Ursa Minor
844 OBJECTSUrsa Minor is a small northern constellation whose chief distinction is Polaris, the star that happens to sit within a degree of the north celestial pole. That makes it the one star that barely moves: everything else turns around it once a day, and its height above the horizon is your latitude. The job is temporary — the Earth's axis traces a circle over about 26,000 years, Thuban held the post when the pyramids were built, and Vega will hold it long after.
Ursa Minor holds 844 catalogued objects: 629 stars, 181 galaxies, 27 exoplanets, 6 neutron stars, 1 star cluster.
[
THE FAMOUS ONES
] 1 ENTRIESNAME
CLASS
MASS
DISTANCE
MAG
CONSTELLATION
Polaris★
F8Ib yellow-white supergiant
—
432.6 ly
1.97 V
Ursa Minor
[
BRIGHTEST OBJECTS
] 12 SHOWNNAME
CLASS
MASS
DISTANCE
MAG
CONSTELLATION
Polaris★
F8Ib yellow-white supergiant
—
432.6 ly
1.97 V
Ursa Minor
Kochab
K4-III orange giant
—
130.9 ly
2.07 V
Ursa Minor
Pherkad
A2III white giant
—
486.8 ly
3.00 V
Ursa Minor
22 ε UMi
G5III yellow giant
—
304.0 ly
4.21 V
Ursa Minor
5 UMi
K4-III orange giant
—
358.8 ly
4.25 V
Ursa Minor
16 ζ UMi
A3Vn white main-sequence star
—
369.0 ly
4.29 V
Ursa Minor
Yildun
A1Van white main-sequence star
~2.40 M☉
172.1 ly
4.35 V
Ursa Minor
RR UMi
M4.5III red giant
—
459.4 ly
4.63 V
Ursa Minor
4 UMi
K3-IIIbFe-0.5 orange giant
—
456.8 ly
4.80 V
Ursa Minor
21 η UMi
F5V yellow-white main-sequence star
~1.54 M☉
96.98 ly
4.95 V
Ursa Minor
15 θ UMi
K5-IIICN0.5 orange giant
—
856.1 ly
5.00 V
Ursa Minor
11 UMi
K4III orange giant
—
398.2 ly
5.02 V
Ursa Minor
[
COMMON QUESTIONS
] 9 ANSWERED- How do I find Polaris?
- Follow the two stars at the end of the Plough's bowl away from the handle, about five times the gap between them. Polaris is not especially bright — it is the fiftieth-brightest star in the sky — and it is the one that stays put while everything around it turns.
- Where in the sky is Ursa Minor?
- Its boundary is centred near right ascension 15h 06m, declination +82.0°. It stands at its highest around midnight in earlyMay, which puts it in the evening sky for the two months after that and behind the Sun half a year later.
- Can I see it from where I live?
- Every part of Ursa Minor clears the horizon from latitudes between the equator and the north pole. Outside that band some or all of the region never rises at all, whatever the time of year — a constellation is fixed on the sky, and it is your latitude that decides how much of the sky you get.
- What is the brightest thing in it?
- The brightest catalogued object in Ursa Minor is Polaris, at apparent magnitude 1.97 (V). That is apparent brightness — how it looks from Earth — so it mixes how much light a thing gives off with how far away it is, and the brightest object in a region is rarely the most interesting one.
- How are the stars in it named?
- The brightest carry Greek letters, assigned by Johann Bayer in 1603 roughly in order of brightness and followed by the Latin genitive of the constellation's name. Fainter stars take a number from John Flamsteed's catalogue, and fainter still a designation from whichever survey recorded them.
- What exactly are the boundaries?
- Lines of constant right ascension and declination, drawn by Eugène Delporte for the IAU in 1930 and referred to the sky as it stood in 1875. Precession has tilted the sky against them since, which is why the boundaries on a modern chart are very slightly askew.
- Are the stars in Ursa Minor actually near each other?
- Almost never. The stars in a constellation lie at wildly different distances and are not related to one another in any way — the pattern is a line of sight from one particular planet. Two stars that look adjacent can be a hundred times further apart than either is from the Sun.
- What is the difference between a constellation and an asterism?
- A constellation is one of the 88 regions the IAU recognises, with a fixed boundary and an official name. An asterism is any memorable pattern that is not one — the Plough inside Ursa Major, the Summer Triangle drawn across three constellations, the Great Square shared between two.
- Why are the names in Latin?
- Because the list was assembled in Latin. Forty-eight of them come down from Ptolemy's catalogue of the second century, and the other forty were coined between the sixteenth and eighteenth centuries to fill the southern sky and the gaps. The genitive form is what star names use: Alpha Orionis means the alpha star of Orion.