A young, hypothetical planet around a cool star.

Artist's concept of the smallest star known to host a planet.

An extrasolar planet with its parent star peeking above its top edge.

A gap in a protoplanetary, or planet-forming, disk surrounding a young star.

An artist's impression of a Jupiter-size extrasolar planet being eclipsed by its parent star.

Artist's concept of an exoplanet known as UCF-1. 01, orbiting a star called GJ 436.

The hottest known planet in the Milky Way, called WASP-12b, is so close to its sunlike star that it is superheated to nearly 2, 800 degrees Fahrenheit.

A hypothetical 10-million-year-old star system.

A Jupiter-like planet soaking up the scorching rays of its nearby sun.

Artist's concept of Kepler 22b, an extrasolar planet found to orbit the habitable zone.

An artist's impression of a unique type of exoplanet.

Artist's concept of the Juno spacecraft in orbit around Jupiter.

Our sun and the star Sirius compared to a red giant.

A rugged planet landscape dimly lit by a distant red star.

Artist's depiction of a gas giant planet surrounded by three moons.

Artist's depiction of a ringed gas giant planet surrounded by it's moons.

This red giant star is much older and bigger than Earth's Sun.

Illustration of the gas giant planet Neptune and its largest moon Triton.

Artist's concept of a Hot Jupiter extrasolar planet orbiting a sun-like star.

Artist's depiction of an Earth-like planet with orbiting moon and a red planet.

A ringed gas giant exoplanet with moons.

A supernova star explodes near a ringed planet.

A gas giant partly hidden in a nebula.

An earth-like planet illuminated by a nearby white dwarf.

A gas giant planet orbiting a red dwarf star.