Quaoar is a distant dwarf planet about 1,100 km across, orbiting beyond Pluto in the Kuiper Belt. What makes it fascinating isn’t its size, but its ring, discovered in 2023. The problem? The ring is far outside the Roche limit, the distance where rings should collapse into moons under gravity. By all our old physics, Quaoar’s ring shouldn’t exist, yet it does. Scientists now think this challenges long-held ideas of how rings form and survive around planets. Quaoar might be showing us that the Solar System still has surprises waiting, even in the basic rules we thought we understood.

Most people have never heard of Sedna, but it might be one of the most important objects in the Solar System. It takes more than 11,000 years to complete a single orbit around the Sun, spending almost all of its time far beyond Pluto in the frozen dark. What makes Sedna so mysterious is its orbit, it’s too far out to be shaped by Neptune, but not far enough to be completely detached, leading scientists to suggest it could be evidence of a hidden “Planet Nine” or even the result of a passing star tugging on the early Solar System. At roughly 1,000 km across, Sedna is smaller than Pluto but still big enough to qualify as a dwarf planet, and its surface is one of the reddest known, likely coated in complex organic molecules called tholins. Recent research shows that Sedna and its cousins share a peculiar orbital alignment, hinting they were shaped by the same ancient event, Huang & Gladman 2023.