10 Biggest Unexplained Mysteries Of The Universe

8. Hoag's Object

Generally speaking there are two types of galaxy in the universe. You've got spiral galaxies like the one we're currently outstaying our welcome in, which consist of multiple distinct 'arms' orbiting around a supermassive black hole in the middle; and elliptical galaxies, which is essentially just a hot mess of stars in a ball.

Hoag's Object looks, at first glance, like a galaxy but instead of conforming to the norms, it's taken the shape of a doughnut.

Similar in size to the Milky Way, this monstrosity was discovered in 1950 and which category it falls into has been defined and redefined over and over for the last 70 years. Many still dispute whether it's a galaxy at all, hence why its name has been relegated to 'object'.

On top of the mystery of what it actually is, scientists are also baffled as to how it would have come to be. It's the only example of any object that looks like this anywhere in the observable universe so it's still unknown how or why this space-donut exists.