Reference Pages
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.
26 October 2011, 01:16 PM ET
The icy dwarf planet Eris is nearly exactly the same size as Pluto.
28 June 2011, 01:38 PM ET
Vesta is the second largest asteroid in the solar system.
08 April 2011, 07:00 AM ET
A look at some of the records people have set over the first 50 years of human spaceflight.
15 November 2010, 01:10 PM ET
The sun is at the heart of our solar system and is the largest object – about 109 times the diameter of Earth. SPACE.com offers an overview of the sun, including its formation, evolution and orbit.
15 November 2010, 01:06 PM ET
Stars are giant, luminous spheres of plasma. SPACE.com offers an overview of stars, including their formation, observation, classification and naming designations.
15 November 2010, 12:59 PM ET
The sun is at the heart of our solar system and 8 planets orbit the sun. Also part of the solar system is the asteroid belt, trans-neptunian region and dwarf planets. Learn more at SPACE.com.
15 November 2010, 12:49 PM ET
Earth is the only planet known to support life. Learn about Earth science facts and the planet’s interior composition, surface and atmosphere.
15 November 2010, 12:46 PM ET
Comets are icy bodies that release gas or dust. SPACE.com offers an overview of comets including physical characteristics, comet formation, collisions and more.
11 November 2010, 11:25 AM ET
Saturn is the sixth planet from the sun and the second largest.
09 November 2010, 02:04 PM ET
The Gas Giant is the Third Largest Planet
09 November 2010, 11:23 AM ET
The Eighth Planet is an Ice Giant
05 November 2010, 11:40 AM ET
Facts about our solar system’s smallest planet and closest planet to the sun.
20 October 2010, 04:59 PM ET
The giant planet with a lot of gas.
04 May 2009, 08:44 AM ET
When stars can't handle their nuclear fuel, they explode in a brilliant burst of light.