UMi · Ursae Minoris
Ursa Minor Constellation
IAU constellation mapUMiUrsa Minor (UMi) is one of the 88 constellations recognised by the International Astronomical Union. It covers 256 square degrees of the northern sky in quadrant NQ3. Its brightest star is Polaris. The Latin genitive of the name is Ursae Minoris, used to form star names within the constellation. In Greek mythology, Ursa Minor is associated with greek tradition. The IAU standardised all constellation boundaries in 1930.
Quick facts
- IAU name
- Ursa Minor
- Abbreviation
- UMi
- Latin genitive
- Ursae Minoris
- Hemisphere
- northern
- Area
- 256 sq deg
- Brightest star
- Polaris
- Quadrant
- NQ3
- Family
- Ursa Major
- Mythology origin
- Greek
- Discovery era
- Ptolemy's 48 (Almagest, c. 150 CE)
Mythology
Ursa Minor, the Little Bear, contains Polaris — the North Star — at the tip of its tail. Polaris lies within about 1 degree of the north celestial pole and has served as a navigational fixed point for sailors and travellers in the northern hemisphere for centuries, allowing determination of geographic latitude and the approximate direction of true north. In Greek mythology Ursa Minor is identified with Arcas, the son of Callisto and Zeus, who was transformed into a bear and placed in the sky alongside his mother (Ursa Major). Alternatively, some sources identify it with one of the bear-nurses of the infant Zeus, who suckled him in the cave on Mount Ida on Crete while Rhea hid him from his father Cronus. The seven main stars of Ursa Minor form an asterism sometimes called the Little Dipper. Polaris (Alpha Ursae Minoris) is currently a yellow supergiant about 433 light-years away and the closest Cepheid variable to Earth. Due to the precession of the equinoxes, the celestial pole traces a circle over a period of about 25,772 years (the Platonic year), so different stars serve as pole stars at different epochs: Thuban in Draco was the pole star around 2700 BCE, and Vega in Lyra will be the pole star around 13,800 CE.
Sources: Aratus Phaenomena 26-36; Hyginus Astronomica 2.2; Apollodorus Bibliotheca 3.8.2.
Overview
Ursa Minor is one of the 88 constellations formally recognised by the International Astronomical Union (IAU). It occupies 256 square degrees of sky in the northern hemisphere sky, best visible at latitudes between +90 and -60 degrees in June. The constellation belongs to the Ursa Major family of constellations. Its Latin genitive is Ursae Minoris, the form used when naming stars within the constellation — for example, the brightest star Polaris may appear in catalogues as Alpha Ursae Minoris or similar. The IAU standardised the boundaries of all 88 constellations in 1930 under the direction of Eugène Delporte, using straight lines of right ascension and declination to eliminate the ambiguities of earlier variable-boundary systems.
Notable stars
The brightest star in Ursa Minor is Polaris. Individual stars within Ursa Minor are conventionally named using Bayer designation — Greek letters followed by the Latin genitive of the constellation name (Ursae Minoris) — introduced by Johann Bayer in his 1603 star atlas Uranometria. Flamsteed numbers (numeric designators followed by Ursa Minor) were added by John Flamsteed in his 1712 catalogue. Variable stars, double stars, and deep-sky objects within the Ursa Minor boundary are catalogued by the IAU with the abbreviation UMi.
History and mythology
The figure of Ursa Minor appears in the classical astronomical tradition. Ptolemy included this constellation in the Almagest (c. 150 CE), the definitive ancient catalogue of 48 constellations, which formed the foundation for Islamic, medieval European, and Renaissance astronomy. The constellation's figure and mythology were transmitted through works such as Aratus's Phaenomena, Eratosthenes's Catasterismi, and Hyginus's Astronomica. See the Mythology section above for the full narrative.
Sources & further reading (2)
- official-iau — accessed 2026-05-06
- encyclopedia — accessed 2026-05-06
Frequently asked questions
What does the name Ursa Minor mean?
Ursa Minor is the Latin name used by the IAU to designate this constellation. The name comes from classical Latin and Greek astronomical tradition. In star catalogues, stars within Ursa Minor are designated using the genitive form of the name (e.g. Alpha Ursa Minor or similar Latin genitive forms) — a naming convention introduced by Johann Bayer in his 1603 atlas Uranometria and still in use today.
How large is Ursa Minor compared to other constellations?
Ursa Minor covers 256 square degrees of sky. The full sphere of the sky contains 41,253 square degrees, so Ursa Minor occupies about 0.6% of the total sky. For comparison, the largest constellation is Hydra at 1303 square degrees; the smallest is Crux at 68 square degrees.
When and where is Ursa Minor visible?
Ursa Minor is primarily a northern hemisphere constellation, best seen from mid-northern latitudes. Southern hemisphere observers may see it low on the horizon depending on their latitude. The brightest star, Polaris, serves as the main visual anchor for locating the constellation. As with all constellations, the best viewing conditions are a dark sky away from artificial light pollution, with the constellation high enough above the horizon to minimise atmospheric absorption.
