New Delhi:
Scientists have solved the mystery behind the origin and diversity of planetary rings that surround Saturn, Neptune and Uranus. Further, they have claimed that the formation of these rings occurred four billion years ago when large objects passed very close to planets and got destroyed.
Our solar system’s giant planets have very diverse rings. Observations display that Saturn's rings constitute 95 per cent icy particles, whereas in comparison Uranus and Neptune’s rings are darker and may constitute of higher rock content.
Researchers at Kobe University and Tokyo Institute of Technology in Japan have conducted the study while focusing on the period called the Late Heavy Bombardment which is believed to have occurred 4 billion years ago in our solar system, when the giant planets underwent orbital migration.
It is thought that thousands of Pluto-sized objects from the Kuiper belt existed beyond Neptune. Researchers calculated the probability that these large objects passed close to the giant planets and were destroyed by their tidal force during the Late Heavy Bombardment.
Results showed that Saturn, Uranus and Neptune experienced close encounters with these large objects multiple times. The team used computer simulations to study disruption of these Kuiper belt objects by tidal force when they passed the vicinity of the giant planets.
They discovered that in many cases fragments comprising 0.1-10 per cent of the initial mass of the passing objects were captured into orbits around the planet.
The combined mass of these captured fragments was found to be sufficient to explain the mass of the current rings around Saturn and Uranus.
The researchers also simulated the long-term evolution of the captured fragments using supercomputers at the National Astronomical Observatory of Japan.
From these simulations they found that captured fragments with an initial size of several kilometers are expected to undergo high-speed collisions repeatedly and are gradually shattered into small pieces.
Such collisions between fragments are also expected to circularize their orbits and lead to the formation of the rings observed today. This model can also explain the compositional difference between the rings of Saturn and Uranus.Compared to Saturn, Uranus and Neptune have higher density.
This means that objects can pass within close vicinity of the planet, where they experience extremely strong tidal forces.
As a result, if Kuiper belt objects have layered structures such as a rocky core with an icy mantle and pass within close vicinity of Uranus or Neptune, in addition to the icy mantle, even the rocky core will be destroyed and captured, forming rings that include rocky composition.
However if they pass by Saturn, only the icy mantle will be destroyed, forming icy rings. This explains the different ring compositions.
(With PTI inputs)
