pluto

Pluto no longer planet, could be again

Pluto was long considered our solar system's ninth planet. Although small, it orbits the sun and has the spherical shape required to be considered a planet.

What keeps Pluto's ocean from freezing?

When NASA's New Horizons spacecraft flew past Pluto in 2015, researchers hoped that its data would help them unravel some of the dwarf planet's mysteries. Instead, the discoveries made during the close-up look at Pluto and its moon Charon revealed more questions that needed answering.