 M ☉
B. ~ 0.2 M ☉
radius A. 1.5 R ☉
B. 0.16 R ☉
Luminosity A. 1.1 L ☉
B. 0.000375 L ☉
Effective temperature A. 5,050 K
B. 3,370 K
Metallicity [Fe / H] A. 1.38
B.
Rotation time A. 28 d
B. 4 d
Age 6.7 billion years
Other names
and catalog entries
Bonn survey BD + 29 ° 3872
Bright Star Catalog HR 7670 [1]
Henry Draper Catalog HD 190360 [2]
SAO catalog SAO 88133 [3]
Tycho catalog TYC 2153-2883-1 [4]
Hipparcos catalog HIP 98767 [5]
Further designations: FY 777
  LHS 3510 LHS 3509

Template: Infobox double star / maintenance / single coordinates

Gliese 777 is a sixth magnitude double star in the constellation Swan . One of the stars is a yellow sub-giant with planetary companions, the other a red dwarf ; the larger of the two can be observed with the naked eye under favorable conditions.

Physical Properties

Gliese 777 A

Gliese 777 A is a star of the spectral class G6, very similar to the Sun. Since the star, at 6.7 billion years, is significantly older than the sun, more metal could also accumulate in it, so its metallicity is approx. 70% higher than that of the sun. It has finished its nuclear fusion of hydrogen in its core and is now starting to inflate into a red giant . To date, two planets orbiting Gliese 777 A have been found.

Gliese 777 B

Gliese 777 B is a red dwarf which orbits the primary star at a distance of 3000  AU , which corresponds to about a thousand times the distance between the primary star and its larger, more distant planetary companion; Gliese 777 B should take decades to complete a circle. Because observation is difficult under such circumstances and research is focused on other objects, little more is known about the system.

Surname Diameter
[million km] 		Radius
[R ☉ ] 		Mass
[M ☉ ] 		Luminosity
[L ☉ ] 		Spectral class
Gliese 777 A 2.09 1.5 0.9 1.1 G6 IV
Gliese 777 B 0.22 0.16 ≈0.2 0.000375 M4.5 V
Sun 1.39 1.0 1.0 1.0 G2 V

The planetary system

Michel Mayor stated in 2002 that he had discovered a companion around Gliese 777 A, which orbits the star at a great distance. The mass of the newly discovered planet was calculated to be about 1.5 times the mass of Jupiter . The size is also very similar to that of Jupiter . Further observations showed further regular movements of the star with an amplitude of 17.1 days. This is seen as a strong indication of another, albeit very small, companion. The mass was estimated to be 18 times the mass of the earth , which is considered extremely small. The practically non-existent eccentricity of the companion (e = 0.01) is also noticeable.

Gliese 777 Ab

Gliese 777 Ab has about 1.502 times the mass of Jupiter, takes about 2890 days to orbit its star and orbits it at a distance of 3.92 ± 0.17 AU. The eccentricity of the orbit is 0.36 ± 0.03. Because of its similarity to Jupiter, the planet is therefore also referred to as the "Jupiter twin".

Gliese 777 Ac

Gliese 777 Ac has about only 6% of the mass of Jupiter, needs about 17 days for one orbit, is only 0.128 ± 0.002 AU away from its star and shows a very low orbital eccentricity of about 0.01.

METI message to Gliese 777

On July 1, 1999, a message was sent in the direction of the Gliese 777 binary star system through the largest European radar system, the 70-meter Eupatoria Planetary Radar. The message will be available on Gliese as early as April 2051 - provided that someone is there and willing to listen.

See also

Web links