We all are little bit familiar with night sky. The astronomical phenomena like Lunar eclipse, meteor showers are our favorites things to watch at dark night. The night sky is full of stars. If we go somewhere in dark places away from light pollution then we can see approximately 4000 to 5000 stars in the night sky. If we try to connects these dots then we will form an imaginary pattern in sky known as constellation.
Constellations
A constellation is a group of visible stars which forms a pattern in the dark night sky. The sky is so vast and there are millions of dim stars are present in it. Therefore, we need to connect a bright star to form a pattern. Of course, these patterns are imaginary. Mostly, patterns represent animal, object or mythological creature.
History
The ancient Greeks gives a name to the constellations with characters from there mythology. Ex Orion- The Hunter, Taurus- The bull etc. Therefore, most constellations have their origin in Greek myths. Every culture in world had their own myths and had a different way of joining the pattern. Chinese astronomy has 31 constellations, while native Americans also drew pattern in the stars, as did Australian Aborigines, the ancient Egyptians and by different cultures over the world. In 1922, the International Astronomical Union [IAU] accepted the modern list of 88 constellations. After that, IAU adopted official constellation boundaries in 1928. Out of 88, forty-eight constellation are known as ancient. This means, these forty-eight constellations are discussed by the Greeks, Babylonians and earlier peoples.
Constellations are classified in mainly two groups. The first group is circumpolar constellation and second one is seasonal constellation. Circumpolar – the constellations which never rise or set. Seasonal – the constellation which arrives in particular period of time in year. In north hemisphere, we will always able to see constellations of northern circumpolar sky. In south hemisphere, we will always see constellations of south circumpolar sky.
Every star or constellation rises or sets earlier by 4 minutes than its previous night. The peoples on the pole only see the half of the constellation in the sky. While people living on equator see all the constellation each year. The group of stars which is not part of constellation is term as Asterism. Example of asterism is big dipper in constellation of ursa major, teapot in constellation of Sagittarius, summer triangle etc. Stars in constellation may appear near to each other in sky but they are actually very far away from each other. All constellation will change over time. After approximately thousands of years, these known patterns will become unrecognizable.
Use of Constellations
How our ancestor used constellations ?
- Before calendars were invented, our ancestors use a constellation to determine seasons. After determining the seasons, they decide when to plant and harvest their crops. For example, in northern hemisphere the constellation Orion indicates the winter season.
- Constellations were also useful in navigation for ships. For example, by finding the pattern of constellation Ursa minor it is easy to spot north star Polaris.
- They used constellation for storytelling and to preserve their tradition and their understanding.
How we can use constellations
The more constellation we recognize, the more we know about where to look for objects like planets, nebulae, galaxies, meteor shower, comets etc. Because, this every object can be found in particular constellation. So, it is must for stargazers, Astro-photographers and a person who study astronomy to recognize most of the constellations.