There are 88 official constellations, recognised by the International Astronomical Union (IAU). Together they cover the whole sky with no gaps, so every star, planet and galaxy you can ever point a telescope at sits inside exactly one of them.
So when people ask how many constellations are there, the short answer is 88. The longer answer is more interesting, because a constellation is not quite what most of us imagine. It is not just a dot-to-dot picture. In this guide you will learn what constellations really are, where the list of 88 came from, and why the stars in a pattern are not the neighbours they appear to be.
What is a constellation?
A constellation is an officially defined area of the sky, with fixed boundaries, named after a traditional pattern of stars. If you are wondering what are constellations in practice, think of them as the countries of the night sky. Every point overhead belongs to one of them, just as every spot on a map belongs to a country.
The patterns came first. People looked up thousands of years ago and joined bright stars into shapes: hunters, bears, scorpions, queens. Astronomers later kept the old names but turned them into tidy regions, so that anyone, anywhere, can say exactly where an object is.
That is why you will see an object described as being “in Orion” or “in Andromeda”. The name tells you which patch of sky to search.
Constellations vs asterisms
Not every famous star pattern is a constellation. Some well-known shapes are asterisms: recognisable patterns that are not official constellations in their own right. Many of them are part of a larger constellation, or even stretch across several.
This is the main difference when people compare a constellation vs an asterism. A constellation is an area with borders. An asterism is just a pattern of stars that is easy to spot.
| Name | Type | What it is |
|---|---|---|
| Ursa Major | Constellation | An official area of sky (the Great Bear) |
| The Plough / Big Dipper | Asterism | A pattern of stars that is part of Ursa Major |
| Orion | Constellation | An official area of sky (the Hunter) |
| Orion’s Belt | Asterism | A pattern of stars within Orion |
| The Summer Triangle | Asterism | A pattern made from the bright stars Vega, Deneb and Altair |
How many constellations are there? The story of the 88
The number 88 was not discovered. It was agreed. The list has been built up over about two thousand years, and it only became official in the twentieth century.
The most influential early list comes from Ptolemy, who catalogued 48 constellations in the Almagest in the 2nd century AD. Many of the names we still use, such as Orion, Cassiopeia and Scorpius, come from that tradition.
Ptolemy’s list left gaps, especially in the far south, which cannot be seen from the Mediterranean. Between the 16th and 18th centuries, European navigators and astronomers added many new constellations to map the southern sky. Nicolas-Louis de Lacaille, for example, named 14 of them in the 1750s.
By the early 1900s there was a problem. Different star atlases used different names and different shapes, and the edges of each constellation were vague. Astronomers needed one shared system.
- 2nd century AD: Ptolemy lists 48 constellations in the Almagest.
- 16th–18th centuries: navigators and astronomers add new constellations to map the southern sky.
- 1922: the IAU adopts the official list of 88, with three-letter abbreviations proposed by Henry Norris Russell.
- 1930: official boundaries, drawn by Eugène Delporte, are published.
Delporte’s boundaries are what turned the patterns into proper regions. Since 1930 the sky has been divided up like a completed jigsaw, with no overlaps and no gaps. That is why we can now say there are exactly 88 constellations, whichever country or observatory you ask.
The two extremes are worth knowing too. The largest constellation is Hydra. The smallest is Crux, better known as the Southern Cross.
This is the key idea to take forward. A constellation is a way of dividing up the sky as we see it, not a family of stars that belong together. Next, we will look at just how far away those stars really are.
How far away are the stars?
Look at the 88 constellations on a chart and they seem to sit on one flat dome. They do not. Each star in a pattern is at its own distance from us, and those distances are so large that kilometres stop being useful. Astronomers use the light-year instead.
A light-year is not a unit of time. It is the distance light travels in one year. Light moves at about 300,000 km/s, so in a year it covers roughly:
1 light-year ≈ 9.46 trillion km
That is 9,460,000,000,000 km. The Moon is about a second of light away, and the Sun about eight minutes. Even the nearest star system, Alpha Centauri, is about 4.37 light-years away, which works out at roughly 41 trillion km.
Stars you can name, and how far they are
- Alpha Centauri: about 4.37 light-years.
- Sirius: about 8.6 light-years.
- Vega: about 25 light-years.
- Arcturus: about 37 light-years.
- Aldebaran: about 65 light-years.
- Polaris: a few hundred light-years. Recent measurements put it at about 430 to 450 light-years away (the Gaia spacecraft measures about 447).
Now compare that with Orion. Its stars range from a few hundred to over a thousand light-years away. They only look grouped because we view them from one spot. Seen from another part of the galaxy, the pattern would be unrecognisable.
Try it yourself. Enter a distance in light-years and the tool below converts it into kilometres and shows how long the light has been travelling.
Test a few stars from the list above. You will see that even the “close” ones are tens of trillions of kilometres away. For more on why starlight behaves the way it does when it reaches us, see the guide to why stars twinkle.
Famous constellations to know
You do not need to learn all 88 constellations. Six well-known ones will let you find your way around the sky, and each is a good starting point for the others. Between them they show how the constellations, asterisms and bright stars fit together.
Orion
Orion is the easiest constellation to recognise. Its three-star Orion’s Belt is an asterism, a pattern inside the larger official constellation. Betelgeuse and Rigel are its two brightest stars.
For the Northern Hemisphere, Orion is a winter evening constellation. In the Southern Hemisphere the same stars appear in summer. Because Orion sits on the celestial equator, you can see it from almost everywhere on Earth.
Ursa Major and the Plough
Ursa Major, the Great Bear, is one of the largest constellations. Its most famous part is the Plough, known as the Big Dipper in North America. The Plough is an asterism, not a constellation in its own right.
Its two end stars, Dubhe and Merak, are the “pointers”. Follow the line they make and you arrive at Polaris, which is how many people first find north.
Ursa Minor
Ursa Minor, the Little Bear, is a faint constellation, but it holds one very important star. Polaris, the North Star, sits almost directly above Earth’s North Pole, so it hardly moves while the rest of the sky turns around it.
Cassiopeia
Cassiopeia is a bright, W-shaped constellation in the northern sky. Its shape makes it easy to spot even in a light-polluted town. It is a handy second signpost on the opposite side of Polaris from the Plough.
Scorpius
Scorpius is a curved constellation of bright stars, shaped like the scorpion it is named after. Its brightest star, Antares, has a distinctly red-orange colour. From the UK it stays low over the southern horizon, so you need a clear view in that direction.
Crux, the Southern Cross
Crux is the smallest of the 88 constellations, yet it may be the most famous one in the Southern Hemisphere. Its four bright stars form a small cross, and it helps sailors and stargazers find south, as we cover later in this guide.
Largest and smallest are common quiz questions. Hydra is the largest constellation and Crux is the smallest. Remember them as a pair and you will rarely get that one wrong.
These six give you a basic sky map. Below is a set of printable star charts to take outside with you.
How to find the North Star
Of all the constellations and star patterns overhead, the most useful trick for a beginner is finding north. You do not need a compass or a phone. You need a clear night and the Plough, the famous pattern of seven stars that forms part of Ursa Major (also called the Big Dipper).
The star you are looking for is Polaris, the North Star. It sits almost directly above Earth’s North Pole, so as the night goes by, the rest of the sky appears to turn around it while Polaris stays put. Follow these steps from anywhere in the Northern Hemisphere.
- Go outside, let your eyes adjust, and face roughly north.
- Find the Plough. It looks like a saucepan with a long, bent handle.
- Pick out the two stars on the outer edge of the “pan”, the side furthest from the handle. These are Dubhe and Merak, the pointer stars.
- Imagine a straight line from Merak through Dubhe and keep going in the same direction.
- The first moderately bright star you meet on that line is Polaris. Face it and you are facing north.
Polaris is not the brightest star in the sky, which surprises many people. It is simply in a very useful place. Its distance is only known roughly: measurements put it at about 430 to 450 light-years away (Gaia gives about 447), so treat any single figure with care.
Polaris is 52° up — what is your latitude? (1 mark)
About 52° N. The altitude of Polaris is approximately equal to the observer’s latitude in the Northern Hemisphere. That is roughly the latitude of southern England.
Finding south with the Southern Cross
Observers in the Southern Hemisphere cannot use Polaris, because it sits below their northern horizon. Unfortunately there is no bright south pole star to take its place. Instead, people use the Southern Cross, or Crux, together with two bright neighbours.
Crux is the smallest of the 88 constellations, yet it is easy to recognise because its four main stars form a small, tilted cross. The nearby stars Alpha and Beta Centauri act as pointers. By combining the long axis of the cross with a line drawn from the pointers, you can estimate where the south celestial pole lies, and from there the direction south.
The Southern Cross is so important in the southern sky that it appears on several national flags. Because it is below the horizon for much of the Northern Hemisphere, many people in the UK have never seen it at all.
Why the sky changes through the night and the year
Many people are surprised that the pattern of constellations they saw last month has shifted. Two motions of Earth cause this, and neither is a mystery once you separate them.
Through the night
Earth spins once a day, so stars appear to rise in the east and set in the west, just as the Sun does. The apparent turning is around the celestial poles, which is why stars near Polaris seem to circle it rather than rise and set.
Through the year
Earth also orbits the Sun once a year, so at night we face a different part of space as the months pass. Stars rise about 4 minutes earlier each night. That adds up to roughly two hours earlier each month, and a whole new set of constellations by the next season.
Orion is a good example. It is a winter evening constellation for the Northern Hemisphere, and the same stars appear in the evening during summer in the Southern Hemisphere. Because Orion sits on the celestial equator, it can be seen from almost everywhere on Earth.
Your latitude matters too
What you can see also depends on where you live. Some constellations can only be seen from one hemisphere, because the curve of Earth hides the far side of the sky. Observers near the poles see a very different sky from observers near the equator. Wherever you are, the stars shine by their own light, which is a different matter from the flickering you notice near the horizon. If you want to know why starlight seems to shimmer, see our guide on why stars twinkle and planets do not.
The pole star changes too: precession
Polaris has not always been the North Star, and it will not be forever. Earth’s axis does not point in a fixed direction. It slowly wobbles, rather like the axis of a spinning top that is starting to lean, and one complete wobble takes about 26,000 years. This slow wobble is called precession.
As the axis traces out its circle, it points at different stars in turn. About 4,500 years ago, when the Egyptian pyramids were built, the pole star was Thuban, in the constellation Draco. In about 12,000 years Vega, one of the stars of the Summer Triangle, will lie close to the pole.
Constellations of the zodiac
The zodiac is a band of constellations that the Sun, Moon and planets appear to move through. It is centred on the ecliptic, the Sun’s apparent path across the sky during the year. Many people know 12 zodiac signs, but the Sun actually passes through 13 constellations, because Ophiuchus, the serpent bearer, lies on the ecliptic too.
The mismatch comes from astrology. Astrology divides the year into 12 equal signs, whereas the real constellations have uneven sizes and the Sun spends different lengths of time in each. Astrology is not science, and it makes no testable predictions. Astronomy, by contrast, uses the same zodiac band for solid, measurable things, such as tracking planets or predicting when the Moon will line up with the Sun. You can read how that works in our article on solar and lunar eclipses and what causes them.
In short: the zodiac constellations are genuine parts of the 88 official constellations, and they are real places on the sky map. Birth-sign horoscopes are a separate matter, and they are not part of astronomy.
Why are constellations important?
Knowing how many constellations there are is a nice fact, but the real question is what people have done with them. For thousands of years, constellations were the first map, clock and calendar that humans had, and they cost nothing to use.
Navigation
Sailors used star patterns to keep their course at night. Polynesian wayfinders crossed huge stretches of open ocean by memorising where stars rise and set along the horizon. In the Northern Hemisphere, the Plough points to Polaris, which gives you north. In the south, the Southern Cross does a similar job.
Calendars and farming
Many cultures used the stars to tell the time of year. Because Earth orbits the Sun, different constellations are up in the evening in different seasons. When a certain pattern appeared before dawn or at dusk, it could signal that it was time to plant, harvest or move herds.
Different cultures, different skies
The 88 official constellations are not the only way to read the sky. The Aboriginal Australian "Emu in the Sky" is made from dark dust lanes in the Milky Way rather than bright stars. Chinese astronomy divided the sky into lunar mansions. Each tradition drew different pictures on the same stars.
A map for modern astronomers
Today, constellations work like postcodes for the sky. Astronomers name stars and galaxies by them, such as Alpha Centauri or the Andromeda Galaxy, so everyone knows roughly where to point a telescope. Space telescopes such as the one described in our guide to NASA’s James Webb Space Telescope rely on this shared map. For the bigger picture of rockets, satellites and observatories, see exploring the universe.
Constellations also connect to deeper questions. Our own star formed in this galaxy, and you can read how in the origin of our solar system. If the scale of it all fascinates you, try beautiful cosmology. And for a gentler comparison, trees more than stars looks at how many trees Earth has compared with stars in our galaxy.
How to see constellations tonight
You do not need a telescope to start. You need a clear night, a little patience and a dark spot. Work through this checklist and tick each step as you go.
- Pick a clear night and check the weather forecast for cloud.
- Get away from street lights and bright windows. Parks, fields and dark car parks are better than town centres.
- Let your eyes adapt for 20–30 minutes. Avoid looking at your phone screen during this time.
- Use a red torch if you need light, because red light disturbs your night vision least.
- Download a star chart or app, and match its view to the direction you are facing.
- Start with something bright and easy, such as the Plough or Orion, then use it to find its neighbours.
- Try binoculars to see more stars and star clusters.
- Come back a few weeks later. Stars rise about 4 minutes earlier each night, so the sky will have shifted.
Flip cards: spot the constellation
Can you remember how to find each pattern? Tap a card to check.
Test yourself
Key points
- There are 88 constellations, recognised by the IAU. They cover the whole sky with no gaps.
- A constellation is an area of sky with boundaries, not just a pattern of stars.
- Asterisms such as the Plough, the Summer Triangle and Orion’s Belt are patterns that are not official constellations.
- Stars in a constellation only look close together. They lie at very different distances.
- Hydra is the largest constellation and Crux is the smallest.
- The Plough’s pointers lead to Polaris, and the Southern Cross helps you find south.
- The zodiac passes through 13 constellations, but astrology is not science.
- For stargazing, find a dark site, let your eyes adapt for 20–30 minutes and use a red torch.
Frequently asked questions about constellations
How many constellations are there?
There are 88 official constellations, recognised by the International Astronomical Union. The list was adopted in 1922, and the boundaries drawn by Eugène Delporte were published in 1930. Together, the 88 constellations cover the entire sky with no gaps between them.
What is a constellation?
A constellation is an officially defined area of the sky, with fixed boundaries, named after a traditional pattern of stars. Every star and object in the sky falls inside exactly one constellation. That makes them useful as a map for astronomers and stargazers.
What is the difference between a constellation and an asterism?
A constellation is an official area of sky, while an asterism is a recognisable pattern of stars that is not one of the 88. The Plough is an asterism within Ursa Major. The Summer Triangle and Orion’s Belt are also asterisms.
What is the largest constellation?
Hydra is the largest of the 88 constellations by area. It stretches across a wide band of sky, which makes it harder to trace than compact patterns such as Orion. It is often seen in sections, one part at a time.
What is the smallest constellation?
Crux, better known as the Southern Cross, is the smallest of the 88 constellations. Despite its tiny area, it is easy to recognise in the southern sky. Observers there use it, together with the pointers Alpha and Beta Centauri, to find south.
How do you find the North Star?
Find the Plough, part of Ursa Major, and follow the two pointer stars, Dubhe and Merak, upwards. They lead to Polaris, the North Star. Polaris sits almost directly above Earth’s North Pole, so its height above the horizon roughly equals your latitude.
Are the stars in a constellation close together?
No. Stars in a constellation only look close together from Earth. They lie at very different distances and are not physically connected. For example, the stars of Orion range from a few hundred to over a thousand light-years away.
Is the zodiac the same as the constellations?
Not exactly. The Sun appears to pass through 13 constellations along the ecliptic, including Ophiuchus. Astrology uses 12 equal signs instead. Astrology is not science, whereas the constellations are real regions of sky used by astronomers.
How can I see constellations at home?
Choose a clear night and find a spot away from bright lights. Let your eyes adapt for 20–30 minutes, use a red torch, and bring a star chart or app. Binoculars can help you see more stars, though they are not essential.
