Milky Way
The center of the Milky Way is in Sagittarius, and is
obscured from view by dust.
The Sun is XXX from center, in the Orion Arm.
The Solar System orbits around the Galaxy in 200 million years.
During the Northern Hemisphere summer, the Milky Way we are viewing across the sky is in the direction of inwards towards the center of the Galaxy, and during the winter we are viewing 'outwards'. Because there is more 'spiral arm' material 'inwards' than 'outwards', the summer Milky Way is brighter. On the other hand, a cold sky is drier than the summer sky, resulting in less scatterring of light allowing us to see the Milky Way with more contrast.
Galaxies are arranged in clusters. The Milky Way belongs to a cluster called the
Local Group. This Local Group is
about 3 million light
years across. Other objects in the Local Group include, for example
The Local Group is a member of the Virgo Supercluster, which contains several
hundred clusters.
The Virgo cluster, one of the other members of the Virgo supercluster (I know the
naming is a bit confusing), is considerably larger than the Local Group - it contains
massive elliptical galaxies in its heart which are about the size of the Local Group in themselves. It also contains M87. A total of about 2500 galaxies have been identified in the cluster.
Introduction
Data
Local Group
Large Magellanic Cloud satellite galaxy of the Milky Way. Spreads across the constellations Dorado and Mensa. It lies about 165-179 thousand light years away. It was the location of supernova
1987A. Although classed as an 'irregular', there are definite signs of a spiral structure.
Small Magellanic Cloud in Tucana. 200,000 light years distant. Spans 4 degrees in the sky.
Virgo Supercluster