Featured Article: Is there a hole in the universe?
While routinely scanning the stars, NASA scientists came across something they didn't expect to see: a vast area of space empty of stars, planets and matter. See more »
astronomy terms library
Astronomy terms are used to describe the various phenomena in space. In this section you can learn what every astronomy term means and how it helps us to better understand the cosmos.
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.
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Does space have a shape?
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?
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Hole in the Universe Quiz
How much do you know about dark matter and the makeup of the universe? Take our quiz and test your knowledge!
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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!
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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?
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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.
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How Dark Matter Works
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.
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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.
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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.
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How Nebulae Work
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.
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How Space Collisions Work
Space collisions are the universe's car wrecks. Only in outer space, it's stars, asteroids and even galaxies doing the smashing.
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How the Big Bang Theory Works
The big bang theory is well-known, but there are many misconceptions about it. Like what? Let's start with this one: There was no bang.
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How the Big Crunch Theory Works
We take much for granted about our universe, like it's getting bigger. What if the universe stopped expanding and started collapsing inward with a giant crunch?
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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.
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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?
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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.
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Is there a hole in the universe?
While routinely scanning the stars, NASA scientists came across something they didn't expect to see: a vast area of space empty of stars, planets and matter.
See more »
The Ultimate Meteorite Quiz
Meteors and meteorites have fascinated human beings for ages, but have you managed to turn your fascination into some hardcore knowledge? Wishing on a star isn’t going to help you now.
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What if we were next to a black hole?
When a star dies, it becomes a black hole. Once something passes through the it's gone for good, never to be seen or heard from again. If we lived next to a black hole, would it suck us in too?
See more »Aberration of Light
Aberration of Light, a phenomenon in which a star or other celestial body, as viewed from the earth, appears to be slightly displaced from its true position.
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