Optical photograph of the dense star clouds of the Milky Way in the constellation of Scorpius Our galaxy the Milky Way has a flattened spiral structure and contains an estimated billion stars The disc is about light years across and the Sun lies within the Orion spiral arm at a distance of about light years from the centre Viewed from Earth the Milky Way appears as a dense band of stars encircling the sky the effect of looking out along the plane of the disc The patchy appearance of the Milky Way is due to interstellar dust obscuring some of the more distant stars