Constellations

For thousands of years, people have gazed up at the stars. They’ve observed how they move across the sky from day to day and season to season. They’ve connected stars that appear close to each other into shapes that remind them of something: animals, objects, and heroes from stories. These star groups become known as constellations. Here’s one of them!

Doesn’t it look like an archer with a bow? It certainly did to the Ancient Greeks who gave it the name of a hunter from one of their myths: Orion. They believed the gods put Orion in the sky. For ancient Egyptians the constellation was related to their god Osiris. And Arab cultures saw the same constellation as a giant.

To this day, some people assign special mystical meaning to certain constellations. Especially important are those constellations that fall along the path the Sun seems to travel across the sky. This region of the sky is called the zodiac. The twelve constellations along it are referred to as zodiac signs. Some people believe that the position of the zodiac signs compared to the position of other celestial bodies matters.

For example, it can determine your personality and fate. Apart from their mythical and mystical significance, constellations have had many practical uses through the ages. Before calendars were invented, people observed the stars to see when the seasons would change. This helped them decide when to start sowing or harvesting their crops. When people in the northern hemisphere saw the constellation of Leo appear, they knew spring was on its way.

Time to plant! When Orion rose over the horizon, winter was coming again. Some constellations remain visible throughout the year. These had a different purpose: navigation. Long before compasses or GPSs, star charts and certain constellations helped travellers figure out where North was.

In the northern hemisphere, they looked for the constellation of Ursa Minor, or the Little Bear. The brightest star of this constellation is called Polaris, or the North Star, and it sits almost directly above the earth’s north pole. This means it barely moves as the planet rotates, and it always indicates North. However, Polaris is only visible from the northern hemisphere. In the southern hemisphere, travellers looked for another constellation: Crux.

No single star of the Crux sits directly above the south pole, but a part of the constellation — the asterism known as the Southern Cross — can be used to find south. Different cultures created their own constellations through history, but in 1922, scientists internationally accepted a list of 88 constellations. Soon after, they redefined a constellation as a region of the sky within which stars form a visible pattern, and created a map that divides the entire celestial sphere into 88 sections — each being one constellation. Every star in the sky, whether already known or newly discovered, belongs to one of the 88 constellations. Each star gets its official name based on the constellation it’s part of.

The stars within one constellation appear close to each other when seen from Earth, but there might be millions and millions of kilometres between them. Still, grouping stars into constellations and giving them names makes it easier for people to find them in the sky, talk about them, and share observations. If you want to study the stars, you don’t need to consult star charts like the astronomers and navigators of the past did. There are apps that will show you the star map when you point your phone at the sky! What constellations do you see?