Theory:

A Constellation is a known pattern of stars in the night sky when seen from the Earth.
Eighty-eight constellations represent the whole celestial sphere as per the IAU (International Astronomical Union).

Many of the old constellations have Greek or Latin names and are often named after mythological characters.
 
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Most of the sky is covered by the more prominent constellation, known as  Ursa Major - Saptha Rishi Mandalam.
This constellation's most remarkable feature is a group of seven bright stars known as big dipper (Seven Sages in Indian astronomy).
 
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Similarly, the little dipper commonly known as Ursa Minor (little bear in Latin) normally lies in northern sky and consists of smaller seven stars.
 
The Pole star Polaris (Dhrua) lies within this constellation.
 
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The constellation Orion (hunter in Greek) contains around \(81\) stars out of which all but \(10\) are too faint to be seen with naked eye.
 
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Different constellations become visible in the sky at different times in the year. This happens due to the revolution of the Earth around the Sun. Unlike galaxy, constellations are mere optical appearance and not real objects.
 
In galaxy, stars are bound by gravity and constitute a system.  In a constellation, one star may be near another very far, but because they are in the same direction appear to be near each other in the sky.
Name of the Constellations:
Indian Name
English Name
Mesham
Aeries
Rishabham
Taurus
Midhunam
Gemini
Kadakam
Cancer
Simmam
Leo
Kanni
Virgo
Thulam
Libra
 Vrischikam
Scorpio
Dhanusu
Sagittarius
Makaram
Capricorn
Kumbam
Aquarius
Meenam
Pisces