Ursa Major
The great ladle of the northern sky, Ursa Major cradles the Big Dipper. It holds the five sibling stars, the six-star system at Mizar, and the myth of Callisto.
Science
The scienceFive of the seven stars that form the Big Dipper are sibling stars of the "Ursa Major Moving Cluster," born from the same nebula about 80 million years ago. Only Dubhe and Alkaid drift in a different direction, so in roughly 100,000 years the familiar ladle shape will be completely undone. Seen through a telescope, the second star of the handle, Mizar, is a multiple star of four suns orbiting one another; add Alcor and it becomes a remarkable six-star system.
Mythology
How it became a constellationThe nymph Callisto, beloved of Zeus, was turned into a bear by the jealousy of the goddess Hera. Years later her son Arcas, now a hunter, met his mother in the forest but could not recognize the bear; at the very moment he drew his bow, Zeus swept them both into the sky as constellations. Still unappeased, Hera asked the god of the sea to forbid these two constellations from ever sinking below the waves to rest, and so both bears wheel through the northern sky all year round.
Observing Guide
how to observe🔭 How to find it
On a spring evening, look high into the northern sky and the ladle-shaped Big Dipper leaps out at once. Draw a line through the two stars at the front of the bowl (Merak to Dubhe) and extend it about five times that gap, and you land on Polaris, the North Star, which is why these two are called the "pointer stars." Right beside Mizar, in the middle of the handle, sits its companion Alcor, visible to the naked eye and famous as an old test of eyesight.
✨ What to look for
The Owl Nebula (M97) and the spiral galaxy M108 lie side by side near the bottom of the bowl, while above the handle the bright spirals Bode's Galaxy (M81) and the Cigar Galaxy (M82) fit into a single field of view. Near Alkaid at the tip of the handle sits M101, a face-on spiral known as the "Pinwheel Galaxy." These galaxies are faint and spread out, however, so they only show their true form under dark skies with binoculars or a telescope rather than in the city.
📍 Where to see it (US · Canada · UK · Australia)
From the UK and Canada the Big Dipper is circumpolar, wheeling around Polaris all night on every night of the year; from the US (~40°N) it is very nearly so, dipping only briefly toward the northern horizon in autumn. Everywhere in the north it rides highest overhead on spring evenings (April–June), the best time to trace it. From Australia the picture reverses: the Dipper hangs low along the northern horizon and appears upside down, and its northernmost stars never clear the horizon at all, so southern observers catch it only partly and fleetingly on autumn nights.