Can a planet float on water?

Scientists announced the discovery of the largest known planet in the universe. TrES-4 has a density similar to balsa wood, and some say this gas giant could float on water. Learn why this planet is so puzzling and how planet hunters make amazing discoveries like these.

How Asteroid Belts Work

Asteroid belts aren't quite the dense fields of gigantic spinning rocks that you may have seen in a "Star Wars" film, but they're still fascinating. In fact, the main asteroid belt may tell us how our entire solar system came into existence.

How Asteroids Work

Eros is 21 miles long and 8 miles thick -- a mini planet! Explore the mission that landed on this asteroid after orbiting it for a year!

How Black Holes Work

A black hole occurs when a massive star dies -- its enormous mass implodes and becomes so heavy that it bends space. So how do astronomers detect something that they can't see?

How Comets Work

Comets are remarkable pieces of our universe's past, and they tell us a great deal about how the universe was formed. Learn about the long but rewarding process of discovering and analyzing comets.

How Deep Impact Works

How do scientists find details about the early days of our solar system? One way is to investigate comets. Find out how the Deep Impact spacecraft fired an impactor into Comet Tempel 1 to get some answers.

How did a meteor make hundreds of people sick?

A ball of fire blazed through southern Peru and left a huge crater -- and then villagers started getting sick. Early reports said the groundwater boiled and the air filled with sulfur. What happened?

How Galaxies Work

So much about galaxies remains a mystery. We know what they're made of and that we live in one (the Milky Way), but we're not sure how they form and evolve.

How Stars Work

When you look up at night and see thousands of stars, have you ever wondered what you are looking at? Learn what stars are and how they live and die!

How the Leonid Meteor Shower Works

Every November, the Leonid meteor shower fills the sky with "shooting stars." This year, the shower is expected to peak twice. Learn how Leonid and other meteor showers work.

How the Milky Way Works

A look at the night sky at any time of year will reveal a faint band of light stretching across the sky -- our solar system's home, the Milky Way. How much do we really know about it?

Is Earth on a collision path with a major asteroid?

There's a 45-million-ton asteroid out there with Earth's name on it. In 2029, it'll be closer to us than our moon is. And that's not even the fly-by that scientists are worried about.

Is there a hole in the universe?

While routinely scanning the stars, NASA came across something they never expected to see: An immense area of space totally empty of stars, planets and matter -- a hole far larger than anything they had ever seen before.

Is there really water on Mars?

Until recently, most people assumed that if Mars had liquid water, it no longer did and hadn't for quite some time. But scientists have recently noticed some anomalies in photos of Mars that may suggest there is water. Could there be life, too?

What if I looked straight at an eclipse of the sun?

You've probably heard that staring at the sun is bad for your eyes. Even a few seconds can damage your eyes. But what if you looked at a solar eclipse?