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.

NASA Terra Satellite Image: Capturing the Fading Colours of the US Fall

NASA Terra Satellite Image; 21 November 2012. There is still a lot of Autumn Fall colours showing over southern Virginia.

Astronomers Determine Colour of our Milky Way Galaxy

A team of University of Pittsburgh astronomers has announced the most accurate determination yet of the color of the (aptly named) Milky Way Galaxy: "a very pure white, almost mirroring a fresh spring snowfall."

Jeffrey Newman, Pitt professor of physics and astronomy, and Timothy Licquia, a PhD student in physics at Pitt, announced the findings during a presentation at the 219th American Astronomical Society (AAS) Meeting in Austin, Texas.

While color is one of the most important properties of galaxies that astronomers study, it has been difficult to make the measurement for the Milky Way, as our solar system is located well within the Galaxy. Because of this, clouds of gas and dust obscure all but the closest regions of the Galaxy from view, preventing researchers from getting the "big picture".

"The problem is similar to determining the overall color of the Earth, when you're only able to tell what Pennsylvania looks like," Newman noted.

To circumvent this problem, Newman and Licquia set out to determine the Milky Way's color by using images from other, more distant galaxies that can be seen more clearly. These galaxies were observed by the Sloan Digital Sky Survey (SDSS), a project in which Pitt had an instrumental role that measured the detailed properties of nearly a million galaxies and has obtained color images of roughly a quarter of the sky.

Without the large set of galaxies studied by SDSS to compare to, an accurate color determination was not possible. The new color measurement is helping the Pitt researchers understand the Milky Way Galaxy's development and how it is related to other objects astronomers observe.

"The problem we faced was similar to determining the outside climate when you are in a room with no windows." said Newman. "You can't see what's happening, but you can look online and find current weather conditions someplace where they should be about the same - the local airport, for example."

The Pitt team identified galaxies similar to the Milky Way in properties that could be determined well for each of them - specifically, their total amount of stars and the rate at which they are creating new stars, which are both related to the brightness and color of a galaxy. The Milky Way Galaxy, the Pitt researchers realized, should then fall somewhere within the range of colors of these matching objects.

"Thanks to SDSS, the large, uniform sample needed to select Milky Way analogs already existed. We just needed to think of the idea for the project, and it was possible," said Newman. "Although it is a relatively small telescope, only 2.5 meters (100 inches) in diameter, SDSS has been one of the most scientifically productive in history, enabling thousands of new projects like this one."

Newman described the overall spectrum of light from the Milky Way as being very close to the light seen when looking at spring snow in the early morning, shortly after dawn. Michael Ramsey, Pitt associate professor of geology, notes that new spring snow is the whitest (natural) thing on Earth.

Many cultures around the world have given the Milky Way names associated with milk - human vision is not sensitive to colors seen in faint light, so the diffuse glow of the Galaxy at night appears white. That association has proven to be very appropriate, given the Milky Way's true color.

Astronomers divide most galaxies into two broad categories based on their colors - relatively red galaxies that rarely form new stars and blue galaxies where stars are still being born. (The brightest stars are generally blue, but they are very short-lived on cosmic scales and die out quickly.) The new measurements place the Milky Way near the division between the two classes.

This adds to the evidence that although the Milky Way is still producing stars, it is "on its way out," according to Newman. "A few billion years from now, our Galaxy will be a much more boring place, full of middle-aged stars slowly using up their fuel and dying off, but without any new ones to take their place. It will be less interesting for astronomers in other galaxies to look at, too: The Milky Way's spiral arms will fade into obscurity when there are no more blue stars left."

The Milky Way's color is exceedingly close to the "cosmic color" measured by Ivan Baldry, a professor of astrophysics at Liverpool John Moores University in England, and his collaborators in 2002; these researchers measured the average color of galaxies in the local universe.

"This close match shows that in many ways the Milky Way is a pretty typical galaxy," said Newman. "This also agrees well with the 'Copernican Principle' embraced by the field of cosmology - that, just as the Earth is not in a special place in the solar system, we should not expect to live in an unusual place in the Universe."

High Speed Image of Coloured salt - Fabian Oefner

Photographer Fabian Oefner has used coloured grains of salt and sent them into the air using different songs. 

He placed the salt on thin plastic foil stretched over a loudspeaker.

When the speakers are turned on it sends the salt into the air and he is able to capture the moment using a high speed flash.

He says: "Depending on the frequency of the sonic wave, different sculptures are created, from gentle and spaced sculptures to high pitch volcano-eruption-like figures."

Picture: FABIAN OEFNER / CATERS NEWS

Volcanic Destruction: 11 Geological Maps of Volcanoes

It's not always obvious what it is that scientists find beautiful about a graph, microscope slide, soil sample or some other aspect of their work.

It just looks like numbers, blobs or dirt to the rest of us but sometimes a scientific result or product is so visually appealing, anyone would want to hang it on their wall as art.

Geological maps are often in this category. And some of the most beautiful geological maps are of volcanoes.

The colours on geological maps represent different rock units of different ages.

With an active lifespan of thousands, or even hundreds of thousands of years, volcanoes produce many layers of ash and flows of lava that will end up as different colours on the map and with the circular shape of many volcanoes and the radiating rock units, the maps can really be striking.

Wired has collected some excellent examples of geological maps of volcanoes from the United States and Japan. You don't have to be a geologist or even a scientist to have trouble picking a favourite.

Check them all out on their website here

Magic Ink: Now available for full colour Printing

Borrowing an idea from nature could lead to technology capable of producing full-colour A4 prints in a fraction of a second, according to South Korean engineers.

Many insects and birds owe their bright colours to the interaction of light with finely-patterned surface textures, rather than relying on pigments. The iridescent colours of a peacock's tail are largely a result of the interaction of light with just one biological material – melanin rods.

Engineers have long experimented with replicating these so-called structural colours in synthetic materials, and now Sunghoon Kwon's team at Seoul National University in South Korea has managed it.

Their M-Ink can be used to produce any colour in the visible spectrum and could lead to a new method of cheap and fast full-colour printing, Kwon says.

Just add nanoparticles

M-Ink contains three ingredients: magnetic nanoparticles 100 to 200 nanometres across, a solvation liquid, and a resin.

The nanoparticles disperse throughout the resin, giving the ink a brown appearance. But when an external magnetic field is applied, the nanoparticles immediately snap to the magnetic field lines, forming chain-like structures.

The regularly-spaced nanoparticle chains interfere with incoming light, so that the light reflected from the surface is of a particular colour. Adjusting the magnetic field strength shifts the spacing of the field lines and changes the colour, says Kwon.

Chameleon Opal: Takes on any Colour

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A new material could give a chameleon a run for its money - it can rapidly change colour to match that of any in the visible spectrum.

The synthetic material can be likened to an opal, a mineral that owes its variety of colours to its layered structure: regions with a high refractive index, in which light travels slowly, are interleaved with regions with a low refractive index. Light waves with a wavelength - or colour - similar to that of the space between layers are scattered in a way that gives opal its iridescent sheen.

The chameleon-like "opal" developed by British and Canadian chemists has a similar layered structure. But their material goes one better than nature. It can rapidly shrink or swell to change the distance between its layered regions, changing the colour of light that it scatters (see video above).

Synaesthesia: Means Wednesday is Indigo Blue!

Synaesthesia, as it turns out, may be up to seven times as common among artists, novelists and composers as it is among other people. What's more, it seems to run in families. For example, the Russian novelist Vladimir Nabokov (see "From father to son") saw letters in colours, as did his mother - who also heard in colours - and as does his son Dmitri. This obviously lends support to the idea that synaesthesia has a genetic underpinning.

If it is genetic - and common - why would evolution have selected for such a condition? According to Cytowic and Eagleman, it is all "to do with creativity - especially an ease for making metaphoric cross-connections". Neuroscientist Vilayanur Ramachandran at the University of California, San Diego, has had a book on metaphor and synaesthesia in the wings for a couple of years, so we may be at the start of a rich theory of synaesthesia, one that could illuminate profound issues in consciousness studies and cognitive science.