This extremely large tilt of its axis is thought to be the result of a collision between the accumulating planet Uranus with another planet-sized body early in the history of the Solar System.

In 2002 the Optical Gravitational Lensing Experiment (OGLE) survey detected that the light from the star periodically dimmed very slightly every 4 days, indicating a planet-sized body transiting the star.

Gummidgy's the only planet-sized body in the system.

In regions where the velocity of the collisions was too high, the shattering of planetesimals was more common than accretion, preventing the formation of planet-sized bodies.

Io, a planet-sized body shoving its way through Jupiter's magnetosphere, was like a giant electrical generator.

Its unusual position is thought to be the result of a collision with a planet-sized body early in the Solar System's history.

Their orbits could have been disrupted by an as-yet-unknown planet-sized body within the Oort cloud.

In the 21st century, several new planet-sized bodies, including Sedna, Quaoar, Haumea, and Eris, have been discovered, but not yet incorporated into mainstream astrological predictions, although some more avant-garde groups have attempted to incorporate them.

There was at least a third, planet-sized body in this system.

In regions where the average velocity of the collisions was too high, the shattering of planetesimals tended to dominate over accretion, preventing the formation of planet-sized bodies.