The European Space Agency’s CHEOPS telescope normally searches for planets outside our solar system, but recently it made a discovery closer to home: a large ring around dwarf planet Quaoar that has researchers intrigued.
The ring has been spotted around the dwarf planet Quaoar, located about 44 times farther from the Sun than Earth in the Kuiper Belt. The planet itself is small, just 690 miles across, but the ring around it is much larger – at seven and a half times its radius.
Due to the planet’s small size and great distance from the Sun, it is difficult to observe even with a powerful space-based telescope like CHEOPS. To observe the dwarf planet, researchers had to wait for it to pass in front of distant background stars, blocking their light in events called occultations. But these events are rare and difficult to predict.
“I was a little skeptical about the possibility of doing this with CHEOPS,” one of the CHEOPS researchers, Isabella Pagano, said in a statement. “But we checked the feasibility.”
It took several attempts, but the team saw some coverage and were very happy with the results. “The Cheops data is amazing for the signal-to-noise ratio,” Pagano said.
These results allowed them to see the dwarf planet and its ring. “Putting it all together, we saw dips in brightness that weren’t caused by Quaoar, but indicated the presence of material in a circular orbit around it. The moment we saw that, we said, ‘Okay, we see a ring around Quaoar,'” said lead researcher Bruno Morgado.
There is something odd about this ring, however. Quaoar has a small moon called Weywot, and astronomers would expect material in the ring to also merge into a moon. As the material approaches a massive body like a planet, gravity pulls it apart once it passes a point called the Roche limit to form a ring. But Quaoar’s ring is well outside the Roche limit.
The team is puzzled by this finding and suspects that it may be due to Quaoar’s very cold temperatures, which prevent the particles in the ring from sticking together to form a moon. But for now, the exact reason remains a mystery.
The research results are published in the journal Nature.