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Astronomy Picture of the Day (General/Chat)

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  • Astronomy Picture of the Day -- Arp 188 and the Tadpole's Tail

    08/24/2014 9:23:44 PM PDT · by SunkenCiv · 11 replies
    NASA ^ | August 25, 2014 | (see photo credit)
    Explanation: Why does this galaxy have such a long tail? In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole...
  • Astronomy Picture of the Day -- Mercury's Transit: An Unusual Spot on the Sun

    08/24/2014 1:39:14 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | August 24, 2014 | (see photo credit)
    Explanation: What's that dot on the Sun? If you look closely, it is almost perfectly round. The dot is the result of an unusual type of solar eclipse that occurred in 2006. Usually it is the Earth's Moon that eclipses the Sun. This time, the planet Mercury took a turn. Like the approach to New Moon before a solar eclipse, the phase of Mercury became a continually thinner crescent as the planet progressed toward an alignment with the Sun. Eventually the phase of Mercury dropped to zero and the dark spot of Mercury crossed our parent star. The situation could...
  • Astronomy Picture of the Day -- The Spectre of Veszprem

    08/23/2014 8:24:37 PM PDT · by SunkenCiv · 2 replies
    NASA ^ | August 23, 2014 | (see photo credit)
    Explanation: The city of Veszprem, Hungary was only briefly haunted by this mysterious spectre. On the morning of August 11, its monstrous form hovered in the mist above municipal buildings near the town center. A clue to its true identity is offered by the photographer, though, who reports he took the picture from the top of a twenty story building with the rising Sun directly at his back. That special geometry suggests this is an example of an atmospheric phenomenon called the Glory or sometimes "the Spectre of the Brocken". Also seen from mountain tops and airplanes when looking opposite...
  • Astronomy Picture of the Day -- Comet Jacques, Heart and Soul

    08/23/2014 8:13:44 PM PDT · by SunkenCiv · 7 replies
    NASA ^ | August 22, 2014 | (see photo credit)
    Explanation: On July 13th, a good place to watch Comet Jacques was from Venus. Then, the recently discovered visitor (C/2014 E2) to the inner solar system passed within about 14.5 million kilometers of our sister planet. But the outbound comet will pass only 84 million kilometers from our fair planet on August 28 and is already a fine target for telescopes and binoculars. Two days ago Jacques' greenish coma and straight and narrow ion tail were captured in this telescopic snapshot, a single 2 minute long exposure with a modified digital camera. The comet is flanked by IC 1805 and...
  • Astronomy Picture of the Day -- Venus and Jupiter at Dawn

    08/23/2014 8:06:08 PM PDT · by SunkenCiv · 4 replies
    NASA ^ | August 21, 2014 | (see photo credit)
    Explanation: On Monday morning, Venus and Jupiter gathered close in dawn skies, for some separated by about half the width of a full moon. It was their closest conjunction since 2000, captured here above the eastern horizon before sunrise. The serene and colorful view is from Istia beach near the city of Capoliveri on the island of Elba. Distant lights and rolling hills are along Italy's Tuscan coast. Of course, the celestial pair soon wandered apart. Brighter Venus headed lower, toward the eastern horizon and the glare of the Sun, while Jupiter continues to rise a little higher now in...
  • Astronomy Picture of the Day -- In the Center of the Lagoon Nebula

    08/23/2014 8:02:31 PM PDT · by SunkenCiv · 1 replies
    NASA ^ | August 20, 2014 | (see photo credit)
    Explanation: The center of the Lagoon Nebula is a whirlwind of spectacular star formation. Visible near the image center, at least two long funnel-shaped clouds, each roughly half a light-year long, have been formed by extreme stellar winds and intense energetic starlight. The tremendously bright nearby star, Herschel 36, lights the area. Walls of dust hide and redden other hot young stars. As energy from these stars pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds which may cause the funnels. This picture, spanning about 5 light years, combines images...
  • Astronomy Picture of the Day -- Contrasting Terrains on Comet Churyumov-Gerasimenko

    08/23/2014 7:58:55 PM PDT · by SunkenCiv · 21 replies
    NASA ^ | August 19, 2014 | (see photo credit)
    Explanation: Where should Philae land? As ESA's robotic spacecraft Rosetta circles toward Comet 67P/ Churyumov-Gerasimenko, a decision must eventually be made as to where its mechanical lander should attempt to touch-down. Reaching the comet earlier this month, Rosetta is sending back detailed pictures of the comet's unusual nucleus from which a smooth landing site will be selected. Pictured above, near the image top, the head of the comet's nucleus shows rugged grooves, while near the image bottom, the body shows a patch-work of areas sometimes separated by jagged hills. Some of the patch-work areas apparent on both the head and...
  • Astronomy Picture of the Day -- Star Trails Over Indonesia

    08/18/2014 7:00:19 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | August 18, 2014 | (see photo credit)
    Explanation: Both land and sky were restless. The unsettled land included erupting Mount Semeru in the distance, the caldera of steaming Mount Bromo on the left, flowing fog, and the lights of moving cars along roads that thread between hills and volcanoes in Bromo Tengger Semeru National Park in East Java, Indonesia. The stirring sky included stars circling the South Celestial Pole and a meteor streaking across the image right. The above 270-image composite was taken from King Kong Hill in mid-June over two hours, with a rising Moon lighting the landscape.
  • Astronomy Picture of the Day -- Jupiter and Venus from Earth

    08/17/2014 6:27:19 AM PDT · by SunkenCiv · 34 replies
    NASA ^ | August 17, 2014 | (see photo credit)
    Explanation: It was visible around the world. The sunset conjunction of Jupiter and Venus in 2012 was visible almost no matter where you lived on Earth. Anyone on the planet with a clear western horizon at sunset could see them. Pictured above in 2012, a creative photographer traveled away from the town lights of Szubin, Poland to image a near closest approach of the two planets. The bright planets were separated only by three degrees and his daughter striking a humorous pose. A faint red sunset still glowed in the background. Early tomorrow (Monday) morning, the two planets will pass...
  • Astronomy Picture of the Day -- No X-rays from SN 2014J

    08/16/2014 4:53:24 AM PDT · by SunkenCiv · 8 replies
    NASA ^ | August 16, 2014 | (see photo credit)
    Explanation: Last January, telescopes in observatories around planet Earth were eagerly used to watch the rise of SN 2014J, a bright supernova in nearby galaxy M82. Still, the most important observations may have been from orbit where the Chandra X-ray Observatory saw nothing. Identified as a Type Ia supernova, the explosion of SN2014J was thought to be triggered by the buildup of mass on a white dwarf star steadily accreting material from a companion star. That model predicts X-rays would be generated when the supernova blastwave struck the material left surrounding the white dwarf. But no X-rays were seen from...
  • Astronomy Picture of the Day -- A Luminous Night

    08/15/2014 6:54:51 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | August 15, 2014 | (see photo credit)
    Explanation: What shines in the world at night? Just visible to the eye, a rare electric blue glow spread along the shores of Victoria Lake on January 16, 2013. Against reflections of a light near the horizon, this digitally stacked long exposure recorded the bioluminescence of Noctiluca scintillans, plankton stimulated by the lapping waves. Above, the night skies of the Gippsland Lakes region, Victoria, Australia shine with a fainter greenish airglow. Oxygen atoms in the upper atmosphere, initially excited by ultraviolet sunlight, produce the more widely seen fading atmospheric chemiluminescence. Washed out by the Earth's rotation, the faint band of...
  • Astronomy Picture of the Day -- Surreal Moon

    08/14/2014 8:11:00 PM PDT · by SunkenCiv · 15 replies
    NASA ^ | August 14, 2014 | (see photo credit)
    Explanation: Big, bright, and beautiful, a Full Moon near perigee, the closest point in its elliptical orbit around our fair planet, rose on August 10. This remarkable picture records the scene with a dreamlike quality from the east coast of the United States. The picture is actually a composite of 10 digital frames made with exposures from 1/500th second to 1 second long, preserving contrast and detail over a much wider than normal range of brightness. At a perigee distance of a mere 356,896 kilometers, August's Full Moon was the closest, and so the largest and most super, of the...
  • Astronomy Picture of the Day -- Rings Around the Ring Nebula

    08/14/2014 8:08:39 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | August 13, 2014 | (see photo credit)
    Explanation: It is a familiar sight to sky enthusiasts with even a small telescope. There is much more to the Ring Nebula (M57), however, than can be seen through a small telescope. The easily visible central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from three different large telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. This remarkable composite image includes narrowband hydrogen image, visible light emission, and infrared light emission. Of course, in this well-studied example of a planetary nebula, the...
  • Astronomy Picture of the Day -- Collapse in Hebes Chasma on Mars

    08/11/2014 11:20:40 PM PDT · by SunkenCiv · 19 replies
    NASA ^ | August 12, 2014 | (see photo credit)
    Explanation: What's happened in Hebes Chasma on Mars? Hebes Chasma is a depression just north of the enormous Valles Marineris canyon. Since the depression is unconnected to other surface features, it is unclear where the internal material went. Inside Hebes Chasma is Hebes Mensa, a 5 kilometer high mesa that appears to have undergone an unusual partial collapse -- a collapse that might be providing clues. The above image, taken by the robotic Mars Express spacecraft currently orbiting Mars, shows great details of the chasm and the unusual horseshoe shaped indentation in the central mesa. Material from the mesa appears...
  • Astronomy Picture of the Day -- Rosetta Approaches Comet Churyumov-Gerasimenko

    08/11/2014 7:28:57 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | August 11, 2014 | (see photo credit)
    Explanation: What does it look like to approach a comet? Early this month humanity received a new rendition as the robotic Rosetta spacecraft went right up to -- and began orbiting -- the nucleus of Comet 67P/Churyumov-Gerasimenko. This approach turned out to be particularly fascinating because the comet nucleus first revealed itself to have an unexpected double structure, and later showed off an unusual and craggily surface. The above 101-frame time-lapse video details the approach of the spacecraft from August 1 through August 6. The icy comet's core is the size of a mountain and rotates every 12.7 hours. Rosetta's...
  • Astronomy Picture of the Day -- A Perseid Below

    08/09/2014 10:33:02 PM PDT · by SunkenCiv · 4 replies
    NASA ^ | August 10, 2014 | (see photo credit)
    Explanation: Denizens of planet Earth typically watch meteor showers by looking up. But this remarkable view, captured on August 13, 2011 by astronaut Ron Garan, caught a Perseid meteor by looking down. From Garan's perspective onboard the International Space Station orbiting at an altitude of about 380 kilometers, the Perseid meteors streak below, swept up dust left from comet Swift-Tuttle heated to incandescence. The glowing comet dust grains are traveling at about 60 kilometers per second through the denser atmosphere around 100 kilometers above Earth's surface. In this case, the foreshortened meteor flash is right of frame center, below the...
  • Astronomy Picture of the Day -- A Luminous Night

    08/09/2014 2:38:00 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | August 09, 2014 | (see photo credit)
    Explanation: What shines in the world at night? Just visible to the eye, a rare electric blue glow spread along the shores of Victoria Lake on January 16, 2013. Against reflections of a light near the horizon, this digitally stacked long exposure recorded the bioluminescence of noctiluca scintillans, plankton stimulated by the lapping waves. Above, the night skies of the Gippsland Lakes region, Victoria, Australia shine with a fainter greenish airglow. Oxygen atoms in the upper atmosphere, initially excited by ultraviolet sunlight, produce the more widely seen fading atmospheric chemiluminescence. Washed out by the Earth's rotation, the faint band of...
  • Astronomy Picture of the Day -- Spiral Galaxy NGC 6744

    08/09/2014 2:35:15 PM PDT · by SunkenCiv · 2 replies
    NASA ^ | August 08, 2014 | (see photo credit)
    Explanation: Big, beautiful spiral galaxy NGC 6744 is nearly 175,000 light-years across, larger than our own Milky Way. It lies some 30 million light-years distant in the southern constellation Pavo. We see the disk of the nearby island universe tilted towards our line of sight. Orientation and composition give a strong sense of depth to this colorful galaxy portrait that covers an area about the angular size of the full moon. This giant galaxy's yellowish core is dominated by the light from old, cool stars. Beyond the core, spiral arms filled with young blue star clusters and pinkish star forming...
  • Astronomy Picture of the Day -- Rosetta's Rendezvous

    08/09/2014 2:32:21 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | August 07, 2014 | (see photo credit)
    Explanation: On August 3rd, the Rosetta spacecraft's narrow angle camera captured this stunning image of the nucleus of Comet 67P/Churyumov-Gerasimenko. After 10 years and 6.5 billion kilometers of travel along gravity assist trajectories looping through interplanetary space, Rosetta had approached to within 285 kilometers of its target. The curious double-lobed shape of the nucleus is revealed in amazing detail at an image resolution of 5.3 meters per pixel. About 4 kilometers across, the comet nucleus is presently just over 400 million kilometers from Earth, between the orbits of Jupiter and Mars. Now the first spacecraft to achieve a delicate orbit...
  • Astronomy Picture of the Day -- Saturn's Swirling Cloudscape

    08/09/2014 2:29:27 PM PDT · by SunkenCiv · 6 replies
    NASA ^ | August 06, 2014 | (see photo credit)
    Explanation: Acquiring its first sunlit views of far northern Saturn in late 2012, the Cassini spacecraft's wide-angle camera recorded this stunning, false-color image of the ringed planet's north pole. The composite of near-infrared image data results in red hues for low clouds and green for high ones, giving the Saturnian cloudscape a vivid appearance. Enormous by terrestrial standards, Saturn's north polar hurricane-like storm is deep, red, and about 2,000 kilometers wide. Clouds at its outer edge travel at over 500 kilometers per hour. Other atmospheric vortices also swirl inside the large, yellowish green, six-sided jet stream known as the hexagon....
  • Astronomy Picture of the Day -- Four Billion BCE: Battered Earth

    08/09/2014 2:26:38 PM PDT · by SunkenCiv · 20 replies
    NASA ^ | August 05, 2014 | (see photo credit)
    Explanation: No place on Earth was safe. Four billion years ago, during the Hadean eon, our Solar System was a dangerous shooting gallery of large and dangerous rocks and ice chunks. Recent examination of lunar and Earth bombardment data indicate that the entire surface of the Earth underwent piecemeal upheavals, hiding our globe's ancient geologic history, and creating a battered world with no remaining familiar land masses. The rain of devastation made it difficult for any life to survive, although bacteria that could endure high temperatures had the best chance. Oceans thought to have formed during this epoch would boil...
  • Astronomy Picture of the Day -- Shadows and Plumes Across Enceladus

    08/08/2014 4:40:10 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | August 04, 2014 | (see photo credit)
    Explanation: Why does Enceladus have ice plumes? The discovery of jets spewing water vapor and ice was detected by the Saturn-orbiting Cassini spacecraft in 2005. The origin of the water feeding the jets, however, remained a topic of research. A leading hypothesis held that the source might originate from a deep underground sea, but another hypothesis indicated that it might just be ice melted off walls of deep rifts by the moon's tidal flexing and heating. Pictured above, the textured surface of Enceladus is visible in the foreground, while rows of plumes rise from ice fractures in the distance. These...
  • Astronomy Picture of the Day -- Dark Shuttle Approaching

    08/03/2014 9:08:12 AM PDT · by SunkenCiv · 12 replies
    NASA ^ | August 03, 2014 | (see photo credit)
    Explanation: What's that approaching? Astronauts on board the International Space Station first saw it in early 2010 far in the distance. Soon it enlarged to become a dark silhouette. As it came even closer, the silhouette appeared to be a spaceship. Finally, the object revealed itself to be the Space Shuttle Endeavour, and it soon docked as expected with the Earth-orbiting space station. Pictured above, Endeavour was imaged near Earth's horizon as it approached, where several layers of the Earth's atmosphere were visible. Directly behind the shuttle is the mesosphere, which appears blue. The atmospheric layer that appears white is...
  • Astronomy Picture of the Day -- NGC 7023: The Iris Nebula

    08/01/2014 10:40:14 PM PDT · by SunkenCiv · 7 replies
    NASA ^ | August 02, 2014 | (see photo credit)
    Explanation: These clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula, NGC 7023 is not the only nebula in the sky to evoke the imagery of flowers, though. Still, this deep telescopic view shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue, characteristic of dust grains reflecting starlight. Central filaments of the dusty clouds glow with a faint reddish...
  • Astronomy Picture of the Day -- Tetons and Snake River, Planet Earth

    07/31/2014 10:57:05 PM PDT · by SunkenCiv · 11 replies
    NASA ^ | August 01, 2014 | (see photo credit)
    Explanation: An alluring night skyscape, this scene looks west across the Grand Teton National Park, Wyoming, USA, Planet Earth. The Snake River glides through the foreground, while above the Tetons' rugged mountain peaks the starry sky is laced with exceptionally strong red and green airglow. That night, the luminous atmospheric glow was just faintly visible to the eye, its color and wavey structure captured only by a sensitive digital camera. In fact, this contemporary digital photograph matches the location and perspective of a well-known photograph from 1942 - The Tetons and The Snake River , by Ansel Adams, renown photographer...
  • Astronomy Picture of the Day -- Veins of Heaven

    07/31/2014 10:53:41 PM PDT · by SunkenCiv · 4 replies
    NASA ^ | July 31, 2014 | (see photo credit)
    Explanation: Transfusing sunlight through a still dark sky, this exceptional display of noctilucent clouds was captured earlier this month above the island of Gotland, Sweden. From the edge of space, about 80 kilometers above Earth's surface, the icy clouds reflect sunlight even though the Sun itself is below the horizon as seen from the ground. Usually spotted at high latitudes in summer months the night shining clouds made a strong showing this July. Also known as polar mesopheric clouds they are understood to form as water vapor driven into the cold upper atmosphere condenses on the fine dust particles supplied...
  • Astronomy Picture of the Day -- M31: The Andromeda Galaxy

    07/31/2014 10:49:52 PM PDT · by SunkenCiv · 7 replies
    NASA ^ | July 30, 2014 | (see photo credit)
    Explanation: Andromeda is the nearest major galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object on Messier's list of diffuse sky objects. M31 is so distant it takes about two...
  • Astronomy Picture of the Day -- A Sky Portal in New Zealand

    07/31/2014 10:44:57 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | July 29, 2014 | (see photo credit)
    Explanation: To some, it may look like a portal into the distant universe. To others, it may appear as the eye of a giant. Given poetic license, both are correct. Pictured above is a standard fisheye view of the sky -- but with an unusual projection. The view is from a perch in New Zealand called Te Mata Peak, a name that translates from the Maori language as "Sleeping Giant". The wondrous panorama shows the band of our Milky Way Galaxy right down the center of the sky, with the Large and Small Magellanic Clouds visible to the right. The...
  • Astronomy Picture of the Day -- The Horsehead Nebula from Blue to Infrared

    07/31/2014 10:39:56 PM PDT · by SunkenCiv · 5 replies
    NASA ^ | July 28, 2014 | (see photo credit)
    Explanation: One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright...
  • Astronomy Picture of the Day -- Rho Ophiuchi Wide Field

    07/27/2014 6:48:52 AM PDT · by SunkenCiv · 4 replies
    NASA ^ | July 27, 2014 | (see photo credit)
    Explanation: The clouds surrounding the star system Rho Ophiuchi compose one of the closest star forming regions. Rho Ophiuchi itself is a binary star system visible in the light-colored region on the image right. The star system, located only 400 light years away, is distinguished by its colorful surroundings, which include a red emission nebula and numerous light and dark brown dust lanes. Near the upper right of the Rho Ophiuchi molecular cloud system is the yellow star Antares, while a distant but coincidently-superposed globular cluster of stars, M4, is visible between Antares and the red emission nebula. Near the...
  • Astronomy Picture of the Day -- NGC 253: Dusty Island Universe

    07/27/2014 6:47:45 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | July 26, 2014 | (see photo credit)
    Explanation: Shiny NGC 253 is one of the brightest spiral galaxies visible, and also one of the dustiest. Some call it the Silver Dollar Galaxy for its appearance in small telescopes, or just the Sculptor Galaxy for its location within the boundaries of the southern constellation Sculptor. First swept up in 1783 by mathematician and astronomer Caroline Herschel, the dusty island universe lies a mere 10 million light-years away. About 70 thousand light-years across, NGC 253 is the largest member of the Sculptor Group of Galaxies, the nearest to our own Local Group of Galaxies. In addition to its spiral...
  • Astronomy Picture of the Day -- Cosmic Crab Nebula

    07/26/2014 8:29:05 AM PDT · by SunkenCiv · 7 replies
    NASA ^ | July 25, 2014 | (see photo credit)
    Explanation: The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this tantalizing wide-field image of the Crab Nebula. A spectacular picture of one of our Milky Way's supernova remnants, it combines optical survey data with X-ray data from the orbiting Chandra Observatory. The composite was created as part of a celebration of Chandra's 15 year long exploration of the high energy cosmos. Like a cosmic dynamo the pulsar powers the X-ray and optical emission from the nebula, accelerating charged particles to extreme energies to produce the jets and rings glowing in...
  • Astronomy Picture of the Day -- ALMA Milky Way

    07/24/2014 2:59:38 PM PDT · by SunkenCiv · 4 replies
    NASA ^ | July 24, 2014 | (see photo credit)
    Explanation: This alluring all-skyscape was taken 5,100 meters above sea level, from the Chajnantor Plateau in the Chilean Andes. Viewed through the site's rarefied atmosphere at about 50% sea level pressure, the gorgeous Milky Way stretches through the scene. Its cosmic rifts of dust, stars, and nebulae are joined by Venus, a brilliant morning star immersed in a strong band of predawn Zodiacal light. Still not completely dark even at this high altitude, the night sky's greenish cast is due to airglow emission from oxygen atoms. Around the horizon the dish antenna units of the Atacama Large Millimeter/submillimeter Array, ALMA,...
  • Astronomy Picture of the Day -- IC 4603: Reflection Nebula in Ophiuchius

    07/24/2014 2:57:38 PM PDT · by SunkenCiv · 4 replies
    NASA ^ | July 23, 2014 | (see photo credit)
    Explanation: Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, evolved stars. The dust is dispersed as the star dies and grows as things stick to it in the interstellar medium. Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the...
  • Astronomy Picture of the Day -- Cave with Aurora Skylight

    07/22/2014 4:05:06 PM PDT · by SunkenCiv · 11 replies
    NASA ^ | July 22, 2014 | (see photo credit)
    Explanation: Yes, but have you ever seen aurora from a cave? To capture this fascinating juxtaposition between below and above, astrophotographer Bjargmundsson spent much of a night alone in the kilometer-long Raufarhólshellir lava cave in Iceland during late March. There, he took separate images of three parts of the cave using a strobe for illumination. He also took a deep image of the sky to capture faint aurora, and digitally combined the four images later. The 4600-year old lava tube has several skylights under which stone rubble and snow have accumulated. Oh -- the person standing on each mound --...
  • Astronomy Picture of the Day -- Spacecraft Rosetta Shows Comet has Two Components

    07/21/2014 8:58:06 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | July 21, 2014 | (see photo credit)
    Explanation: Why does this comet's nucleus have two components? The surprising discovery that Comet 67P/Churyumov–Gerasimenko has a double nucleus came late last week as ESA's robotic interplanetary spacecraft Rosetta continued its approach toward the ancient comet's core. Speculative ideas on how the double core was created include, currently, that Comet Churyumov–Gerasimenko is actually the result of the merger of two comets, that the comet is a loose pile of rubble pulled apart by tidal forces, that ice evaporation on the comet has been asymmetric, or that the comet has undergone some sort of explosive event. Pictured above, the comet's unusual...
  • Astronomy Picture of the Day -- A Solar Filament Erupts

    07/21/2014 8:53:26 AM PDT · by SunkenCiv · 7 replies
    NASA ^ | July 20, 2014 | (see photo credit)
    Explanation: What's happened to our Sun? Nothing very unusual -- it just threw a filament. Toward the middle of 2012, a long standing solar filament suddenly erupted into space producing an energetic Coronal Mass Ejection (CME). The filament had been held up for days by the Sun's ever changing magnetic field and the timing of the eruption was unexpected. Watched closely by the Sun-orbiting Solar Dynamics Observatory, the resulting explosion shot electrons and ions into the Solar System, some of which arrived at Earth three days later and impacted Earth's magnetosphere, causing visible aurorae. Loops of plasma surrounding an active...
  • Astronomy Picture of the Day -- Alicante Beach Moonrise

    07/19/2014 4:44:12 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | July 19, 2014 | (see photo credit)
    Explanation: In this beach and skyscape from Alicante, Spain, July's Full Moon shines in the dark blue twilight, its reflection coloring the Mediterranean waters. Near the horizon, the moonlight is reddened by its long path through the atmosphere, but this Full Moon was also near perigee, the closest point to Earth along the Moon's elliptical orbit. That made it a Supermoon, a mighty 14% larger and 30% brighter than a Full Moon at apogee, the Moon's farthest orbital swing. Of course, most warm summer nights are a good time to enjoy a family meal oceanside, but what fish do you...
  • Astronomy Picture of the Day -- Ou4: A Giant Squid Nebula

    07/19/2014 4:41:59 AM PDT · by SunkenCiv · 5 replies
    NASA ^ | July 18, 2014 | (see photo credit)
    Explanation: A mysterious, squid-like apparition, this nebula is very faint, but also very large in planet Earth's sky. In the mosaic image, composed with narrowband data from the 2.5 meter Isaac Newton Telescope, it spans some 2.5 full moons toward the constellation Cepheus. Recently discovered by French astro-imager Nicolas Outters, the remarkable nebula's bipolar shape and emission are consistent with it being a planetary nebula, the gaseous shroud of a dying sun-like star, but its actual distance and origin are unknown. A new investigation suggests Ou4 really lies within the emission region SH2-129 some 2,300 light-years away. Consistent with that...
  • Astronomy Picture of the Day -- 3D Homunculus Nebula

    07/19/2014 4:36:33 AM PDT · by SunkenCiv · 3 replies
    NASA ^ | July 17, 2014 | (see photo credit)
    Explanation: If you're looking for something to print with that new 3D printer, try out a copy of the Homunculus Nebula. The dusty, bipolar cosmic cloud is around 1 light-year across but is slightly scaled down for printing to about 1/4 light-nanosecond or 80 millimeters. The full scale Homunculus surrounds Eta Carinae, famously unstable massive stars in a binary system embedded in the extensive Carina Nebula about 7,500 light-years distant. Between 1838 and 1845, Eta Carinae underwent the Great Eruption becoming the second brightest star in planet Earth's night sky and ejecting the Homunculus Nebula. The new 3D model of...
  • Astronomy Picture of the Day -- The Moon Eclipses Saturn

    07/16/2014 2:18:00 PM PDT · by SunkenCiv · 12 replies
    NASA ^ | July 16, 2014 | (see photo credit)
    Explanation: What happened to half of Saturn? Nothing other than Earth's Moon getting in the way. As pictured above on the far right, Saturn is partly eclipsed by a dark edge of a Moon itself only partly illuminated by the Sun. This year the orbits of the Moon and Saturn have led to an unusually high number of alignments of the ringed giant behind Earth's largest satellite. Technically termed an occultation, the above image captured one such photogenic juxtaposition from Buenos Aires, Argentina that occurred early last week. Visible to the unaided eye but best viewed with binoculars, there are...
  • Astronomy Picture of the Day -- A Blue Bridge of Stars between Cluster Galaxies

    07/15/2014 2:02:13 PM PDT · by SunkenCiv · 14 replies
    NASA ^ | July 15, 2014 | (see photo credit)
    Explanation: Why is there a blue bridge of stars across the center of this galaxy cluster? First and foremost the cluster, designated SDSS J1531+3414, contains many large yellow elliptical galaxies. The cluster's center, as pictured above by the Hubble Space Telescope, is surrounded by many unusual, thin, and curving blue filaments that are actually galaxies far in the distance whose images have become magnified and elongated by the gravitational lens effect of the massive cluster. More unusual, however, is a squiggly blue filament near the two large elliptical galaxies at the cluster center. Close inspection of the filament indicates that...
  • Astronomy Picture of the Day -- Auroras over Northern Canada

    07/14/2014 4:45:11 PM PDT · by SunkenCiv · 8 replies
    NASA ^ | July 14, 2014 | (see photo credit)
    Explanation: Gusting solar winds and blasts of charged particles from the Sun resulted in several rewarding nights last December for those anticipating auroras. The above image captured dramatic auroras stretching across a sky near the town of Yellowknife in northern Canada. The auroras were so bright that they not only inspired awe, but were easily visible on an image exposure of only 1.3 seconds. A video taken concurrently shows the dancing sky lights evolving in real time as tourists, many there just to see auroras, respond with cheers. The conical dwellings on the image right are teepees, while far in...
  • Astronomy Picture of the Day -- Planetary Nebula NGC 2818 from Hubble

    07/13/2014 6:09:41 AM PDT · by SunkenCiv · 7 replies
    NASA ^ | July 13, 2014 | (see photo credit)
    Explanation: NGC 2818 is a beautiful planetary nebula, the gaseous shroud of a dying sun-like star. It could well offer a glimpse of the future that awaits our own Sun after spending another 5 billion years or so steadily using up hydrogen at its core, and then finally helium, as fuel for nuclear fusion. Curiously, NGC 2818 seems to lie within an open star cluster, NGC 2818A, that is some 10,000 light-years distant toward the southern constellation Pyxis (the Compass). At the distance of the star cluster, the nebula would be about 4 light-years across. But accurate velocity measurements show...
  • Astronomy Picture of the Day -- SN 1006 Supernova Remnant

    07/12/2014 4:20:54 AM PDT · by SunkenCiv · 6 replies
    NASA ^ | July 12, 2014 | (see photo credit)
    Explanation: A new star, likely the brightest supernova in recorded human history, lit up planet Earth's sky in the year 1006 AD. The expanding debris cloud from the stellar explosion, found in the southerly constellation of Lupus, still puts on a cosmic light show across the electromagnetic spectrum. In fact, this composite view includes X-ray data in blue from the Chandra Observatory, optical data in yellowish hues, and radio image data in red. Now known as the SN 1006 supernova remnant, the debris cloud appears to be about 60 light-years across and is understood to represent the remains of a...
  • Astronomy Picture of the Day -- Spotty Sunrise over Brisbane

    07/10/2014 9:26:58 PM PDT · by SunkenCiv · 4 replies
    NASA ^ | July 11, 2014 | (see photo credit)
    Explanation: In this composite cityscape, dawn's first colors backdrop the lights along Brisbane's skyline at the southeastern corner of Queensland, Australia, planet Earth. Using a solar filter, additional exposures made every 3.5 minutes follow the winter sunrise on July 8 as planet-sized sunspots cross the visible solar disk. The sunspots mark solar active regions with convoluted magnetic fields. Even as the maximum in the solar activity cycle begins to fade, the active regions produce intense solar flares and eruptions launching coronal mass ejections (CMEs), enormous clouds of energetic particles, into our fair solar system.
  • Astronomy Picture of the Day -- M51: X-Rays from the Whirlpool

    07/10/2014 8:36:47 PM PDT · by SunkenCiv · 8 replies
    NASA ^ | June 10, 2014 | (see photo credit)
    Explanation: What if we X-rayed an entire spiral galaxy? This was done (again) recently by NASA's Chandra X-ray Observatory for the nearby interacting galaxies known as the Whirlpool (M51). Hundreds of glittering x-ray stars are present in the above Chandra image of the spiral and its neighbor. The image is a conglomerate of X-ray light from Chandra and visible light from the Hubble Space Telescope. The number of luminous x-ray sources, likely neutron star and black hole binary systems within the confines of M51, is unusually high for normal spiral or elliptical galaxies and suggests this cosmic whirlpool has experienced...
  • Astronomy Picture of the Day -- How to Identify that Light in the Sky

    07/10/2014 8:33:02 PM PDT · by SunkenCiv · 9 replies
    NASA ^ | June 09, 2014 | (see photo credit)
    Explanation: What is that light in the sky? Perhaps one of humanity's more common questions, an answer may result from a few quick observations. For example -- is it moving or blinking? If so, and if you live near a city, the answer is typically an airplane, since planes are so numerous and so few stars and satellites are bright enough to be seen over the din of artificial city lights. If not, and if you live far from a city, that bright light is likely a planet such as Venus or Mars -- the former of which is constrained...
  • Astronomy Picture of the Day -- Open Cluster NGC 290: A Stellar Jewel Box

    07/10/2014 8:29:52 PM PDT · by SunkenCiv · 2 replies
    NASA ^ | June 08, 2014 | (see photo credit)
    Explanation: Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color. The photogenic cluster, pictured above, was captured recently by the orbiting Hubble Space Telescope. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars. NGC 290 lies about 200,000 light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC). The open cluster contains hundreds of stars and spans about 65...
  • Astronomy Picture of the Day -- M16 and the Eagle Nebula

    07/10/2014 8:26:31 PM PDT · by SunkenCiv · 8 replies
    NASA ^ | June 07, 2014 | (see photo credit)
    Explanation: A star cluster around 2 million years young, M16 is surrounded by natal clouds of dust and glowing gas also known as The Eagle Nebula. This beautifully detailed image of the region includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the left edge of the frame is another...