Quaoar is among about 3,000 dwarf worlds in our Solar Systems Kuiper Belt. Astronomers discovered it in 2002. Its only half as large as Pluto, about 1,121 km (697 mi) in diameter. Quaoar has a tiny moon named Weywot, and the world and its moon are extremely difficult to observe in detail.
Astronomers took advantage of an occultation to study the dwarf planet Quaoar and found that it has something unforeseen: a ring where a moon must be.
Occultations are observational gold to astronomers. When an object they want to observe lines up straight in front of a distant star, occultations happen. The star backlights the item drawing out all type of information.
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Outdoors Quaoars Roche Limit, a ring of particles sits where a moon must be.
Quaoars ring is at a distance of nearly 7 and a half times the worlds radius.
In contrast to all other recognized dense rings, Quaoars ring orbits well outside the classical Roche limit.”.
“Quaoars ring is the 3rd example of a dense ring around a little body discovered in the Solar System, suggesting that more still wait for discovery,” the authors compose. “Meanwhile, the big distance of this ring from Quaoar suggests that the classical concept that dense rings endure just inside the Roche limitation of a planetary body must be modified.”.
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In this case, a number of ground-based telescopes seen as small Quaoar occulted a remote star. However the ESAs CHEOPS area telescope also enjoyed. What the telescopes saw surprised astronomers. Outdoors Quaoars Roche Limit, a ring of debris sits where a moon must be.
These findings are in a paper titled “A dense ring of the trans-Neptunian object Quaoar outside its Roche limit.” The paper is published in the journal Nature, and the lead author is Bruno Morgado. Morgado is from the Universidade Federal do Rio de Janeiro, Brazil.
The Roche Limit is the distance from a planet within which a moon will be torn apart by the planets gravity. Outside the Roche Limit, dust and debris are anticipated to naturally coalesce into a moon. Saturns familiar rings are inside the gas giants Roche Limit, and the same is real for all other items with rings that astronomers can see. Quaoars ring is at a distance of practically seven and a half times the planets radius.
The ring wasnt discovered in a single moment. Throughout that duration, Quaoar occulted numerous distant stars, and each time it did, astronomers observed how it blocked the light. Astronomers currently knew about Quaoars tiny moon Weywot, a things just about 80 km (50 miles) in size; there was something else there.
The Hubble Space Telescope captured this image of Quaoar and its moon Weywot on 14 February 2006. Image Credit: By Hubble Space Telescope/Michael E. Brown, Public Domain, https://commons.wikimedia.org/w/index.php?curid=78835233
The ring wasnt discovered by mishap. Astronomers needed to understand ahead of time exactly when occultations would happen in order to study Quaoar and the other Trans-Neptunian Objects (TNOs.) And the occultations had to be accurate.
Bruno Sicardy is an astronomy professor at the Paris Observatory at the Sorbonne. He led a job called Lucky Star that identified upcoming occultations by Quaoar so several telescopes could observe them.
The ESAs Gaia objective made identifying these occultations simpler. Gaia is a star-mapping task of unmatched scope and precision. It permitted Sicardy to determine a lot more future occultations and observing chances for little Quaoar.
This is where the ESAs CHEOPS comes in. CHEOPS means CHaracterising ExOPlanet Satellite, and its a space telescope that studies neighboring bright stars that host known exoplanets. Kate Isaak, the ESAs Project Scientist for the Cheops mission, questioned if CHEOPS could contribute by observing a few of Quaoars occultations. She connected to Lucky Star employee Isabella Pagano to see if CHEOPS might assist.
Artists impression of Cheops, ESAs Characterising Exoplanet Satellite, in orbit above Earth. In this view, the satellites telescope cover is open. Image Credit: ESA/ ATG medialab
” I was a little skeptical about the possibility to do this with CHEOPS,” admits Pagano, “But we examined the feasibility.”
Severe precision is needed to observe Quaoars occultations of far-off stars, and that developed Paganos hesitation. The group first used CHEOPS to observe an occultation by Pluto however were not successful.
They attempted again with an occultation by Quaoar, and this time it paid off. “The CHEOPS information are incredible for signal-to-noise,” said Pagano. Since CHEOPS is an area telescope, it does not need to compete with Earths unpleasant atmosphere and all the sound it introduces into observations. That clearness suggested that the dips in starlight could not be associated to Earths atmosphere. Secondary observations with ground-based telescopes confirmed it.
He also included amateur observations of Quaoar as it occulted different stars over the years. “The minute we saw that, we said, Okay, we are seeing a ring around Quaoar.”.
This figure reveals some of the observational information from the research study. Its from the HiPERCAM instrument on the Gran Canarias Telescope. The observed flux (black points) and the models (red lines) are plotted against the time relative to the observer closest technique. The blue-shaded areas are bigger in corresponding underlying panels and reveal two occultations. Image Credit: Morgado et al. 2023.
The ring isnt uniform. The authors explain it as clumpy in their paper and similar to Saturns F-ring. The clumps are likely kilometre-sized moonlets, and they clash with one another and produce strands of tiny particles that re-accrete into larger objects again in a steady-state procedure.
” In summary, our observations are consistent with a dense, irregular Quaoars ring,” the authors write. “The term dense implies that collisions play a key role in its characteristics. However, in contrast to all other known thick rings, Quaoars ring orbits well outside the classical Roche limitation.”.
Quaoar isnt the only little things with rings. Quaoars isnt.
This illustration from the research study shows the environment around Quaoar. The co-rotation radius is where the orbital period of the particles in the ring match Quaoars rotation. The green and blue reveal the limitations of the mean-motion resonance and the spin-orbit resonance of Weywat Quaoar, respectively.
” So, what is so appealing about this discovery around Quaoar is that the ring of product is much further out than the Roche limit,” said Giovanni Bruno, INAFs Astrophysical Observatory of Catania, Italy, who is among the papers authors.
Quaoars ring appears to reverse a piece of foundational understanding. Particles this far away from a planet ought to coalesce into a moon. “As a result of our observations, the classical concept that thick rings make it through only inside the Roche limitation of a planetary body need to be completely modified,” said Giovanni.
Its too quickly to conclude why the rings are enduring up until now away from the dwarf planet. The freezing temperature level out there in the Kuiper Belt might be the cause because it could prevent the icy grains from sticking to one another. Just more observations can validate that.
Whatever triggers the ring, this unorthodox usage of CHEOPS played an essential function in finding it.
Astronomers arent done with Quaoar. They intend to observe more occultations to see what they can see and to refine their observations. At the same time, theyll want to develop a theory on why the worlds ring endures up until now from the world.
“Quaoars ring is the 3rd example of a dense ring around a little body found in the Solar System, recommending that more still await discovery,” the authors write. “Meanwhile, the large distance of this ring from Quaoar implies that the classical idea that thick rings make it through just inside the Roche limitation of a planetary body must be modified.”.
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