Everyone knows the Star Wars galaxy is located "far, far away." But how realistic are the alien worlds described in the science fiction saga?

After almost two years of debate, scientists agree that NASA's Voyager 1 spacecraft has entered the outer edge of our solar system.

Andromeda, our closest galactic neighbor, is three times larger than previously thought, scientists say.

A U.S. nonprofit plans to launch the world's first solar-sail-powered spacecraft on Tuesday. In theory, the vehicle is capable of continuous acceleration, project scientists say.

Advances in x-ray astronomy are helping to solve some enduring mysteries about black holes, scientists say.

Flying whales, flesh-dissolving tadpoles, and other beasts abound in a National Geographic Channel special that asks, What would aliens really be like?

The first flybys of Titan portray Saturn's largest moon as an icy, planet-like rock where the rain is methane and ice volcanoes may spew frozen "cryomagma."

During the 15 years since it was launched, the Hubble Space Telescope has racked up an impressive array of discoveries and snapshots of our universe.

NASA's orbiting Spitzer Space Telescope has spied a huge ring of cosmic debris around a "twin" of our own sun.

In 1905 Albert Einstein published revolutionary theories that gave us physics as we know it. Now a new theory may be the one he "spent 30 years searching for."

Half of the known planetary systems outside our solar system could harbor Earthlike planets conducive to life, a new study says.

By peering into the deep belly of the universe, scientists have learned how massive black holes, galaxies, and stars grow together.

Jupiter's moon Europa appears to have key ingredients for life, scientists say, adding that the time to explore it is now.

NASA's Spitzer Space Telescope has detected light from two distant planets. The scientific first opens a new era in which scientists can directly observe the extrasolar worlds that orbit distant stars.

A stream of scientific analysis confirms that water once soaked Mars, raising the possibility of life there. Now, scientists say they may know where to look for it.