And it’s right in our solar system.
running out of radii
Lurking at the far reaches of the solar system, a dwarf planet named Quaoar has astronomers scratching their heads as the sheer size of its newly discovered ring virtually defies explanation.
While Quaoar is only about half the size of Pluto, its faint ring system blasts the current theorized maximum of ring sizes out of the water, according to a new study published in the journal Nature.
Known as the Roche limit, it asserts that an object held together only by its own gravity can get closest to a planet before being pulled apart by the larger body’s gravity — eventually forming a ring — about two and a half planet radii. Quaoar’s ring is over seven.
“It used to be thought impossible to have rings that far out, so in short the ring of Quaoar is a real challenge to explain theoretically,” said study author Vik Dhillon, a professor of astrophysics at the University of Sheffield live science.
Conversely, once you’ve passed the Roche limit, a planet’s gravity should be too weak to prevent orbiting masses from clumping together and eventually forming satellites — at least that’s what was thought.
“Rings formed outside the Roche limits are not said to be stable; they should rapidly coalesce into small moons, consuming all ring material,” Dhillon explained. “With this discovery, we have a ring not only outside the Roche limit, but well beyond it.”
The discovery was only made thanks to the use of a Spain-based instrument called HiPERCAM, which Dhillon and his colleagues developed, and a fortuitous occultation where Quaoar passed in front of a bright background star, providing just enough light to spot its predecessor hidden ring , appearing in starlight as two dips.
longing for explanation
While capturing the ring is a feat in itself, explaining its size might prove even more difficult.
According to lead author Bruno Morgado, an astronomer at Federal University of Rio de Janeiro, the simplest explanation is that the ring is young and hasn’t had time to reconstruct itself, he said popular science.
But from the team’s simulations, they estimate that it would only take a few decades for that to happen, meaning there’s a “small chance” that we’d observe the process in the first place.
Perhaps it could be a previously unknown object whose gravity impedes the formation of small moons. But in all likelihood, the researchers write in the study, it may be time to reconsider the Roche limit.
More about rings: James Webb discovers asteroids with their own Saturn-like rings