The Uranus Impactor was a hypothetical planet that was hypothesized to have collided with Uranus around 3 to 4 billion years ago, causing it to have a 98° tilt and eventually form its rings and natural satellites. It was hypothesized to be roughly 2 times the size of Earth.[2] This makes it a "Super-Earth", a type of planet with a mass higher than Earth, but less than the Ice Giants.[3]
Collision
The planet is likely to have been a large Uranus trojan that had an unstable gravitational stability and couldn't cooperate with Uranus's gravity, so the two planets collided with each other.
This knocked Uranus out of its stable rotation and tilted it into rotating on its side. The debris leftover from the collision clumped together into a thin ring system, and also Uranus's 27 natural satellites.[4] No traces of the planet is found nowadays, only in Uranus's rings and moons.
Formation
It is likely that the planet formed out of the same mixture as Uranus and Neptune, but couldn't develop a gaseous envelope likely due to the other Jovian planets attracting most of the gas.
It is unknown what compounds and materials it was composed of, but it is likely that it was formed out of the same materials as what the other ice giants' cores are made of. It is theorized that the planet was composed of silicate iron and nickel, with multiple layers of ice and a few traces of water and normal rock.
Because of its abundance of water, if it was located somewhere between Earth and Mars, most of its ice could've melted and developed a global ocean with liquid water, making it habitable.
Second Theory
In 2022 a second theory was proposed in which it is believed a giant ancient moon may have gravitational interacted with Uranus to tilt it on it's side, this moon then may have crashed into the planet and the remaining debris may have formed Uranus' moons, this theory also proposes that the Impactor may have been captured by Uranus within it's first billions of years and is this ancient moon.[5][6]
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