NASA Cassini image: Saturn's rainbow rings

Credit: NASA/JPL/University of Colorado

This colourful 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 centre, were acquired by Cassini's Ultraviolet Imaging Spectrograph, (UVIS), as the spacecraft entered into orbit around Saturn on 30 June 2004.

Cassini's Ultraviolet Imaging Spectrograph, (UVIS)

UVIS, as its name suggests, carries out observations in ultraviolet wavelengths.

During the Saturn orbit insertion manoeuvre, 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 colour 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.

Ultraviolet Imaging Spectrograph, (UVIS)

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.

Lightning bolt striking through a Rainbow

Stormchaser Travis Heying photographed a lightning bolt striking through a rainbow over the Little Arkansas River near his home in Wichita, Kansas.

Fortunately, this spectacle happened right on his doorstep.

Picture: TRAVIS HEYING / MCT / CATERS NEWS

NASA Aqua Image: A Rare 'Glory' Rainbow captured

Credit: Jeff Schmaltz, LANCE MODIS Rapid Response

A view from space of a rainbow-like optical phenomenon called a Glory, consisting of brilliant lines of colour, taken by NASA's Aqua satellite.

A Glory is an optical phenomenon that resembles an iconic saint's halo about the shadow of the observer's head. 

The effect is believed to happen due to classical wave tunneling, when light nearby the droplet tunnels through air inside the droplet and, in the case of Glory, is emitted backwards due to resonance effects.

Credit: Michael Studinger. 

In this image, taken over Antarctica's Brunt Ice Shelf, a Glory surrounds the shadow of the DC-8 plane that is flying NASA's IceBridge mission to survey the state of Antarctic ice. 

NASA Aqua Satellite Image: Double Rainbow Seen from Space

NASA's Aqua satellite caught an arresting image of a rainbow-like optical phenomenon called a glory over the Pacific Ocean on June 20.

Glories can be seen on Earth with the naked eye when looking down upon fog or water vapor, as when climbing a mountain or looking down upon clouds from an airplane.

The phenomenon is caused by light scattered backward toward the viewer by individual water droplets, producing an oscillating pattern of colors ranging from blue to green to red to purple and back to blue again.

From the ground or an airplane, glories appear as circular rings of color. In the satellite image, the lines of color appear straight against a backdrop of stratocumulus clouds. That's because the satellite takes pictures perpendicular to its path, producing images of horizontal cross sections of the glory rings.

Capture a Rainbow in a Glass Lens

The rainbow trap is a gilded 4.5-millimetre-wide lens perched atop a gold-coated glass slide (Image: Vera Smolyaninova/Towson University, Baltimore, Maryland)

Oh, to catch a rainbow. Well, it's been done for the first time ever – and with just a simple lens and a plate of glass at that.

The technique could be used to store information using light, a boon for optical computing and telecommunications.

All-optical computing devices promise to be faster and more efficient than current technology, but they suffer from the drawback that signals have to be converted back and forth from optical to electrical. The ability to "slow" light to a crawl or even trap it helps, as information in the light can then be manipulated directly.

In 2007, Ortwin Hess of the University of Surrey in Guildford, UK, and colleagues proposed a technique to trap light inside a tapering waveguide, which is a structure that guides light waves down its length. The waveguide in question would use metamaterials – exotic materials that can bend light sharply.

The idea is that as the waveguide tapers, the components of the light are made to stop in turn at ever narrower points. That's because any given component of the light cannot pass through an opening that's smaller than its wavelength. This leads to a "trapped rainbow".

Gilded waveguide
While numerical models showed that such waveguides would work in theory, making them out of metamaterials remained a distant dream. Now Vera Smolyaninova of Towson University in Baltimore, Maryland, and colleagues have used a convex lens to create the tapered waveguide and trap a rainbow of light.

They coated one side of a 4.5-millimetre-diameter lens with a gold film 30 nanometre thick, and laid the lens – gold-side down – on a flat glass slide which was also coated with film of gold. Viewed side-on, the space between the curved lens and the flat slide was a layer of air that narrowed to zero thickness where the lens touched the slide – essentially a tapered waveguide.

When they shone a multi-wavelength laser beam at the open end of the gilded waveguide, a trapped rainbow formed inside. This could be seen as a series of coloured rings when the lens was viewed from above with a microscope: the visible light leaked through the thin gold film.