The distant planet Xena (aka 2003 UB 313) reflects 86% of the light falling on it, according to New Scientist (hat-tip to , “making it about as bright as fresh snow and brighter than every other solar system body except Saturn’s moon Enceladus. Spectral observations suggest its surface is covered with frozen methane, like Pluto.”

I reckon it’s actually a large alien spaceship, which has got covered with methane dust over the centuries. Abandoned? Dormant? Awake, and preparing to come and say hello? You decide.