Powerful fine stuff. It wasn’t enough that Jupiter lined up with the full moon last night. Across northern Minnesota an ice halo encircled the pair for much of the evening making the show a skywatchers’ delight. Halos around sun and moon are visible any time of year, but they may be a little more common in winter, when ice crystals abound in the atmosphere.
Moonlight is refracted or bent by minute, six-sided, pencil-shaped ice crystals in cirrostratus clouds into a soft circle of light 22 degrees (about two fists held at arm’s length) in diameter. Because the blue part of light is refracted at a greater angle, halos have a pale blue outer circumference. Red is bent least, lending a ruddy tint to the inner edge.
Clouds are amazing creatures. Their shapes, growth and decay, how they create lightning, rain, halos and coronas make for endless and enjoyable study. I’m nearly as enamored of clouds as I am of stars, though a week of cloudy nights does give pause.
NASA released some wild new images of a swirling vortex of clouds ringing Saturn’s north polar region. The Cassini probe shot the photos from a high, tilted orbit for one of the most amazing perspectives on the planet’s atmosphere ever. Similar storm clouds have been seen racing around the planet’s south pole, but this is the first time we’ve had a bird’s eye view of Saturn’s other pole in visible light.
Why the long wait to see the north pole? Because it’s been in shadow for the past few years the way our north pole is in shadow (sun never rises) during the winter months. Since Saturn’s axis is tipped 27 degrees, similar to Earth’s 23.5 tilt, the planet experiences seasons, too. With one difference.
Saturn takes nearly 30 years to orbit the sun, so each season spans about 7.5 Earth years.
With spring now underway in the ringed planet’s northern hemisphere, the slanted rays of the low sun graze the polar regions the way sunlight touches the treetops at sunrise, lighting up the clouds in dramatic fashion. Wish we could see that in our telescopes! Check out another photo HERE.