Reference Pages
05 July 2012, 04:25 PM ET
Callisto is thought to be a long dead world, with hardly any geologic activity on its surface.
03 July 2012, 05:40 PM ET
Europa is an icy moon of Jupiter and one of the four so-called Galilean moons.
03 July 2012, 03:23 PM ET
Jupiter’s fifth moon is the most volcanically active body in the solar system.
02 July 2012, 06:39 PM ET
Some comets come from this region of space beyond the planet Neptune.
02 July 2012, 03:56 PM ET
This enormous cloud of gas and dust is a star nursery.
23 June 2012, 12:51 PM ET
American astronaut Edwin "Buzz" Aldrin made history as the second man to walk on the moon in 1969, just after Neil Armstrong in the Apollo 11 mission.
14 June 2012, 01:13 PM ET
Beyond Neptune, the Kuiper Belt is a vast region of icy objects called Kupier Belt Objects (KBOs) and dwarf planets Pluto, Eris, Maumea and Makemake.
11 June 2012, 05:51 PM ET
Most asteroids orbit between Mars and Jupiter in the Main Asteriod Belt. But some space rocks stray out of the main belt and threaten Earth.
11 June 2012, 10:07 AM ET
This list of famous astronomers includes great scientists in history who mastered many fields and modern astronomers who helped popularize astronomy.
08 June 2012, 03:15 PM ET
There used to be nine planets. Now there are eight. Whichever you prefer, here is a list of them in the order they appear in the solar system.
08 June 2012, 10:55 AM ET
Dutch scientist Christiaan Huygens proposed the earliest theory about the nature of light, and he proposed Saturn was a ringed planet.
07 June 2012, 10:29 AM ET
Cosmology by definition is the branch of astronomy involving the origin and evolution of the universe, from the Big Bang to the future of the cosmos.
06 June 2012, 06:23 AM ET
Astronomy is the study of the sun, moon, stars, planets and other objects and phenomena in space. It has a long, rich history.
04 June 2012, 09:01 AM ET
Earth's Sister Planet
04 June 2012, 08:02 AM ET
Carl Sagan was a scientist and educator best known for his TV series Cosmos, the Pale Blue Dot image of Earth and quotes about life and Earth.
30 May 2012, 01:08 PM ET
Cosmologist Stephen Hawking is regarded as a brilliant theoretical physicist. His work on black holes and the big bang are topics of popular books.
29 May 2012, 02:22 PM ET
Sir Isaac Newton invented calculus and explained optics. His most significant work involved forces and the development of a universal law of gravity.
22 May 2012, 08:37 PM ET
The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light.
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.
23 April 2012, 07:22 PM ET
Variable stars change brightness. But there are many reasons why.
13 April 2012, 06:30 AM ET
Titan is the only moon in the solar system with a thick atmosphere. See more Titan facts here.
10 April 2012, 10:38 AM ET
Pluto, the most famous dwarf planet, lost its planet status in 2006. Learn more about dwarf planets of the solar system here.
03 April 2012, 11:15 AM ET
Learn about the science behind the northern and southern lights.
09 November 2011, 11:17 AM ET
Here's a look at all the Mars missions to date, with those that failed in bold.