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Explanation: What has the Curiosity rover come across on Mars? Dubbed Mount Remarkable, the rolling robot has chanced upon this notable 5-meter tall mound during its continuing journey around and, eventually, up 5.5-kilometer high Mt. Sharp. Unsure of the density of the surrounding layered sandstone, the human team on Earth has instructed the car-sized rover on Mars to drill into a rock on the side of Mt. Remarkable to investigate. Quite possibly, water involved in creating the dense sandstone could have helped to support ancient life on the red planet. Mt. Sharp, the unusual central peak of Gale Crater, has...

Explanation: Our Sun has become quite a busy place. Taken only two weeks ago, the Sun was captured sporting numerous tumultuous regions including active sunspot regions AR 2036 near the image top and AR 2036 near the center. Only four years ago the Sun was emerging from an unusually quiet Solar Minimum that had lasted for years. The above image was recorded in a single color of light called Hydrogen Alpha, inverted, and false colored. Spicules cover much of the Sun's face like a carpet. The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool...

Explanation: How do you calibrate a huge gravitational lens? In this case the lens is the galaxy cluster Abell 383, a massive conglomeration of galaxies, hot gas, and dark matter that lies about 2.5 billion light years away (redshift z=0.187). What needs calibrating is the mass of the cluster, in particular the amount and distribution of dark matter. A new calibration technique has been tested recently that consists of waiting for supernovas of a very specific type to occur behind a galaxy cluster, and then figuring out how much the cluster must have magnified these supernovas through gravitational lensing. This...

Explanation: If Scorpius looked this good to the unaided eye, humans might remember it better. Scorpius more typically appears as a few bright stars in a well-known but rarely pointed out zodiacal constellation. To get a spectacular image like this, though, one needs a good camera, color filters, and a digital image processor. To bring out detail, the above image not only involved long duration exposures taken in several colors, but one exposure in a very specific red color emitted by hydrogen. The resulting image shows many breathtaking features. Vertically across the image left is part of the plane of...

Explanation: The yellowish star near center in this dusty telescopic skyview is T Tauri, prototype of the class of T Tauri variable stars. Just next door is the yellow cosmic cloud historically known as Hind's Variable Nebula (NGC 1555). Over 400 light-years away, at the edge of an otherwise invisible molecular cloud, both star and nebula are seen to vary significantly in brightness but not necessarily at the same time, adding to the mystery of the intriguing region. T Tauri stars are now generally recognized as young (less than a few million years old), sun-like stars still in the early...

Explanation: Captured one night last May this eight frame mosaic starts on the left, down Northside Drive through Yosemite National Park. It ends thousands of light-years away though, as the arc of the Milky Way tracks toward the center of our galaxy on the right, far beyond the park's rugged skyline. That night was still moonless when the storm clouds retreated, so the rocky faces of the surrounding mountains are lit by campfires and artifical lights. Yosemite Falls is at the left. The granite face of Half Dome juts above the far horizon, near the center of the view. The...

Explanation: In skies over Brisbane at the southeastern corner of Queensland, Australia, Planet Earth, the Sun and New Moon set together on April 29. There the celestial line-up, the first solar eclipse of 2014, was seen as a partial solar eclipse. This dramatic composite is a digital stack of images taken about 5 minutes apart with telephoto lens and solar filter. It follows the eclipse in progress, approaching a western horizon where crepuscular rays from cloud banks in silhouette joined the silhouetted Moon. From Brisbane, the maximum eclipse phase with the Moon covering about 25% of the Sun occurred just...

Explanation: If you look closely, you will see something quite unusual about this setting Sun. There are birds flying to the Sun's left, but that's not so unusual. A dark sea covers the Sun's bottom, and dark clouds cover parts of the middle, but they are also not very unusual. More unusual is the occulted piece at the top right. And that's no occulting cloud -- that's the Moon. Yesterday the Moon moved in front of part of the Sun as visible from Australia, and although many locations reported annoying clouds, a partially eclipsed Sun would occasionally peek through as...

Explanation: Sometimes it is hard to believe what you see in the sky. While leading his annual aurora tour last month near Fairbanks in central Alaska, astrophotographer John Chumack and his company saw a most unusual aurora. This bright aurora appeared to change into the shape of a jumping dog, complete with a curly tail. He was able to capture the fleeting natural apparition in the above image with a 15-second exposure through a wide-angle lens. By coincidence, he also captured a background sky filled with familiar highlights. Planets visible include bright Jupiter through the dog's front legs and reddish...

Explanation: Why would a bright full Moon suddenly become dark? Because it entered the shadow of the Earth. Almost two weeks ago this exact event happened as the Moon underwent a total lunar eclipse. That eclipse, visible from the half of the Earth then facing the Moon, was captured in numerous spectacular photographs and is depicted in the above time lapse video covering about an hour. The above video, recorded from Mt. Lemmon Sky Center in Arizona, USA, keeps the Earth shadow centered and shows the Moon moving through it from west to east. The temporarily good alignment between Earth,...

Explanation: A spacesuit floated away from the International Space Station eight years ago, but no investigation was conducted. Everyone knew that it pushed by the space station crew. Dubbed Suitsat-1, the unneeded Russian Orlan spacesuit filled mostly with old clothes was fitted with a faint radio transmitter and released to orbit the Earth. The suit circled the Earth twice before its radio signal became unexpectedly weak. Suitsat-1 continued to orbit every 90 minutes until it burned up in the Earth's atmosphere after a few weeks. Pictured above, the lifeless spacesuit was photographed in 2006 just as it drifted away from...

Explanation: It's eclipse season, and on April 29 around 06:00 UT the shadow of the new Moon will reach out and touch planet Earth, though only just. Still, if you're standing on the continent of Antarctica within a few hundred kilometers of 79 degrees 38.7 minutes South latitude and 131 degrees 15.6 minutes East longitude you could see an annular solar eclipse with the Sun just above the horizon. Because the Moon will be approaching apogee, the most distant point in the elliptical lunar orbit, its apparent size will be too small to completely cover the solar disk. A rare,...

Explanation: "Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..." begins the description of the 5th entry in 18th century astronomer Charles Messier's famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one...

Explanation: Earth's annual Lyrid meteor shower peaked before dawn on April 22nd, as our fair planet plowed through dust from the tail of long-period comet Thatcher. Even in the dry and dark Atacama desert along Chile's Pacific coast, light from a last quarter Moon made the night sky bright, washing out fainter meteor streaks. But brighter Lyrid meteors still put on a show. Captured in this composited earth-and-sky view recorded during early morning hours, the meteors stream away from the shower's radiant near Vega, alpha star of the constellation Lyra. The radiant effect is due to perspective as the parallel...

Explanation: From planet Earth, we see this strongly distorted pair of galaxies, cataloged as Arp 81, as they were only about 100 million years after their close encounter. The havoc wreaked by their mutual gravitational interaction during the encounter is detailed in this color composite image showing twisted streams of gas and dust, a chaos of massive star formation, and a tidal tail stretching for 200 thousand light-years or so as it sweeps behind the cosmic wreckage. Also known as NGC 6622 (left) and NGC 6621, the galaxies are roughly equal in size but are destined to merge into one...

Explanation: It is bigger than a bread box. In fact, it is much bigger than all bread boxes put together. Galaxy cluster ACT-CL J0102-4915 is one of the largest and most massive objects known. Dubbed "El Gordo", the seven billion light years (z = 0.87) distant galaxy cluster spans about seven million light years and holds the mass of a million billion Suns. The above image of El Gordo is a composite of a visible light image from the Hubble Space Telescope, an X-ray image from the Chandra Observatory showing the hot gas in pink, and a computer generated map...

Explanation: It is one of the more massive galaxies known. A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This sharp view of the gorgeous island universe shows off a striking yellow nucleus and galactic disk. Dust lanes, small, pink star-forming regions, and young blue star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions. NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way and captured by this...

Explanation: Why did a picturesque 2010 volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well-populated areas. The Eyjafjallajökull volcano in southern Iceland began erupting on 2010 March 20, with a second eruption starting under the center of a small glacier on 2010 April 14. Neither eruption was unusually powerful. The second eruption, however, melted a large amount of glacial ice which then cooled and fragmented lava into gritty glass particles that were carried up with the rising volcanic plume....

Explanation: Planet Kepler-186f is the first known Earth-size planet to lie within the habitable zone of a star beyond the Sun. Discovered using data from the prolific planet-hunting Kepler spacecraft, the distant world orbits its parent star, a cool, dim, M dwarf star about half the size and mass of the Sun, some 500 light-years away in the constellation Cygnus. M dwarfs are common, making up about 70 percent of the stars in our Milky Way galaxy. To be within the habitable zone, where surface temperatures allowing liquid water are possible, Kepler-186f orbits close, within 53 million kilometers (about the...

Explanation: This is not a scene from a sci-fi special effects movie. The green beam of light and red lunar disk are real enough, captured in the early morning hours of April 15. Of course, the reddened lunar disk is easy to explain as the image was taken during this week's total lunar eclipse. Immersed in shadow, the eclipsed Moon reflects the dimmed reddened light of all the sunsets and sunrises filtering around the edges of planet Earth, seen in silhouette from a lunar perspective. But the green beam of light really is a laser. Shot from the 3.5-meter telescope...