The Astronomical League has announced the winners of this year's S&T Astronomy Day Award — and this year there's a tie for the top spot!

A controversial vote to define "planet" two years ago created more confusion than clarity. So scientists, educators, and curious hangers-on have gathered to get a better handle on what to call the menagerie of worlds that inhabit our solar system and those of other stars.

The Cassini spacecraft is returning the data from Monday's close flyby of icy Enceladus, and NASA is putting up the first raw images.

At its recent national convention in Des Moines, Iowa, the Astronomical League continued its tradition of recognizing the talents and enthusiasm of exceptional teenage stargazers.

Think our planetary family is normal? Think again. It turns out that the Sun and its retinue formed when the interstellar mix was just right — not too much gas, not too little, and stirred gently for just the right amount of time.

Astronomers use a novel method of weighing distant galaxies to measure their masses and find that there's more matter than the galaxies' light can easily explain.

Studying the effect of galaxy clusters on the background radiation from the early universe, University of Hawaii astronomers have added to the pile of evidence for dark energy.

From near the North Pole down to Siberia and China, thousands of travelers watched the August 1st total eclipse of the Sun. Meanwhile, millions more across Europe and Asia made the most of their partial eclipse.

Known for its mysteriousness, one of the galaxy's most massive stars gears up for its periodic pundit-perplexing event. Will Eta Carinae finally reveal its secrets?

It's not covered by a global ocean, as theorists once thought. But Saturn's big moon does sport pools of liquid ethane big enough to float anyone's boat/

The U.S. space agency was founded 50 years ago today. You can celebrate by finding your favorite NASA photograph.

Thanks to a quintet of identical spacecraft, space physicists have settled a decades-old debate over what triggers violent electromagnetic substorms inside Earth's magnetosphere.

From more than 30 million miles away, a NASA spacecraft snapped away as the Moon made a graceful pass in front of Earth's colorful disk.

Astronomers find that the organic compounds common throughout our galaxy and others suddenly disappear along M101's outer edge.