HowStuffWorks Space & Solar System Guide  Tags: howstuffworks science solar_system space planet sun moon space_exploration shuttles spacecraft astronaut stars meteor asteroid galaxy earth earth_science space_tourism  

How much do you know about dark matter and the makeup of the universe? Take our quiz and test your knowledge!

Most astronomers believe that visible matter makes up only a fraction of the universe. The rest is stuff we can't see -- so-called dark matter.

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.

Nebulae are collections of dust and gases scattered across the galaxy. They're the sites where stars are born and what's left behind after they die.

Space collisions are the universe's car wrecks. Only in outer space, it's stars, asteroids and even galaxies doing the smashing.

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?

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...

Some scientists believe that space is infinite. But is it? If it isn't, what form does space take? Is it a dodecahedron or a triple torus?

When satellites go off to places like Jupiter or Saturn (or even out of the solar system), they follow crazy orbits. They will often loop around a planet to get a "gravity assist" or "gravity boost." How does that work? I

If "nature abhors a vacuum," then why doesn't the vacuum of space suck away all of the Earth's atmosphere?