The Milky Way
The broad band of faint white light stretching in an arc from the north-east to south-east horizon is known as the Milky Way, or Te Ikaroa to Māori. The light comes from clusters of millions of stars so distant from earth they cannot be seen individually. The view is spectacular on dark nights away from densely populated areas – city lights brighten the sky to such an extent that only some stars are visible. In New Zealand the Milky Way is best seen during winter, when the bright central region is directly overhead.
The Milky Way is a spiral galaxy. Our solar system belongs to it, along with 250 billion other stars, and vast clouds of gas and dust. Galaxies are large assemblages of stars bound together by gravity. We have an interior view of the galaxy, looking edge-on towards its centre. If we were to look down on the Milky Way it would appear as a spinning Catherine wheel. Side on, it is disc-shaped with a central bulge. It is this bulge, the widest region of the galaxy, located around the constellations of Scorpius and Sagittarius, that is such a feature of winter skies in the southern hemisphere.
Named after the 16th-century Portuguese circumnavigator Fernão de Magalhães (Ferdinand Magellan), and described by him in 1519, are two hazy patches of light near the South Celestial Pole. Although far from impressive when viewed with the naked eye, the Large and Small Magellanic Clouds are significant features, for they are actually satellite galaxies of the Milky Way. Like the Milky Way they contain an assemblage of millions of stars, gas and dust. At 190,000 light years away, the Small Magellanic Cloud is one of the most distant objects visible with the naked eye.
Just west of the Small Magellanic Cloud is 47 Tucanae, one of the brightest globular clusters in the Milky Way. It appears as a single fuzzy star, but viewed with a good telescope a spherical collection of thousands of stars is apparent.