Astronomers at the University of California at Berkeley measured the temperature of the mysterious rings surrounding Uranus for the first time using data from the Atacama Large Millimeter Array (ALMA) and the Very Large Telescope (VLT).
They found that the largest, most visible ring – called an 'epsilon ring' – has some unusual features compared to other rings surrounding the distant ice giant.
'Basically, Saturn's ice rings are wide, bright, and have a range of particle sizes, from micron-sized dust in the innermost D-ring to tens of meters in the main rings,' says Imke de Pater, a professor at the University of California at Berkeley and lead author of the study published on this week in the Astronomical Journal. 'A small fraction is absent from the main rings of Uranus; the brightest ring, epsilon, is made up of golf-ball-sized and larger stones. '
Astronomers first discovered that Uranus has rings – just like its solar system buddies Jupiter, Neptune and Saturn – back in 1977. But many questions regarding their composition and origin remained unanswered.
Now, thanks to new data, astronomers have determined that the rings exist at temperatures of -196 degrees Celsius, about -321 degrees Fahrenheit, or about the boiling point of liquid nitrogen at standard pressure.
Other planets in our solar system have rings of larger particles or powdery dust, or a mixture of both. For example, the rings of Jupiter and Neptune are mostly made up of small particles.
But the rings of Uranus had dust between the rings, while the rings themselves had no dust at all.
“We already know that the epsilon ring is a little weird because we don't see small particles,” said UC Berkeley graduate student Edward Molter.
The rings are also “extremely narrow compared to those of Saturn,” Molter explained. “The widest, epsilon ring is 20 to 100 kilometers wide, while Saturn's rings are hundreds or tens of thousands of kilometers wide.”
So what caused the rings to form? Was it a mysterious planet that slammed into Uranus, causing it to deviate from the plane of the Sun and release a bunch of particles?
However, the discovery may give us insight into the nature and origin of the rings of Uranus.
“This is a step towards understanding the composition and whether all rings come from the same starting material or is different for each ring,” added Molter.
Sources: Photo: ALMA (ESO / NAOJ / NRAO)
