Lambda Boötis is a

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

in the northern

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 ...

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 ...

. Its name is a

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

that is Latinized from λ Boötis, and abbreviated Lam Boo or λ Boo. It has the official name Xuange, pronounced . With an

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 +4.18, it is faintly visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

. 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, it is distant from Earth. This star is drifting closer to the Sun with a

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 −8 km/s. LamBooLightCurve

This is a white hued

A-type main-sequence star An A-type main-sequence star (A) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

with 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 gratin ...

of A0p λB. It is the prototype of a group of rare stars known as

Lambda Boötis star Lambda (; uppercase , lowercase ; , ''lám(b)da'') is the eleventh letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoeni ...

s, all of which are dwarf stars with unusually low abundances of

metals A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against no ...

in their spectra. Its diameter has been directly measured to be 1.7 times that of the Sun. This is a

Delta Scuti variable A Delta Scuti variable (sometimes termed dwarf cepheid when the V-band amplitude is larger than 0.3 mag.) is a class of pulsating star, comprising several sub-classes of object with A- or F-type spectra. The variables follow a period-luminosity ...

star with a period of and an amplitude of 0.0020 in visual magnitude. This star displays an

infrared excess An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are of ...

that may be the result of a

circumstellar disk A Circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the res ...

of orbiting debris, or else a bow wave from its motion through the

interstellar medium The interstellar medium (ISM) is the matter and radiation that exists in the outer space, space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as cosmic dust, dust and cosmic rays. It f ...

Nomenclature

''λ Boötis'' ( Latinised to ''Lambda Boötis'') is the star's

. In

Chinese astronomy Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The Ancient China, ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categori ...

, Lambda Boötis is called 玄戈,

Pinyin Hanyu Pinyin, or simply pinyin, officially the Chinese Phonetic Alphabet, is the most common romanization system for Standard Chinese. ''Hanyu'' () literally means 'Han Chinese, Han language'—that is, the Chinese language—while ''pinyin' ...

: ''Xuángē'', meaning 'sombre lance', because this star is marking itself and standing alone in the ''Sombre Lance'' asterism,

Purple Forbidden enclosure The Purple Forbidden enclosure ( Zǐ wēi yuán) is one of the San Yuan ( Sān yuán) or Three Enclosures. Stars and constellations of this group lie near the north celestial pole and are visible all year from temperate latitudes in the Northern ...

(see :

Chinese constellations Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" ( Chinese ''xīng guān''). The Chinese asterisms are generally smaller than the constellations of Hellenisti ...

). 玄戈 (''Xuángē'')

westernized Westernization (or Westernisation, see spelling differences), also Europeanisation or occidentalization (from the ''Occident''), is a process whereby societies come under or adopt what is considered to be Western culture, in areas such as industry, ...

into ''Heuen Ko'', but that name was assigned to

Gamma Boötis Gamma Boötis is a binary star system in the northern constellation of Boötes the herdsman, forming the left shoulder of this asterism. Its name is a Bayer designation that is Latinised from γ Boötis, and abbreviated Gamma Boo or � ...

by R. H. Allen, with the meaning of 'the heavenly spear'. In 2016, the

IAU 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 ...

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalog and standardize proper names for stars. The WGSN approved the name ''Xuange'' for Lambda Boötis on 30 June 2017 and it is now so included in the List of IAU-approved Star Names. This star, along with the ''Aselli'' (

Theta Boötis Theta Boötis is a star in the northern constellation of Boötes the herdsman, forming a corner of the upraised left hand of this asterism. Its name is a Bayer designation that is Latinized from θ Boötis, and abbreviated Theta Boo or ...

Iota Boötis Iota Boötis is a wide binary star system in the constellation Boötes, approximately 96 light-years from Earth. Its name is a Bayer designation that is Romanization of Greek, Latinized from ι Boötis, and abbreviated Iota Boo or ι Boo. ...

and

Kappa Boötis Kappa Boötis is a double star in the constellation Boötes. Its name is a Bayer designation that is Romanization of Greek, Latinized from κ Boötis, and abbreviated Kappa Boo or κ Boo. This star has the traditional name Asellus Tertius ...

), were ''Al Aulād al Dhiʼbah'' (ألعولد ألذعب - ''al aulād al dhiʼb''), "the Whelps of the Hyenas". ''Al Aulād al Dhiʼbah'' or ''Aulad al Thiba'' was the title of this star in a 1971

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

memorandum.

References

External links

* * {{DEFAULTSORT:Lambda Bootis A-type main-sequence stars Lambda Boötis stars Delta Scuti variables Circumstellar disks Boötes Bootis, Lambda 5351 BD+46 1949 Bootis, 19 3837 125162 069732 Xuange