But catching an occultation can be tricky. To see one, astronomers need to be “at the right place at the right time,” says Morgado. This is especially difficult for a space telescope because it’s hard to predict exactly where the orbiting observatory will be when an occultation occurs.
“What’s unique with this is the fact that, for the first time, they’ve used a satellite in space to perform a stellar occultation,” says O’Rourke. It’s only possible to “know the ring exists because of the quality of Cheops, because [the telescope] is outside the atmosphere. So, there are no special effects from the atmosphere which might affect the signal.”
Data from the Cheops space telescope also has a very high signal-to-noise ratio, which made it possible for the astronomers to be confident they were really seeing an out-of-place ring around Quaoar. The team also analyzed occultation data collected by astronomers around the world, including observations made by citizen scientists.
Pushing the Limit
The new study is part of a bigger project called Lucky Star, which uses occultations to study dwarf planets in the outer solar system like Quaoar.
These distant objects preserve primordial material from the system’s earliest days. Their orbits also provide clues about how the worlds’ orbits evolved over time, offering scientists a glimpse into the distant past. And, as Quaoar’s rings show, dwarf planets can also teach researchers a lot about how ring systems and moons form.
At this point, only two other small bodies in the solar system, Haumea and Chariklo, are known to host rings. However, Morgado expects that to change in the future.
“We believe that many more rings are [out] there,” says Morgado. “We need to keep observing, and also to look far, far away from the bodies just to see if there is something there. Because the Roche limit may not be the limit anymore.”
