Second 'impossible' ring found around dwarf planet: Why it's important
Earlier this year, scientists were amazed when they found a ring around the faraway dwarf planet, Quaoar, which lies beyond Neptune. The planet's ring, which is akin to the one that Saturn possesses, lies at a distance that is law-defying, per researchers. Now, it turns out that the mini planet does not have just one but two such 'impossible' rings.
Why are they called 'impossible' rings?
The newly discovered ring around Quaoar lies beyond what's called the Roche limit—the distance within which the gravitational field of a celestial body is strong enough to prevent any smaller body from being held together by gravity. Orbiting material within this limit will likely disperse and form rings. Outside the Roche limit, the material would usually coalesce into a moon.
Quaoar's rings lie beyond the Roche limit
For the dwarf planet Quaoar, the Roche limit is estimated to be roughly 1,170 kilometers. Quaoar's newly discovered ring lies roughly 2,400 kilometers from the center of the planet, which means the ring should have collapsed to form a moon, but that hasn't happened. The other 'impossible' ring lies farther away at nearly 4,100 kilometers from Quaoar's center.
How did the scientists find the rings?
Quaoar's rings were not detected using telescopes. Instead, scientists discovered them using a rather indirect method. Observations were made when distant stars passed behind Quaoar, as a result of which starlight was blocked. Quaoar passed in front of four distant stars, between 2018 to 2021, and astronomers from Earth were able to take a look at these eclipses, what's known as stellar occultations.
Starlight dimming led to the discovery of the first ring
The dimming of the starlight was what pointed to the existence of the first ring. In August 2022, another stellation occultation occurred which led to the discovery of the second ring and it also provided more information about the first ring.
Another stellar occultation is supposed to occur on May 13
What's exciting is that an occultation is supposed to occur on May 13. It will be visible to telescopes in the US and Canada. "This event involves a bright star and will be useful to constrain the Quaoar shape better, in addition to being a good opportunity to obtain more details about these two remarkable rings," said Chrystian Luciano Pereira, from National Observatory, Brazil.
