People have been inventing constellations for thousands of years.
The night sky was very important before artificial lighting. It was both familiar and mysterious. It seems to hold patterns and pictures. In these patterns, people might see the animals they relied on, or maybe gods and heroes. The star pictures became what we call constellations.

Constellations are useful.
You might think of a constellation as just a little picture in the sky, a bit of fun. But long ago constellations were reminders of a society's important stories, traditions and religion. And since we see a changing sky as Earth orbits the Sun, the constellations can also be a calendar. Even today they help us learn about the sky and map it.

Half of the modern constellations came from ancient lands around the Mediterranean Sea.
Some of our constellations go back over five thousand years ago to Mesopotamia, where modern Iraq and Syria are. Long afterwards, the Greeks adopted some of the old constellations and created many of their own. The Romans used the Greek constellations, but gave them Latin names. The astronomer Ptolemy (90-168 AD) described 48 constellations in his famous work Almagest. This book was an essential part of astronomy for well over a thousand years.

Not all of the constellations are ancient.
You can't see the whole southern hemisphere sky from the Mediterranean regions. That meant that Europeans didn't know some parts of the southern sky until the sixteenth century. That was when explorers and merchants traveled the distant southern seas. Dutch explorers Pieter Dirkszoon Keyser and Frederick de Houtman made star observations in the southern hemisphere between 1595 and 1597. They created twelve new constellations, mostly representing exotic animals. Johann Bayer included them in his star atlas Uranometria in 1603.

In the eighteenth century, French astronomer Nicolas-Louis de Lacaille (1713-1762) observed the sky in South Africa for a year. He created fourteen new constellations still in use today. He named them for such things as a navigator's compass (Pyxis) and an artist's easel (Pictor). You can guess what the constellations Microscopium and Telescopium are.

Modern constellations aren't just star pictures.
The International Astronomical Union (IAU) has divided the sky into 88 official constellations. Each one includes the familiar star figure, but the constellation is an area of sky. So, for example, if we say an object is “in Orion”, it means we can see it in the area of sky belonging to Orion.

Some star pictures aren't constellations.
Most people can recognize the Big Dipper (called the Plough in Britain). But it isn't one of the 88 constellations, it's part of the constellation Ursa Major (Great Bear). A star pattern that's part of one or more constellations is called an asterism.

The stars in a constellation aren't actually close together.
We can't tell how far away stars are by looking at them. Even though they're at all different distances, it's as if they're all projected onto a screen that surrounds Earth. For example, in the southern constellation Centaurus, two bright stars, Alpha Centauri and Beta Centauri, seem to be next to each other. But Alpha Centauri is the Solar System's nearest neighboring star – it's 4.32 light years away. Beta Centauri is nearly a hundred times farther away than that.

There are genuine star groups.
Unlike constellations, star clusters really are groups of stars. They were born from the same nebula, and gravity keeps them together. The best known star cluster is probably the Pleiades which has about a thousand stars in it. It's over 400 light years away, but several of the stars are bright enough to see from Earth without a telescope or binoculars.

Every constellation has a Latin name with a three-letter abbreviation.
We still use Latin constellation names, but to make it simpler, each one has an abbreviation. For example, Ursa Minor is UMi. On star maps, you might also see some of a constellation's stars labeled with Greek letters. In the case of Ursa Minor, its brightest star (which is the pole star, Polaris) is also known as Alpha Ursae Minoris, which we can write as αUMi.