KERALA PSC / ASTRONOMY / GALAXIES / NOTES

 KERALA PSC / ASTRONOMY / GALAXIES / NOTES

KERALA PSC / ASTRONOMY / GALAXIES / NOTES

 

·       A galaxy is the congregation (group) of millions or billions of stars held together by gravity

·       Galaxies were formed 12 billion years ago

·       Milky Way is our home galaxy. It form a part of about 24 galaxies. It is a spiral galaxy. The galactic nucleus is about 3200 light years from the sun

·       Structurally galaxies are classified into three-Spiral galaxies, Elliptical galaxies, Irregular galaxies

·       Spiral Galaxy: Greater concentration of stars in the centre, old ones near the centre and younger ones in the arms.

Ø The Milky Way and Andromedia are examples of spiral galaxies

Ø The solar system is in the outskirts (edge) of the milky way galaxy

·       Elliptical Galaxies: About two third of all galaxies are Elliptical Galaxies. It consists mostly of very old stars.

·       Irregular Galaxies: It consists of about one tenth of all galaxies. It comprises mostly of young stars

·       The two nearest galaxies to our milky way are the Large Magellanic Cloud and the Small Magellanic Cloud, named after Magellan, who discovered them.

·       Our galaxy called the milky way or Akash Ganga belongs to a cluster of some 24 galaxies called the Local Group

·       The two largest galaxies in the group are the Milky Way and the Andromeda Galaxy

·       The movement of the entire solar system around the galactic centre of the Milky Way is known as galactic movement.

 

KERALA PSC / ASTRONOMY / GALAXIES / NOTES