At its most basic: one star, eight planets, five dwarf planets, over 200 moons, and a few billion smaller bodies scattered across billions of kilometers. That's it. But every one of those objects has a story.
The Sun holds more than 99% of the system's total mass. Everything else, from Jupiter at the size of 1,300 Earths to dust grains drifting in the outer dark, exists within its gravitational reach. The eight planets orbit in roughly the same flat plane, called the ecliptic, which is why our solar system looks like a disk rather than a sphere.
Between Mars and Jupiter, the asteroid belt separates the rocky inner planets from the gas and ice giants further out. Past Neptune, the Kuiper Belt begins. It's a ring of icy objects that includes Pluto, Eris, and other dwarf planets. Further still, astronomers suspect a vast shell of frozen debris called the Oort Cloud marks the system's true outer edge, though no spacecraft has reached it.
The whole thing formed about 4.6 billion years ago from a collapsing cloud of gas and dust. That collapse triggered the Sun's birth, and the leftover material flattened into a disk that eventually clumped into planets. You can still trace the fingerprints of that process in the way planets are arranged today.
We've sent probes into nearly every corner of this system. Voyager 1 has crossed into interstellar space, New Horizons flew past Pluto, Perseverance is drilling into Martian rock, and the JUICE mission is heading toward Jupiter's moons to look for buried oceans. There's a lot left to understand.
