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What is a Constellation?

Constellations are groups of stars that form patterns in the night sky, often named after animals, creatures, or mythological people resembling the outline or pattern. The word ‘constellation’ comes from the Latin ‘constellacio’ which means ‘set of stars’.

Of the billions of stars in the universe, only a fraction make up the shapes of our constellations. These include stars that are easily seen with the naked eye. 

It may look like all the stars in a constellation are all at the same distance from Earth, however, a constellation may contain several stars from varying distances.

nightscape photography

The difference in the size of the star and its brightness will affect our ability to view all stars in the constellation, with some appearing more or less noticeable. 

Constellations will gradually shift west throughout the year due to the Earth’s orbit around the Sun.

Therefore, there are constellations known for the different seasons since viewers are looking at a different set of constellations from summer to winter. For example, Cygnus is a prominent summer constellation, and Orion is a prominent winter constellation. 

This also means that not all constellations can be seen from every location on Earth and that some can only be seen from northern or southern latitudes.

For example, Crux and Carina are only visible from the southern hemisphere and Ursa Major/Minor and Cassiopeia are only visible in the northern hemisphere. 

Constellation Versus Asterism

A constellation differs from an asterism in that an asterism is a well-known and/or obvious group or pattern of stars but is not a formally-named constellation (i.e. Winter and Summer Triangle).

These star groupings are still used to navigate the night sky and many contain or share stars within a constellation. 

For example, the Winter Triangle asterism is a pattern of stars made up of Betelgeuse, Sirius, and Procyon which are stars from the constellations Orion, Canis Major, and Canis Minor.

three stars

Another example of an asterism in the night sky is The Big Dipper. This pattern of stars is one of the most familiar sights in the northern sky.

The Big Dipper is a prominent group of stars within the larger constellation of Ursa Major (The Great Bear). The stars in an asterism are usually close together, and about the same brightness. 

the big dipper

The Big Dipper is one of the most familiar asterisms in the night sky (not a constellation).

Origins of Constellations 

The earliest constellations told stories of beliefs, creation or mythology with many cultures and countries adopting their own constellations.

Some of these early constellations became part of the current list of constellations that are internationally recognized, while others changed significantly over time, were limited to certain cultures or countries, or eliminated altogether.  

The majority of constellation names we are familiar with came from the ancient Greek and Roman civilizations. There are 48 constellations from traditional Western constellations.

Constellations from the southern sky were added when European explorers began traveling to this hemisphere in the 15th century. 

Around 1920, the International Astronomical Union (IAU) formally accepted and recognized the modern and ancient list of 88 constellations, and later adopted official boundaries to cover the celestial sphere.

Each star within the constellation boundary is considered to be part of that constellation, even if it is not part of the actual pattern.

Of the 88 constellations, 36 lie predominantly in the northern sky, and 52 in the southern sky. 

Scorpius constellation star chart

Scorpius constellation boundary by IAU and Sky and Telescope.

Northern and Southern Sky Constellations

Northern and Southern Sky Constellations


Constellation List

Latin Name English Name/ Description
Andromeda Princess of Ethiopia
Antlia Air pump
Apus Bird of Paradise
Aquarius Water bearer
Aquila Eagle
Ara Altar
Aries Ram
Auriga Charioteer
Bootes Herdsman
Caelum Graving tool
Camelopardalis Giraffe
Cancer Crab
Canes Venatici Hunting dogs
Canis Major Big dog
Canis Minor Little dog
Capricornus Sea goat
Carina Keel of Argonauts' ship
Cassiopeia Queen of Ethiopia
Centaurus Centaur
Cepheus King of Ethiopia
Cetus Sea monster (whale)
Chamaeleon Chameleon
Circinus Compasses
Columba Dove
Coma Berenices Berenice's hair
Corona Australis Southern crown
Corona Borealis Northern crown
Corvus Crow
Crater Cup
Crux Cross (southern)
Cygnus Swan
Delphinus Porpoise
Dorado Swordfish
Draco Dragon
Equuleus Little horse
Eridanus River
Fornax Furnace
Gemini Twins
Grus Crane
Hercules Hercules, son of Zeus
Horologium Clock
Hydra Sea serpent
Hydrus Water snake
Indus Indian
Lacerta Lizard
Leo Lion
Leo Minor Little lion
Lepus Hare
Libra Balance
Lupus Wolf
Lynx Lynx
Lyra Lyre or harp
Mensa Table mountain
Microscopium Microscope
Monoceros Unicorn
Musca Fly
Norma Carpenter's Level
Octans Octant
Ophiuchus Holder of serpent
Orion Orion, the hunter
Pavo Peacock
Pegasus Pegasus, the winged horse
Perseus Perseus, hero who saved Andromeda
Phoenix Phoenix
Pictor Easel
Pisces Fishes
Piscis Austrinus Southern fish
Puppis Stern of the Argonauts' ship
Pyxis Compass on the Argonauts' ship
Reticulum Net
Sagitta Arrow
Sagittarius Archer
Scorpius Scorpion
Sculptor Sculptor's tools
Scutum Shield
Serpens Serpent
Sextans Sextant
Taurus Bull
Telescopium Telescope
Triangulum Triangle
Triangulum Australe Southern triangle
Tucana Toucan
Ursa Major Big bear
Ursa Minor Little bear
Vela Sail of the Argonauts' ship
Virgo Virgin
Volans Flying fish
Vulpecula Fox

Table data from Astrophysics Science Division (ASD) at NASA/ GSFC.

Famous Constellations


Cassiopeia is a large constellation in the northern hemisphere, known as the ‘W’ constellation based on the pattern that is formed by its five brightest stars. There are a total of eight stars in this constellation which is located opposite the Big Dipper asterism.

Neighboring constellations are Andromeda, Camelopardalis, Cepheus, Lacerta, and Perseus.

Cassiopeia contains several deep-sky objects including; Messier 52, Messier 103, the Heart Nebula and the Soul Nebula, the Pacman Nebula, and the White Rose Cluster.

In Greek mythology, queen Cassiopeia is the wife of King Cepheus and mother to Andromeda. It is said that Cassiopeia was punished for her vanity by the sea god Poseidon by remaining upside down in the sky for six months of the year.

Cassiopeia Cons


Centaurus is the ninth largest constellation in the sky and is located in the southern hemisphere. It contains Alpha Centauri and Beta Centauri, two of the top ten brightest stars in the sky and Centaurus A which is one of the brightest galaxies in the night sky.

Neighboring constellations include Antlia, Carina, Circinus, Crux, Hydra, Libra, Lupus, Musca, and Vela.

This constellation contains no Messier objects.

The Centaurus constellation represents a half-man, half-horse creature from Greek mythology and is usually associated with another wise centaur. 


Cygnus is located in the northern hemisphere and contains the Northern Cross, a well-known asterism. 

Neighboring constellations include; Cepheus, Draco, Lacerta, Lyra, Pegasus, and Vulpecula.

Cygnus contains several well-known nebulae including; the Pelican Nebula, the North America Nebula, the Crescent Nebula, Sadr Region, the Eastern/Western Veil Nebula as well as Messier 29, Messier 39.

The mythology of the Cygnus constellation involves Leda, the Spartan queen who was seduced by Zeus in the form of a swan. Leda then gave birth to two sets of twins, one set mortal (father by Leda’s husband) and one set immortal (fathered by Zeus).

Cygnus constellation


Orion is one of the best known, brightest constellations in the night sky and contains one of the most noticeable asterisms in the night sky, Orion’s belt.

Neighboring constellations include Eridanus, Gemini, Lepus, Monoceros, and Taurus.

The constellation Orion contains Rigel and Betelgeuse, two of the ten brightest stars in the night sky, in addition to the Orion Nebula (Messier 42), De Mairan’s Nebula (Messier 43), the Horsehead Nebula, and the Trapezium Cluster.

While there are many different myths of this constellation, Orion is known as the hunter with two hunting dogs, represented by Canis Major and Canis Minor.

Orion the Hunter


Perseus is a northern constellation, known for its annual meteor shower in the summer.

Neighboring constellations include Andromeda, Aries, Auriga, Camelopardalis, Cassiopeia, Taurus, and Triangulum.

There are many deep-sky objects in Persius including Messier 34, the Double Cluster, the California Nebula (NGC 1499) and the Little Dumbbell Nebula (Messier 76).

According to Greek mythology, the Perseus constellation is a representation of the Greek hero who was the son of Danaë, daughter of King Acrisius. Danaë and Perseus were locked in a wooden chest by the King. The chest was found by a fisherman who took them in and raised Perseus as his son. Perseus would later marry Andromeda and have many children. 

Perseus constellation

Ursa Major 

Ursa Major, the great bear, is well-known and one of the oldest constellations dating back to ancient times. The brightest stars in the constellation also form the Big Dipper asterism with four stars shaping a bowl and three define a handle. 

It is the largest northern constellation and contains Bode’s Galaxy, the Cigar Galaxy, the Owl Nebula, and the Pinwheel Galaxy (M101).

There are many legends that associate Ursa Major with a bear. According to the ancient Greeks, the bear represents Callisto, a beautiful nymph Zeus fell in love with. Callisto was turned into a bear by Zeus’ jealous wife, Hera. 

Ursa Major drawing

Zodiac Constellations 

Of the 88 accepted and recognized constellations, there are twelve constellations that also belong to the zodiac. These constellations are located along the plane of the ecliptic, where the sun will pass through these constellations throughout the course of one year. 

Zodiac constellations

The zodiac constellations as seen from Earth. (ABC: Julie Ramsden)

The zodiac is divided into twelve signs that are loosely tied to the constellations. In ancient times they were used to determine the time of year. Today they are mostly associated with horoscopic astrology. 

The word zodiac comes from ‘zōidiakos’, which means ‘circle of animals’ in Greek, with seven of the zodiac constellations represented by animals.

The twelve zodiac constellations include:

  • Aries (Ram)
  • Aquarius
  • Cancer (Crab)
  • Capricornus (Goat)
  • Gemini
  • Leo (Lion)
  • Libra
  • Pisces (Fish)
  • Sagittarius
  • Scorpius (Scorpion)
  • Taurus (Bull)
  • Virgo

Constellation Facts

  • There are 88 recognized constellations
  • A total of 36 lie predominantly in the northern sky
  • A total of 52 lie predominantly in the southern sky
  • There are official constellation boundaries that cover the entire celestial sphere. Each star within the boundary are considered to be part of the constellation even if they are not represented in the pattern of the constellation.
  • There are twelve constellations part of the zodiac which is tied to astrology
  • The largest constellation by area is Hydra
  • The smallest constellation by area is Crux
  • Asterisms are different from constellations. The Big Dipper is not a constellation, but an asterism that involves stars from the constellation Ursa Major

Constellation Apps

If you are interested in learning more about the constellations, there are several planetarium applications available for your cell phone. Below are three options that are free for download (with in-app store purchases) for Android or Apple phones. 

Stellarium – is a planetarium available as a phone app or on your web browser. It shows realistic star maps, so you can identify stars, constellations, planets, etc.

Star Walk – is an interactive star-gazing phone application that will show you celestial objects. There is a second, paid edition of this app (Star Walk 2) as well as the free version. 

Skyview Lite – a star-gazing phone application for identifying the stars, constellations, etc. 

For a more detailed review of the above applications and for a larger list of useful astronomy applications, visit ‘The 19 Best Astronomy Apps for Stargazing’ post.

astronomy apps