How big is our galaxy?
On a scale of 1 to 10, our galaxy is about a 6 or 7. The 1's would be dwarf galaxies, some of which actually orbit the Milky Way. The 10's are giant spirals and elliptical galaxies that form the cores of super-clusters of galaxies. Our galaxy contains at least 200 billion stars. The dwarf galaxies contain millions of stars, and the giant spirals and ellipticals contain upwards of a trillion stars.
The luminous material of the Milky Way stretches about 100,000 light-years across, with our Sun situated about 27,000 light-years from the center. Astronomers are limited to seeing whatever glows in space, but they think a large chunk of the Milky Way may be invisible, and as yet unmeasurable. Our galaxy actually could be much bigger.
The Milky Way is the second-largest galaxy in what astronomers call the Local Group. The slightly larger Andromeda Galaxy and many smaller elliptical and irregular galaxies also populate the group, which spans about 6.5 million light-years.
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