(ORDO NEWS) — Rings in the solar system are not that rare. Half of the planets have them, while others may have them in the past. Some asteroids have rings, such as the dwarf planet Haumea. Even the Sun has rings of sorts.
Now astronomers have found an entirely new ring system. Only this one made them scratch their heads, as it is unlike anything else in the solar system.
Quaoar, a small dwarf planet that hangs in the Kuiper Belt beyond Pluto, is also surrounded by a dense ring. – a ring rotating at such a great distance that it still has to be glued together like the moon.
This discovery means that scientists may need to rethink our understanding of how moons and rings form and how they are affected by gravitational interactions. with his larger companion.
Measuring only 1,110 kilometers (690 miles) across, the quaoar was discovered in 2002 and has grown over the years into a rather interesting little ball of rock. It shows signs of icy volcanism, and it even has a pretty little moon called Weywot, just 170 kilometers across.
But in 2021, astronomers noticed something else. They watched as Quaoar, a dark shadow in the far reaches of the solar system, moved into position to obscure a star in the distance, a kind of observation called an eclipse.
Observations from a ground-based telescope in Australia have shown that the dwarf planet may have a ring.
Led by astronomer Bruno Morgado of the Federal University of Rio de Janeiro in Brazil, a team of astronomers set out to see if they could find more evidence.
But you can’t just point a telescope at a tiny dwarf planet in the deep darkness of the Kuiper belt and hope to see every detail, let alone see the rings themselves.
Instead, the researchers had to rely on data collected by several ground-based telescopes between 2019 and 2020 to look for additional occultations, as well as occultation observations he and his team collected in 2021 using data from the European Space Agency (ESA) characterizing the ExOPlanet satellite. (Cheops). Space-based Cheops was needed to show that ground-based hints of the ring were not the result of atmospheric distortion.
Ultimately, the combined data provided more than just a hint.
“When we put everything together, we saw a drop in brightness that was not caused by Quaoar, but indicated the presence of material in a circular orbit around it,” says Morgado. “The moment we saw this, we said, ‘OK, we see a ring around Quaoar.’
The data allowed the researchers to characterize the ring, and that’s when it got really weird. The ring orbits the dwarf planet at a distance of 4100 kilometers from the center of Quaoar, or about 7.4 Quaoar radii. (Weyvot, for reference, is much further away, at a distance of 24 radii). But the border of Kwaoar Roche is only 1780 kilometers from the center of Kwaoar.
The Roche limit is the critical distance from a body at which tidal forces, i.e. gravity, will tear it apart into a jumble of debris as the gravity of the body exceeds the gravity needed to hold the smaller body together.
Once a large object crosses the Roche limit, you can reasonably expect it to turn into rubble, which soon teases into a ring. Beyond the Roche limit, you must find undamaged moons.
Of course, debris can exist beyond the Roche limit, but it should still stick together in a relatively short period of time, just a few decades, and merge into a kind of moon. No other body in the Solar System has rings outside the Roche limit.
“What is particularly intriguing about this discovery around Quaoar is that the ring of matter is much further than the Roche limit,” says astronomer Giovanni Bruno of the National Institute of Astrophysics in Italy.
“As a result of our observations, the classical notion that dense rings exist only within the Roche limit of a planetary body needs to be carefully revised.”
More research is needed to find out why the ring didn’t turn into a moon, but there are several possible explanations.
First, the rubble that makes up the ring, for some reason, rather bounces off each other than sticks together. Another possibility is that Weywoot, or even the as yet undiscovered moon of Quaoar, is creating gravitational perturbations that keep the collision rate in the ring high enough to prevent sticking.
But the discovery also suggests it might be possible. there should be more such rings orbiting smaller solar system objects yet to be found. Perhaps in one of them we can also find some answers.
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