Neptune

A distant, Neptune-size planet 500 light-years from Earth appears to be the youngest fully formed exoplanet ever found crossing its star, raising questions about how it formed so close, so quickly.

Some astronomers are now scanning the sky in an attempt to find the newly proposed Planet Nine, while others are tackling another mystery: How did it come to be?

A new study models what Planet Nine might look like and how detectable it may be — if the hypothesized world does indeed exist.

Has a big, faraway "Planet Nine" shaped the odd orbits of a handful of objects in the outer solar system? Or did these small bodies do this to themselves?

On Jan. 24, 1986, NASA's robotic Voyager 2 probe zoomed by Uranus, giving humanity its first up-close look at the seventh planet from the sun.

Scientists announced the discovery of a potential "Planet Nine" in our solar system on Jan. 20, 2016. See images of this strange giant world in our neighborhood here.

Witnessing an aurora first-hand is a truly awe-inspiring experience no matter what planet you may be on.

It's officially autumn, and time once again to seek out the two most distant planets of our solar system, Uranus and Neptune.

An illustrated Web comic by the cartoonist Boulet explains his passion for stargazing, and takes readers on an awe-inspiring tour of the cosmic landscapes made visible by science.

NASA began an early feasibility study for missions to the distant, mostly-ignored ice-giants Uranus and Neptune, a senior agency official said here Aug. 24.

From gorgeous views of Pluto and its largest moon Charon to an amazing shot of the International Space Station crossing the moon's face, don't miss these amazing space images.