Alpha Pavonis (α Pavonis, abbreviated Alpha Pav, α Pav), formally named Peacock , is a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in ...

in the southern constellation of Pavo, near the border with the constellation Telescopium.

Nomenclature

''α Pavonis'' ( Latinised to ''Alpha Pavonis'') is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

. The historical name ''Peacock'' was assigned by His Majesty's Nautical Almanac Office in the late 1930s during the creation of the Air Almanac, a navigational almanac for the

Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...

. Of the fifty-seven stars included in the new almanac, two had no classical names: Alpha Pavonis and Epsilon Carinae. The RAF insisted that all of the stars must have names, so new names were invented. Alpha Pavonis was named "Peacock" ('pavo' is Latin for 'peacock') whilst Epsilon Carinae was called "Avior". In 2016, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

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 List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Peacock'' for this star and ''Avior'' for Epsilon Carinae. In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, (), meaning ''

Peacock Peafowl is a common name for three bird species in the genera ''Pavo (genus), Pavo'' and ''Afropavo'' within the tribe Pavonini of the family Phasianidae, the pheasants and their allies. Male peafowl are referred to as peacocks, and female pea ...

'', refers to an asterism consisting of α Pavonis, η Pavonis, π Pavonis, ν Pavonis, λ Pavonis, κ Pavonis, δ Pavonis, β Pavonis, ζ Pavonis, ε Pavonis and γ Pavonis. Consequently, α Pavonis itself is known as (, en, the Eleventh Star of Peacock.)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 30 日
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Properties

At an apparent magnitude of 1.94, this is the brightest star in Pavo. 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 object ...

measurements, this star is about distant from the

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 surf ...

. It has an estimated six times the

Sun's mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of ...

and 6 times the Sun's radius, but 2,200 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 nomin ...

. 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

photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...

is 17,700 K, which gives the star a blue-white hue. It has a

stellar classification 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 t ...

of B3 V, although older studies have often given it a

subgiant 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 ...

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 th ...

. It is classified as B2.5 IV in the Bright Star Catalogue. Stars with the mass of Alpha Pavonis are believed not to have a convection zone near their surface. Hence the material found in the outer atmosphere is not processed by the

nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifest ...

occurring at the core. This means that the surface abundance of elements should be representative of the material out of which it originally formed. In particular, the surface abundance of

deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...

should not change during the star's main sequence lifetime. The measured ratio of deuterium to hydrogen in this star amounts to less than , which suggests this star may have formed in a region with an unusually low abundance of deuterium, or else the deuterium was consumed by some means. A possible scenario for the latter is that the deuterium was burned through while Alpha Pavonis was a

pre-main-sequence star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope o ...

. The system is likely to be a member of the

Tucana-Horologium association The Tucana-Horologium association (Tuc-Hor), or Tucana Horologium moving group, is a stellar association with an age of 45 ± 4 Myr and it is one of the largest stellar associations within . The association has a similar size to the Beta Pictoris m ...

that share a common motion through space. The estimated age of this association is 45 million years. α Pavonis star has a

peculiar velocity Peculiar motion or peculiar velocity refers to the velocity of an object relative to a '' rest frame'' — usually a frame in which the average velocity of some objects is zero. Galactic astronomy In galactic astronomy, peculiar motion refers ...

of relative to its neighbors.

Companions

Three stars have been listed as visual companions to α Pavonis: two ninth magnitude stars at about four arc minutes; and a 12th magnitude F5 main sequence star at about one arc minute. The two ninth magnitude companions are only 17 arc seconds from each other. α Pavonis A is a spectroscopic binary consisting of a pair of stars that orbit around each other with a period of 11.753 days. However, in part because the two stars have not been individually resolved, little is known about the companion except that it has a mass of at least . One attempt to model a composite

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 color ...

estimated components with spectral types of B0.5 and B2, and a brightness difference between the two components of 1.3 magnitudes.

References

External links

Peacock
- Jim Kaler's Stars {{DEFAULTSORT:Alpha Pavonis Pavonis, Alpha B-type subgiants 193924 100751 7790 Pavo (constellation) Spectroscopic binaries

Durchmusterung objects