The dwarf planet Quaoar has a hoop that’s too large for its metaphorical fingers. Whereas all different rings within the photo voltaic system lie inside or close to a mathematically decided distance of their dad or mum our bodies, Quaoar’s ring is far farther out.
“For Quaoar, for the ring to be outdoors this restrict could be very, very unusual,” says astronomer Bruno Morgado of the Federal College of Rio de Janeiro. The discovering might drive a rethink of the foundations 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 excellent distance from Earth, it’s arduous to get a transparent image of the world.
So Morgado and colleagues watched Quaoar block the sunshine from a distant star, a phenomenon known 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 information 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 recognized 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 will not be the place we anticipate,” Morgado says.
Identified rings round different objects lie inside or close to what’s known as the Roche restrict, an invisible line the place the gravitational drive of the primary physique peters out. Contained in the restrict, that drive can rip a moon to shreds, turning it into a hoop. Exterior, the gravity between smaller particles is stronger than that from the primary physique, and rings will coalesce into one or a number of moons.
“We all the time consider [the Roche limit] as simple,” Morgado says. “One aspect is a moon forming, the opposite aspect is a hoop steady. And now this restrict will not be a restrict.”
For Quaoar’s far-out ring, there are just a few attainable explanations, Morgado says. Perhaps the observers caught the ring at simply the precise second, proper earlier than it turns right into a moon. However that fortunate timing appears unlikely, he notes.
Perhaps Quaoar’s recognized moon, Weywot, or another unseen moon contributes gravity that holds the ring steady by some means. Or perhaps the ring’s particles are colliding in such a method 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 statement is strong, says Jewitt, who helped uncover the primary objects within the Kuiper Belt within the Nineteen Nineties. However there’s no technique to know but which of the reasons is appropriate, if any, partially as a result of there aren’t any theoretical predictions for such far-out rings to check with Quaoar’s scenario.
That’s par for the course in terms of the Kuiper Belt. “Every little thing within the Kuiper Belt, mainly, has been found, not predicted,” Jewitt says. “It’s the alternative of the classical mannequin of science the place folks predict issues after which affirm or reject them. Individuals 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, may assist reveal what’s happening.
“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.