Science & history · Asterism guide
The Big Dipper
The Big Dipper, called the Plough in Britain, is seven bright stars in the shape of a ladle. It is not a constellation: it is an asterism, a pattern inside Ursa Major. It is also the most useful signpost in the northern sky.
About this picture
NASA/Goddard Space Flight Center Scientific Visualization Studio. Gaia DR2: ESA/Gaia/DPAC. Constellation figures based on those developed for the IAU by Alan MacRobert of Sky and Telescope magazine (Roger Sinnott and Rick Fienberg). NASA's page (opens in a new tab).
The map is a composite of 1.7 billion catalogued stars, not a photograph from one place: it shows stars far too faint for the eye, and no weather, Moon or city light. It is drawn here in this chart's projection, with each star where it was in 2000; the fastest-moving bright star has shifted about a minute of arc since, far less than a pixel here.
How to spot it: Seven bright stars in the shape of a ladle. Source (opens in a new tab)
An asterism, not a constellation
Seven stars inside Ursa Major: a famous pattern, but only part of a constellation.
The IAU's 88 constellations (opens in a new tab) are areas that together cover the whole sky. Asterisms are distinct: widely recognised patterns that are not constellations, and the IAU's own first example is these seven stars, the Plough in Europe, the Big Dipper in America and the Northern Dipper in Chinese tradition.
Ridpath (opens in a new tab) explains that the seven stars form the rump and long tail of the Great Bear, Ursa Major, whose other stars are much fainter. NASA (opens in a new tab) adds that the Big and Little Dippers sit close together in the northern sky and are generally easy to see.
Sources for this section International Astronomical Union, The Constellations (opens in a new tab); Ian Ridpath, Star Tales: Ursa Major (opens in a new tab); Preston Dyches, What Are Asterisms?, NASA Science (2021, updated 2024) (opens in a new tab)
A signpost
Its bowl points to Polaris and its handle arcs to Arcturus.
The two stars at the end of the bowl point to Polaris (opens in a new tab), the North Star, at the tip of the Little Dipper's handle. The National Park Service (opens in a new tab) gives the old rule for the distance: extend the line about five times the gap from the outermost star of the bowl.
Follow the curve of the handle away from the bowl instead, about the width of an outstretched hand, and you arc to Arcturus (opens in a new tab), the bright orange star of Boötes.
The National Park Service (opens in a new tab) also records the part the night sky played for people escaping slavery in the United States, who found their way north by it; the Dipper was known then as the drinking gourd.
Sources for this section Preston Dyches, What is the North Star and How Do You Find It?, NASA Science (2021, updated 2024) (opens in a new tab); Julie West, North Star to Freedom, U.S. National Park Service (2018) (opens in a new tab); NASA Science, What's Up: September 2021 (opens in a new tab)
How to find it
From mid-northern latitudes it never sets; from far enough south it never rises.
By this site's calculation (opens in a new tab), the Dipper's middle stands about 74° up in the north at its highest from 40°N and is highest at about 9 p.m. local time in mid-May. It swings around the pole through the night and the year, standing on its handle, upside down or level by turns; the computed block gives the latitudes where it never sets and where it never rises.
Its stars are among the brighter ones: ESA's list (opens in a new tab) of the brightest stars includes Alioth, Dubhe and Alkaid within its top 40.
Sources for this section Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), as computed by this site's star engine (opens in a new tab); ESA, Hipparcos: The 50 Brightest Stars (opens in a new tab)
Many names
Plough, wagon, seven oxen, drinking gourd: the same seven stars, many pictures.
The Romans saw seven plough oxen, Septentrio (opens in a new tab), and Germanicus Caesar called the stars a plough because of their shape. Homer called the bear the Wain, a wagon, and Petrus Apianus in 1524 drew three horses pulling a cart.
The IAU (opens in a new tab) gives the Northern Dipper as its Chinese name, and the drinking gourd (opens in a new tab) is the name it carries in the story of the Underground Railroad.
Keep in mind The “Ladle” of the Chinese Book of Poetry is a different dipper: James Legge's note (opens in a new tab) places it in Sagittarius, as the Sagittarius guide explains.
Sources for this section Ian Ridpath, Star Tales: Ursa Major (opens in a new tab); International Astronomical Union, The Constellations (opens in a new tab); Julie West, North Star to Freedom, U.S. National Park Service (2018) (opens in a new tab); The Shih King (Book of Poetry), Minor Odes, Fifth Decade, Ode 9 (Ta Tung), tr. James Legge (Sacred Books of the East vol. 3, 1879), Project Gutenberg #9394 (opens in a new tab)
Where on Earth, and when
The whole key pattern rises from anywhere north of about 28°S.
South of about 41°S, none of it rises.
North of about 41°N, the whole key pattern never sets.
Its middle climbs at least 20° high, the finder's threshold for a suggestion, from anywhere north of about 14°S.
It is highest in the evening sky, at about 9 p.m. local time, in mid-May, from either hemisphere, wherever it rises. With daylight saving time, that is nearer 10 p.m. on the clock.
Worked out by this site from the Bright Star Catalogue, for a flat, clear horizon. Hills, buildings, haze and city light all cut into this; the air also lifts objects near the horizon by about half a degree. For your own place and night, use the sky finder.
Sources
- Astronomy International Astronomical Union, The Constellations (opens in a new tab) for constellations as areas, the Dipper as an asterism and its names · checked 27 September 2026
- History Ian Ridpath, Star Tales: Ursa Major (opens in a new tab) for the figure and the Roman and Greek names · checked 27 September 2026
- Astronomy Preston Dyches, What Are Asterisms?, NASA Science (2021, updated 2024) (opens in a new tab) for the Dippers as easy asterisms · checked 27 September 2026
- Astronomy Preston Dyches, What is the North Star and How Do You Find It?, NASA Science (2021, updated 2024) (opens in a new tab) for the pointers to Polaris · checked 27 September 2026
- History Julie West, North Star to Freedom, U.S. National Park Service (2018) (opens in a new tab) for the five-times rule and the drinking gourd · checked 27 September 2026
- Astronomy NASA Science, What's Up: September 2021 (opens in a new tab) for arc to Arcturus · checked 27 September 2026
- Astronomy ESA, Hipparcos: The 50 Brightest Stars (opens in a new tab) for the brightness of its stars · checked 27 September 2026
- Astronomy Bright Star Catalogue, 5th Revised Ed. (Hoffleit & Warren 1991), as computed by this site's star engine (opens in a new tab) for its height from 40°N and best month
