Gliese 806 is a star in the northern constellation of Cygnus, located about a degree to the southeast of the bright star Deneb. [9] It is invisible to the naked eye with an apparent visual magnitude of +10.79. [2] The star is located at a distance of 39.3 light years from the Sun based on stellar parallax. [1] It is drifting closer with a radial velocity of −24.6 km/s, and is predicted to come to within 30.1 light-years in ~198,600 years. [10] The star hosts two known planetary companions. [4]
The stellar classification of Gliese 806 is dM1.5, [3] which indicates this is a small red dwarf star – an M-type main-sequence star that is generating energy through core hydrogen fusion. It is roughly three [6] billion years old and is spinning with a projected rotational velocity of 0.46 km/s. [5] The star has 42% of the mass and radius of the Sun. It is radiating 0.3% of the luminosity of the Sun from its photosphere at an effective temperature of 3,586 K. [3]
In 1989, Marcy and Benitz detected a periodicity of 416 days in radial velocity variation, inferring the possible presence of a companion with a mass of about 0.011 M☉. [11] However, this candidate object was never confirmed.
More recently, observations by TESS have found a candidate transiting planet with a period of less than a day. [8] In January 2023, this planet was confirmed and a second, non-transiting planet found via radial velocity observations. A third radial velocity signal was also found, but the study was unable to confirm it as having a planetary origin. All known planets are super-Earths, and the inner transiting planet Gliese 806 b is likely to be rocky. [4]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | 1.90±0.17 M🜨 | 0.01406±0.00030 | 0.9263237±0.0000009 | — | 87.7+0.6 −0.5 ° | 1.331±0.023 R🜨 |
c | ≥5.80±0.30 M🜨 | 0.0523±0.0011 | 6.64064±0.00025 | — | — | — |
(unconfirmed) | ≥8.50±0.45 M🜨 | 0.0844±0.0017 | 13.60588±0.00065 | — | — | — |
Gliese 876 is a red dwarf star 15.2 light-years away from Earth in the constellation of Aquarius. It is one of the closest known stars to the Sun confirmed to possess a planetary system with more than two planets, after GJ 1061, YZ Ceti, Tau Ceti, and Wolf 1061; as of 2018, four extrasolar planets have been found to orbit the star. The planetary system is also notable for the orbital properties of its planets. It is the only known system of orbital companions to exhibit a near-triple conjunction in the rare phenomenon of Laplace resonance. It is also the first extrasolar system around a normal star with measured coplanarity. While planets b and c are located in the system's habitable zone, they are giant planets believed to be analogous to Jupiter.
Groombridge 34 is a binary star system in the northern constellation of Andromeda. It was listed as entry number 34 in A Catalogue of Circumpolar Stars, published posthumously in 1838 by British astronomer Stephen Groombridge. Based upon parallax measurements taken by the Gaia spacecraft, the system is located about 11.6 light-years from the Sun. This positions the pair among the nearest stars to the Solar System.
HD 219134 is a main-sequence star in the constellation of Cassiopeia. It is smaller and less luminous than the Sun, with a spectral class of K3V, which makes it an orange-hued star. HD 219134 is relatively close to our system, with an estimated distance of 21.34 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers. This star has a magnitude 9.4 optical companion at an angular separation of 106.6 arcseconds.
Gliese 849, or GJ 849, is a small, solitary star in the equatorial constellation of Aquarius. It has a reddish hue and is invisible to the naked eye with an apparent visual magnitude of 10.41. The distance to this star is 28.8 light-years based on parallax, but it is drifting closer to the Sun with a radial velocity of −15.3 km/s. It has a pair of confirmed gas giant companions.
Gliese 412 is a pair of stars that share a common proper motion through space and are thought to form a binary star system. The pair have an angular separation of 31.4″ at a position angle of 126.1°. They are located 15.8 light-years distant from the Sun in the constellation Ursa Major. Both components are relatively dim red dwarf stars.
Gliese 176 is a small star with an orbiting exoplanet in the constellation of Taurus. With an apparent visual magnitude of 9.95, it is too faint to be visible to the naked eye. It is located at a distance of 30.9 light years based on parallax measurements, and is drifting further away with a heliocentric radial velocity of 26.4 km/s.
Gliese 682 or GJ 682 is a red dwarf. It is listed as the 53rd-nearest known star system to the Sun, being 16.3 light years away from the Earth. Even though it is close by, it is dim with a magnitude of 10.95 and thus requires a telescope to be seen. It is located in the constellation of Scorpius, near the bright star Theta Scorpii. The star is in a crowded region of sky near the Galactic Center, and so appears to be near a number of deep-sky objects from the Solar System's perspective. The star is only 0.5 degrees from the much more distant globular cluster NGC 6388.
XO-2 is a binary star system about 490 light-years away in the constellation Lynx. It consists of two components, XO-2N and XO-2S, both of which host planetary systems.
Gliese 521 is a double star in the northern constellation of Canes Venatici. The system is located at a distance of 43.6 light-years from the Sun based on parallax measurements, but is drawing closer with a radial velocity of −65.6 km/s. It is predicted to come as close as 15.70 light-years from the Sun in 176,900 years. This star is too faint to be visible to the naked eye, having an apparent visual magnitude of +10.26 and an absolute magnitude of 10.24.
Gliese 676 is a 10th-magnitude wide binary system of red dwarfs that has an estimated minimum separation of 800 AU with an orbital period of greater than 20,000 years. It is located approximately 54 light years away in the constellation Ara. In 2009, a gas giant was found in orbit around the primary star, in addition to its confirmation in 2011 there was also a strong indication of a companion; the second gas giant was characterised in 2012, along with two much smaller planets.
HD 126614 is a trinary star system in the equatorial constellation of Virgo. The primary member, designated component A, is host to an exoplanetary companion. With an apparent visual magnitude of 8.81, it is too faint to be seen with the naked eye. The system is located at a distance of 239 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −33 km/s.
Gliese 179 is a small red dwarf star with an exoplanetary companion in the equatorial constellation of Orion. It is much too faint to be visible to the naked eye with an apparent visual magnitude of 11.94. The system is located at a distance of 40.5 light-years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of –9 km/s. It is a high proper motion star, traversing the celestial sphere at an angular rate of 0.370″·yr−1.
Gliese 221, also known as BD-06 1339, is a star with an exoplanetary companion in the equatorial constellation of Orion. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 9.70 and an absolute magnitude of 8.15. Using parallax measurements, the distance to this system can be estimated as 66.2 light-years. It is receding from the Sun with a radial velocity of +23 km/s. This is a high proper motion star, traversing the celestial sphere at an angular rate of 0.333″·yr−1.
Gliese 555 is a small star with one or more orbiting exoplanets in the constellation Libra. It has the variable star designation HN Librae, abbreviated HN Lib. With an apparent visual magnitude of 11.32, it can only be viewed through a telescope. The system is located at a distance of 20.4 light years based on parallax measurements, but is drifting closer to the Sun with a radial velocity of −1.4 km/s. It does not appear to belong to any known stellar moving group or association.
GJ 1151 is a star located in the northern circumpolar constellation of Ursa Major at a distance of 26.2 light-years from the Sun. It has a reddish hue and is too faint to be visible to the naked eye with an apparent visual magnitude of 14.0 The star is moving closer with a radial velocity of −36 km/s, and has a relatively large proper motion, traversing the celestial sphere at a rate of 1.815″·yr−1.
GJ 3293 is a star in the constellation of Eridanus, that is orbited by four planets, two of which are located within the star's habitable zone. It is located at the celestial coordinates: Right Ascension 04h 28m 35.71911s, Declination −25° 10′ 09.2979″. With an apparent visual magnitude of 11.96, this star is too faint to be seen with the naked eye. It can be viewed with a telescope having an aperture of at least 4 in (10 cm). The estimated distance to GJ 3293 is 65.9 light-years, based on its stellar parallax. GJ 3293 is significantly smaller and cooler than the Sun.
HD 189567 is a star with a pair of orbiting exoplanets, located in the southern constellation of Pavo. It is also known as Gliese 776, CD-67 2385, and HR 7644. The star has an apparent visual magnitude of 6.07, which is bright enough for it to be dimly visible to the naked eye. It lies at a distance of 58 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −10.5 km/s.
Gliese 328, also known as BD+02 2098, is a M-type main-sequence star located 66.9 light-years away in the constellation Hydra. Its surface temperature is 3989 K. Gliese 328 is depleted in heavy elements compared to the Sun, with a metallicity Fe/H index of −0.13. The age of the star is unknown. Gliese 328 exhibits an activity cycle similar to that of the Sun, with a period around 2000 d.
GJ 1002 is a nearby red dwarf star, located 15.8 light-years away from the Solar System in the constellation of Cetus. The star has 12% the mass and 14% the radius of the Sun, and a temperature of 3,024 K. It hosts a system of two known exoplanets.
Gliese 514, also known as BD+11 2576 or HIP 65859, is a M-type main-sequence star, in the constellation Virgo 24.85 light-years away from the Sun. The proximity of Gliese 514 to the Sun was known exactly since 1988.