Gliese 832 (Gl 832 or GJ 832) is a

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

star of

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

M2V in the southern

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 first constellati ...

Grus. The

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...

of 8.66 means that it is too faint to be seen with the naked eye. It is located relatively close to the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, at a distance of 16.2

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s and has a high

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

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. This star achieved

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

some 52,920 years ago when it came within an estimated of the Sun. Gliese 832 emits X-rays. Despite the strong flare activity, Gliese 832 is producing on average less ionizing radiation than the Sun. Only at extremely short radiation wavelengths (<50nm) does its radiation intensity rise above the level of the quiet Sun, but does not reach levels typical for the active Sun.

Planetary system

Gliese 832 hosts one known planet, with a second planet having been refuted in 2022. No additional planets were found as of 2024.

Gliese 832 b

In September 2008, it was announced that a

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 Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

-like planet, designated Gliese 832 b, had been detected in a long-period, near-circular orbit around this star, with a false alarm probability of a negligible 0.05%. It would induce an

astrometric 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. History ...

perturbation on its star of at least 0.95

milliarcsecond A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of Angular unit, angular measurement equal to of a Degree (angle), degree. Since one degree is of a turn (geometry), turn, or ...

s and is thus a good candidate for being detected by astrometric observations. Despite its relatively large angular distance, direct imaging is problematic due to the star–planet contrast. The planet was detected astrometrically by two different 2023 studies, determining its inclination and revealing a

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

close to the mass of Jupiter.

Gliese 832 c

Gliese 832 c was the second reported planet in the Gliese 832 system, believed to be of

super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...

mass (

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

about 5 times the mass of Earth). It was announced to orbit in the optimistic

habitable zone In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...

but outside the conservative habitable zone of its parent star. The planet Gliese 832 c was believed to be in, or very close to, the right distance from its sun to allow liquid water to exist on its surface. However, doubts were raised about the existence of planet c by a 2015 study, which found that its orbital period is close to the stellar rotation period. The existence of the planet was refuted in 2022, when a study found that the

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

signal shows characteristics of a signal originating from stellar activity, and not from a planet.

Limits on additional planets

A 2016 study found that additional planets are possible in the region between the two planets thought to exist at the time, in particular planets less than 15

Earth mass An Earth mass (denoted as ''M''🜨, ''M''♁ or ''M''E, where 🜨 and ♁ are the astronomical symbols for Earth), is a unit of mass equal to the mass of the planet Earth. The current best estimate for the mass of Earth is , with a relative ...

es orbiting between 0.25-2.0 AU. As of 2024, no additional planets had been found and Gliese 832 b remains the only known planet in the system. The radial velocity data sets an upper limit of 1.5 Earth masses on any undetected planet with a period up to 100 days.

Search for cometary disc

If this system has a comet disc, it is not "brighter than the fractional dust luminosity 10⁻⁵" according to a 2012 Herschel study.

Notes

References

{{DEFAULTSORT:Gliese 832 Local Bubble M-type main-sequence stars Grus (constellation) Planetary systems with one confirmed planet Astronomical X-ray sources CD-49 13515 0832 204961 106440 J21333397-4900323 139754153