20 Uranus spins sideways

This gas giant of the outer Solar System is pretty weird on closer inspection. First, the planet rotates on its side, appearing to roll around the Sun like a ball. The most likely explanation for the planet’s unusual orientation – about 90 degrees sideways compared to the other planets – is that it underwent some sort of titanic collision in the ancient past. Uranus’ tilt causes what NASA considers to be the most extreme seasons in the Solar System. For about a quarter of each Uranus year – or 21 Earth years, as each Uranus year is 84 years long – the Sun shines directly over the north or south pole of the planet. That means for more than two decades on Earth, half of Uranus never sees the Sun at all.