New data from Webb suggests two of Uranus’ outer rings are starkly different
Click for original image.
Using new infrared data obtained by the Webb Space Telescope in February 2025 and combined with optical data previously obtained by the ground-based Keck Observatory in 2007 and the Hubble Space Telescope in 2003 and 2013, astronomers now think that two adjacent outer rings of Uranus are completely different from each other, with one ring largely created by icy material thrown off the moon Mab.
The infrared image to the right was taken by Webb, and shows the two subject rings, dubbed v and μ.
Though they orbit the same planet, Uranus’s μ and ν rings are fundamentally different. Prior observations with the combined Keck Observatory and HST showed that the μ ring appeared blue, a signature of extremely small particles, while the ν ring’s reddish hue points to a more typical dusty ring. Why the rings were so different remained a mystery, though.
When JWST came on-line and observed Uranus, the research team used all its data, taken at different infrared wavelengths, in combination with Keck Observatory and HST observations to construct a complete spectrum from the visible through to infrared. By analyzing how sunlight reflects off the rings, the team identified a strong absorption feature near a wavelength of 3 microns (3 millionths of a meter) visible in the infrared for both rings. Beyond that shared feature, the differences become clear when simulating the detailed spectra: the μ ring closely matches the spectral signature of water ice, while the ν ring is clearly composed of rocky material, mixed with approximately 10–15% carbon-rich organic compounds commonly found in the outer solar system.
The μ ring seems to be made up of tiny icy grains knocked off the planet’s small (12-km sized) moon, Mab, by micrometeorite impacts. Interestingly, the icy composition of the μ ring also confirms that the moon Mab is composed mostly of water-ice.
According to the paper’s abstract, the v ring is dusty and, “like typical dusty rings, is sourced from collisions between, and micrometeoroid impacts on, larger but as yet unseen parent bodies orbiting within this ring. These bodies must be composed in part of organic materials [molecules with carbon as one component].”
This data really only raises more questions than it answers. For one, what are those larger objects within the v ring? Without a nearby orbiter there is no way to find them. For another, this new data really doesn’t explain why these two adjacent rings are so different. What processes force such a distinct distribution of materials?
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Click for original image.
Using new infrared data obtained by the Webb Space Telescope in February 2025 and combined with optical data previously obtained by the ground-based Keck Observatory in 2007 and the Hubble Space Telescope in 2003 and 2013, astronomers now think that two adjacent outer rings of Uranus are completely different from each other, with one ring largely created by icy material thrown off the moon Mab.
The infrared image to the right was taken by Webb, and shows the two subject rings, dubbed v and μ.
Though they orbit the same planet, Uranus’s μ and ν rings are fundamentally different. Prior observations with the combined Keck Observatory and HST showed that the μ ring appeared blue, a signature of extremely small particles, while the ν ring’s reddish hue points to a more typical dusty ring. Why the rings were so different remained a mystery, though.
When JWST came on-line and observed Uranus, the research team used all its data, taken at different infrared wavelengths, in combination with Keck Observatory and HST observations to construct a complete spectrum from the visible through to infrared. By analyzing how sunlight reflects off the rings, the team identified a strong absorption feature near a wavelength of 3 microns (3 millionths of a meter) visible in the infrared for both rings. Beyond that shared feature, the differences become clear when simulating the detailed spectra: the μ ring closely matches the spectral signature of water ice, while the ν ring is clearly composed of rocky material, mixed with approximately 10–15% carbon-rich organic compounds commonly found in the outer solar system.
The μ ring seems to be made up of tiny icy grains knocked off the planet’s small (12-km sized) moon, Mab, by micrometeorite impacts. Interestingly, the icy composition of the μ ring also confirms that the moon Mab is composed mostly of water-ice.
According to the paper’s abstract, the v ring is dusty and, “like typical dusty rings, is sourced from collisions between, and micrometeoroid impacts on, larger but as yet unseen parent bodies orbiting within this ring. These bodies must be composed in part of organic materials [molecules with carbon as one component].”
This data really only raises more questions than it answers. For one, what are those larger objects within the v ring? Without a nearby orbiter there is no way to find them. For another, this new data really doesn’t explain why these two adjacent rings are so different. What processes force such a distinct distribution of materials?
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News