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Eclipsed Moonlight Credit & Copyright: Jerry Lodriguss (Catching the Light) Explanation: Moon watchers blessed with clear skies over the Americas, Europe, Africa and western Asia enjoyed a total lunar eclipse this week. Catching eclipsed moonlight, astroimager Jerry Lodriguss offers this view of the inspiring celestial event with the shadowed Moon accompanied by wandering planet Saturn at the left, and bright Regulus, alpha star of the constellation Leo, above. The engaging composite picture was made by combining a filtered, telephoto image of the Moon and surrounding starfield with a telescopic exposure. The combination dramatizes the reddened moonlight while clearly showing...

Orion's Horsehead Nebula Credit & Copyright: Victor Bertol Explanation: The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the dark indentation to the red emission nebula seen just below and left of center in the this photograph. The brightest star on the left is located in the belt of the familiar constellation Orion. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright red emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After...

Moon Slide Slim Credit & Copyright: Stefan Seip (TWAN) Explanation: No special filters - or even a telescope - are required to enjoy a leisurely lunar eclipse. In fact, watched from all over the night side of planet Earth, these regular celestial performances have entertained many casual skygazers. Still, this eye-catching picture of a lunar eclipse may look unfamiliar. To make it, astroimager Stefan Seip set his camera on a tripod and locked the shutter open during the total lunar eclipse of March 3, 2007. The resulting image records the trail of the Moon (and narrower trails of stars) sliding...

Columbus Laboratory Installed on Space Station Credit: STS-122 Crew, Expedition 16 Crew, ESA, NASA Explanation: The International Space Station (ISS) has been equipped with a powerful new scientific laboratory. The Space Shuttle Atlantis delivered the Columbus Laboratory to the ISS and installed the seven meter long module over the past week. Columbus has ten racks for experiments that can be controlled from the station or the Columbus Control Center in Germany. The first set of experiments includes the Fluid Science Laboratory that will explore fluid properties in the microgravity of low Earth orbit, and Biolab which supports experiments on microorganisms....

BLG-109: A Distant Version of our own Solar System Illustration Credit: KASI, CBNU, ARCSEC, NSF Explanation: How common are planetary systems like our own? Perhaps quite common, as the first system of planets like our own Solar System has been discovered using a newly adapted technique that, so far, has probed only six planetary systems. The technique, called gravitational microlensing, looks for telling brightness changes in measured starlight when a foreground star with planets chances almost directly in front of a more distant star. The distant star's light is slightly deflected in predictable ways by the gravity of the closer...

Young Stars in the Rho Ophiuchi Cloud Credit: NASA JPL-Caltech, Harvard-Smithsonian CfA Explanation: Cosmic dust clouds and embedded newborn stars glow at infrared wavelengths in this tantalizing false-color view from the Spitzer Space Telescope. Pictured is of one of the closest star forming regions, part of the Rho Ophiuchi cloud complex some 400 light-years distant near the southern edge of the pronounceable constellation Ophiuchus. The view spans about 5 light-years at that estimated distance. After forming along a large cloud of cold molecular hydrogen gas, newborn stars heat the surrounding dust to produce the infrared glow. An exploration of the...

Long Stem Rosette Credit & Copyright: Adam Block (Caelum Observatory) and Tim Puckett Explanation: The Rosette Nebula (aka NGC 2237) is not the only cosmic cloud of gas and dust to evoke the imagery of flowers. But it is the one most often suggested as a suitable astronomy image for Valentine's Day. Of the many excellent Rosette Nebula pictures submitted to APOD editors, this view seemed most appropriate, with a long stem of glowing hydrogen gas in the region included in the composition. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals...

Elliptical Galaxy NGC 1132 Credit: NASA, ESA, M. West (ESO, Chile), and CXC / Penn. State / G. Garmire, et al. Explanation: NGC 1132 is one smooth galaxy -- but how did it form? As an elliptical galaxy, NGC 1132 has little dust and gas, and few stars have formed in it recently. Although many elliptical galaxies are in clusters of galaxies, NGC 1132 appears as a large, isolated galaxy toward the constellation of the River (Eridanus). To probe the history of this intriguing trillion-star ball, astronomers imaged NGC 1132 in both visible light with the Hubble Space Telescope and...

Echoes from RS Pup Credit: Pierre Kervella (Obs. de Paris), Antoine Mérand (CHARA), et al., ESO Explanation: This dusty reflection nebula surrounds pulsating star RS Pup, some 10 times more massive than the Sun and on average 15,000 times more luminous. In fact, RS Pup is a Cepheid type variable star; a class of stars whose brightness is used to estimate distances to nearby galaxies as one of the first steps in establishing the cosmic distance scale. As RS Pup pulsates over a period of about 40 days, its regular changes in brightness are also seen along the nebula delayed...

Saturn's Moon Epimetheus from the Cassini Spacecraft Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA Explanation: How did Epimetheus form? No one is yet sure. To help answer that question, this small moon has recently been imaged again in great detail by the robot spacecraft Cassini now orbiting Saturn. Epimetheus sometimes orbits Saturn in front of Janus, another small satellite, but sometimes behind. The above image, taken last December, shows a surface covered with craters indicating great age. Epimetheus spans about 115 kilometers across. Epimetheus does not have enough surface gravity to restructure itself into a sphere. The flattened face...

Abell 2218: A Galaxy Cluster Lens Credit: Andrew Fruchter (STScI) et al., WFPC2, HST, NASA Explanation: Gravity can bend light, allowing huge clusters of galaxies to act as telescopes. Almost all of the bright objects in this Hubble Space Telescope image are galaxies in the cluster known as Abell 2218. The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it. As a result, multiple images of these background galaxies are distorted into long faint arcs -- a simple lensing effect analogous to viewing distant street lamps through a...

The Bay of Rainbows Credit & Copyright: Alan Friedman Explanation: Dark, smooth regions that cover the Moon's familiar face are called by Latin names for oceans and seas. The naming convention is historical, though it may seem a little ironic to denizens of the space age who recognize the Moon as a mostly dry and airless world, and the smooth, dark areas as lava-flooded impact basins. For example, this elegant lunar vista, a careful mosaic of telescopic images, looks across the expanse of the northwestern Mare Imbrium, or Sea of Rains, into the Sinus Iridum - the Bay of Rainbows....

NGC 4013 and the Tidal Stream Image Credit & Copyright: R Jay Gabany (Blackbird Observatory) - collaboration; D.Martínez-Delgado(IAC, MPIA), M.Pohlen (Cardiff), S.Majewski (U.Virginia), J.Peñarrubia (U.Victoria), C.Palma (Penn State) Explanation: Nearly 50 million light-years away in the constellation Ursa Major, NGC 4013 was long considered an isolated island universe. Seen edge-on, the gorgeous spiral galaxy was known for its flattened disk and central bulge of stars, cut by silhouetted dust lanes. But this deep color image of the region reveals a previously unknown feature associated with NGC 4013, an enormous, faint looping structure extending (above and toward the left) over 80...

A Sunspot in the New Solar Cycle Credit & Copyright: Greg Piepol Explanation: A new cycle has begun on our Sun. Over the past year, the Sun's magnetic field has reset and now a new 11 year period is beginning. Pictured above in a specific color of light emitted by hydrogen is sunspot 10982, one of the first sunspots of the new solar cycle. The two dark lines visible just above and to either side of the bright sunspot are cool filaments held aloft by the Sun's magnetic field. Hot and cold regions are shown as regions of relative...

A Spider Shaped Crater on Mercury Credit: MESSENGER, NASA, JHU APL, CIW Explanation: Why does this crater on Mercury look like a spider? When the robotic MESSENGER spacecraft glided by the planet Mercury last month, it was able to image portions of the Sun's closest planet that had never been seen before. When imaging the center of Mercury's extremely large Caloris Basin, MESSENGER found a crater, pictured above, with a set of unusual rays emanating out from its center. A crater with such troughs has never been seen before anywhere in our Solar System. What isn't clear is the relation...

The First Explorer Credit: Courtesy of Marshall Space Flight Center, NASA Explanation: Fifty years ago (on January 31, 1958) the First Explorer, was launched into Earth orbit by the Army Ballistic Missile Agency. Inaugurating the era of space exploration for the United States, Explorer I was a thirty pound satellite that carried instruments to measure temperatures, and micrometeorite impacts, along with an experiment designed by James A. Van Allen to measure the density of electrons and ions in space. The measurements made by Van Allen's experiment led to an unexpected and startling discovery -- an earth-encircling belt of high energy...

Young Star Cluster Westerlund 2 Credit: X-ray; Y.Nazé, G.Rauw, J.Manfroid (Université de Liège), CXC, NASA Infrared; E.Churchwell (University of Wisconsin), JPL, Caltech, NASA Explanation: Dusty stellar nursery RCW 49 surrounds young star cluster Westerlund 2 in this remarkable composite skyscape from beyond the visible spectrum of light. Infrared data from the Spitzer Space Telescope is shown in black and white, complimenting the Chandra X-ray image data (in false color) of the hot energetic stars within the cluster's central region. Looking toward the grand southern constellation Centaurus, both views reveal stars and structures hidden from optical telescopes by obscuring dust. Westerlund...

Asteroid 2007 TU24 Passes the Earth> Credit: Green Bank Radio Telescope, Arecibo Radio Telescope Explanation: Asteroid 2007 TU24 passed by the Earth yesterday, posing no danger. The space rock, estimated to be about 250 meters across, coasted by just outside the orbit of Earth's Moon. The passing was not very unusual -- small rocks strike Earth daily, and in 2003 a rock the size of a bus passed inside the orbit of the Moon, being detected only after passing. TU24 was notable partly because it was so large. Were TU24 to have struck land, it might have caused a magnitude...

A Solar Eclipse Painting from the 1700s Painting Credit: Cosmas Damian Asam; Digital Image Copyright: Jay Pasachoff Explanation: Is this painting the earliest realistic depiction of a total eclipse of the Sun? Some historians believe it is. The above painting was completed in 1735 by Cosmas Damian Asam, a painter and architect famous in early eighteenth century Germany. Clearly drawn is not only a total solar eclipse, but the solar corona and the diamond ring effect visible when sunlight flows only between mountains on the Moon. The person depicted viewing these eclipse phenomena is St. Benedict. Roberta J. M. Olson...

Mercury on the Horizon Credit & Copyright: Juan Carlos Casado Explanation: Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it never wanders far from the Sun in Earth's sky. If trailing the Sun, Mercury will be visible low on the horizon for only a short while after sunset. If leading the Sun, Mercury will be visible only shortly before sunrise. So at certain times of the year an informed skygazer with a little determination can usually pick Mercury out from a site with an unobscured horizon. Above, a lot of determination has been...