The Kuiper Belt’s dwarf planet Quaoar hosts an impossible ring

The dwarf planet Quaoar has a hoop that’s too massive for its metaphorical fingers. Whereas all different rings within the photo voltaic system lie inside or close to a mathematically decided distance of their mother or father our bodies, Quaoar’s ring is far farther out.

“For Quaoar, for the ring to be outdoors this restrict may be very, very unusual,” says astronomer Bruno Morgado of the Federal College of Rio de Janeiro. The discovering could pressure a rethink of the principles governing planetary rings, Morgado and colleagues say in a research revealed February 8 in Nature.

Quaoar is an icy physique about half the scale of Pluto that’s situated within the Kuiper Belt on the photo voltaic system’s edge (SN: 8/23/22). At such an incredible distance from Earth, it’s laborious to get a transparent image of the world.

So Morgado and colleagues watched Quaoar block the sunshine from a distant star, a phenomenon referred to as a stellar occultation. The timing of the star winking out and in of view can reveal particulars about Quaoar, like its dimension and whether or not it has an environment.

The researchers took knowledge from occultations from 2018 to 2020, noticed from all around the world, together with Namibia, Australia and Grenada, in addition to area. There was no signal that Quaoar had an environment. However surprisingly, there was a hoop. The discovering makes Quaoar simply the third dwarf planet or asteroid within the photo voltaic system identified to have a hoop, after the asteroid Chariklo and the dwarf planet Haumea (SN: 3/26/14; SN: 10/11/17).

Much more surprisingly, “the ring just isn’t the place we anticipate,” Morgado says.

Recognized rings round different objects lie inside or close to what’s referred to as the Roche restrict, an invisible line the place the gravitational pressure of the principle physique peters out. Contained in the restrict, that pressure can rip a moon to shreds, turning it into a hoop. Outdoors, the gravity between smaller particles is stronger than that from the principle physique, and rings will coalesce into one or a number of moons.

“We all the time consider [the Roche limit] as easy,” Morgado says. “One facet is a moon forming, the opposite facet is a hoop steady. And now this restrict just isn’t a restrict.”

For Quaoar’s far-out ring, there are a number of potential explanations, Morgado says. Perhaps the observers caught the ring at simply the fitting second, proper earlier than it turns right into a moon. However that fortunate timing appears unlikely, he notes.

Perhaps Quaoar’s identified moon, Weywot, or another unseen moon contributes gravity that holds the ring steady by some means. Or possibly the ring’s particles are colliding in such a manner that they keep away from sticking collectively and clumping into moons.

The particles must be significantly bouncy for that to work, “like a hoop of these bouncy balls from toy shops,” says planetary scientist David Jewitt of UCLA, who was not concerned within the new work.

The remark is stable, says Jewitt, who helped uncover the primary objects within the Kuiper Belt within the Nineties. However there’s no technique to know but which of the reasons is appropriate, if any, partly as a result of there are not any theoretical predictions for such far-out rings to match with Quaoar’s state of affairs.

That’s par for the course in terms of the Kuiper Belt. “All the things within the Kuiper Belt, mainly, has been found, not predicted,” Jewitt says. “It’s the alternative of the classical mannequin of science the place individuals predict issues after which verify or reject them. Folks uncover stuff without warning, and everybody scrambles to clarify it.”

Extra observations of Quaoar, or extra discoveries of seemingly misplaced rings elsewhere within the photo voltaic system, might assist reveal what’s occurring.

“I’ve little doubt that within the close to future lots of people will begin working with Quaoar to attempt to get this reply,” Morgado says.