Explanation: Dramatic prominences can sometimes be seen looming just beyond the edge of the sun. Such was the case last week as a giant prominence, visible above on the right, highlighted a Sun showing increased activity as it comes off an unusually quiet Solar Minimum. A changing carpet of hot gas is visible in the chromosphere of the Sun in the above image taken in a very specific color of light emitted by hydrogen. A solar prominence is a cloud of solar gas held just above the surface by the Sun's magnetic field. The Earth would easily fit below the prominence on the right. Although very hot, prominences typically appear dark when viewed against the Sun, since they are slightly cooler than the surface. A quiescent prominence typically lasts about a month, and may erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar System. The next day, the same prominence looked slightly different.
Explanation: On the right, surrounded by blue spiral arms, is spiral galaxy M81. On the left, marked by red gas and dust clouds, is irregular galaxy M82. This stunning vista shows these two mammoth galaxies locked in gravitational combat, as they have been for the past billion years. The gravity from each galaxy dramatically affects the other during each hundred million-year pass. Last go-round, M82's gravity likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms. But M81 left M82 with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays. In a few billion years only one galaxy will remain.
Explanation: Distorted galaxy NGC 2442 can be found in the southern constellation of the flying fish, (Piscis) Volans. Located about 50 million light-years away, the galaxy's two spiral arms extending from a pronounced central bar have a hook-like appearance in wide-field images. But this mosaicked close-up, constructed from Hubble Space Telescope data, follows the galaxy's structure in amazing detail. Obscuring dust lanes, young blue star clusters and reddish star forming regions surround a core of yellowish light from an older population of stars. The sharp Hubble data also reveal more distant background galaxies seen right through NGC 2442's star clusters and nebulae. The image spans about 75,000 light-years at the estimated distance of NGC 2442.
Explanation: A young crescent Moon shares the western sky with sister stars of the Pleiades cluster in this pretty, evening skyscape recorded on the March equinox from San Antonio, Texas. In the processed digital image, multiple exposures of the celestial scene were combined to show details of the bright lunar surface along with the Pleiades stars. Astronomical images of the well-known Pleiades often show the cluster's alluring blue reflection nebulae, but they are washed-out here in the bright moonlight. Still, during this particular night, skygazers in South and Central America could even watch the 5 day old Moon occult or pass in front of some of the brighter Pleiades stars.
Explanation: Stark shadows of mountains and crater walls stand out along the lunar terminator, or shadow line between night and day, in this telescopic image. Of course, if viewed from the lunar surface near the terminator line, the Sun would be rising and still close to the lunar horizon. But the picture's inset at the left highlights a more elusive lunar sunrise phenomenon. Streaming through a gap in the eastern wall of 45 kilometer wide Hesiodus crater, the low-angle sunlight produces a long sunrise ray playing along the otherwise shadowed crater floor. Sunrise rays are short-lived and can be rewarding to spot for Moon enthusiasts with telescopes. Seen in Hesiodus and other craters, the ray timing can be calculated based on the observer's location. This picture of a first quarter Moon was recorded at 23:45 UT on February 22nd from Stuttgart, Germany. In the inset, the larger crater Pitatus is at the right. For location, Hesiodus and Pitatus are circled at the bottom of the picture.