Zeta Pegasi or ζ Pegasi, formally named Homam (), is a single

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

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 origins of the e ...

Pegasus Pegasus ( grc-gre, Πήγασος, Pḗgasos; la, Pegasus, Pegasos) is one of the best known creatures in Greek mythology. He is a winged divine stallion usually depicted as pure white in color. He was sired by Poseidon, in his role as hor ...

. With an apparent visual magnitude of +3.4, this star is bright enough to be seen with the naked eye and is one of the brighter members of Pegasus.

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 place it at a distance of around from the Sun.

Nomenclature

''ζ Pegasi'' ( Latinised to ''Zeta Pegasi'') 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. ...

. It bore the traditional name ''Homam'', meaning "Man of High Spirit" or "Lucky Star of High Minded". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name ''Homam'' for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names. 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 va ...

, (), meaning '' Thunder and Lightning'', refers to an asterism consisting ζ Pegasi, ξ Pegasi, σ Pegasi, 55 Pegasi, 66 Pegasi and 70 Pegasi. Consequently, the Chinese name for ζ Pegasi itself is (), "the First Star of Thunder and Lightning".

Properties

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 B8 V, which identifies it as a large B-type main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. The radius of this star is about four times that of the Sun. It is a

slowly pulsating B star A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are main-sequence stars of spectral type B2 ...

that varies slightly in luminosity with a period of hours, completing 1.04566 cycles per day. Zeta Pegasi is about 120 million years old and is rotating rapidly with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

in the range of . 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 its outer envelope is around , giving it the characteristic blue-white glow of a B-type star. Zeta Pegasi has been examined for infrared excess that may indicate the presence of circumstellar matter, but none was found. This star does have two optical companions. The first is a magnitude 11.6 star at an

angular separation Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

of along a position angle of 139°, as of 1997. The second is an 11th magnitude star at a separation of with a position angle of 5°. Zeta Pegasi is not known to be a member of a

stellar association A stellar association is a very loose star cluster, looser than both open clusters and globular clusters. Stellar associations will normally contain from 10 to 100 or more stars. The stars share a common origin, but have become gravitationally u ...

References

{{DEFAULTSORT:Zeta Pegasi B-type main-sequence stars Slowly pulsating B stars Pegasus (constellation) Pegasi, Zeta Durchmusterung objects Pegasi, 42 214923 112029 8634 Homam