Physical geographyThe universe and The Solar System

The UniverseThe Universe is infinite. It has neither beginning nor the end.Universe include stars, planets, satellites, comets, meteors, etc.The universe is about 13.7 billion years old.The universe, believably spread over a distance of 156 billion light years, is still expanding.The universe came into being by Big Bang Theory.

GalaxiesA galaxy is a giant family of millions of stars, held together by its own gravitational field.The Universe is organized into galaxies of stars, along with gas and dust.Our galaxy is called the Milky Way, member of the cluster of galaxies which has 35 members.It looks like fairly flat disc with a thick cloud of stars in the centre.About 25% of galaxies are of spiral shape.

Our GalaxyThe Milky Way is more predominant in the southern hemisphere.Its a flat disc, bulging at it centre, with diameter of 100,000 light years and the thickness of the disc is 500 -2000 light years.It has two spiral arms, the sun lies nearly 33,000 light years away from its centre. The galaxy is rotatingAt the center there is swirling masses of gas and stars which takes about million years to circuit the centre. The rotation speed near sun is less, i.e., 250km.per second.Were about 25,000 light-years from the center of the galaxy.It turns out were not located in one of the Milky Ways two primary spiral arms. Instead were located in minor arm of galaxy.Our local spiral arm is sometimes Orion Arm, sometimes Orion Spur. Its between the Sagittarius and Perseus Arms of the milky Way.