Monday Bites: Shining, Having Fun

 Monday Bites: Shining, Having Fun 

Credit: NASA, ESA, CSA, STScI. 

Dark and narrow, Uranus's rings are hard to spot. Unlike Saturn's rings, which consist of water mixed with some organic impurities, the chemical makeup of Uranus's rings stands unclear. Their very low reflectance allows astronomers to wager on the presence of some dark, possibly organic material.

In optical light, Uranus rises as a featureless world with apparently nothing going on. The most advanced optical telescopes fitted with state-of-the-art imaging systems and CCD detectors fail to reveal any of the rings, except for the bright and wide epsilon ring. Surprisingly enough, far away from expectations, the epsilon ring looks like a wispy trail.  

In infrared light, the entire landscape changes drastically. With around 2% methane in its atmosphere, Uranus shines like a pearl across infrared wavelengths. Now, through JWST's NIRCam, the previously unattractive planetary disc reveals a changing atmosphere. Rolling on its side, having an axial tilt of ninety-eight degrees, Uranus lives through extreme seasonal variations. For a quarter of the time during its eighty-four-year orbit around the Sun, one pole bathes in continuous sunlight, whereas the other dives into eternal night. During summer and winter solstice, Uranus's rings turn to the Sun face-on and stand edge-on during the equinoxes. The polar cap brightens as long it continues to face the Sun and darkens when away. 

Uranus has thirteen distinct ring systems divided among three groups: nine narrow main rings identified in 1977 — a serendipitous discovery from a different rung of observation, followed by two dusty rings discovered during Voyager 2's exploration of the ice giant, and over that, HST added two more, the nu and the mu rings, during 2003-2005. 

The little blue spots on the periphery of the nu ring are the nine among twenty-seven of Uranus's moons.