Our Solar system consists of the stars, the Sun, and all the planets that orbit around it including the Earth. It also includes numerous moons, asteroids, comets, rocks and dust. The Sun is simply one star amongst the hundreds of billions of the stars present in the Milky Way Galaxy. It is located at the centre of the Solar system. It is the major source of energy for life on Earth. Galaxies come in many sizes. Milky Way is big but there are bigger galaxies than that, like our very own neighbour Andromeda Galaxy. The universe is full of billions of galaxies. NASA’s telescopes have made it possible to study the galaxies beyond the Milky Way in detailed manner and also to explore the distant of observable universe. A galaxy is a gravitationally bound system of stars, stellar remnants, gas, dust, interstellar gas and the dark matter.
POSITION OF THE SUN
The sun lies between the Sagittarius and the Perseus Arms of the Milky Way. The sun is placed on the Orion Arm of the Milky Way Galaxy. The sun and our entire solar system, orbits around the centre of the Milky Way Galaxy. We move at the average velocity of 828,000 km/hr. Even then, it would take around 230 million years to make one complete orbit around the Milky Way which is a spiral galaxy. The Earth and the rest of our solar system lie around 28,000 light years away from the centre of the Milky Way.
The Milky Way looks brighter in the Northern Hemisphere. The diameter of the disk of the Milky Way is c.1,00,000 light years and the average thickness of the Milky Way is 10,000 light years with increase of 30,000 light years at the nucleus. Milky Way is amongst the oldest of galaxies with the study estimating it to be at least 13.6 billion years old or 800 million years. The oldest of the stars is 13.4 billion years old but the formation of proper galaxy as we know today, had to form out of the globular clusters and elliptical galaxies, which took time. The Milky Way is a barred spiral galaxy which is estimated to contain 100-400 billion stars. It can be seen as a hazy band of white light, 30 degrees wide arcing across the sky. Zone of Avoidance is the area of sky which is obscured by the Milky Way.