A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices. The 88 modern constellations are formally defined regions of the sky together covering the entire celestial sphere. (Wikipedia)
Since ancient times men have given a name to each object to recognize it among others. More than 5000 years ago, the Babylonians gave a name to the brightest stars and constellations.
A constellation is a set of stars more or less extended which represents a particular form to which men have given a name. These forms relate either to legendary heroes or objects used by men.
The most famous is the constellation Ursa Major (Latin Ursa Major) in the Northern Hemisphere, a photograph of which is presented below. You easily recognize the 7 stars that compose it and give it a shape that looks like a pan. One of them (the 2nd starting from the left) is a double star, it’s Mizar and Alcor, two little stars that you can see with the naked eye if you have a good view.
A little higher up in the sky, you can discover the Polar star but it is paler. All the sky seems to be spinning around her. If you continue in the same direction according to the time, you will see a big W, it is Cassiopeia. These three constellations and some others are still visible in the sky on the north side, in summer as in winter.
On the other hand, some constellations rise and fall like the Sun because they are located lower on the horizon. In winter, for example, the constellation Orion is clearly visible, forming an immense rectangle in the center of which are 3 small stars lined up sideways and a small light spot a little lower which is the famous Orion nebula, M42. There are 88 constellations.
Not all the stars you can see are all at the same distance and some are also brighter, more colorful or larger than the others. But all the stars you see, even in a powerful telescope belong to our Galaxy, the Milky Way. It contains more than 200 billion stars like the Sun! There are billions of galaxies in the universe like the Milky Way. We will talk about it in a next chapter devoted to the Milky Way and other galaxies.