Alien rings (2/9/23)

Good afternoon, and happy Thursday. It's been an exciting week in space science.

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Put a ring on it

Scientists are finding rings in mysterious places. This week, a paper published in Nature described a ring around the dwarf planet Quaoar, which resides in our own solar system beyond Neptune’s orbit.

The tricky thing is, calculations of Quaoar’s gravity indicate that the ring shouldn’t be there.

Wait, Quaoar who? Scientists aren’t even sure that this member of the Kuiper belt even qualifies as a dwarf planet. To fit the criteria, a body needs to have enough mass to pull itself into a roughly round shape, but so far, no one’s gotten a good enough look to verify whether that’s the case. Quaoar does have a moon, though, called Weywot, which orbits at a distance 24 times the dwarf planet’s radius. 

Wobbly and uneven: Researchers first noticed that something funky was going on around Quaoar when the dwarf planet passed between Earth and a handful of distant stars. They noticed that the starlight dimmed slightly before and after Quaoar transited those stars.

The evidence pointed to an uneven ring, a few hundred miles wide in some parts and only a handful of miles wide in others. This ring is, on average, ~2,500 miles from the surface of the planet, which is ~700 miles in diameter.

To be clear…Quaoar is not the only Kuiper belt object with a ring. Several others have been found over the years, but in general, these rings are small and pretty closely wound around their planets.

But it is the only one discovered so far with rings that lie significantly outside a threshold called the Roche limit. The Roche limit describes the relationship between a planetary body and its rings, stipulating that outside a given distance determined by the mass of the central body, loose material tends to coagulate and form a moon. By that reasoning, Quaoar's ring should not be stable.

So…why rings? Quaoar’s ring is still being investigated. Recent observations reinforce the findings that a ring exists in the originally posited location, but scientists are still modeling the forces that may be preventing the ring from forming a moon. Extreme temperatures, as well as the presence of Weywot, are being investigated as potential explanations.

Other News from the Cosmos

• Curiosity stumbled upon a metallic Martian meteorite. (Say that five times fast.)

• JWST identified its smallest target yet: a main belt asteroid delightfully described as about the size of the Roman Colosseum.

• Europe has been experiencing a major drought for the past few years. Satellite data show that groundwater levels have been abnormally low since 2018.

• Moon dust launched to a point between the Earth and Sun could potentially counteract climate change, according to a hypothetical study.

• A lagoon in Spain was used as an analog for the Mars environment to better understand how microbial communities might have evolved over drying periods.

• CAPSTONE, NASA’s pathfinder mission to a lunar orbit to be used for the Gateway station later on, is back up and running following a communications issue.

• Charon, Pluto’s moon, has deep, unexplained chasms across its surface. A Southwest Research Institute (SwRI) study found that these ridges likely formed when the moon’s underwater ocean froze.

• Jupiter has 92 confirmed moons, putting it back ahead of Saturn in the rankings.

The View from Space