TEMPE, Ariz. a Quick: What’s the order of the planets in the solar system? Need a little help? Maybe the following mnemonic rings a bell: “My Very Educated Mother Just Served Up Nine Pizzas.” It’s ...

Across the Milky Way, planets slightly larger than Earth but smaller than Neptune appear around most stars. Yet our own solar ...

Astronomers have found that a weird space rock at the edge of the solar system is locked in a rhythmic dance with Neptune. The object, designated 2020 VN40, is part of a family of distant solar system ...

Super-Earths and sub-Neptunes, planets with sizes between Earth and Neptune, constitute approximately one-third of known exoplanets but are absent in our solar system. Their prevalence elsewhere and ...

Discover why the solar system's planets are arranged as they are, shaped by formation conditions and planetary migration.

The International Astronomical Union (IAU) defines a planet as a celestial body orbiting the Sun, possessing sufficient mass for a nearly spherical shape, and having cleared its orbital neighborhood ...

Astronomers using planet-hunting satellites have discovered a rare solar system with six planets moving completely in sync with one another, as if they were untouched by any outside force since being ...