Reference Pages
21 May 2012, 09:03 AM ET
Johannes Kepler used mathematics to calculate the path of the planets.
16 May 2012, 05:09 PM ET
There are 13 popular constellations in the Zodiac. But these are just some of the star constellations astronomers use to divide the sky.
14 May 2012, 04:14 PM ET
Galaxies are composed of stars, dust, and dark matter, all held together by gravity. They come in a variety of shapes, sizes, and ages.
12 May 2012, 11:41 AM ET
Often lauded as the father of modern cosmology, Edwin Powell Hubble made significant discoveries and had a space telescope named for him.
08 May 2012, 02:23 PM ET
The Andromeda galaxy is the most distant object in the sky that you can see with your unaided eye. It's also on a collision course with our Milky Way.
08 May 2012, 12:35 PM ET
Italian astronomer Galileo Galilei made a number of inventions and discoveries that remain important to astronomy and science in general today.
07 May 2012, 09:35 AM ET
What is the North Star? And how do I find it?
04 May 2012, 02:51 PM ET
Nibiru has been linked to NASA, and is also sometimes referred to or confused with Planet X, another supposed world for which there is no evidence.
03 May 2012, 07:44 PM ET
A blue moon is not typically blue, but it can be. Find out the error that led to today's definition of blue moon and learn when is the next blue moon.
26 October 2011, 01:16 PM ET
The icy dwarf planet Eris is nearly exactly the same size as Pluto.
03 August 2007, 10:45 AM ET