Rho Boötis, Latinised from ρ Boötis, is a single, orange-hued star in the northern constellation of Boötes. It is visible to the naked eye with an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of 3.59. Based upon parallax measurements, it is located at a distance of 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 is moving toward the Sun with a radial velocity of −13.6 km/s. There is an optical companion, a magnitude 11.5 star, located 34.7 arcseconds away along a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the ...

of 345° (as of 2013). This is an

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

K-type

giant star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

, currently on the

red-giant branch The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass sta ...

, with a stellar classification of K4 III and an estimated age of 10 billion years. Since 1943, the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...

of this star has served as one of the stable anchor points by which other stars are classified. It has around 1.2 times the mass of the Sun and has expanded to 22 times the Sun's girth. The star is radiating 132 times the

Sun's luminosity 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 ...

from its enlarged photosphere at an effective temperature of about . Rho Boötis is classified as a

RS Canum Venaticorum variable An RS Canum Venaticorum variable is a type of variable star. The variable type consists of close binary stars having active chromospheres which can cause large stellar spots. These spots are believed to cause variations in their observed luminosi ...

. Koen and Eyer examined the Hipparcos data for this star, and found that it varied with a period of 5.214 days, and an amplitude of 0.0027 magnitudes.

Nomenclature

Rho Boötis is known by several different names, including ρ Boo, 25 Boötis, BD+31° 2628,

FK5 The Catalogue of Fundamental Stars is a series of six astrometric catalogues of high precision positional data for a small selection of stars to define a celestial reference frame, which is a standard coordinate system for measuring positions of s ...

534, HD 127665, HIP 71053, HR 5429, and

SAO SAO or Sao may refer to: Places * Sao civilisation, in Middle Africa from 6th century BC to 16th century AD * Sao, a town in Boussé Department, Burkina Faso * Saco Transportation Center (station code SAO), a train station in Saco, Maine, U.S. ...

64202. In

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...

, (), meaning '' Celestial Lance'', refers to an asterism consisting of ρ Boötis, ε Boötis and σ Boötis. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are ofte ...

for ρ Boötis itself is (, en, the Third Star of Celestial Lance).

References

{{DEFAULTSORT:Rho Bootis Rho Bootis A Gěng Hé sān Suspected variables Bootis, Rho Boötes Durchmusterung objects Bootis, 25 127665 071053 5429