Ursa Major

The constellation Ursa Major as it can be seen by the unaided eye.
Ursa Major and Ursa Minor in relation to Polaris
Ursa Major shown on a carved stone, c.1700, Crail, Fife
H. A. Rey's alternative asterism for Ursa Major can be said to give it the longer head and neck of a polar bear, as seen in this photo, from the left side.
Ursa Major as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.
Johannes Hevelius drew Ursa Major as if being viewed from outside the celestial sphere.
Starry Night Over the Rhone by Vincent van Gogh (1888)
Polaris and the Big Dipper on the flag of Alaska.

Constellation in the northern sky, whose associated mythology likely dates back into prehistory.

- Ursa Major

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Circumpolar star

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.

Northern circumpolar stars appearing to revolve around the north celestial pole. Note that Polaris, the bright star near the center, remains almost stationary in the sky. The north pole star is constantly above the horizon throughout the year, viewed from the Northern Hemisphere. (The graphic shows how the apparent positions of the stars move over a 24-hour period, but in practice, they are invisible in daylight, in which sunlight outshines them.)
Circumpolar star trails in a long-exposure photo of several hours. Note that the stars near the celestial pole leave shorter trails with the long exposure.
Circumpolar star trails captured with an extended exposure

Before the definition of the Arctic was formalized as the region north of the Arctic Circle which experiences the Midnight sun, it more broadly meant those places where the 'bear' constellations (Ursa Major, the Great Bear, and Ursa Minor, the Little Bear) were high in the sky.


Area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.

Babylonian tablet recording Halley's Comet in 164 BC.
Egyptian star chart and decanal clock, from the ceiling of Senenmut's tomb, c. 1473 BC
Chinese star map with a cylindrical projection (Su Song)
Sketch of the southern celestial sky by Portuguese astronomer João Faras (1 May 1500).
A celestial map from the Golden Age of Netherlandish cartography, by the Dutch cartographer Frederik de Wit
Ottoman period celestial map, signs of the Zodiac and lunar mansions.
Equirectangular plot of declination vs right ascension of stars brighter than apparent magnitude 5 on the Hipparcos Catalogue, coded by spectral type and apparent magnitude, relative to the modern constellations and the ecliptic.
The Emu in the sky – a constellation defined by dark clouds rather than by stars. The head of the emu is the Coalsack with the Southern Cross directly above. Scorpius is to the left.
Inca dark cloud constellations in the Mayu (Celestial River), also known as the Milky Way. The Southern Cross is above Yutu, while the eyes of the Llama are Alpha Centauri and Beta Centauri.

Another example is the northern asterism popularly known as the Big Dipper (US) or the Plough (UK), composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major.

Ursa Minor

Ursa Minor, with Draco looping around it, as depicted in Urania's Mirror, a set of constellation maps published in London c. 1825
The constellation Ursa Minor as it can be seen by the naked eye (with connections and label added). Notice the seven stars of Ursa Major that form the Big Dipper and then make a line from the outermost Big Dipper stars (sometimes called the "pointers") to Polaris.
Ursa Minor and Ursa Major in relation to Polaris
NGC 6217

Ursa Minor (Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation in the Northern Sky.


Constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere.

The constellation of Boötes overlaid on the ancient Egyptian foreleg constellation
Boötes as depicted in Urania's Mirror, a set of constellation cards published in London c.1825. In his left hand he holds his hunting dogs, Canes Venatici. Below them is the constellation Coma Berenices. Above the head of Boötes is Quadrans Muralis, now obsolete, but which lives on as the name of the early January Quadrantid meteor shower. Mons Mænalus can be seen at his feet.
The constellation Boötes as it can be seen by the naked eye
A digital rendering of Tau Boötis b
Evolution of the HD 128311 system over time
A Quadrantid captured by an all-sky camera during a 4-second exposure
A bright Quadrantid observed at twilight

According to one version, he was a son of Demeter, Philomenus, twin brother of Plutus, a plowman who drove the oxen in the constellation Ursa Major.

Proper motion

Astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars.

Relation between proper motion and velocity components of an object. A year ago the object was d units of distance from the Sun, and its light moved in a year by angle μ radian/s. If there has been no distortion by gravitational lensing or otherwise then μ = is the distance (usually expressed as annual velocity) transverse (tangential or perpendicular) to line of sight from the Sun. The angle is shaded light blue from the sun to the object's start point and its year later position as if it had no radial velocity. In this diagram the radial velocity happens to be one of the sun and object parting, so is positive.
The celestial north and south poles are above/below CNP, CSP; the origin of all 24 hours of Right Ascension (the measure of absolute celestial east–west position), the March equinox (center of the sun's position then) at the J2000 epoch, is vector V. In red the diagram adds the components of proper motion across the celestial sphere. An ideal time to measure exactly such a small annual shift is at culmination. The culmination of the star is daily reached when the observer (and earth) passes as shown by the blue arrows "beneath" the star. The positive axes of the two components of its usually annually measured or published shift in proper motion are the exaggerated red arrows, note: the right arrows point to the east horizon. One red annotation is subtly shorter as the cosine of a star resting at 0° declination is 1, so such a star's east or west shift would not need to be multiplied by the cosine of its declination. The proper motion vector is μ, α = right ascension, δ = declination, θ = position angle (simply the 90° compliment of declination).
Barnard's Star, showing position every 5 years 1985–2005.
Proper motion of 61 Cygni in one year intervals.

Ursa Major or Crux, for example, look nearly the same now as they did hundreds of years ago.

Double star

Pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes.

Astronomers have mistakenly reported observations of a double star in place of J 900 and a faint star in the constellation of Gemini.
Artist's impression of the discs around the young stars HK Tauri A and B.

Mizar, in Ursa Major, was observed to be double by Benedetto Castelli and Galileo.

Canes Venatici

One of the 88 constellations designated by the International Astronomical Union .

Canes Venatici as depicted in Hevelius's star atlas. Note that, per the conventions of the time, the image is mirrored.
Canes Venatici can be seen in the orientation it appears to the eyes in this 1825 star chart from Urania's Mirror.
The constellation Canes Venatici as it is seen by the naked eye in twilight
Messier 51, the Whirlpool Galaxy, photographed by the Hubble Space Telescope.
NGC 4248 is located about 24 million light-years away.<ref>{{cite web|title=A cosmic atlas|url=https://www.spacetelescope.org/images/potw1730a/|website=Hubble Space Telescope|publisher=European Space Agency|access-date=24 July 2017|date=24 July 2017|url-status=live|archive-url=https://web.archive.org/web/20170731061118/https://www.spacetelescope.org/images/potw1730a/|archive-date=2017-07-31}}</ref>
NGC 4242 is a dim galaxy in Canes Venatici.<ref>{{cite web|title=Dim and diffuse|url=https://www.spacetelescope.org/images/potw1729a/|website=Hubble Space Telescope|publisher=European Space Agency|access-date=17 July 2017|date=17 July 2017|url-status=live|archive-url=https://web.archive.org/web/20170719140840/https://www.spacetelescope.org/images/potw1729a/|archive-date=2017-07-19}}</ref>
NGC 4631 photographed by the Hubble Space Telescope.
NGC 4707 is a spiral galaxy roughly 22 million light-years from Earth.<ref>{{cite web|title=Astro-pointillism|url=https://www.spacetelescope.org/images/potw1651a/|website=Hubble Space Telescope|publisher=European Space Agency|access-date=19 December 2016|date=19 December 2016|url-status=live|archive-url=https://web.archive.org/web/20161220175659/https://www.spacetelescope.org/images/potw1651a/|archive-date=2016-12-20}}</ref>

In classical times, they were listed by Ptolemy as unfigured stars below the constellation Ursa Major in his star catalogue.

Asterism (astronomy)

Observed pattern or group of stars in the sky.

A picture of stars, with a group of appearingly bright blue and white stars. The bright stars together are identified as the asterism Coathanger resembling a coathanger, in the constellation Vulpecula.
Some major asterisms on a celestial map (the projection exaggerates the stretching)
The Big Dipper asterism
The "Teapot" asterism in Sagittarius. The Milky Way appears as "steam" coming from the spout.
The "37" or "LE" of NGC 2169, in Orion. It is visible through a pair of binoculars.

For example, the asterism known as the Big Dipper comprises the seven brightest stars in the constellation Ursa Major.

Big Dipper

The asterism of the Big Dipper (shown in this star map in green) lies within the constellation of Ursa Major.
The Big Dipper seen from Fujian
The Hall of the Big Dipper in a Taoist temple, Wuhan
The Big Dipper's bowl and part of the handle photographed from the International Space Station. Mizar and Alcor are at the upper right.
The Big Dipper (Ursa Major) photographed by Prof. Chen Hualin in Dakawa, Morogoro, Tanzania at midnight on February 16, 2018
4D proper moving in -/+ 150 000 years.
Guide to using Big Dipper to locate Arcturus, Spica, and Polaris
The "Starry Plough", used by Irish nationalists and leftists

The Big Dipper (US, Canada) or the Plough (UK, Ireland) is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude.

Alpha Ursae Majoris

α Ursae Majoris A and faint companion binaries

Alpha Ursae Majoris, Latinised from α Ursae Majoris, formally named Dubhe, is, despite being designated "α" (alpha), the second-brightest object in the northern constellation of Ursa Major.