Planetary Rings of Uranus ‘Glow’ in Cold Light

Summary: Using the both ALMA and the VLT, astronomers have imaged the cold, rock-strewn rings encircling the planet Uranus. Rather than observing the reflected sunlight from these rings, ALMA and the VLT imaged the millimeter and mid-infrared “glow” naturally emitted by the frigidly cold particles of the rings themselves.

The rings of Uranus are invisible to all but the largest telescopes — they weren’t even discovered until 1977 — and they stand out as surprisingly bright in new thermal images of the planet taken by two large telescopes in Chile.

The thermal glow gives astronomers another window onto the rings, which have been seen only because they reflect a little light in the visible, or optical, range and in the near-infrared. The new images taken by the Atacama Large Millimeter/submillimeter Array (ALMA)

and the Very Large Telescope (VLT) allowed the team for the first time to measure the temperature of the rings: a cool 77 Kelvin, or 77 degrees above absolute zero — the boiling temperature of liquid nitrogen and equivalent to 320 degrees below zero Fahrenheit.

The observations also confirm that Uranus’s brightest and densest ring, called the epsilon ring, differs from the other known ring systems within our solar system, in particular the spectacularly beautiful rings of 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,” said Imke de Pater, a UC Berkeley professor of astronomy. “The small end is missing in the main rings of Uranus; the brightest ring, epsilon, is composed of golf ball-sized and larger rocks.”

By comparison, Jupiter’s rings contain mostly small, micron-sized particles (a micron is a thousandth of a millimeter). Neptune’s rings are also mostly dust, and even Uranus has broad sheets of dust between its narrow main rings.

“We already know that the epsilon ring is a bit weird, because we don’t see the smaller stuff,” said graduate student Edward Molter. “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.”

Rings could be former asteroids captured by the planet’s gravity, remnants of moons that crashed into one another and shattered, the remains of moons torn apart when they got too close to Uranus, or debris remaining from the time of formation 4.5 billion years ago.

The new data were published this week in The Astronomical Journal. De Pater and Molter led the ALMA observations, while Michael Roman and Leigh Fletcher from the University of Leicester in the United Kingdom led the VLT observations.

“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 hundreds or tens of thousands of kilometers wide.”

The lack of dust-sized particles in Uranus’s main rings was first noted when Voyager 2 flew by the planet in 1986 and photographed them. The spacecraft was unable to measure the temperature of the rings, however.

To date, astronomers have counted a total of 13 rings around the planet, with some bands of dust between the rings. The rings differ in other ways from those of Saturn.

“It’s cool that we can even do this with the instruments we have,” Molter said. “I was just trying to image the planet as best I could and I saw the rings. It was amazing.”

Both the VLT and ALMA observations were designed to explore the temperature structure of Uranus’ atmosphere, with VLT probing shorter wavelengths than ALMA.

“We were astonished to see the rings jump out clearly when we reduced the data for the first time,” Fletcher said.

This presents an exciting opportunity for the upcoming James Webb Space Telescope, which will be able provide vastly improved spectroscopic constraints on the Uranian rings in the coming decade.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


Contact: Charles E. Blue: Public Information Officer
[email protected]; 434-296-0314

Reference: “Thermal emission from the Uranian ring system,” E.M. Molter, et al., the Astrophysical Journal. Preprint:

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The Berkeley research was funded by the National Aeronautics and Space Administration (NNX16AK14G). Work at the University of Leicester was supported by the European Research Council (GIANTCLIMES) under the European Union’s Horizon 2020 research and innovation program (723890).

In Other News…

Adam Cohen, president of the entity that won the Corfo tender: “Our goal is to generate between 25 to 50 new companies in 10 years”

With the focus on putting the Clean Technologies Institute (ICTL) into operation soon is the Associated Universities, Inc. (AUI), the entity that won the Corfo tender that is being questioned by another of the consortiums that was in competition.

CORFO Selects AUI to Build and Manage the Chilean Instituto de Tecnologías Limpias

Santiago, Chile—On January 4th, the Corporación de Fomento de la Producción de Chile (CORFO) Council met to award the Chilean Instituto de Tecnologías Limpias (ICTL) construction, management, and operations to AUI.

CORFO Selects AUI to Build and Manage the Chilean Institute for Clean Technologies

AUI is honored by today’s decision by the Corporación de Fomento de la Producción de Chile (CORFO) to award the Chilean Institute for Clean Technologies (ICTL) construction, management, and operations contract to our team.

CORFO Awards Institute of Clean Technologies to a Consortium Led by AUI

The Corfo Council today awarded the Clean Technologies Institute (ICTL), the largest Research and Development (R&D) center and which will be located in the Antofagasta Region, to a consortium led by AUI (Associated Universities Inc)

Naperville bioscience lab taking aim at creating system to dramatically cut COVID-19 test processing time

A Naperville-based bioscience laboratory could help address the backlog of COVID-19 testing across the country and eventually assist the United States in more quickly confronting a future virulent pandemic.

New Partnership Emerges to Battle COVID-19

Naperville, IL—Today AUI and Radiance Diagnostics signed a memorandum of understanding to provide COVID-19 testing, support, and laboratory administration for the federal, state, and local government and businesses that require research and development assistance.

Cybersecurity in a fishbowl: How North Carolina’s Board of Elections handled it

The following is press coverage on NCSBE Cybersecurity, courtesy of Election security has never been more scrutinized than the 2020 presidential elections. It left election boards fighting not only to protect the election from outside influences but...

Industrial Cybersecurity: A Culture Change

The following is an article from UPDATE, the official publication of Utah Petroleum Association, Issue 4 2020.  Reliable operational technology (OT) or industrial control systems (ICS) underpin every facet of American lives. Without them, our defenses, our economy,...

How would Trump or Biden deal with grid hacking threats?

POLITICS How would Trump or Biden deal with grid hacking threats? Christian Vasquez, E&E News reporter Published: Tuesday, November 3, 2020 President Trump and Democratic presidential nominee Joe Biden have a few competing plans for the nation's cybersecurity —...

Big Astronomy Planetarium Show Premieres September 26

Big Astronomy planetarium show premieres September 26 Turn your phone into a planetarium with innovative and immersive 360° streaming San Francisco – The Big Astronomy worldwide premiere is coming soon to a smart phone or connected device near you! On September 26 at...

You are now leaving AUI

You will be redirected to the related partnering organization's website.

You will be redirected to
in 4 seconds...

Click the link above to continue or CANCEL