Where does the solar system end?
You might think of the solar system as being the Sun, a bunch of planets*, and various asteroids and comets.
But it’s more complicated than that. Nothing in the Universe ever really has sharp boundaries when you look at it closely. And just because some stuff is big and bright, and other stuff faint and distant, doesn’t mean you can just pick and choose where the city limits lie.
Neptune may be the outermost big planet, but there’s a whole slew of icy objects out past it. And some are way, way past it. And, not surprisingly, they’re weird.
What may be surprising is how much these tiny, distant chunks of frozen water plying the deep black have affected the history of our solar system, and even our very planet. A large fraction of your body is water, and a large fraction of that may have come from the Space Beyond Neptune.
How? Why, I’m glad you asked. Let this guy and his loud shirt tell you all about it.
*How many? Oh, roughly a dozen. Maybe fewer.