The Milky Way
The Milky Way, as seen from the Earth (AAO)
The Milky Way is a spiral galaxy, with a central bulge of intermediate size. The disk is composed by 4 spiral arms, being the Sun placed between the arm of Sagittarius and the arm of Perseus. The Milky Way has a diameter of 80 000 light years and an estimated amount of about 200 billion stars. The Sun travels around the Milky Way once every 240 million years.