Yeah it looks cool but don't let it get close.

It almost sounds like a riddle. We know where comets come from, even though we've never seen their home.

Some comets come back into the inner solar system again and again every few decades. But some visit once and only once, slipping close to the sun and then evacuated from the solar system altogether. These comets are totally unpredictable. They come from random directions on the sky, and we don't even know they're there until they come close enough that the heat from the sun starts evaporating all of their ices, turning on their famous tails that stretch millions of miles.

These once-in-a-lifetime comets approach from a region of our solar system known as the Oort cloud, named after Jan Oort, the guy who first figured it out. The Oort cloud lies well beyond the orbit of any planet. Our rough estimates put the inner boundary at somewhere around one or two thousand times further away from the sun than the Earth is. And the outermost edges? The Oort cloud could stretch as far as a lightyear away from our sun.

Like the name suggests, the Oort cloud is kind of cloudy, and surrounds our solar system like a wide but tenuous shell. Inside the Oort cloud there are trillions upon trillions of comets, each one just waiting for their chance to get destabilized from their orbit and come crashing into the inner solar system.

But we have never ever seen an object in the Oort cloud. So how do we know it exist?

Well Jan Oort gave us the answer. These kinds of comets appear from any direction on the sky without warning. So whatever their origin point is, it has to be outside the plane of the planets of our solar system.

After you watch a comet or two for long enough, you can reconstruct their orbit to figure out where they started from. And these irregulars comets all come from the starting point at least 1,000 times away further than the sun than the Earth is.

The conclusion: there is a reservoir of comets ready to rain down on us at a moment's notice. The Oort cloud.

Read more:

The Oort Cloud Is Trying To Kill Us With Comets - Forbes