Seen from ice moon Tethys, rings and shadows would display fantastic views of the Saturnian system. Haven’t dropped in on Tethys lately? Then this gorgeous ringscape from the Cassini spacecraft will have to do for now. Caught in sunlight just below and left of picture center in 2005, Tethys itself is about 1,000 kilometers in diameter and orbits not quite five saturn-radii from the center of the gas giant planet. At that distance (around 300,000 kilometers) it is well outside Saturn’s main bright rings, but Tethys is still one of five major moons that find themselves within the boundaries of the faint and tenuous outer E ring. Discovered in the 1980s, two very small moons Telesto and Calypso are locked in stable locations along Tethys’ orbit. Telesto precedes and Calypso follows Tethys as the trio circles Saturn.

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Mysterious Hanny’s Voorwerp, Dutch for “Hanny’s Object”, is really enormous, about the size of the Milky Way Galaxy and glowing strongly in the greenish light produced by ionized oxygen atoms. It is thought to be a tidal tail of material left by an ancient galaxy merger, illuminated and ionized by the outburst of a quasar inhabiting the center of distant spiral galaxy IC 2497. Its exciting 2007 discovery by Dutch schoolteacher Hanny van Arkel while participating online in the Galaxy Zoo project has since inspired a search and discovery of eight more eerie green cosmic features. Imaged in these panels by the Hubble Space Telescope, all eight appear near galaxies with energetic cores. Far outside their associated galaxies, these objects are also likely echoes of quasar activity, illuminated only as light from a core quasar outburst reaches them and ultimately fading tens of thousands of years after the quasar outburst itself has faded away. Of course a galaxy merger like the impending merger of our own Milky Way and the Andromeda Galaxy, could also trigger the birth of a quasar that would illuminate our distant future version of Hanny’s Voorwerp.

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Two pictures captured on April 1 are combined in this creative day and night composite. Separated in time by about 10 hours the images otherwise match, looking along the coast at Östersund Sweden. The relative times were chosen to show the Sun and a nearly full Moon at the same place in the cold, early springtime sky. In the night scene Jupiter also shines above the waterfront lights, while Sun and Moon are both surrounded by a beautiful circular ice halo. The Sun and Moon halos really do align, each with an angular radius of 22 degrees. That radius is a constant, not determined by the brightness of Sun or Moon but only by the hexagonal geometry of atmospheric ice crystals and the reflection and refraction of light. Of course tomorrow, April 4, will find the Sun and Moon on opposite sides of planet Earth for a total lunar eclipse.

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How will cows survive on the Moon? One of the most vexing questions asked about space, scientists have spent decades debating this key issue. Finally, after extensive computer modeling and over a dozen midnight milkings, engineers have designed, built, and now tested the new Lunar Grazing Module (LGM), a multi-purpose celestial bovine containment system. By now, many of you will not be surprised to be wished a Happy April Fool’s Day from APOD. To the best of our knowledge, there are no current plans to launch cows into space. For one reason, cows tend to be large animals that don’t launch easily or cheaply. As friendly as cows may be, head-to-head comparisons show that robotic rovers are usually more effective as scientific explorers. The featured image is of a thought-provoking work of art named “Mooooonwalk” which really is on display at a popular science museum.

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During a total solar eclipse, the Sun’s extensive outer atmosphere, or corona, is an inspirational sight. Streamers and shimmering features that engage the eye span a brightness range of over 10,000 to 1, making them notoriously difficult to capture in a single photograph. But this composite of 29 telescopic images covers a wide range of exposure times to reveal the crown of the Sun in all its glory. The aligned and stacked digital frames were recorded in the cold, clear skies above the Arctic archipelago of Svalbard, Norway during the Sun’s total eclipse on March 20 and also show solar prominences extending just beyond the edge of the solar disk. Remarkably, even small details on the dark night side of the New Moon can be made out, illuminated by sunlight reflected from a Full Earth. Of course, fortunes will be reversed on April 4 as a Full Moon plunges into the shadow of a New Earth, during a total lunar eclipse.

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