Reference Pages
20 June 2013, 02:59 PM ET
This large constellation contains the most stars with known planets. It is the 15th largest constellation overall.
19 June 2013, 07:26 PM ET
The brightness of a star is measured several ways: how it appears from Earth, how bright it would appear from a standard distance and how much energy it emits.
17 June 2013, 05:21 PM ET
This faint constellation is the only one named for an inanimate object.
14 June 2013, 03:48 PM ET
Valentina Tereshkova was the first woman to go into space. She flew Vostok 6 in 1963, spending almost three days in space and orbiting Earth 48 times.
10 June 2013, 06:38 PM ET
Aquarius is best viewed in the fall. The constellation's stars are not very bright.
05 June 2013, 07:39 PM ET
Pisces is one of the largest constellations, and also one of the faintest.
03 June 2013, 05:24 PM ET
Also known as Capricorn, this is one of the faintest constellations.
24 May 2013, 06:34 PM ET
Griffith Observatory is dedicated to astronomy education for the general public, and allows ordinary folks to get a peek through its telescopes.
22 May 2013, 05:28 PM ET
Texas' McDonald Observatory is embarking on a search for dark energy.
15 May 2013, 04:01 PM ET
More than 800 extrasolar planets have been discovered.
13 May 2013, 01:10 PM ET
The sun's unceasing activity affects our planet beyond providing obvious light and heat.
06 May 2013, 03:28 PM ET
Arecibo Observatory has been used to send a SETI message as well as for scanning the skies for approaching asteroids.
01 May 2013, 06:03 PM ET
Dark matter emits no light, and cannot be directly observed, but scientists think that it and dark energy make up most of the mass of the universe.
01 May 2013, 05:55 PM ET
Dark energy is a mysterious quantity that makes up, along with dark matter, most of the mass of the universe.
30 April 2013, 07:14 PM ET
The world's time zones and hemispheres are divided into east and west by the prime meridian at the Royal Observatory in Greenwich.
29 April 2013, 05:41 PM ET
A wormhole is a theoretical passage through space-time that could create shortcuts for long journeys across the universe.
26 April 2013, 04:32 PM ET
Lowell Observatory is best known for the discovery of Pluto. Astronomers there have also studied Halley's Comet and discovered an exoplanet in 2007.
25 April 2013, 04:39 PM ET
After years competing in spaceflight, the United States and the Soviet Union did a joint mission for the first time in 1975.
24 April 2013, 03:33 PM ET
The moons of Saturn — 62 in all — come in a variety of sizes and compositions.
24 April 2013, 07:13 AM ET
Since launch in 1990, the Hubble Space Telescope (HST) has provided amazing images that have led to discoveries. Explore Hubble's history and facts.
23 April 2013, 03:26 PM ET
Eugene Cernan, the last Apollo astronaut to walk on the moon, left something behind: his daughter's initials in the dust.
23 April 2013, 03:22 PM ET
Harrison "Jack" Schmitt was the first trained scientist, rather than a former test pilot, to go to the moon. He collected evidence of volcanic activity during the Apollo 17 mission.
23 April 2013, 03:19 PM ET
As command module pilot, Ron Evans spent more time orbiting the moon than any other astronaut.
22 April 2013, 05:51 PM ET
Hyperion is a potato-shaped moon of Saturn with an erratic rotation and eccentric orbit.
19 April 2013, 05:30 PM ET
Numerous craters on Saturn's moon Tethys shine brightly, suggesting the presence of water-ice.
18 April 2013, 05:44 PM ET
The contrast between its light and dark faces keeps Saturn's moon Iapetus hidden in shadows.
16 April 2013, 02:18 PM ET
Charlie Duke was the voice on the radio talking to the Apollo 11 crew during landing. A few years later, he walked on the moon himself on Apollo 16.
16 April 2013, 02:16 PM ET
Astronaut John Young, the ninth man to walk on the moon, flew on three NASA programs: Gemini, Apollo and the space shuttle.
16 April 2013, 02:08 PM ET
Ken Mattingly missed his ride on Apollo 13, but made it to the moon on Apollo 16. He also commanded two shuttle missions.
12 April 2013, 02:29 PM ET
With a giant crater covering much of its surface, Mimas resembles a real-life Death Star from the "Star Wars" movies.
09 April 2013, 01:53 PM ET
Rhea, Saturn's second-largest moon, has a wispy oxygen atmosphere.
08 April 2013, 06:15 PM ET
David Scott's mission to the moon focused on science and featured the first lunar road trip.