Starship Asterisk*

Because of dwarf planet Pluto’s elliptical orbit, Pluto is sometimes closer to the Sun (and us) than Neptune is.

Neptune cannot support life as we know it.

Voyager 2 is the only spacecraft to have visited Neptune. No spacecraft has orbited this distant planet to study it at length and up close.

Neptune has at least five main rings and four more ring arcs, which are clumps of dust and debris likely formed by the gravity of a nearby moon.

Neptune has 14 known moons which are named after sea gods and nymphs in Greek mythology.

Neptune's atmosphere is made up mostly of molecular hydrogen, atomic helium and methane.

Neptune is an ice giant. Most of its mass is a hot, dense fluid of "icy" materials – water, methane and ammonia – above a small rocky core.

Neptune takes about 16 hours to rotate once (a Neptunian day), and about 165 Earth years to orbit the sun (a Neptunian year).

Neptune orbits our Sun, a star, and is the eighth planet from the Sun at a distance of about 2.8 billion miles (4.5 billion kilometers).

Neptune is about four times wider than Earth. If Earth were a large apple, Neptune would be the size of a basketball.

Like Venus, Uranus rotates east to west. But Uranus is unique in that it rotates on its side.

Uranus cannot support life as we know it.

Voyager 2 is the only spacecraft to fly by Uranus. No spacecraft has orbited this distant planet to study it at length and up close.

Uranus has 13 known rings. The inner rings are narrow and dark and the outer rings are brightly colored.

Uranus has 27 known moons, and they are named after characters from the works of William Shakespeare and Alexander Pope.

Uranus has an atmosphere made mostly of molecular hydrogen and atomic helium, with a small amount of methane.

Uranus is an ice giant. Most of its mass is a hot, dense fluid of "icy" materials – water, methane and ammonia – above a small rocky core.

Uranus takes about 17 hours to rotate once (a Uranian day), and about 84 Earth years to complete an orbit of the Sun (a Uranian year).

Uranus orbits our Sun, a star, and is the seventh planet from the Sun at a distance of about 1.8 billion miles (2.9 billion kilometers).

Uranus is about four times wider than Earth. If Earth were a large apple, Uranus would be the size of a basketball.

About two tons of Saturn’s mass came from Earth—the Cassini spacecraft was intentionally vaporized in Saturn’s atmosphere in 2017.

Saturn cannot support life as we know it, but some of Saturn's moons have conditions that might support life.