Asteroids, comets, the Kuiper belt, the Oort cloud, rings, and moons

The planets themselves formed about 4.6 billion years ago as dust and ice in the disk around the young Sun clumped together (accretion); rocky planets formed close to the hot Sun, while the giant planets formed farther out, where ices could also condense. The solar system also holds huge numbers of smaller bodies, many of them leftovers from that process. Most asteroids are rocky or metallic objects in the main belt between Mars and Jupiter, where Jupiter's gravity kept the material from building a planet. Beyond Neptune lies the Kuiper belt, a region of icy bodies, including dwarf planets like Pluto, that is the source of many short-period comets. Far beyond it is the Oort cloud, a vast, roughly spherical cloud of icy bodies thought to extend tens of thousands of astronomical units from the Sun, the source of long-period comets. A comet is an icy body that grows a glowing head and tails when it nears the Sun and its ices turn to gas, and its tails point away from the Sun. All four giant planets have rings made of countless particles of ice and rock, and moons form in different ways: alongside their planet, by capture, or, as with Earth's Moon, most likely from debris after a giant impact. Because these small bodies preserve early solar system material, they help reveal how the planets formed, and tracking near-Earth asteroids is part of planetary defense.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report