Before the 1990s, we had no idea how the solar system compared to the rest of the galaxy.
We'd never found a planet around a foreign star, so for all we knew, our solar system was special.
But in 1992, radio astronomers published their discovery of the first two exoplanets, and soon after that, the floodgates opened.
In the years since, powerful telescopes have revealed more than 3500 exoplanets in the galaxy, and research now suggests that nearly every star has at least one planet.
So in that respect, our solar system is just another face in the crowd, but we're still kind of a weird one.
Because out of thousands of other systems, none look quite like ours.
We could be special after all.
The question is why.
Scientists have had a basic understanding of how the solar system formed since at least 1755, when the philosopher Immanuel Kant proposed the nebular hypothesis.
He leaned on the work of other scientists of his day, and hypothesized that the Sun and planets evolved out of a cloud that collapsed under its own gravity to form a disk.
