Ringed Planet That Defies Known Physics Discovered in Outer Reaches of Our Solar System

It turns out that Saturn isn’t the only married planet in the solar system. A European telescope has found a new dwarf planet right here at home, and it too has a ring.

The largest object found to orbit our sun since Pluto was discovered in 1930, Quaoar is the third-largest dwarf planet or planetoid of the 3,000 that orbit the sun out beyond Neptune.

A collaboration between the European Space Agency’s ground-based telescopes and the space-based telescope Cheops, began observing Quaoar between 2018 and 2021, during which astronomers discovered it has a ring about 7 times the planet’s 690-mile diameter.

This was found via the common detecting method of occultation—which is the process of measuring the drop in light from a light source that comes when an orbiting exoplanet eclipses it. The astronomers looked at the data and determined that there was something more than just a planet blocking the light behind Quaoar.

“When we put everything together, we saw drops in brightness that were not caused by Quaoar, but that pointed to the presence of material in a circular orbit around it. The moment we saw that we said, ‘Okay, we are seeing a ring around Quaoar,’” stated Bruno Morgado, the leader of the research, who combined the Cheops data with that from large professional observatories around the world and amateur citizen scientists, all of whom had observed Quaoar occult various stars over the last few years.

Quaoar’s ring is awesome without a doubt, but it isn’t the only dwarf planet to be found that has one. The centaur 10199 Chariklo, orbiting between Saturn and Uranus, and Haumea, another dwarf planet beyond Neptune, both have rings.

But Quaoar’s is unique because it breaks a longstanding principle in astronomy that details when disks of dust and debris will inevitably coalesce and form a moon.

Any celestial object with an appreciable gravitational field will have a limit within which an approaching celestial object will be pulled to pieces. This is known as the Roche limit.

“So, what is so intriguing about this discovery around Quaoar is that the ring of material is much farther out than the Roche limit,” says Giovanni Bruno, at the Astrophysical Observatory of Catania, Italy, and member of the research group.

“As a result of our observations, the classical notion that dense rings survive only inside the Roche limit of a planetary body must be thoroughly revised.”