31 May 2014, 03:54 AM ET
The exact number of stars is impossible to know because we aren't sure how big the universe is.
29 May 2014, 12:39 AM ET
Grasshopper was a reusable rocket prototype tested by the company SpaceX in preparation for more ambitious launches.
22 May 2014, 09:28 PM ET
Many astronomers define a planet as an object that orbits the sun (but not another object), is round (or nearly so) and has cleared the area around its orbit.
21 May 2014, 11:10 AM ET
Astronomers have several ways to count stars, but getting a definitive answer to how many there are in a galaxy is "surprisingly difficult."
09 May 2014, 03:11 AM ET
Quaoar is a planetoid that lies in the Kuiper Belt, a region of space beyond Pluto that is filled with icy bodies.
07 May 2014, 10:10 PM ET
Ikaros is a Japanese spacecraft that was the first to successfully use a solar sail at some distance from Earth.
07 May 2014, 01:44 AM ET
Do you have the right stuff? Becoming an astronaut doesn't just happen overnight. It takes many years of education and experience to meet the basic qualifications.
05 May 2014, 10:00 AM ET
The astronaut was also the fifth man to walk on the moon.
03 May 2014, 03:53 AM ET
Astronomers use many terms to describe what happens during an eclipse, and this glossary shows some of the more common things they say.
02 May 2014, 03:32 AM ET
Redshift and blueshift describe how light changes as objects in space move closer or farther away from us.
01 May 2014, 01:22 AM ET
Comet C/2011 W3 Lovejoy is a comet on its way to the outer solar system. It survived a close brush with the sun in December 2011. It is one of four comets discovered by amateur astronomer Terry Lovejoy.
30 April 2014, 02:22 AM ET
Sedna is a dwarf planet candidate that is one of the most distant bodies found in our solar system.
23 April 2014, 01:58 AM ET
Guion "Guy" Bluford is a former NASA astronaut who was the first African-American to fly into space. He flew four shuttle missions.
22 April 2014, 02:24 AM ET
The Triangulum Galaxy (M33) that is about 3 million light-years away from Earth. Among its most distinctive features are ionized hydrogen clouds, which are massive regions of starbirth.
17 April 2014, 01:10 AM ET
The Atacama Large Millimeter/submillimeter Array (ALMA) is a telescope array that peers through stardust to see planetary systems under construction.
16 April 2014, 01:50 AM ET
The Sombrero Galaxy, also called M104 or NGC 4594, is about 28 million light-years from our planet in the constellation Virgo. It is so named because the halo surrounding its disc is unusually large, making it look like a sombrero.
15 April 2014, 01:29 AM ET
The Whirlpool Galaxy is a spiral galaxy that is relatively close to Earth — about 30 million light-years away.
11 April 2014, 01:10 AM ET
The Large Magellanic Cloud (LMC) is a satellite dwarf galaxy that is among the closest galaxies to Earth.
02 April 2014, 04:19 AM ET
Where are the aliens? That is the question that the Fermi Paradox seeks to answer. Given our solar system's relatively young age, the theory says that aliens should have visited us already.
01 April 2014, 02:18 AM ET
Astronomers say there are 100 billion to 200 billion galaxies in the universe. But accurately counting the number of galaxies depends on several factors.
28 March 2014, 05:35 PM ET
A look at the U.S. Air Force's unmanned X-37B space plane, which has flown three secret, long-duration missions in Earth orbit to date.
26 March 2014, 03:55 AM ET
The Drake Equation is used to estimate the number of communicating civilizations in the cosmos, or more simply put, the odds of finding intelligent life in the universe.
21 March 2014, 11:31 PM ET
The Hubble Constant is the unit of measurement used to describe the expansion of the universe. The cosmos has been getting bigger since the Big Bang kick-started the growth about 13.82 billion years ago.
17 March 2014, 10:45 AM ET
Gravitational waves are the "smoking gun" of the Big Bang. Predicted by Albert Einstein's theory of general relativity in 1916, a massive object like Earth distorts space-time around it like a bowling ball dropped on a trampoline.
04 March 2014, 02:05 AM ET
NASA's Kepler Space Telescope is an observatory in space dedicated to finding planets outside our solar system.
28 February 2014, 08:39 PM ET
Yes, the moon rotates on its axis. The moon's rate of rotation nearly matches its orbital period, which keep the same side facing Earth.
28 February 2014, 08:34 PM ET
Space is the zone above and around our planet where there is no air to breathe or to scatter light. Space is a vacuum, but it is far from empty.
27 February 2014, 11:57 PM ET
Scientists have calculated that Earth is 4.54 billion years old, with an error range of 50 million years.
27 February 2014, 12:53 AM ET
Artificial satellites from Earth have only populated space since 1957, but there are now hundreds of thousands of objects from our planet in orbit.
13 February 2014, 10:27 PM ET
If you wanted to pay a visit to the red planet, how long would it take? The answer depends on a number of things …
13 February 2014, 10:53 AM ET
Ganymede would easily be classified as a planet if were orbiting the sun rather than Jupiter.
12 February 2014, 07:34 PM ET
Edmond Halley is best remembered for predicting the orbit of the comet that was later named after him. Besides astronomy, he also made significant discoveries in the fields of geophysics, mathematics, meteorology and physics.