Uranus has 13 invisible rings that shine new images

Uranus infrared view over two days in July 2004.Lawrence Sromovsky, University of Wisconsin-Madison / W.W. Keck Observatory

Four decades after their discovery, the 13 mysterious rings surrounding Uranus have again surprised astronomers this summer.

In June, the new images captured for the first time their warm glow. Well, hot for Uranus.

At -320 degrees Fahrenheit, the rings are 10 degrees warmer than the surface of the planet, the coldest of our solar system. Scientists have determined the temperature of the rings with these thermal images.

The results were described in a study published in the Astronomical Journal last month. To capture the images, the researchers used the Atacama Large Millimeter Array and the Very Large Telescope in Chile to measure the thermal structure of the Uranus atmosphere. They were surprised to find that they had raised the thermal readings of the rings of the planet.

"It's cool that we can even do that with the instruments we have," said Edward Molter, a graduate student at the University of California at Berkeley and senior author of the study, in a press release. "I was just trying to imagine the planet my best and I saw the rings. It was amazing."

This composite image shows for the first time the heat of the Uranus rings, allowing scientists to determine their temperature: an icy 77 Kelvin (-320 Fahrenheit).Image of UC Berkeley by Edward Molter and Imke de Pater

Molter and his co-author, Imke de Pater, professor of astronomy, have created the composite image above, which shows the thermal glow of the rings at radio wave lengths. The dark bands of the image capture molecules that absorb radio waves. In the case of Uranus, it is likely to be hydrogen sulfide. The yellow spot is the North Pole of the planet, where these molecules are rare.

"We were amazed to see the rings jump clearly when we first downsized the data," said Leigh Fletcher, Telescope Observer.

The study confirmed that the epsilon ring of Uranus – the brightest, widest and densest ring on the planet – is unique among the other rings of our solar system .

Saturn's ice rings, bright enough and wide enough to be viewed with a standard telescope, consist of particles of different sizes, ranging from a thousandth of a millimeter wide to ice blocks of the same size. 'a house. The rings of Jupiter and Neptune are mainly composed of these tiny particles of dust.

These images of the ALMA and VLT telescopes captured the Uranus ring system at different wavelengths. The planet itself is hidden because it is very bright compared to the rings.Edward Molter, Imke of Pater, Michael Roman and Leigh Fletcher

The Urnaus epsilon ring, however, contains only rocks at least the size of a golf ball.

"We already know that the epsilon ring is a bit odd because we do not see the smallest things," said Molter. "Something has swept the little things, or everything is greedy.We do not know it.It is a step forward to understand their composition and find out if all the rings come from the same source material or are different for each ring . "

Astronomers first identified the rings of Uranus in 1977. They took so long to notice them because they are much thinner and darker than the rings of Saturn. They reflect only very small amounts of light in the visible, with more reflection in the infrared and near infrared light ranges.

"They are really dark, like charcoal," said Molter.

Voyager 2 photographed the first close-up images of Uranus in 1986. At the time, astronomers thought that the planet had only nine rings. The spaceship showed them two more.NASA / JPL-Caltech

After Voyager 2 flew over Uranus and took the first pictures of the planet closely, in 1986, scientists found the absence of tiny particles of dust in its rings.

The reasons for this unique ring composition are still unknown: the Uranus rings could come from asteroids that fell into orbit around Uranus, remains of moons that would have crashed or torn by the gravity of the planet, or debris left by the formation. of the solar system.

NASA's James Webb Space Telescope, which is expected to be launched in 2021, will help to observe the mysterious rings in more detail.