A meteor that is brighter than any of the planets is known as what?

A meteor that is brighter than any of the planets is referred to as a fireball. Fireballs are extremely bright meteors that can light up the night sky and are often visible over considerable distances. They are typically caused by larger meteoroids entering the Earth's atmosphere at high speeds and creating a spectacular display due to the intense heat and pressure generated as they disintegrate.

In contrast, the other terms have distinct meanings: siderites are a type of meteorite that contain metallic iron and are found on Earth after surviving their passage through the atmosphere. Meteorites refer to the fragments of meteoroids that have successfully landed on the Earth's surface, while iceballs are not a recognized term in this context, likely referring to icy celestial bodies rather than meteors. Thus, the term fireball specifically designates the brightest category of meteors, making it the correct choice.