Gliese 676

Last updated
Gliese 676 A/B
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Ara
Right ascension 17h 30m 11.20s [1]
Declination –51° 38′ 13.1″ [1]
Apparent magnitude  (V)9.59
Characteristics
Spectral type M0V [2] /M3V
Apparent magnitude  (B)11.05/14.8
Apparent magnitude  (J)6.711
Apparent magnitude  (H)6.082
Apparent magnitude  (K)5.825
B−V color index 1.46
Astrometry
Radial velocity (Rv)−39.82±0.14 [3]  km/s
Proper motion (μ)RA: −258.759±0.034 [3]   mas/yr
Dec.: −185.119±0.025 [3]   mas/yr
Parallax (π)62.5786 ± 0.0303  mas [3]
Distance 52.12 ± 0.03  ly
(15.980 ± 0.008  pc)
Absolute magnitude  (MV)8.55
Details
Mass 0.631±0.017 [4] /0.29 [5]   M☉
Radius 0.617+0.028
−0.027 [4]   R☉
Luminosity 0.08892±0.00220 [4]   L☉
Temperature 4,014+94
−90 [4]   K
Metallicity [Fe/H]0.23±0.10 [5]   dex
Rotation 41.2±3.8 d [2]
Other designations
CD–51°10924, HIP 85647, LTT 6947/6948, NLTT 44859, NSV 8846
Database references
SIMBAD data
Exoplanet Archive data

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. [6] 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.

Contents

Planetary system

The first planet discovered, b, is a super-jovian first characterised in October 2009. The planet was formally announced in 2011, [5] along with the first recognition of a trend not attributable to the companion star. Even after fitting a planet and a trend, it was noted that the residual velocities were still around 3.4 m/s, significantly larger than the instrumental errors of around 1.7 m/s. This tentatively implied the existence of other bodies in orbit, though nothing more could be said at the time. [5]

The star was a test case for the HARPS-TERRA software for better reduction of data from the HARPS spectrometer in early 2012. [7] Even with significantly lower margins of error on the data, less data was accessible than what was used in 2011. Still, the team reached a very similar conclusion to the previous team with a model of a planet and a trend. The residual velocities were still somewhat excessive, giving more weight to the existence of other bodies in the system, though still no conclusions could be made.

Between the time of the previous analysis and June 2012, the rest of the radial-velocity measurements used in 2011 were made public, [6] allowing them to be reduced using HARPS-TERRA. These were then analysed via a Bayesian probability analysis, which was previously used to discover HD 10180 i and j, which confirmed planet b and made a first characterisation of planet c, [8] which was previously only described as a trend. After the first two signals were introduced, the next most powerful signal was at around 35.5 days, with an analytic false alarm probability of 0.156. Through 104 trials, the false alarm probability was found to be 0.44%, low enough for it to be included as a periodic, planetary signal. With a minimum mass of around 11 Earths, the planet lies at the accepted border between Super-Earths and gaseous, Neptune-like bodies of 10 Earths. After accepting the third signal, a strong peak at 3.6 days became apparent. With a false alarm probability much lower than that of the previously accepted body, it was immediately accepted. With a minimum mass of around 4.5 Earths, it is a small Super-Earth.

As of 2012, this system holds the record for the widest range of masses in a single planetary system, [6] and also shows a hierarchy reminiscent of the solar system, with the gas giants at large distances from the star while the smaller bodies are much closer-in.

In 2016, the true mass of Gliese 676 Ab was measured via astrometry. [8] A 2022 study revised this mass estimate, along with measuring the true mass of Gliese 676 Ac. [9] There are two Super-Jupiter planets: "b" with a period of 1051 days (2.9 years) and a mass of 5.79  MJ, and "c" with a period of 13900 days (38.1 years) and a mass of 13.49  MJ, which is at the borderline between planets and brown dwarfs. [9]

The Gliese 676 A planetary system [6] [8] [9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
d≥4.4±0.3  M🜨 0.0413±0.00143.6005±0.00020.262+0.090
−0.101		——
e≥8.1±0.7  M🜨 0.187±0.00735.39+0.03
−0.04		0.125+0.119
−0.087		——
b5.792+0.469
−0.477  MJ 		1.735+0.056
−0.060		1051.4±0.40.319±0.00348.919+3.312
−2.781 ° 		—
c13.492+1.046
−1.127  MJ 		9.726+0.629
−0.793		13921.4+1238.4
−1518.2		0.295+0.033
−0.049		33.690+1.362
−1.324 ° 		—

See also

Related Research Articles

<span class="mw-page-title-main">Gliese 876</span> Star in the constellation Aquarius

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.

Gliese 777, often abbreviated as Gl 777 or GJ 777, is a binary star 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, two extrasolar planets are known to orbit the primary star.

<span class="mw-page-title-main">Gliese 667</span> Triple star system in the constellation Scorpius

Gliese 667 is a triple-star system in the constellation Scorpius lying at a distance of about 7.2 parsecs from Earth. All three of the stars have masses smaller than the Sun. There is a 12th-magnitude star close to the other three, but it is not gravitationally bound to the system. To the naked eye, the system appears to be a single faint star of magnitude 5.89.

<span class="mw-page-title-main">Gliese 581d</span> Contested super-Earth orbiting Gliese 581

Gliese 581d is a doubtful, and frequently disputed, exoplanet candidate orbiting within the Gliese 581 system, approximately 20.4 light-years away in the Libra constellation. It was the third planet claimed in the system and the fourth or fifth in order from the star. Multiple subsequent studies found that the planetary signal in fact originates from stellar activity, and thus the planet does not exist, but this remains disputed.

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 832 is a red dwarf of spectral type M2V in the southern constellation Grus. The apparent visual magnitude of 8.66 means that it is too faint to be seen with the naked eye. It is located relatively close to the Sun, at a distance of 16.2 light years and has a high proper motion of 818.16 milliarcseconds per year. Gliese 832 has just under half the mass and radius of the Sun. Its estimated rotation period is a relatively leisurely 46 days. The star is roughly 6 billion years old.

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.

<span class="mw-page-title-main">Gliese 581e</span> Terrestrial planet orbiting Gliese 581

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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.

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.

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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.

References

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  7. ↑ Anglada-Escudé, Guillem; Butler, R. Paul (2012). "The HARPS-TERRA Project. I. Description of the Algorithms, Performance, and New Measurements on a Few Remarkable Stars Observed by HARPS". The Astrophysical Journal Supplement Series. 200 (2): 15. arXiv: 1202.2570 . Bibcode:2012ApJS..200...15A. doi:10.1088/0067-0049/200/2/15. S2CID   118528839.
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