APOD3.4

This is a picture of Comet McNaught's tail. It is visible in the southern hemisphere after sunset. This picture was taken by the comet's discoverer, Robert H. McNaught, from Siding Spring Observatory in Australia. Comet McNaught is the brighest comet in decades.

APOD3.3

This is an infrared picture of the center of our galaxy. The stars are moving relatively quickly, which is evidence that there is a large gravitational force at the center of the galaxy. This is interpreted as a massive black hole, with a mass 1 million times that of our sun with a diamater of a fifth of a lightyear.

APOD3.2

The big dipper, pictured here, is an asterism of Ursa Major. By connecting the two stars at the end of the dipper, you can find Polaris. Five of the stars in the asterism are relatively close to eachother. Apparent configuration of these stars changes over time due to relative stellar motion.

APOD3.1

From May 2005 through December 2006, twenty full moons at the same scale are pictured here. The moon has an orbit that is not exactly circular, so the apparent change in size is genuine.