There are a few different definitions of constellations, but many people think of constellations as a group of stars. Often, it's a group of stars that looks like a particular shape in the sky and has been given a name. These stars are far away from Earth. They are not connected to each other at all. Some stars in a constellation might be close while others are very far away. But, if you were to draw lines in the sky between the stars like a dot-to-dot puzzle and use lots of imagination the picture would look like an object, animal, or person.

Over time, cultures around the world have had different names and numbers of constellations depending on what people thought they saw. Since the dawn of recorded civilization, stars played a key role in religion and proved vital to navigation, according to the International Astronomical Union. Astronomy, the study of the heavens, may be the most ancient of the sciences. The invention of the telescope and the discovery of the laws of motion and gravity in the 17th century prompted the realization that stars were just like the sun, all obeying the same laws of physics. In the 19th century, photography and spectroscopy the study of the wavelengths of light that objects emit  made it possible to investigate the compositions and motions of stars from afar, leading to the development of astrophysics.

The earliest Greek work that purported to treat the constellations as constellations, of which there is certain knowledge, is the Phainomena of Eudoxus of Cnidus (c. 395–337 BCE). The original is lost, but a versification by Aratus (c. 315–245 BCE), a poet at the court of Antigonus II Gonatas, king of Macedonia, is extant, as is a commentary by Hipparchus (mid-2nd century BCE).

Three hundred years after Hipparchus, the Alexandrian astronomer Ptolemy (100–170 CE) adopted a very similar scheme in his Uranometria, which appears in the seventh and eighth books of his Almagest, the catalog being styled the “accepted version.” The names and orientation of the 48 constellations therein adopted are, with but few exceptions, identical with those used at the present time.

There are 88 constellations known to us till this time. We can see them in the northern and southern sky at night. The ancient people of many civilizations named the constellations of northern and southern hemispheres. Some examples of constellations in the northern hemispheres are Leo, Pisces, Ursa 1 Major, Cassiopeia, Andromeda, etc. and some examples of southern hemispheres constellations are telescopian, Musca, Tucana, etc.

The Earth with its inclined axis revolves around the sun from west to east. This is why some of the constellations of one season cannot be seen in the other season at the same time from the same place. Some constellations can be seen from both the hemispheres too but at different watch time.

The position of the pole star can be located with the help of Ursa Major. All constellations appear to revolve around the pole star which remains stationary throughout the year. This is because it is straight above the North Pole on the axis of rotation of earth.

Ancient cultures saw patterns in the heavens that resembled people, animals or common objects - constellations that came to represent figures from myth, such as Orion the Hunter, a hero in Greek mythology. Astronomers now often use constellations in the naming of stars. The International Astronomical Union, the world authority for assigning names to celestial objects, officially recognizes 88 constellations. Usually, the brightest star in a constellation has "alpha," the first letter of the Greek alphabet, as part of its scientific name. The second brightest star in a constellation is typically designated "beta," The third brightest "gamma,".

Hydra, named after a mythical water snake, is the largest constellation to grace our sky. It is situated in the Southwestern part of the sky and stretches over a quarter of it. Its total spans 1,303 square degrees, which is 3% of the celestial sphere. Hydra takes about 7 hours to rise into view and can be seen from many parts of the world. Hydra has 19 stars that make up the constellation, and several can be seen on a clear night with the naked eye.

Stars move across our night sky, and constellations can be seen at sunset at different times of the year. The star patterns seen on any night are determined by the time, season, the stargazer’s latitude, and observational conditions. The rising constellations revolve around our planet and where it travels in space, so wherever you are on Earth, many constellations are hidden by our planet.

Star maps have been divided into maps representing the northern and southern hemispheres. Some constellations in the northern hemisphere are circumpolar and can be seen all around; others are only visible in certain seasons. Constellations are helpful for navigation. This was especially useful in ancient times when people traveled by boat; the constellations would help guide travelers in the right direction.

Not all constellations can be identified in the same way, and some are more obvious than others. As a result, unless the conditions are ideal and your map is perfect, you may struggle to spot the constellation. Every space observatory on the planet has its own constellation map created based on what can be seen from the site at various times of the year.

In earlier times, farmers would use constellations to determine the best times for growing crops. Every season had its unique constellations that were easily identifiable. Farmers used these constellations to create a calendar for all their agricultural needs and to forecast the weather for the coming seasons.

For example, the rise and fall of Taurus would indicate that it was a growing season. Taurus is a summer constellation, and most crops in the northern hemisphere were meant to be sewn in spring. Cygnus signifies spring, which is the harvest season. The rise of the constellation would indicate it was time to harvest the summer crops and plant winter ones.

The constellation Orion can be seen worldwide due to its location in the night sky. It is one of the sky’s most visible and recognizable constellations and is named after the hunter in Greek mythology. Orion is the 26th largest constellation, covering an area of 594 square degrees. It includes two of the 10 brightest stars in the sky, Rigel and Betelgeuse, and other famous stars, making it a stargazer’s dream. While all the stars in the sky move and change position, the North Star stays in the same place. It is also known as Polaris and is part of the Ursa Minor constellation. Earth’s axis points almost directly to the North Star and doesn’t rise or set, so it appears to stay in one position.