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Quaoar has a ring [1]

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Date: 2023-02-17  

Well, well, well.

It looks like all those snooty astronomers who assigned me to second-class planetary status are eating their words now.

A small icy world far beyond Neptune possesses a ring like the ones around Saturn. Perplexingly, the ring is at a distance where simple gravitational calculations suggest there should be none. “That’s very strange,” said Bruno Morgado, a professor at the Federal University of Rio de Janeiro in Brazil. Dr. Morgado is the lead author of a paper published in the journal Nature on Wednesday that describes the ring that encircles Quaoar, a planetary body about 700 miles in diameter that orbits the sun at a distance of about four billion miles. Quaoar (pronounced KWA-wahr, the name of the creator god for the Indigenous Tongva people who live around Los Angeles) is a little less than half the diameter of Pluto and about a third of the diameter of Earth’s moon. It is likely to be big enough to qualify as a dwarf planet, pulled by its gravity into a round shape. But no one can say that for sure, because images taken by even the most powerful telescopes have revealed Quaoar as only an indistinct blob. The blob also has a moon, Weywot (the son of Quaoar in Tongva belief).

It’s nice to have the New York Times refer to Quaoar as a “planetary body” instead of a Kuiper Belt Object or the equally insulting Dwarf Planet.

But an indistinct blob? C’mon man.

Of course, nobody can figure out how Quaoar got this planetary status symbol. Not every planet has a ring. Earth doesn’t have one. Mars and Venus don’t have one.

The smart people all say Quaoar shouldn’t have one either.

In 1848, Édouard Roche, a French astronomer, calculated what is now known as the Roche limit. Material orbiting closer than this distance would tend to be pulled apart by tidal forces exerted by the parent body. Thus, a ring within the Roche limit would tend to remain a ring, while a ring of debris outside the Roche limit would usually coalesce into a moon. ….. At a distance of 2,500 miles, it is way beyond the Roche limit, which the scientists calculated to be 1,100 miles. At that distance, according to the physics underlying Roche’s calculations, the particles should have coalesced into a moon in 10 to 20 years, Dr. Morgado said. “It really shouldn’t be there,” he said. “We should look at this limit again and better understand how the satellites are formed.” A potential explanation for Quaoar’s distant ring is the presence of Weywot. The moon may have created gravitational disturbances that prevented the ring particles from accreting into another moon. At the ultracold temperatures in the outer solar system, icy particles are also bouncier and are less likely to stick together when they collide.

So Quaoar is full of surprises. Who knows what other surprises might be lurking way out there.

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[1] Url: https://www.dailykos.com/stories/2023/2/17/2152259/-Quaoar-has-a-ring

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