A dwarf planet beyond Neptune has a mysterious ring that astronomers can't explain

Feb 8, 2023
In theory, the ring should have developed at the same time as Quaoar. However, it is possible that the ring used to be a a small Kuiper Belt object and was broken apart by another Kuiper Belt object, and then drifted near Quaoar and then gently settled into orbit around it. Too bad we can't redirect the New Horizons spacecraft to investigate. It would be fascinating to get images of Quaoar and its ring system!
Here is some of my who, what, when, where, how, and why investigations on this subject.

ASTRONOMERS DISCOVER UNEXPECTED RING AROUND DISTANT DWARF PLANET, https://skyandtelescope.org/astronomy-news/astronomers-discover-unexpected-ring-around-distant-dwarf-planet/

"...In Nature, the team reports the presence of a ring 4,100 kilometers from the center of Quaoar, far beyond its classical Roche limit of 1,780 km. Morgado says the ring is dense and irregular. “It has a very thin region about 5 km wide and also a large region about 300 km wide, depending on which part of the ring was probed,” he notes. If the material could all be collected into a single moon, it would be about 10 km in diameter, less than a tenth of Weywot’s size. A few thin, light rings exist beyond the Roche limit elsewhere in the solar system — like the tenuous rings beyond Saturn's F ring — but nothing so massive as the ring around Quaoar. “We were very surprised by the existence of such a ring,” says Morgado. A ring at this distance shouldn’t be stable; it ought to either collapse together or drift apart over time. Though it might have formed after a recent collision in the Quaoar system, that seems unlikely because such a ring should only last a few decades. Other hypotheses Morgado and colleagues pondered include orbital resonances with Quaoar and its moon Weywot, or unusual interactions involving ring particles. In the end, they conclude it might be time to rethink the classical Roche limit."

A reference I see cited, ref - A dense ring of the trans-Neptunian object Quaoar outside its Roche limit, https://www.nature.com/articles/s41586-022-05629-6, 08-Feb-2023.

There are more papers on Quaoar too.

My observation. NASA ADS Abstract, Search for confine material around the TNO (50000) Quaoar, https://ui.adsabs.harvard.edu/abs/2022DPS....5410505M/abstract, December 2022. “The Trans-Neptunian Object (50000) Quaoar, classified as a cubewano, is a dwarf planet candidate with a diameter of 1110 km, a semi-major axis of 43.7 au, and an orbital eccentricity of 0.04. Its satellite Weywot orbits at 13,300 km from the primary object, and its diameter is about 90 km from its flux, assuming the same albedo as Quaoar. It allows the determination of Quaoar's mass of 1.20 x 10^21 kg and bulk density of 2,000 kg.m^-3. Over the years, several campaigns were conducted within the ERC Lucky Star project to observe stellar occultations by Quaoar and Weywot. Besides measuring Quaoar's and Weywot's sizes and shapes, those campaigns aimed at searching for material around this TNO. In this talk, we will present the results of our search for confined material (e.g., rings) around Quaoar based on observations with high photometric accuracy, such as the one observed by the large telescope facility of the Gran Telescopio Canarias (10.4 meters), the CHEOPS space telescope (0.32 meters), and citizen astronomers in Australia and Namibia (between 0.35 and 0.75 meters). The events analysed in this work were observed between 2018 and 2021. Such rings are already known to exist around other small bodies of our Solar System: the Centaur object Chariklo and the dwarf planet Haumea. In particular, these two ring systems, despite significant differences in sizes and heliocentric distances, both orbit close to the 1/3 Spin-Orbit Resonance (SOR) with the central body, meaning that the latter completes three rotations while a ring particle completes one orbital revolution. That makes the 1/3 SOR location an interesting region for searching for such rings. In particular, considering Quaoar's rotation period of 17.6788 hours, that will put the 1/3 SOR at about 4,200 km (7.5 Quaoar radii) away from Quaoar's center, and this would be well outside the Roche limit of the central body of 1.780 km (3.2 Quaoar radii), assuming that the bulk density of particles would be around 400 kg.m-3 (typical of Saturnian small satellites). This will be discussed in detail during the presentation. Acknowledgments. The work leading to these results has received funding from the European Research Council under the European Community's H2020 2014-2021 ERC Grant Agreement no. 669416 "Lucky Star".

My note. Using 1.2 x 10^21 kg = 1.2 x 10^24 g, a=43.7 au, e=0.04, I calculate P = 2.8890E+02 years or 288.9 years. In 1 Gyr, 3.4614E+06 revolutions around the Sun. How long can the ring system be maintained? Is the ring system evidence for a much younger ring age?
Feb 9, 2023
I'm new here, but I had to comment.
The Astrophysicist is Giovanni Bonanno. Giovanni Bruno was a 17th century astronomer and philosopher. I do think the article, since it is running in some fairly reputable company (ESA and INAF), needs to be corrected.



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