The Rings of Uranus

Saturn’s rings are so prominent that they easily visible from Earth with a small telescope. All the other gas giant planets have ring as well, but they weren’t discovered until we were able to look at those planets from above the Earth’s atmosphere. Here are some pictures of the ring system around Uranus taken by the Hubble Space Telescope as our point of view shifted over several years. The next time the rings will be edge-on will be in 2049.

Image Credit: NASA / ESA / STScI

Daphnis Makes Waves

daphnis-wavesDaphnis is one of Saturns small moons that is embedded in the Keeler gap in the ring system. This  image from Cassini shows it kicking up waves as it orbits.

Daphnis is only about 8 km across, but its gravity is powerful enough to disrupt the particles  near the edge of the A ring at the Keeler gap’s edge. Wave-like features form as the moon moves along.

Image Credit: NASA

Ring Details

ring-detailsSaturn’s rings are made up of many smaller ringlets that blur together when seen from a distance, but when imaged up close, their structures show a wide range of variation. Ring scientists are debating the nature of these features—whether they have always appeared this way or whether they have evolved over time.

Image Credit: NASA

Broken Rings?

broken ringsThat’s not a gap in Saturn’s rings. It’s the planet’s shadow. During most of Saturn’s year, the planet’s shadow extends well beyond the edge of the rings.  However, with summer solstice fast approaching, the Sun is higher in Saturn’s sky and most of Saturn’s A ring is completely shadow-free.

Saturn’s large moon Titan, its northern hemisphere in sunlight of late spring, hangs above the rings.

Image Credit: NASA

Crossed Rings?

Criss-cross RingsNope, but at first glance, Saturn’s rings seem to be intersecting themselves in an impossible way. This view from the Cassini spacecraft shows the rings in front of the planet and the shadows of the rings on the planets clouds. Because rings like the A ring and Cassini Division are not entirely opaque, those shadows can be seen through the rings themselves. If you look closely, you can spot the moon Pan near image’s center. Pan orbits in a space call the Encke Gap and keeps that band essentially clear.

Image Credit: NASA

A Great Divide

A Great DivideThe rings of Saturn are very thin, but they are very, very wide; the Cassini Division (seen here between the bright B ring and dimmer A ring) is almost as wide as the planet Mercury. The 4,800-km-wide division in Saturn’s rings is probably caused by the moon Mimas. Particles within the division orbit Saturn almost exactly twice for every time Mimas orbits. That results in a series of gravitational nudges from the moon which sculpt the outer edge of the B ring and keep its particles from drifting into the Cassini Division.

Image Credit: NASA

B and C in UV

RingsInUVOn 1 July, 2004, the Cassini spacecraft arrived at Saturn, marking the end of the spacecraft’s nearly seven-year journey through the solar system and the beginning of its tour of Saturn and the planet’s rings and moons.

This picture was taken in ultraviolet on 30 June, 2004 during Cassini’s orbital insertion maneuver. It shows, from left to right, the outer portion of the C ring and inner portion of the B ring which begins a little more than halfway across the image. The “dirty” particles are indicated by red, and “cleaner: ice particles shown in turquoise.

Saturn’s ring system is labeled from the inside out with the D, C, B and A rings followed by the F, G and E rings.

Image Credit: NASA

New Moon?

new_moonThe Cassini spacecraft has documented the formation of a small icy object within the rings of Saturn that might be a new moon. It may also provide clues about the formation of some of the planet’s known moons.

Images taken with Cassini‘s narrow angle camera show disturbances at the very edge of Saturn’s A ring, the outermost of the planet’s large, bright rings. One of the disturbances is an arc about 1,200 km long and 10 km wide that is roughly 20 percent brighter than the surrounding ring.

The object is not expected to grow any larger, and may even be falling apart, but the process of its formation and outward movement in the ring aids in our understanding of how Saturn’s icy moons, including the cloud-wrapped Titan and ocean-holding Enceladus, may have formed in more massive rings long ago. It also provides insight into how Earth and other planets in our solar system may have formed and migrated away from the Sun.

Image Credit: NASA

Saturn’s Rings in Infrared

Rings in IRHo, hum. Another picture of Saturn’s rings.

This one was made by the Cassini spacecraft using an infrared filter. The bright spot on the rings is the “opposition surge” where the Sun-Ring-Spacecraft angle passes through zero degrees. The size and magnitude of this bright spot to analyze the surface properties of the ring particles.

Image Credit: NASA

Planetary Rings

RingsThese belong to Jupiter, not Saturn. The ring system of Jupiter was imaged by the Galileo spacecraft in 1996. This image the west ansa (the edge of a ring system) of Jupiter’s main ring has a resolution of 24 km per pixel. Plotting the brightness of ring from the inner-most edge of the image to the outer-most through the thickest part of the ring, shows the “dips” in brightness caused by perturbations from satellites. Two small satellites, Adrastea and Metis, which are not seen in this image, orbit through the outer portion of the ansa much like the small moon that shepherd Saturn’s rings.

Image Credit: NASA

An Unusual View of Saturn

saturn_irThis high-contrast, false-color mosaic from the Cassini spacecraft shows an infrared view of a slice of the Saturn system as it was backlit by the sun on 19 July, 2013. The exaggerated contrast brings out subtleties not initially visible. For example, structures in Saturn’s wispy E ring, which we believe to be made of ice from the moon Enceladus, stand out this exaggerated view.

The data for the image by Cassini’s visual and infrared mapping spectrometer. It covers a swath about 8,000 km wide across Saturn and its rings and about 540,000 km across that includes the planet and its rings out to the E ring, Saturn’s second most distant ring.

Image Credit: NASA

Saturn and Meteors

Saturn_meteorsThe solar system is full of small, speeding objects. These objects frequently pummel planetary bodies. Saturn’s rings are the only location besides Earth, the Moon, and Jupiter where astronomers have been able to observe impacts as they occur. The meteoroids at Saturn are estimated to range from about a centimeter up to several meters in size. NASA’s Cassini spacecraft has found the first direct evidence of small meteoroids breaking into streams of rubble as they crashed into Saturn’s rings.

The Saturnian equinox in summer 2009 was an excellent time to see the debris kicked up by meteoroid impacts. The very low sun angle on the rings caused the clouds of debris to stand out brightly against the darkened rings. The tiny particles forming these clouds have a range of orbital speeds around Saturn, and the clouds they form are pulled into diagonal, extended bright streaks as can be seen in the five pictures above.

The objects hitting the rings in these photos were probably roughly the same size as the Russian meteor of last February.

Image Credits: NASA

Jupiter’s Rings

Saturn’s rings are so prominent that they can be seen through a small telescope from Earth, but the other gas giant planets, Jupiter, Uranus, and Neptune, have ring systems as well. Jupiter's Rings

Jupiter’s rings were discovered by Voyager 1 in a single image that was targeted specifically to search for a possible ring system. Voyager 2 was reprogrammed en route to take a more complete set of pictures. The image above is from that series. We now known that the system has three major components. The Main ring is about 7,000 km wide and has an abrupt outer boundary roughly 129,000 km from the center of the planet. This ring encompasses the orbits of two small moons, Adrastea and Metis, which probably are the source for the material that makes up most of the ring. The main ring merges gradually into the Halo on the side toward Jupiter. The halo is a broad, faint, donut of material about 20,000 km thick and extending halfway from the main ring down to the planet’s cloudtops.

Around the main ring is the broad and exceedingly faint Gossamer ring. It extends out beyond the orbit of the moon Amalthea and is probably composed of dust particles less than 10 µm in diameter. That’s roughly the size of cigarette smoke particles. It extends to an outer edge of about 129,000 km from the center of the planet and inward to about 30,000 km. The origin of the ring is probably material knocked loose by micrometeorite bombardment of the tiny moons orbiting within the ring.

Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields make up the Jovian magnetosphere or magnetic environment which extends up to 7 million km toward the Sun and stretches outward 750 million km in a windsock shape to Saturn’s orbit.

Image Credit: NASA

Tethys and the Rings

We have no idea how old Saturn’s rings are. One possibility is that the rings were formed relatively recently in our Solar System’s history. It could be that only 100 million or so years ago a moon-sized object broke up near Saturn. One bit of evidence for young rings is the fact that the rings are so bright and relatively unaffected by numerous small dark spots caused by meteor strikes. However, a recent discovery raises the possibility that some of Saturn’s rings could be billions of years old—almost as old as Saturn itself. Inspection of images taken by the Saturn-orbiting Cassini spacecraft indicates that some of Saturn’s ring particles temporarily bunch and collide, effectively refinishing the surfaces of the ring particles by uncovering fresh bright ices. This picture taken by Cassini shows Saturn’s rings in their true colors. Tethys, one of Saturn moons, is visible in front of the darker rings.

Image Credit: NASA