Chi Virginis (χ Vir, χ Virginis) is a

double star In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a bi ...

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 ...

Virgo Virgo may refer to: *Virgo (astrology), the sixth astrological sign of the zodiac *Virgo (constellation), a constellation *Virgo Cluster, a cluster of galaxies in the constellation Virgo *Virgo Stellar Stream, remains of a dwarf galaxy *Virgo Supe ...

. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measurements, it is approximately from

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 ...

. It has an apparent visual magnitude of 4.65, which is bright enough to be seen with the unaided eye under suitable viewing conditions. This star has a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of K2 III, with the

luminosity class 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 ...

"III" indicating that this is a

giant star A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moo ...

that has consumed the hydrogen at its core and evolved away from the

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

. It has a mass about double that of the Sun and has expanded to 23 times the Sun's radius, giving it a luminosity of 182 times the

luminosity of the Sun The solar luminosity (), is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal s ...

. The

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of the star's outer envelope is about 4,395 K, which gives the star the orange hue typical of K-type stars. The abundance of elements other than hydrogen and helium, what astronomers term the star's

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

, is slightly higher than in the Sun. This star has three optical companions. At an angular separation of 173.1

arcsecond A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

s is a magnitude +9.1 star, which is of

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

K0. A 10th magnitude star is located 221.2 arcseconds away, and the third is a magnitude +9.1 K2 star 321.2 arcseconds away. None of these have been confirmed as a physical companion.

Planetary system

In July 2009, it was discovered that Chi Virginis has a massive planet with a high

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

of 0.46. It is orbiting with a period of about 835 days and has a mass at least 11 times greater 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 ...

. There are indications of a second planet orbiting with a period of 130 days, but this has not been firmly established. In May 2015, the existence of a second planet candidate, , (Chi Virginis c, about three times the mass of Jupiter and having an orbit roughly that of Venus) was announced by Chilean astronomer

Maritza Soto Maritza Soto Vásquez (born 1990) is a Chilean astronomer who discovered the exoplanets , K2-237b, and K2-238b. Career On 19 August 2015, Soto confirmed the existence of exoplanet . From La Silla Observatory, she discovered a planet 293 light ...

. The two-planet model could not be confirmed, and 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 ...

variations attributed to the second planet might instead be caused by a

starspot Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in gene ...

. A 2021 review of planets around giant stars lists this second planet as "questionable".

References

{{DEFAULTSORT:Chi Virginis Virginis, Chi Virginis, 026 Virgo (constellation) K-type giants 110014 061740 4813 BD-07 3452 Planetary systems with two confirmed planets

Planetary system

See also

References