Look up at the night sky and you'll see stars, sure. But you're also seeing planets—billions and billions of them. At least.

An environment that shifted between open grassland and closed woodland in East Africa roughly 2 million years ago may be responsible for driving human evolution.

Taking into consideration its size, an ancient relative of piranhas weighing about 20 pounds delivered a bite with a force more fierce than prehistoric whale-eating sharks, the four-ton ocean-dwelling Dunkleosteus terrelli and – even – Tyrannosaurus rex.

Here's a satellite image of the United States at night.

Scientists found treasure when they studied a meteorite that was recovered April 22, 2012 at Sutter's Mill, the gold discovery site that led to the 1849 California Gold Rush.

A new study indicates that clay minerals, rocks that usually form when water is present for long periods of time, cover a larger portion of Mars than previously thought.

A survey of 18 giant black holes shows that at least ten may weigh between 10 and 40 billion times the mass of the sun. Astronomers have dubbed these "ultramassive" black holes.

Just in time for the holidays, NASA's Cassini spacecraft, in orbit around Saturn for more than eight years now, has delivered another glorious, backlit view of the planet Saturn and its rings.

Working with fossils found in Tanzania, scientists have discovered what may be the oldest known dinosaur.

The NASA/ESA Hubble Space Telescope celebrates the holiday season with a striking image of the planetary nebula NGC 5189.