Uranus is among the farthest planets in our solar system, and as such, it’s incredibly difficult to observe with lower-range and mid-range telescopes. Only the largest scientific telescopes can observe it and its rings. In fact, the rings of Uranus weren’t discovered until 1977, and now new heat images taken by two telescopes in the deserts of Chile reveal the rings’ mesmerizing brightness.
Using thermal glow, astronomers can study the rings of Uranus from a different perspective and see them much better than they could through other telescopes. The new heat images were taken by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Telescope (VLT). The observations show that the brightest and densest ring, also known as the epsilon ring, is different than other ring systems in our solar system, even different than the spectacular ring system on Saturn.
“Saturn’s mainly icy rings are broad, bright and have a range of particle sizes, from micron-sized dust in the innermost D ring, to tens of meters in size in the main rings,” University of California, Berkeley astronomy professor Imke de Pater said in a statement. “The small end is missing in the main rings of Uranus; the brightest ring, epsilon, is composed of golf ball-sized and larger rocks.”
Jupiter’s ring system is made of small, micron-sized particles, while Neptune’s rings are made mostly of dust. Two of Uranus’ main rings have a sheet of dust.
“We already know that the epsilon ring is a bit weird, because we don’t see the smaller stuff,” graduate student Edward Molter said. “Something has been sweeping the smaller stuff out, or it’s all glomming together. We just don’t know. This is a step toward understanding their composition and whether all of the rings came from the same source material, or are different for each ring.”
The rings likely formed from smaller asteroids that were captured by the planet’s gravity and then smashed. The rings are also believed to consist of remnants of moons the planet had before they crashed into an asteroid or that got too close to the planet and got torn apart. They could also be dust particles captured by the planet during the early days of the solar system when the planet was still forming and its surroundings were chaotic. The findings were published in the Astronomical Journal but are currently available on the free pre-print website arXiv.
“The rings of Uranus are compositionally different from Saturn‘s main ring, in the sense that in optical and infrared, the albedo is much lower: they are really dark, like charcoal,” Molter said. “They are also extremely narrow compared to the rings of Saturn. The widest, the epsilon ring, varies from 20 to 100 kilometers wide, whereas Saturn’s are 100’s or tens of thousands of kilometers wide.”
Until now, researchers were able to count 13 rings on Uranus, and there was also a band of dust between the rings.
“It’s cool that we can even do this with the instruments we have,” he said. “I was just trying to image the planet as best I could and I saw the rings. It was amazing.”