Calor magnus, also known as hairy plum or melone del paradiso, is a subterranean evergreen tree found around the poles of arctic and subarctic astronomical objects including planets, moons, and some large asteroids. The fruit of the tree is chemiluminescent as a result of several exothermic processes involving chemicals extracted and synthesized by the tree, which in turn produces the light and heat required for the tree to survive.

Owing to its unique properties, the hairy plum has numerous applications across energy production, unmanned mining, imperial cuisine, and bio-weapon technology.