Beyond Neptune is a unique region of our solar system known as the Kuiper Belt. This particular area of space is a lot like the asteroid belt, except that it's much further away from the Sun and that the objects are icier than those found just beyond Mars.
Because of how far away these objects are from us, they're challenging to study. To make matters worse, many of them are dark in color, so observing them with the Hubble Space Telescope is a no-go.
Scientists think that the Kuiper Belt might hold some meaningful answers about the formation of our solar system, especially considering that Kuiper Belt Objects (KBOs) are believed to be very old. That said, it isn't surprising why astronomers have so much interest in exploring the region.
NASA's New Horizons spacecraft is on its way to visit a Kuiper Belt Object known as 2014 MU69. It'll be the first time astronomers ever study a KBO up close, and it just might help us answer some questions about what it's like so far away from the Sun.