How many constellations are there?
The International Astronomical Union recognizes 88 constellations. They cover the whole sky, so every star belongs to exactly one of them. The modern boundaries were set in the late 1920s, and many of the names go back to Greek and Roman tradition, with others added in later centuries, mostly to fill southern skies that ancient Mediterranean observers could not see.
A constellation is an area of sky, much like a country on a map. The pattern of bright stars most people think of as “the constellation” is often just part of it.
Constellations versus asterisms
An asterism is an informal pattern of stars. The Big Dipper is the classic example: it is part of the larger constellation Ursa Major. The Summer Triangle and the Great Square of Pegasus are asterisms too. Beginners often learn asterisms first because they are compact and easy to recognize, then use them to find the surrounding constellations.
Ursa Major and the Big Dipper
Ursa Major, the Great Bear, is one of the best-known constellations in the Northern Hemisphere. Its Big Dipper is a seven-star shape of a bowl and handle. For many mid-northern observers it is visible all year, though it sits low on autumn evenings.
A classic trick uses the two stars at the end of the bowl, called the pointers. Follow the line through them away from the bowl and you reach Polaris, the North Star, at the end of the handle of the Little Dipper. Polaris is not especially bright, but it stays almost fixed in the northern sky. See the stories behind the constellations for the myths about the bear.
Orion
Orion is probably the most recognizable winter constellation, and it is visible from nearly everywhere on Earth. Three stars in a short row form the belt, framed by the bright red-orange Betelgeuse and blue-white Rigel. Below the belt, a fuzzy patch in the “sword” is the Orion Nebula, which you can see as a smudge without equipment under dark skies and which looks much better in binoculars; see what it looks like through a telescope for the telescope view.
Extending the line of the belt points one way toward Sirius, the brightest star in the night sky, in Canis Major, and the other way toward the Pleiades star cluster and the orange star Aldebaran in Taurus.
Cassiopeia
Cassiopeia looks like a stretched “W” or “M” depending on its orientation. It sits on the opposite side of Polaris from the Big Dipper, so when one is low the other is usually high. That makes it a reliable backup guide to north. It is circumpolar from most northern locations, meaning it never sets.
Cygnus and the Summer Triangle
Cygnus, the Swan, is often called the Northern Cross. It lies along the Milky Way in summer and autumn. Its brightest star, Deneb, is one corner of the Summer Triangle, together with Vega in Lyra and Altair in Aquila. The triangle is a handy anchor for summer evenings.
Scorpius
Scorpius is one of the few constellations that really resembles its namesake. A curved tail ends in a hook, and the reddish star Antares marks the heart. It is a summer constellation, best seen from the southern part of the Northern Hemisphere because it stays low for far-northern observers. Southern Hemisphere viewers see it high overhead.
Leo
Leo, the Lion, is a spring constellation with a recognizable backward-question-mark shape called the Sickle, ending in the bright star Regulus. The rest of the constellation forms a triangle to the east that represents the hindquarters.
Crux, the Southern Cross
Crux is the smallest of the 88 constellations by area, but it is famous in the Southern Hemisphere. Its four bright stars form a compact cross, and two nearby stars in Centaurus act as pointers. It is mostly out of view from northern latitudes, though observers in the far southern United States can glimpse it low on the horizon in spring.
Which is the largest constellation?
Hydra, the water snake, is the largest of the 88 by area, stretching a long way across the sky but containing mostly faint stars. Virgo and Ursa Major are also among the largest. Large does not mean bright, which is why a compact pattern like Orion feels more prominent. For more curious picks beyond the famous few, see cool and unusual constellations worth spotting.
Finding them by season
- Winter (Northern Hemisphere): Orion, Taurus, Canis Major, Gemini.
- Spring: Leo, Ursa Major high in the sky, Boötes.
- Summer: Scorpius, Cygnus, Lyra, Aquila.
- Autumn: Pegasus, Andromeda, Cassiopeia, and the long river Eridanus rising later in the evening.
Seasons are reversed in the Southern Hemisphere, and the exact visibility depends on your latitude and the time of night. A planisphere or a free planetarium app will show what is up right now.
Tips for learning the sky
- Start with one anchor, such as the Big Dipper or Orion, and hop outward.
- Get away from bright lights and give your eyes about 20 minutes to adapt, as described in our stargazing for beginners guide.
- Use a red light to read charts without losing your night vision.
- Learn a few constellations per season instead of all of them at once.
Frequently asked questions
What are the names of the 88 constellations? The full list is maintained by the IAU, and it includes Andromeda, Aquarius, Aries, Cancer, Canis Major, Capricornus, Cassiopeia, Crux, Cygnus, Draco, Gemini, Hydra, Leo, Libra, Lyra, Orion, Pegasus, Perseus, Pisces, Sagittarius, Scorpius, Taurus, Ursa Major, Ursa Minor and Virgo, among many others.
Who are some famous stars? Sirius, Canopus, Arcturus, Vega, Betelgeuse, Rigel and Polaris are among the best known.
Are the stars in a constellation close to each other? Usually not. They only line up from our point of view, and the true distances to the stars in one pattern can differ enormously.