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  • Astronomy Picture of the Day -- A Dark and Dusty Sky

    05/22/2015 4:25:13 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | May 22, 2015 | (see photo credit)
    Explanation: In the dusty sky toward the constellation Taurus and the Orion Arm of our Milky Way Galaxy, this broad mosaic follows dark and faint reflection nebulae along the region's fertile molecular cloud. The six degree wide field of view starts with long dark nebula LDN 1495 stretching from the lower left, and extends beyond the (upside down) bird-like visage of the Baby Eagle Nebula, LBN 777, at lower right. Small bluish reflection nebulae surround scattered fainter Taurus stars, sights often skipped over in favor of the constellation's better known, brighter celestial spectacles. Associated with the young, variable star RY...
  • Astronomy Picture of the Day -- NGC 6240: Merging Galaxies

    05/21/2015 3:55:01 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | May 21, 2015 | (see photo credit)
    Explanation: NGC 6240 offers a rare, nearby glimpse of a cosmic catastrophe in its final throes. The titanic galaxy-galaxy collision takes place a mere 400 million light-years away in the constellation Ophiuchus. The merging galaxies spew distorted tidal tails of stars, gas, and dust and undergo fast and furious bursts of star formation. The two supermassive black holes in the original galactic cores will also coalesce into a single, even more massive black hole and soon, only one large galaxy will remain. This dramatic image of the scene is a composite of narrowband and near-infrared to visible broadband data from...
  • Astronomy Picture of the Day -- A Cliff Looming on Comet 67P

    05/20/2015 4:46:01 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | May 20, 2015 | (see photo credit)
    Explanation: What that looming behind this gravel-strewn hill on Comet Churyumov–Gerasimenko? A jagged cliff. The unusual double-lobed nucleus of Comet 67P/Churyumov–Gerasimenko lends itself to unusual and dramatic vistas, another of which has been captured by the Rosetta spacecraft that arrived at the comet last September. The featured cometscape, taken last October and digitally enhanced, spans about 850 meters across. Meanwhile, Comet Churyumov–Gerasimenko continues to sprout jets as it nears its closest approach to the Sun in August. Along the way, Rosetta will continue listening for signals from Philae, a probe that landed on the nucleus but rebounded to an unknown...
  • Astronomy Picture of the Day -- Globular Star Cluster 47 Tucanae

    05/19/2015 2:30:13 PM PDT · by SunkenCiv · 12 replies
    NASA ^ | May 19, 2015 | (see photo credit)
    Explanation: Globular star cluster 47 Tucanae is a jewel box of the southern sky. Also known as NGC 104, it roams the halo of our Milky Way Galaxy along with over 150 other globular star clusters. The second brightest globular cluster (after Omega Centauri) as seen from planet Earth, 47 Tuc lies about 17,000 light-years away and can be spotted naked-eye near the Small Magellanic Cloud in the constellation of the Toucan. The dense cluster is made up of hundreds of thousands of stars in a volume only about 120 light-years across. Recent observations have shown that 47 Tuc's white...
  • Astronomy Picture of the Day -- Auroras and Star Trails over Iceland

    05/18/2015 9:57:36 AM PDT · by SunkenCiv · 19 replies
    NASA ^ | May 18, 2015 | (see photo credit)
    Explanation: It was one of the quietest nights of aurora in weeks. Even so, in northern- Iceland during last November, faint auroras lit up the sky every clear night. The featured 360-degree panorama is the digital fusion of four wide-angle cameras each simultaneously taking 101 shots over 42 minutes. In the foreground is serene Lake Myvatn dotted with picturesque rock formations left over from ancient lava flows. Low green auroras sweep across the sky above showing impressive complexity near the horizon. Stars far in the distance appear to show unusual trails -- as the Earth turned -- because early exposures...
  • Astronomy Picture of the Day -- NGC 2440: Pearl of a New White Dwarf

    05/17/2015 11:50:08 AM PDT · by SunkenCiv · 15 replies
    NASA ^ | May 17, 2015 | (see photo credit)
    Explanation: Like a pearl, a white dwarf star shines best after being freed from its shell. In this analogy, however, the Sun would be a mollusk and its discarded hull would shine prettiest of all! In the above shell of gas and dust, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The glowing stellar pearl can be seen as the bright dot near the image center. The portion of NGC 2440 shown spans about one light year. The center of our Sun will eventually become a white dwarf, but not for another five...
  • Astronomy Picture of the Day -- Ares 3 Landing Site: The Martian Revisited

    05/16/2015 5:45:12 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | May 16, 2015 | (see photo credit)
    Explanation: This close-up from the Mars Reconnaissance Orbiter's HiRISE camera shows weathered craters and windblown deposits in southern Acidalia Planitia. A striking shade of blue in standard HiRISE image colors, to the human eye the area would probably look grey or a little reddish. But human eyes have not gazed across this terrain, unless you count the eyes of NASA astronauts in the scifi novel The Martian by Andy Weir. The novel chronicles the adventures of Mark Watney, an astronaut stranded at the fictional Mars mission Ares 3 landing site corresponding to the coordinates of this cropped HiRISE frame. For...
  • Astronomy Picture of the Day -- Jupiter, Ganymede, Great Red Spot

    05/15/2015 4:03:11 AM PDT · by SunkenCiv · 14 replies
    NASA ^ | May 15, 2015 | (see photo credit)
    Explanation: In this sharp snapshot, the Solar System's largest moon Ganymede poses next to Jupiter, the largest planet. Captured on March 10 with a small telescope from our fair planet Earth, the scene also includes Jupiter's Great Red Spot, the Solar System's largest storm. In fact, Ganymede is about 5,260 kilometers in diameter. That beats out all three of its other fellow Galilean satellites, along with Saturn's Moon Titan at 5,150 kilometers and Earth's own Moon at 3,480 kilometers. Though its been shrinking lately, the Great Red Spot's diameter is still around 16,500 kilometers. Jupiter, the Solar System's ruling gas...
  • Astronomy Picture of the Day -- Dwarf Planet, Bright Spot

    05/14/2015 3:45:01 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | May 14, 2015 | (see photo credit)
    Explanation: Now at Ceres, Dawn's camera recorded this closer view of the dwarf planet's northern hemisphere and one of its mysterious bright spots on May 4. A sunlit portrait of a small, dark world about 950 kilometers in diameter, the image is part of a planned sequence taken from the solar-powered spacecraft's 15-day long RC3 mapping orbit at a distance of 13,600 kilometers (8,400 miles). The animated sequence shows Ceres' rotation, its north pole at the top of the frame. Imaged by Hubble in 2004 and then by Dawn as it approached Ceres in 2015, the bright spot itself is...
  • Astronomy Picture of the Day -- The Magnificent Horsehead Nebula

    05/14/2015 3:42:44 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | May 13, 2015 | (see photo credit)
    Explanation: Sculpted by stellar winds and radiation, a magnificent interstellar dust cloud by chance has assumed this recognizable shape. Fittingly named the Horsehead Nebula, it is some 1,500 light-years distant, embedded in the vast Orion cloud complex. About five light-years "tall", the dark cloud is cataloged as Barnard 33 and is visible only because its obscuring dust is silhouetted against the glowing red emission nebula IC 434. Stars are forming within the dark cloud. Contrasting blue reflection nebula NGC 2023, surrounding a hot, young star, is at the lower left. The gorgeous featured image combines both narrowband and broadband images....
  • Astronomy Picture of the Day -- Two Worlds, One Sun

    05/12/2015 3:51:10 AM PDT · by SunkenCiv · 8 replies
    NASA ^ | May 12, 2015 | (see photo credit)
    Explanation: How different does sunset appear from Mars than from Earth? For comparison, two images of our common star were taken at sunset, one from Earth and one from Mars. These images were scaled to have same angular width and featured here side-by-side. A quick inspection will reveal that the Sun appears slightly smaller from Mars than from Earth. This makes sense since Mars is 50% further from the Sun than Earth. More striking, perhaps, is that the Martian sunset is noticeably bluer near the Sun than the typically orange colors near the setting Sun from Earth. The reason for...
  • Astronomy Picture of the Day -- The Sky from Mauna Kea

    05/11/2015 6:45:55 AM PDT · by SunkenCiv · 11 replies
    NASA ^ | May 11, 2015 | (see photo credit)
    Explanation: What if you could stand at the top of a volcano and peer out across the universe? It the timing is right, you might see an amazing panorama like the one featured here. In this case, the volcano is the Hawaii's Mauna Kea, and the time was a clear night last summer In the foreground of this south-facing panorama lies a rugged landscape dotted with rocks and hardy plants. Slightly above and further out, a white blanket of clouds spreads horizontally to the horizon, seemingly dividing heaven and Earth. City lights illuminate the clouds and sky on the far...
  • Astronomy Picture of the Day -- MyCn18: An Hourglass Planetary Nebula

    05/09/2015 10:04:47 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | May 10, 2015 | (see photo credit)
    Explanation: The sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a Sun-like star's life occurs as its outer layers are ejected - its core becoming a cooling, fading white dwarf. In 1995, astronomers used the Hubble Space Telescope (HST) to make a series of images of planetary nebulae, including the one above. Here, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the hourglass. The unprecedented sharpness of the HST images has revealed surprising details of...
  • Astronomy Picture of the Day -- Trio Leo

    05/09/2015 6:58:09 AM PDT · by SunkenCiv · 18 replies
    NASA ^ | May 09, 2015 | (see photo credit)
    Explanation: This popular group is famous as the Leo Triplet - a gathering of three magnificent galaxies in one field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top). All three are large spiral galaxies but they tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628 is seen edge-on, with obscuring dust lanes cutting across the plane of the galaxy, while the disks of M66 and M65 are both inclined enough to show...
  • Astronomy Picture of the Day -- When Vega is North

    05/08/2015 4:16:18 AM PDT · by SunkenCiv · 9 replies
    NASA ^ | May 08, 2015 | (see photo credit)
    Explanation: In only about 12,000 years Vega will be the North Star, the closest bright star to our fair planet's North Celestial Pole. By then, when you fix your camera to a tripod long exposures of the night sky will show the concentric arcs of star trails centered on a point near Vega as Earth rotates on its axis. Of course, presently the bright star conveniently near the North Celestial Pole is Polaris, but that will change as the Earth's axis of rotation precesses, like the wobble of a spinning top with a precession period of about 26,000 years. If...
  • Astronomy Picture of the Day -- At the Limit of Diffraction

    05/07/2015 12:34:26 AM PDT · by SunkenCiv · 12 replies
    NASA ^ | May 07, 2015 | (see photo credit)
    Explanation: Did you ever want to just look through the eyepiece of a large telescope in space? If you could, you would see a sharp view that was diffraction limited. Unaffected by atmospheric blurring that ultimately plagues earthbound observers, the angular resolution of your diffraction limited view would be determined only by the wavelength of light and diameter of the telescope lens or mirror; the larger the diameter, the sharper the image. Still, in this working earth-based snapshot a new active adaptive optics system (MagAO) is being used to cancel out the atmospheric blurring in a visual observation of famous...
  • Astronomy Picture of the Day -- Summer Triangles over Japan

    05/06/2015 4:16:35 AM PDT · by SunkenCiv · 17 replies
    NASA ^ | May 06, 2015 | (see photo credit)
    Explanation: Have you ever seen the Summer Triangle? The bright stars Vega, Deneb, and Altair form a large triangle on the sky that can be seen rising in the early northern early spring during the morning and rising in the northern fall during the evening. During summer months, the triangle can be found nearly overhead near midnight. Featured here, the Summer Triangle asterism was captured last month from Gunma, Japan. In the foreground, sporting a triangular shape of its own, is a flowering 500 year old cherry tree, standing about 15 meters tall. The triangular shape of the asterism is...
  • Astronomy Picture of the Day -- Gravitational Anomalies of Mercury

    05/05/2015 4:09:19 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | May 05, 2015 | (see photo credit)
    Explanation: What's that under the surface of Mercury? The robotic MESSENGER spacecraft that had been orbiting planet Mercury for the past four years had been transmitting its data back to Earth with radio waves of very precise energy. The planet's gravity, however, slightly changed this energy when measured on Earth, which enabled the reconstruction of a gravity map of unprecedented precision. Here gravitational anomalies are shown in false-color, superposed on an image of the planet's cratered surface. Red hues indicate areas of slightly higher gravity, which in turn indicates areas that must have unusually dense matter under the surface. The...
  • Astronomy Picture of the Day -- An Unexpected Aurora over Norway

    05/04/2015 5:49:42 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | May 04, 2015 | (see photo credit)
    Explanation: Sometimes the sky lights up unexpectedly. A trip to northern Norway to photograph auroras was not going as well as hoped. It was now past midnight in Steinsvik, Troms, in northern Norway, and the date was 2014 February 8. Despite recent activity on the Sun, the skies were disappointing. Therefore, the astrophotographer began packing up to go. His brother began searching for a missing lens cap. When the sky suddenly exploded with spectacular aurora. Reacting quickly, a sequence detailing dramatic green curtains was captured, with the bright Moon near the image center, and the lens-cap seeking brother on the...
  • Astronomy Picture of the Day -- Moonrise Through Mauna Kea's Shadow

    05/03/2015 4:12:45 PM PDT · by SunkenCiv · 10 replies
    NASA ^ | May 03, 2015 | (see photo credit)
    Explanation: How can the Moon rise through a mountain? It cannot -- what was photographed here is a moonrise through the shadow of a large volcano. The volcano is Mauna Kea, Hawai'i, USA, a frequent spot for spectacular photographs since it is arguably the premier observing location on planet Earth. The Sun has just set in the opposite direction, behind the camera. Additionally, the Moon has just passed full phase -- were it precisely at full phase it would rise, possibly eclipsed, at the very peak of the shadow. The Moon is actually rising in the triangular shadow cone of...
  • Astronomy Picture of the Day -- M51: The Whirlpool Galaxy

    05/02/2015 4:37:29 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | May 02, 2015 | (see photo credit)
    Explanation: Follow the handle of the Big Dipper away from the dipper's bowl until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (right), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular...
  • Astronomy Picture of the Day -- MESSENGER's Last Day on Mercury

    05/01/2015 4:58:04 AM PDT · by SunkenCiv · 8 replies
    NASA ^ | May 01, 2015 | (see photo credit)
    Explanation: The first to orbit Mercury, the MESSENGER spacecraft came to rest on this region of Mercury's surface yesterday. Constructed from MESSENGER image and laser altimeter data, the scene looks north over the northeastern rim of the broad, lava filled Shakespeare basin. The large, 48 kilometer (30 mile) wide crater Janacek is near the upper left edge. Terrain height is color coded with red regions about 3 kilometers above blue ones. MESSENGER'S final orbit was predicted to end near the center, with the spacecraft impacting the surface at nearly 4 kilometers per second (over 87,000 miles per hour) and creating...
  • Astronomy Picture of the Day -- Across the Sun

    04/30/2015 4:05:05 AM PDT · by SunkenCiv · 13 replies
    NASA ^ | April 30, 2015 | (see photo credit)
    Explanation: A long solar filament stretches across the relatively calm surface of the Sun in this telescopic snap shot from April 27. The negative or inverted narrowband image was made in the light of ionized hydrogen atoms. Seen at the upper left, the magnificent curtain of magnetized plasma towers above surface and actually reaches beyond the Sun's edge. How long is the solar filament? About as long as the distance from Earth to Moon, illustrated by the scale insert at the left. Tracking toward the right across the solar disk a day later the long filament erupted, lifting away from...
  • Astronomy Picture of the Day -- Comet Churyumov Gerasimenko in Crescent

    04/29/2015 9:23:34 AM PDT · by SunkenCiv · 14 replies
    NASA ^ | April 29, 2015 | (see photo credit)
    Explanation: What's happening to Comet 67P/Churyumov-Gerasimenko? As the 3-km wide comet moves closer to the Sun, heat causes the nucleus to expel gas and dust. The Rosetta spacecraft arrived at the comet's craggily double nucleus last July and now is co-orbiting the Sun with the giant dark iceberg. Recent analysis of data beamed back to Earth from the robotic Rosetta spacecraft has shown that water being expelled by 67P has a significant difference with water on Earth, indicating that Earth's water could not have originated from ancient collisions with comets like 67P. Additionally, neither Rosetta nor its Philae lander detected...
  • Astronomy Picture of the Day -- Massive Nearby Spiral Galaxy NGC 2841

    04/28/2015 3:48:02 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | April 28, 2015 | (see photo credit)
    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...
  • Astronomy Picture of the Day -- Space Station over Lunar Terminator

    04/27/2015 1:58:50 PM PDT · by SunkenCiv · 12 replies
    NASA ^ | April 27, 2015 | (see photo credit)
    Explanation: What's that in front of the Moon? It's the International Space Station. Using precise timing, the Earth-orbiting space platform was photographed in front of a partially lit Moon last year. The featured image was taken from Madrid, Spain with an exposure time of only 1/1000 of a second. In contrast, the duration of the transit of the ISS across the entire Moon was about half a second. The sun-glinting station can be seen just to the dark side of the day / night line known as the terminator. Numerous circular craters are visible on the distant Moon, as well...
  • Astronomy Picture of the Day -- Planetary Nebula Mz3: The Ant Nebula

    04/26/2015 10:39:08 AM PDT · by SunkenCiv · 13 replies
    NASA ^ | April 26, 2015 | (see photo credit)
    Explanation: Why isn't this ant a big sphere? Planetary nebula Mz3 is being cast off by a star similar to our Sun that is, surely, round. Why then would the gas that is streaming away create an ant-shaped nebula that is distinctly not round? Clues might include the high 1000-kilometer per second speed of the expelled gas, the light-year long length of the structure, and the magnetism of the star visible above at the nebula's center. One possible answer is that Mz3 is hiding a second, dimmer star that orbits close in to the bright star. A competing hypothesis holds...
  • Astronomy Picture of the Day -- Cluster and Starforming Region Westerlund 2

    04/25/2015 3:55:15 PM PDT · by SunkenCiv · 7 replies
    NASA ^ | April 25, 2015 | (see photo credit)
    Explanation: Located 20,000 light-years away in the constellation Carina, the young cluster and starforming region Westerlund 2 fills this cosmic scene. Captured with Hubble's cameras in near-infrared and visible light, the stunning image is a celebration of the 25th anniversary of the launch of the Hubble Space Telescope on April 24, 1990. The cluster's dense concentration of luminous, massive stars is about 10 light-years across. Strong winds and radiation from those massive young stars have sculpted and shaped the region's gas and dust, into starforming pillars that point back to the central cluster. Red dots surrounding the bright stars are...
  • Astronomy Picture of the Day -- Blue Tears and the Milky Way

    04/24/2015 11:29:31 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | April 24, 2015 | (see photo credit)
    Explanation: Lapping at rocks along the shore of the Island of Nangan, Taiwan, planet Earth, waves are infused with a subtle blue light in this sea and night skyscape. Composed of a series of long exposures made on April 16 the image captures the faint glow from Noctiluca scintillans. Also known as sea sparkles or blue tears, the marine plankton's bioluminescence is stimulated by wave motion. City lights along the coast of mainland China shine beneath low clouds in the west but stars and the faint Milky Way still fill the night above. Over the horizon the galaxy's central bulge...
  • Astronomy Picture of the Day -- Meteor in the Milky Way

    04/23/2015 4:22:06 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | April 23, 2015 | (see photo credit)
    Explanation: Earth's April showers include the Lyrid Meteor Shower, observed for more than 2,000 years when the planet makes its annual passage through the dust stream of long-period Comet Thatcher. A grain of that comet's dust, moving 48 kilometers per second at an altitude of 100 kilometers or so, is swept up in this night sky view from the early hours of April 21. Flashing toward the southeastern horizon, the meteor's brilliant streak crosses the central region of the rising Milky Way. Its trail points back toward the shower's radiant in the constellation Lyra, high in the northern springtime sky...
  • Astronomy Picture of the Day -- Colorful Star Clouds in Cygnus

    04/22/2015 9:55:00 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | April 22, 2015 | (see photo credit)
    Explanation: Stars can form in colorful surroundings. Featured here is a star forming region rich in glowing gas and dark dust toward the constellation of the Swan (Cygnus), near the bright star Sadr. This region, which spans about 50 light years, is part of the Gamma Cygni nebula which lies about 1,800 light years distant. Toward the right of the image is Barnard 344, a dark and twisted dust cloud rich in cool molecular gas. A dramatic wall of dust and red-glowing hydrogen gas forms a line down the picture center. While the glowing red gas is indicative of small...
  • Astronomy Picture of the Day -- Vesta Trek: A Digital Model of Asteroid Vesta

    04/21/2015 5:23:54 AM PDT · by SunkenCiv · 10 replies
    NASA ^ | April 21, 2015 | (see photo credit)
    Explanation: You can explore asteroid Vesta. Recently, NASA's robotic spaceship Dawn visited Vesta, the second largest object in our Solar System's main asteroid belt, which lies between Mars and Jupiter. During a year-long stopover, Dawn's cameras photographed Vesta's entire surface, documenting all of the minor planet's major mountains and craters. These images have now been combined into a digital model that allows anyone with a full-featured browser to fly all around Vesta, virtually, and even zoom in on interesting surface features, by just dragging and clicking. If desired, the initially flat 2D map can be wrapped into a nearly spherical...
  • Astronomy Picture of the Day -- Total Solar Eclipse over Svalbard

    04/20/2015 1:27:54 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | April 20, 2015 | (see photo credit)
    Explanation: Going, going, gone. That was the feeling in Svalbard, Norway last month during a total eclipse of the Sun by the Moon. In the featured image, the eclipse was captured every three minutes and then digitally merged with a foreground frame taken from the same location. Visible in the foreground are numerous gawking eclipse seekers, some deploying pretty sophisticated cameras. As the Moon and Sun moved together across the sky -- nearly horizontally from this far north -- an increasing fraction of the Sun appears covered by the Moon. In the central frame, the Moon's complete blockage of the...
  • Astronomy Picture of the Day -- Ring Galaxy AM 0644-741 from Hubble

    04/19/2015 4:10:07 AM PDT · by SunkenCiv · 14 replies
    NASA ^ | April 19, 2015 | (see photo credit)
    Explanation: How could a galaxy become shaped like a ring? The rim of the blue galaxy pictured on the right is an immense ring-like structure 150,000 light years in diameter composed of newly formed, extremely bright, massive stars. That galaxy, AM 0644-741, is known as a ring galaxy and was caused by an immense galaxy collision. When galaxies collide, they pass through each other -- their individual stars rarely come into contact. The ring-like shape is the result of the gravitational disruption caused by an entire small intruder galaxy passing through a large one. When this happens, interstellar gas and...
  • Astronomy Picture of the Day -- The Great Crater Hokusai

    04/18/2015 5:27:28 AM PDT · by SunkenCiv · 10 replies
    NASA ^ | April 18, 2015 | (see photo credit)
    Explanation: One of the largest young craters on Mercury, 114 kilometer (71 mile) diameter Hokusai crater's bright rays are known to extend across much of the planet. But this mosaic of oblique views focuses on Hokusai close up, its sunlit central peaks, terraced crater walls, and frozen sea of impact melt on the crater's floor. The images were captured by the MESSENGER spacecraft. The first to orbit Mercury, since 2011 MESSENGER has conducted scientific explorations, including extensive imaging of the Solar System's innermost planet. Now running out of propellant and unable to counter orbital perturbations caused by the Sun's gravity,...
  • Astronomy Picture of the Day -- M46 Plus Two

    04/17/2015 10:30:16 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | April 17, 2015 | (see photo credit)
    Explanation: Galactic or open star clusters are young. These swarms of stars are born together near the plane of the Milky Way, but their numbers steadily dwindle as cluster members are ejected by galactic tides and gravitational interactions. In fact, this bright open cluster, known as M46, is around 300 million years young. It still contains a few hundred stars within a span of 30 light-years or so. Located about 5,000 light-years away toward the constellation Puppis, M46 also seems to contain contradictions to its youthful status. In this pretty starscape, the colorful, circular patch above and right of the...
  • Astronomy Picture of the Day -- One-Armed Spiral Galaxy NGC 4725

    04/16/2015 4:56:15 AM PDT · by SunkenCiv · 11 replies
    NASA ^ | April 16, 2015 | (see photo credit)
    Explanation: While most spiral galaxies, including our own Milky Way, have two or more spiral arms, NGC 4725 has only one. In this sharp color composite image, the solo spira mirabilis seems to wind from a prominent ring of bluish, newborn star clusters and red tinted star forming regions. The odd galaxy also sports obscuring dust lanes a yellowish central bar structure composed of an older population of stars. NGC 4725 is over 100 thousand light-years across and lies 41 million light-years away in the well-groomed constellation Coma Berenices. Computer simulations of the formation of single spiral arms suggest that...
  • Astronomy Picture of the Day -- Mystic Mountain Dust Pillars

    04/16/2015 4:54:26 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | April 15, 2015 | (see photo credit)
    Explanation: It's stars versus dust in the Carina Nebula and the stars are winning. More precisely, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed. Located in the Carina Nebula and known informally as Mystic Mountain, these pillar's appearance is dominated by the dark dust even though it is composed mostly of clear hydrogen gas. Dust pillars such as these are actually much thinner than air and only appear as mountains due to relatively small amounts of opaque interstellar dust. About 7,500 light-years distant, the featured image...
  • Astronomy Picture of the Day -- Through the Shadow of the Moon

    04/14/2015 4:17:02 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | April 14, 2015 | (see photo credit)
    Explanation: What would it look like to fly through a total eclipse of the Sun? On a typical place on Earth in the path of the dark shadow of the Moon during a total eclipse, an observer would see the Moon cross the face of the Sun, completely blocking it for a few minutes. A particularly clear view of the darkness created on Earth during last month's total solar eclipse was captured by an aircraft flying through the Moon's umbral shadow. One second of time in the featured time-lapse video corresponds to about one minute of real time. The Moon's...
  • Astronomy Picture of the Day -- Milky Way over Erupting Volcano

    04/13/2015 7:30:07 AM PDT · by SunkenCiv · 10 replies
    NASA ^ | April 13, 2015 | (see photo credit)
    Explanation: The view was worth the trip. Battling high winds, cold temperatures, and low oxygen, the trek to near the top of the volcano Santa Maria in Guatemala -- while carrying sensitive camera equipment -- was lonely and difficult. Once set up, though, the camera captured this breathtaking vista during the early morning hours of February 28. Visible on the ground are six volcanoes of the Central America Volcanic Arc, including Fuego, the Volcano of Fire, which is seen erupting in the distance. Visible in the sky, in separate exposures taken a few minutes later, are many stars much further...
  • Astronomy Picture of the Day -- Sentinels of the Arctic

    04/12/2015 1:22:50 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | April 12, 2015 | (see photo credit)
    Explanation: Who guards the north? Judging from the above photograph, possibly giant trees covered in snow and ice. The featured picture was taken a few winters ago in Finnish Lapland where weather can include sub-freezing temperatures and driving snow. Surreal landscapes sometimes result, where common trees become cloaked in white and so appear, to some, as watchful aliens. Far in the distance, behind this uncommon Earthly vista, is a more common sight -- a Belt of Venus that divided a darkened from sunlit sky as the Sun rose behind the photographer. Of course, in the spring, the trees thaw and...
  • Astronomy Picture of the Day -- Venus in the West

    04/11/2015 4:04:12 PM PDT · by SunkenCiv · 11 replies
    NASA ^ | April 11, 2015 | (see photo credit)
    Explanation: In the coming days, Venus shines near the western horizon at sunset. To find Earth's sister planet in twilight skies just look for the brilliant evening star. Tonight very close to the Pleiades star cluster, Venus dominates this springtime night skyscape taken only a few days ago near the town of Lich in central Germany. Also known as the Seven Sisters, the stars of the compact Pleiades cluster appear above Venus in this picture. The budding tree branches to its left frame bright star Aldebaran, the eye of Taurus the Bull, and the V-shaped Hyades star cluster.
  • Astronomy Picture of the Day -- NGC 2903: A Missing Jewel in Leo

    04/11/2015 4:02:08 PM PDT · by SunkenCiv · 8 replies
    NASA ^ | April 10, 2015 | (see photo credit)
    Explanation: Barred spiral galaxy NGC 2903 is only some 20 million light-years distant. Popular among amateur astronomers, it shines in the northern spring constellation Leo, near the top of the lion's head. That part of the constellation is sometimes seen as a reversed question mark or sickle. One of the brighter galaxies visible from the northern hemisphere, NGC 2903 is surprisingly missing from Charles Messier's catalog of lustrous celestial sights. This colorful image from a small ground-based telescope shows off the galaxy's gorgeous spiral arms traced by young, blue star clusters and pinkish star forming regions. Included are intriguing details...
  • Astronomy Picture of the Day -- A Golden Gate Eclipse

    04/09/2015 4:05:11 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | April 09, 2015 | (see photo credit)
    Explanation: Shadows play on the water and in the sky in this panoramic view of the April 4 total lunar eclipse over San Francisco's Golden Gate Bridge. Just within planet Earth's shadow the Full Moon's disk is still easy to spot at its brief total phase. The urban night skyscape was composed to cover the wide range of brightness visible to the eye. The shortest total lunar eclipse of the century, this eclipse was also the third in a string of four consecutive total lunar eclipses, a series known as a tetrad. Coming in nearly six month intervals, the previous...
  • Astronomy Picture of the Day -- Full Moon in Earth's Shadow

    04/08/2015 2:13:21 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | April 08, 2015 | (see photo credit)
    Explanation: Last week the Full Moon was completely immersed in Earth's dark umbral shadow, just briefly though. The total phase of the April 4, 2015 lunar eclipse lasted less than 5 minutes, the shortest total lunar eclipse of the century. In fact, sliding just within the Earth's umbral shadow's northern edge, the lunar north stayed relatively bright, while a beautiful range of blue and red hues emerged across the rest of the Moon's Earth-facing hemisphere. The reddened light within the shadow that reaches the lunar surface is filtered through the lower atmosphere. Seen from a lunar perspective it comes from...
  • Astronomy Picture of the Day -- In the Heart of the Virgo Cluster

    04/07/2015 7:58:09 AM PDT · by SunkenCiv · 7 replies
    NASA ^ | April 07, 2015 | (see photo credit)
    Explanation: The Virgo Cluster of Galaxies is the closest cluster of galaxies to our Milky Way Galaxy. The Virgo Cluster is so close that it spans more than 5 degrees on the sky - about 10 times the angle made by a full Moon. With its heart lying about 70 million light years distant, the Virgo Cluster is the nearest cluster of galaxies, contains over 2,000 galaxies, and has a noticeable gravitational pull on the galaxies of the Local Group of Galaxies surrounding our Milky Way Galaxy. The cluster contains not only galaxies filled with stars but also gas so...
  • Astronomy Picture of the Day -- NGC 3293: A Bright Young Star Cluster

    04/06/2015 5:36:01 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | April 06, 2015 | (see photo credit)
    Explanation: Hot blue stars shine brightly in this beautiful, recently formed galactic or "open" star cluster. Open cluster NGC 3293 is located in the constellation Carina, lies at a distance of about 8000 light years, and has a particularly high abundance of these young bright stars. A study of NGC 3293 implies that the blue stars are only about 6 million years old, whereas the cluster's dimmer, redder stars appear to be about 20 million years old. If true, star formation in this open cluster took at least 15 million years. Even this amount of time is short, however, when...
  • Astronomy Picture of the Day -- Saturn, Tethys, Rings, and Shadows

    04/05/2015 2:49:41 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | April 05, 2015 | (see photo credit)
    Explanation: 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...
  • Astronomy Picture of the Day -- Voorwerpjes in Space

    04/04/2015 4:02:23 AM PDT · by SunkenCiv · 2 replies
    NASA ^ | April 04, 2015 | (see photo credit)
    Explanation: 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...
  • Astronomy Picture of the Day -- Sun and Moon Halo

    04/03/2015 5:04:14 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | April 03, 2015 | (see photo credit)
    Explanation: 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 stersund 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...