Ursa Major: The Great Bear in the Night Sky
Ursa Major is one of the largest and most famous constellations in the sky. It is home to the Big Dipper, an asterism so recognizable that many people mistake it for a constellation in its own right. Spanning a vast region of the northern sky, Ursa Major is circumpolar from most northern latitudes, meaning it never sets below the horizon. Point your phone at the sky with StarGlobe to locate it instantly.
How to Find Ursa Major
The easiest way to find Ursa Major is to look for the Big Dipper. From mid-northern latitudes, this pattern of seven bright stars is visible every clear night of the year, though its orientation changes with the seasons. In spring, the Big Dipper is nearly overhead during evening hours with its bowl facing downward. In autumn, it skims the northern horizon with its bowl facing upward.
The Big Dipper itself forms only the hindquarters and tail of the Great Bear. The full constellation extends well beyond this famous asterism, with additional stars forming the bear's head, legs, and paws. These fainter stars require darker skies to appreciate, but they outline a surprisingly large figure that covers over 1,280 square degrees, making Ursa Major the third-largest constellation.
The Stars of the Big Dipper
The seven stars of the Big Dipper each have traditional names. Starting from the bowl and working toward the handle, they are Dubhe, Merak, Phecda, Megrez, Alioth, Mizar, and Alkaid. Alioth is actually the brightest of the group, shining at magnitude 1.77.
Mizar, the middle star of the handle, is a famous double star. Even without optical aid, sharp-eyed observers can spot its companion Alcor nearby. Through a telescope, Mizar itself splits into two components, making the Mizar-Alcor system a favorite test of eyesight and a rewarding telescopic target.
Five of the Big Dipper's stars, excluding Dubhe and Alkaid, share a common motion through space. They belong to the Ursa Major Moving Group, one of the nearest stellar associations to the Sun. Over thousands of years, this shared motion will gradually distort the familiar Dipper shape.
Pointer Stars and Celestial Navigation
The two stars at the front edge of the Dipper's bowl, Dubhe and Merak, are known as the Pointer Stars. Drawing a line through them and extending it about five times their separation leads directly to Polaris, the North Star, in Ursa Minor. This trick has been used by navigators and travelers for centuries and remains one of the most valuable techniques for orienting yourself under the stars.
The handle of the Dipper offers another useful guide. Following the arc of the handle away from the bowl leads to Arcturus, the bright orange star in Bootes. Continuing that same arc further south reaches Spica in Virgo. Astronomers summarize this with the mnemonic: arc to Arcturus, speed on to Spica.
Deep Sky Objects in Ursa Major
Ursa Major contains several notable galaxies. M81 and M82, also known as Bode's Galaxy and the Cigar Galaxy, form a striking pair visible in binoculars under dark skies. M81 is a grand-design spiral galaxy roughly 12 million light-years away, while M82 is a starburst galaxy undergoing intense star formation triggered by gravitational interaction with its neighbor.
The Pinwheel Galaxy, M101, lies near the end of the Dipper's handle. This face-on spiral galaxy is one of the largest in the nearby universe, spanning nearly 170,000 light-years. The Owl Nebula, M97, is a planetary nebula located near the bottom of the Dipper's bowl, named for two dark spots that give it a face-like appearance in telescopes.
Perhaps most remarkably, Ursa Major contains the Hubble Deep Field, a tiny patch of sky near Megrez where the Hubble Space Telescope captured one of the most iconic images in astronomy, revealing thousands of distant galaxies in what appeared to be an empty region.
Mythology and Cultural Heritage
The association of these stars with a bear is ancient and remarkably widespread. Greek mythology tells of Callisto, a nymph transformed into a bear by Zeus or Hera, then placed in the sky by Zeus to save her from a hunter. Her son, Arcas, became Ursa Minor.
Native American traditions also see a bear in these stars, though different nations interpret the surrounding stars in varying ways. Some Iroquois and Algonquian stories describe the three handle stars as hunters pursuing the bear. In Hindu tradition, the seven stars represent the Saptarishi, seven great sages. Chinese astronomy incorporated them into a celestial bureaucracy, with the Dipper representing a cosmic chariot.
Best Time to Observe
Because Ursa Major is circumpolar from latitudes above about 40 degrees north, it is technically visible year-round. However, the constellation is at its highest and most impressive during spring evenings, from March through June. During this period, the Big Dipper passes nearly overhead for observers in the northern United States, southern Canada, and central Europe.
From the Southern Hemisphere, Ursa Major is difficult or impossible to observe depending on your latitude. Observers south of about 30 degrees south can see only the uppermost parts of the constellation briefly above the northern horizon.
Neighboring Constellations
Ursa Major is bordered by a number of constellations. Draco winds between it and Ursa Minor. Leo lies to the south, and Canes Venatici sits just below the Dipper's handle. Lynx occupies the space to the southwest. To find all these patterns and trace the connections between them, open StarGlobe and explore the sky above you.
Quick Facts
Ursa Major spans 1,280 square degrees, making it the third-largest constellation. Its brightest star, Alioth, shines at magnitude 1.77. The constellation contains seven Messier objects and hosts numerous galaxies accessible with amateur equipment. Its right ascension ranges from about 8h 08m to 14h 29m, and its declination from about +28 to +73 degrees. Use StarGlobe to track the Big Dipper's position as it wheels around the pole throughout the night.
