THE MILKY IS THE NAME GIVEN TO THE FAINT BRAND OF LIGHT that stretches across the night sky. This light comes from the stars and nebulae in our galaxy, known as the milky way Galaxy or simply as "the Galaxy". The Galaxy is shaped like a spiral, with a dense central bulge tha is encircled by four arms spiralling outwards and surrounded by a less dense halo. We cannot see the spiral shape because the solar System is in one of the spiral arms, The Orionarm (Also called the local arm). From our position, the centre of the galaxy is completely obscured by dust clouds: as a result, optical maps give only a limited view of the Galaxy. However, a more complete picure can be obtained by studying radio infra - red and other radiation. The central bulge of the Galaxy is relatively small, dense stars are situated; Some of these stars may be as old as the galaxy itself (Possibly 15 billion years). The Spiral arms contain mainly hot, young, blue stars as well as nebulae (clouds of dust and gas inside which stars are born). The Galaxy is vast about 100,000 light years across (a light year is about 9,460 billion kilometres); The Entire galaxy is rotating in space, although the inner stars travel faster than those further one lap of the galaxy about every 220 million years.