We have seen magnificent images of Saturn’s rings. But did you know, it is not the only planet with a ring? All four outer planets — Jupiter, Saturn, Uranus, and Neptune — have rings. But the rings of Uranus have had scientists scratching their heads for decades. They have known about 11 such rings since the 1970s, and discovered two more in 2005, taking the number to 13. Altogether, these rings pervade the orbits of the planet’s 27 moons.
We are yet to find out a lot of things about the planet’s rings, including what exactly they are made of. The rings of Uranus contain pieces larger than golf balls, and no dust, unlike the rings of other outer planets. There is debris between the rings, and the widths of the rings are around 20 to 100 kilometres, about 100 times narrower than the rings of Saturn. They are also much darker than the rings of the outer planets, making them difficult to study with telescopes.
Uranus is different from other planets — its axis of rotation is tilted 98º to the plane of the solar system. Till today, scientists do not know what caused this. But its rings might offer some clue.
As the planet rotates flat on its belly, its rings appear vertical in images taken of the planet. Astronomers think that Uranus was hit by an object twice as massive as the Earth, during the formation of the solar system, tilting its axis forever. This collision could not only have given birth to the rings from the resulting debris, but over time, the rings themselves could have caused the orbit to tilt further. As the axes of rotation of the planet and the debris from the collision were not aligned, they could have gotten together in a fierce battle to settle into equilibrium. This could explain why the strange tilt of the planet’s axis, and why all its moons and rings lie in the same plane around it.
Scientists have barely started scratching the surface of the mysterious rings. Who knows what discovery lies ahead?