HD 131496 is an

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

subgiant star A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

with an orbiting

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

in the constellation

Boötes Boötes ( ) is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from , which comes from 'herder, herdsman' or 'plowman' (literally, 'o ...

. With an apparent visual magnitude of 7.9 it is too faint to be visible to the naked eye. It is located at a distance of 432

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 based on

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

measurements, and is drifting further away with a heliocentric

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 ...

of 1.4 km/s. At an age of around three billion years, this star has 1.6 times the mass of the Sun and has expanded to 4.3 times the Sun's radius. It is radiating around ten times the luminosity of the Sun from its

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

at an

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 4,927 K. Stars like HD 131496 are sometimes referred to as "retired A-stars", since they would have been

A-type star A type or type A may refer to: Science * A-type asteroid, a type of relatively uncommon inner-belt asteroids * A type blood, a type in the ABO blood group system * A-type inclusion, a type of cell inclusion * A-type potassium channel, a type of ...

s while on the

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

. This name is most commonly used in connection with the search for

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detect ...

s, where they are useful because these evolved stars are cooler and have more

spectral line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission (electromagnetic radiation), emission or absorption (electromagnetic radiation), absorption of light in a narrow frequency ...

s than their main sequence counterparts, making planet detection easier. HD 131496 and its planet, HD 131496b, were chosen as part of the 2019

NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) were various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, notably exoplanets. The accepted names would later be cons ...

campaign organised by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

, which assigned each country a star and planet to be named. HD 131496 was assigned to

Andorra Andorra, officially the Principality of Andorra, is a Sovereignty, sovereign landlocked country on the Iberian Peninsula, in the eastern Pyrenees in Southwestern Europe, Andorra–France border, bordered by France to the north and Spain to A ...

. The winning proposal for the name of the star was Arcalís, after a mountain peak in northern Andorra where the Sun shines through a gap twice a year at fixed dates, leading to its use as a primitive Solar calendar. The planet was named Madriu, after a glacial valley and river in southeastern Andorra that forms the major part of the Madriu-Perafita-Claror

UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

Planetary system

An exoplanet was discovered in 2011. It has a mass at least 2.2 times that of Jupiter and is orbiting at a distance of 2.09

astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

s (AU) once every 883 days.

References

{{Stars of Boötes K-type subgiants Planetary systems with one confirmed planet Boötes Durchmusterung objects 131497 072845

Arcalís HD 131496 is an evolved subgiant star with an orbiting exoplanet in the constellation Boötes. With an apparent visual magnitude of 7.9 it is too faint to be visible to the naked eye. It is located at a distance of 432 light-years ba ...