Black Opal is Australia’s national gemstone, and black opal is the rarest and most valuable of its kind, at times selling at prices that rival the best diamonds. The stone must have a rich, black background, but base colors come in all shades of gray, which is why opinions vary on what is a “true” black opal. Found in the Lightning Ridge area in northwestern New South Wales, black opals are natural, solid stones that absorb scattered white light, giving it brilliant spectral colors. (Source)

Study proposes explanation for how cephalopods see color, despite black and white vision

For years, camera-makers have sought ways to avoid chromatic aberration—the color fringes that occur when various wavelengths of light focus at different distances behind a lens.                                

But where photographers see a problem, some sea creatures see possibility.

A new study, co-authored by the father-and-son team of Christopher and Alexander Stubbs, suggests that chromatic aberration may explain how cephalopods—the class of animals that includes squid, octopi and cuttlefish—can demonstrate such remarkable camouflage abilities despite only being able to see in black and white. The study is described in a July 4, 2016 paper in the Proceedings of the National Academy of Sciences.

“Spectral discrimination in color blind animals via chromatic aberration and pupil shape”, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1524578113

Chambered Nautilus, at Pairi Daiza, Brugelette, Belgium. Credit: © Hans Hillewaert/CC BY-SA 4.0/Wikipedia    

Up and Over

Cassini orbited in Saturn’s ring plane – around the planet’s equator – for most of 2015. This enabled a season of flybys of the planet’s icy moons, but did not allow for angled views of the rings and the planet’s poles, like this one. But in early 2016, the spacecraft began to increase its orbital inclination, climbing higher over the poles in preparation for the mission’s final spectacular orbits in 2017.

This view looks toward the sunlit side of the rings from about 16 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Feb. 26 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

The view was obtained at a distance of approximately 1.7 million miles (2.8 million kilometers) from Saturn. Image scale is 103 miles (165 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute