Astronomers See "Warm" Glow of Uranus's Rings
by Staff Writers
Berkeley CA (SPX) Jun 21, 2019
The rings of Uranus are invisible to all but the largest telescopes - they weren't even discovered until 1977 - but they're surprisingly bright in new heat images of the planet taken by two large telescopes in the high deserts of 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 100's 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," he 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.
Research Report: Thermal Emission from the Uranian Ring System
On Pluto the Winter is approaching, and the atmosphere is vanishing into frost
Lisbon, Portugal (SPX) May 21, 2019
With less than a fifth of the Moon's mass, Pluto can still retain an atmosphere, though a tenuous envelope of gas produced by the periodical sublimation of nitrogen ices. A study that followed the evolution of Pluto's atmosphere for fourteen years shows its seasonal nature, and predicts that it will now start to condensate as frost. This study1 was published in the journal Astronomy and Astrophysics and had the participation of Pedro Machado, of Instituto de Astrofisica e Ciencias do Espaco (IA2) ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.|