RING FOUND BEYOND DWARF PLANET'S ROCHE LIMIT: WHY THIS MATTERS

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Last Updated17/02/2023

As per a new study, astronomers have found a ring around a dwarf planet, located in the Kuiper Belt at the solar system’s edge, called Quaoar.
The ring, however, is positioned much further away from the planet than is usual and defies theoretical explanations.
According to the study, the ring lies far away from the Roche limit — a mathematically determined distance beyond which rings aren’t supposed to exist.

With an estimated radius of 555 km, Quaoar is roughly half the size of Pluto and orbits beyond Neptune.
It also has a moon of its own, which is known as Weywot.
It is too small & distant to be observed directly, so the ring was detected with the help of a phenomenon called stellar occultation.

It occurs when, as seen from Earth, a bright star passes behind a planet.
It allows astronomers to observe the sharp silhouette of the planet for a brief period of time.
The rare phenomenon is used by researchers to analyse a planet’s atmosphere & determine if it has a ring around it.
In 1977, scientists discovered the Uranian ring system with the help of stellar occultation.
During 2018 - 2021, the dwarf planet passed in front of four stars, helping researchers observe the shadow of the eclipses.

The Earth’s gravity pulls on the moon.
However, one side of the moon is closer to the planet and hence, the pull is stronger on the side facing the Earth.
The result is the so-called tidal force, which either stretches or compresses the moon from all sides.
What helps the moon keep it together is its own gravity. It counteracts the effect of the tidal force.
But if you bring the moon closer to the Earth, the tidal force will overcome the satellite’s gravity and then disintegrate it, turning the moon into a ring.
The minimum distance at which this happens is known as the Roche limit.
It is named after the French astronomer Édouard Roche, who discovered the limit in 1848.
It is applicable to any planet and the celestial bodies around it.
Eg, Saturn. The rings that you see around the planet are within the Roche limit and therefore, there are no moons in that area.