Saturn's C and B Rings in Ultraviolet Light

This colorful cosmic rainbow portrays a section of Saturn’s beautiful rings, four centuries after they were discovered by Galileo Galilei.

Saturn’s rings were first observed in 1610. Despite using his newly created telescope, Galileo was confounded by what he saw: he referred to the peculiar shapes surrounding the planet as “Saturn’s children”. Only later did Christiaan Huygens propose that the mysterious shapes were actually rings orbiting the planet. These were named in the order in which they were discovered, using the first seven letters of the alphabet: the D-ring is closest to the planet, followed by C, B, A, F, G and E.

The data for this image, which shows the portion of the C-ring closest to Saturn on the left, with the B-ring beginning just right of center, were acquired by Cassini’s Ultraviolet Imaging Spectrograph, or UVIS, as the spacecraft entered into orbit around Saturn on 30 June 2004.

UVIS, as its name suggests, carries out observations in ultraviolet wavelengths. During the Saturn orbit insertion maneuver, when Cassini flew closest to the rings, UVIS could resolve features up to 97 km across. The region shown in this image spans about 10,000 km.

The variation in the color of the rings arises from the differences in their composition. Turquoise-hued rings contain particles of nearly pure water ice, whereas reddish rings contain ice particles with more contaminants.

Saturn’s prominent and complex ensemble of rings is the best studied in the Solar System, but it is still not known how the rings formed. One suggestion is that they formed at the same time as the planet and that they are as old as the Solar System. Another idea is that they formed when icy material was pulled from another body into Saturn’s gravitational field, in which case the rings could be younger than the planet.

One thing is sure: as Cassini searches for answers it is providing amazing images of these rainbow rings.

The Cassini–Huygens mission is a cooperative project of NASA, ESA and Italy’s ASI space agency.

This image was first published at the NASA Cassini website, in 2004.

Image credit: NASA/JPL/University of Colorado

Saturn and Shadows

Saturn's rings cast shadows on the planet, except their shadows appear to be inside out! The edge of the outermost A ring can be seen at the top left corner of the image. Moving towards the bottom of the page, one can see the faint Cassini Division, the opaque B ring and the innermost C ring, which contains several ringlets that appear dark against Saturn in this geometry. The bottom half of the image features the shadows of these rings in reverse order superposed against the disk of the planet: the C ring, the B ring, the Cassini Division and the inner half of the A ring.

This view looks toward the unilluminated side of the rings from about 28 degrees below the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on December 2, 2013 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 57 degrees. Image scale is 45 miles (72 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Saturn's D-Ring

Saturn's D ring is easy to overlook since it's trapped between the brighter C ring and the planet itself. But this dusty ring has plenty to teach us. In this view, all that can be seen of the D ring is the faint and narrow arc as it stretches from top right of the image.

If all goes as planned, Cassini will pass between the D ring and Saturn in its final orbits in 2017. Scientists expect to gather unprecedented data from these orbits.

Also visible in this image are 12 stars.

This view looks toward the unilluminated side of the rings from about 41 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 21, 2013.

The view was obtained at a distance of approximately 1.5 million miles (2.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. Image scale is 8.7 miles (14 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Titan Ringlet and Bending Wave in Saturn's Rings

A dynamical interplay between Saturn's largest moon, Titan, and its rings is captured in this view from NASA's Cassini spacecraft.

At every location within Saturn's rings, particles orbit with a particular period, or rhythm. This image is focused on two separate and nearby locations in the rings where those rhythms are in synchrony with different aspects of Titan's 16-day orbit, creating signature effects that point from a distance back towards Titan.

The Titan Ringlet, embedded within the Colombo Gap at the center of this image, is slightly oval-shaped and always points its long axis towards Titan. The behavior and orientation of the ringlet are controlled by a gravitational resonance between Titan's 16-day orbit and the rate at which ring particles' oval-shaped paths rotate ("precess") around the planet. Because the particles' orbit precession is sensitively tied to Saturn's internal gravity structure, the radial location of the Titan Ringlet supplies scientists with the best available measurement of the outer layers of Saturn's interior.

Just inward of the gap is a very narrow feature that transitions from bright at the top of the image to dark at the bottom. This is a bending, or vertical, wave generated by a similar resonance with Titan, but this time it involves a synchronicity between the out-of-plane motion of Titan, which is on an inclined (tilted) orbit and similar motions of the ring particles with their own inclined orbits. In this image, taken near Saturn's 2009 equinox when sunlight hit the rings nearly edge-on, the vertical structure of the bending wave is obvious because of shadows giving it an unusual bright-to-dark appearance.

Also visible because of the shallow illumination angle is the vertical corrugation that crosses the entire C ring. This is the after-effect of a large impactor that is believed to have hit the inner Saturnian rings around the year 1983. Looking like a pattern of faint stripes, the corrugation is best seen on the right-hand side of the image, where other ring structure is sparse.

This view looks toward the sunlit side of the rings from about 9 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on September 20, 2009.

The view was obtained at a distance of approximately 288,000 miles (463,000 kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 13 degrees. Image scale is 1 mile (2 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Note: For more information, see Cassini Sees Saturn and Moons in Holiday Dress.

Saturn

A swing high above Saturn by NASA's Cassini spacecraft revealed this stately view of the golden-hued planet and its main rings. The view is in natural color, as human eyes would have seen it. This mosaic was made from 36 images in three color filters obtained by Cassini's imaging science subsystem on October 10, 2013. The observation and resulting image mosaic were planned as one of three images for Cassini's 2013 Scientist for a Day essay contest.

Saturn sports differently colored bands of weather in this image. For instance, a bright, narrow wave of clouds around 42 degrees north latitude appears to be some of the turbulent aftermath of a giant storm that reached its violent peak in early 2011. The mysterious six-sided weather pattern known as the hexagon is visible around Saturn's north pole.

When Cassini arrived in 2004, more of the northern hemisphere sported a bluish hue and it was northern winter. The golden tones dominated the southern hemisphere, where it was southern summer. But as the seasons have turned and northern spring is in full swing, the colors have begun to change in each hemisphere as well. Golden tones have started to dominate in the northern hemisphere and the bluish color in the north is now confined to a tighter circle around the north pole. The southern hemisphere has started getting bluer, too.

The rings shown here include Saturn's main rings. The innermost D ring, and the C, B and A rings are easily seen. The F ring is also there, but not easily seen without enhancing the contrast of the image. (Rings were named in order of their discovery rather than their position around Saturn.) The rings also cast a shadow on Saturn at the limb of the planet in the lower right quadrant.

Cassini is currently in a set of tilted orbits known as "inclined orbits" that allow it to swing up over the north pole and below the south pole. Much of Cassini's time is spent close to the equatorial plane, where most of Saturn's rings and moons are located.

Image credit: NASA/JPL-Caltech/SSI/Cornell

Note: For more information, see Cassini Swings Above Saturn to Compose a Portrait.

Clouds from Meteor Impacts with Saturn's Rings

Five images of Saturn's rings, taken by NASA's Cassini spacecraft between 2009 and 2012, show clouds of material ejected from impacts of small objects into the rings. Clockwise from top left are two views of one cloud in the A ring, taken 24.5 hours apart, a cloud in the C ring, one in the B ring, and another in the C ring. Arrows in the annotated version point to the cloud structures, which spread out at visibly different angles than the surrounding ring features.

The clouds of ejected material were visible because of the angle sunlight was hitting the Saturn system and the position of the spacecraft. The first four images were taken near the time of Saturn equinox, when sunlight strikes the rings at very shallow angles, nearly directly edge-on. During Saturn equinox, which occurs only every 14.5 Earth years, the ejecta clouds were caught in sunlight because they were elevated out of the ring plane. The last image was taken in 2012 at a very high-phase angle, which is the sun-Saturn-spacecraft angle. This geometry enabled Cassini to see the clouds of dust-sized particles in the same way that dust on a surface is easier to see when the viewer is looking toward a light source.

The angle that the clouds are canted gives the time elapsed since the cloud was formed (see PIA14941). The A ring cloud formed 24 hours before its first apparition in the top left box; it formed 48.5 hours before the top middle image. The other three clouds were approximately 13 hours, four hours, and one hour old (respectively) at the times they were seen. See PIA11674 for more information on ring impacts.

Photo credit: NASA/JPL-Caltech/Space Science Institute/Cornell

Note: For more information, see PIA14941: A Race Around Saturn, PIA14942: A Race Around Saturn (Animation), NASA Probe Observes Meteors Colliding with Saturn's Rings, and Cassini Catches Meteors Hitting Saturn's Rings.

Golden Night on Saturn

Saturn's B and C rings shine in diffuse, scattered light as the Cassini spacecraft looks on the planet's night side. The southern hemisphere is lit by sunlight reflecting off the rings, while the north shines much more feebly in the dim light that filters through the rings and is scattered on the northern hemisphere.

The fine, innermost rings are seen silhouetted against the southern hemisphere of the planet before partially disappearing into shadow.

The color of the rings appears more golden because of the increased scattering in the rings brought about by the high phase angle and the view being toward rings' the unlit side. Saturn also looks more golden because of the high phase angle here.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained by the Cassini spacecraft wide-angle camera on September 28, 2006 at a distance of approximately 1.4 million kilometers (900,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 151 degrees. Image scale is 83 kilometers (51 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Saturn

The giant planet Saturn, as observed with the VLT NAOS-CONICA Adaptive Optics instrument on December 8, 2001; the distance was 1,209 million km. It is a composite of exposures in two near-infrared wavebands (H and K) and displays well the intricate, banded structure of the planetary atmosphere and the rings. Note also the dark spot at the south pole at the bottom of the image. One of the moons, Tethys, is visible as a small point of light below the planet. It was used to guide the telescope and to perform the adaptive optics "refocusing" for this observation. More details in the text.

This image of Saturn, the second-largest planet in the solar system, was obtained at a time when Saturn was close to summer solstice in the southern hemisphere. At this moment, the tilt of the rings was about as large as it can be, allowing the best possible view of the planet's South Pole. That area was on Saturn's night side in 1982 and could therefore not be photographed during the Voyager encounter. The dark spot close to the South Pole is a remarkable structure that measures approximately 300 km across. The bright spot close to the equator is the remnant of a giant storm in Saturn's extended atmosphere that has lasted more than 5 years.

The present photo provides what is possibly the sharpest view of the ring system ever achieved from a ground-based observatory. Many structures are visible, the most obvious being the main ring sections, the inner C-region (here comparatively dark), the middle B-region (here relatively bright) and the outer A-region, and also the obvious dark "divisions," including the well-known, broad Cassini division between the A- and B-regions, as well as the Encke division close to the external edge of the A-region and the Colombo division in the C-region. Moreover, many narrow rings can be seen at this high image resolution, in particular within the C-region.

Photo credit: ESO

Vertical Structures in Saturn's B-Ring

Vertical structures, among the tallest seen in Saturn's main rings, rise abruptly from the edge of Saturn's B ring to cast long shadows on the ring in this image taken by NASA's Cassini spacecraft two weeks before the planet's August 2009 equinox.

Part of the Cassini Division, between the B and the A rings, appears at the top of the image, showing ringlets in the inner division.

In this image, Cassini's narrow angle camera captured a 1,200-kilometer-long (750-mile-long) section arcing along the outer edge of the B ring. Here, vertical structures tower as high as 2.5 kilometers (1.6 miles) above the plane of the rings -- a significant deviation from the vertical thickness of the main A, B and C rings, which is generally only about 10 meters (about 30 feet).

Cassini scientists believe that this is one prominent region at the outer edge of the B ring where large bodies, or moonlets, up to a kilometer or more in size, are found. It is possible that these bodies significantly affect the ring material streaming past them and force the particles upward, in a "splashing" manner.

This image and others like it (see PIA11669) are only possible around the time of Saturn's equinox, which occurs every half-Saturn-year, or about every 15 Earth years. The illumination geometry that accompanies equinox lowers the Sun's angle to the ring plane and causes structures jutting out of the plane to cast long shadows across the rings. The "season" of equinox allows shadows to appear on the rings in the months before and after equinox, but the actual equinox occurred August 11, 2009, as the Sun shone directly edge-on to the ring plane.

This view looks toward the southern, sunlit side of the rings from about 32 degrees below the ring plane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 26, 2009. The view was acquired at a distance of approximately 336,000 kilometers (209,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 132 degrees. Image scale is 2 kilometers (1 mile) per pixel.

Photo credit: NASA/JPL/Space Science Institute