“New Discovery: Two Rings Around Dwarf Planet Quaoar in the Kuiper Belt”

why it matters

Scientists still don’t fully understand how the dust and gas in the early solar system combined to form moons and planets.

Like the first ring around the Quaoar, which was announced in February by a team of astronomers, the second ring lies outside the Roche limit. Material orbiting near this distance tends to be torn apart by tidal forces. Thus, a ring within the Roche limit will tend to remain a ring, whereas a debris ring outside the Roche limit will usually coalesce into a moon.

For Quaoar, the Roche limit is calculated to be 1,100 miles. The second ring, at 1,500 miles from the center of the Quaoar, is even closer than the ring announced in February, which has a radius of about 2,500 miles.

background

Quaoar (pronounced KWA-wahr, the name of a creator god native to the Tongva who lives around Los Angeles) orbits the Sun in the Kuiper Belt, the region of frozen debris beyond Neptune that includes Pluto.

The ring is not visible in the telescope image. Instead, astronomers find it indirectly, when distant stars pass behind the Quaoar, blocking the starlight. From 2018 to 2021, Quaoar passed in front of four stars, and astronomers on Earth were able to observe a shadow eclipse, also known as a stellar eclipse.

They also noticed some dimming of the starlight before and after the star’s flash, indicating the presence of the first rings.

Another occultation took place on Aug. 9 last year, and astronomers are once again pointing telescopes, large and small, at the Quaoar in hopes of learning more about the rings.

The new observations reveal more details including a narrow, dense core in a ring only a few miles wide, which is surrounded by more dispersed material. The note also reveals the second episode.

Then, how

Another disappearance will occur on May 13, visible to telescopes in the United States and Canada.

“This event includes a bright star and will be useful for better constraining the shape of Quaoar, as well as a great opportunity to get more details about these two extraordinary rings,” said Mr. Pereira.

A possible explanation for Quaoar’s distant rings is the existence of the moon Weywot. The moon may have caused gravitational perturbations that prevented ring particles from accumulating on additional moons. Both rings occur at locations close to what is known as resonance with Weywot, and resonance may become more important than the Roche limit for determining whether a ring turns into a moon or stays a ring.