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Zeta Ursae Minoris, which is Latinized from ζ Ursae Minoris, is a single 
The stellar classification of Zeta UMi is A3Vn, a notation that indicates this is an A-type main-sequence star with broad "nebulous" absorption lines in its stellar spectrum, spectrum due to rapid rotation. Based on Photometry (astronomy), photometric data, some light variable star, variability was suspected by Robert Horace Baker, R. A. Baker in 1926, and it may be a Delta Scuti variable. It is a pulsating variable star, with a period of 15.8 hours, and it also undergoes eclipsing binary, eclipses. The star is spinning with a projected rotational velocity of 210 km/s, which is creating an equatorial bulge that is estimated to be 10% larger than the polar radius.
Zeta Ursae Minoris is about 180 million years old with 6.15 times the radius of the Sun. It is radiating 227 times the luminosity of the Sun from its photosphere at an effective temperature of 8,720 K. This anomalously high temperature and an absolute magnitude of –0.98 may indicate it is on the verge of stellar evolution, evolving into a giant star. An infrared excess has been detected from an orbiting circumstellar disk. A black body fit to the data yields a mean dust temperature of 160 K and an orbital radius of .
In some Arabic star charts it is listed as أخفى الفرقدين ''ʼakhfā al-farqadayn'', meaning "the dimmer of the two calves", and paired with η Ursae Minoris as ''ʼanwar al-farqadayn'', "the brighter of the two calves". The names may originally refer to a pair of Ibexes, and are more properly applied to γ UMi and β UMi, respectively, the brighter two stars in the rectangle of Ursa Minor.
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 circumpolar constellation
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest po ...
of Ursa Minor
Ursa Minor (Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, h ...
, forming the northernmost part of the bowl in this "little dipper" asterism. The star has a white hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.28. It is located at a distance of approximately 369 light-year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s from the Sun based on 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 ...
, but is drifting further closer with a radial velocity
The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...
of about –13 km/s.
The stellar classification of Zeta UMi is A3Vn, a notation that indicates this is an A-type main-sequence star with broad "nebulous" absorption lines in its stellar spectrum, spectrum due to rapid rotation. Based on Photometry (astronomy), photometric data, some light variable star, variability was suspected by Robert Horace Baker, R. A. Baker in 1926, and it may be a Delta Scuti variable. It is a pulsating variable star, with a period of 15.8 hours, and it also undergoes eclipsing binary, eclipses. The star is spinning with a projected rotational velocity of 210 km/s, which is creating an equatorial bulge that is estimated to be 10% larger than the polar radius.
Zeta Ursae Minoris is about 180 million years old with 6.15 times the radius of the Sun. It is radiating 227 times the luminosity of the Sun from its photosphere at an effective temperature of 8,720 K. This anomalously high temperature and an absolute magnitude of –0.98 may indicate it is on the verge of stellar evolution, evolving into a giant star. An infrared excess has been detected from an orbiting circumstellar disk. A black body fit to the data yields a mean dust temperature of 160 K and an orbital radius of .
In some Arabic star charts it is listed as أخفى الفرقدين ''ʼakhfā al-farqadayn'', meaning "the dimmer of the two calves", and paired with η Ursae Minoris as ''ʼanwar al-farqadayn'', "the brighter of the two calves". The names may originally refer to a pair of Ibexes, and are more properly applied to γ UMi and β UMi, respectively, the brighter two stars in the rectangle of Ursa Minor.
References
{{DEFAULTSORT:Zeta Ursae Minoris A-type main-sequence stars Delta Scuti variables Suspected variables Circumstellar disks Ursa Minor (constellation) Bayer objects, Ursae Minoris, Zeta Durchmusterung objects Flamsteed objects, Ursae Minoris, 16 Hipparcos objects, 077055 Bright Star Catalogue objects, 5903 Henry Draper Catalogue objects, 142105