Sunday, November 1, 2015

The Large Cloud of Magellan

The Large Cloud of Magellan: APOD: 2015 August 27 - The Large Cloud of Magellan



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2015 August 27


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The Large Cloud of Magellan
Image Credit & Copyright: Carlos Fairbairn
Explanation: The 16th century Portuguese navigator Ferdinand Magellan and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two fuzzy cloud-like objects easily visible to southern hemisphere skygazers are known as the Clouds of Magellan, now understood to be satellite galaxies of our much larger, spiral Milky Way galaxy. About 160,000 light-years distant in the constellation Dorado, the Large Magellanic Cloud (LMC) is seen here in a remarkably deep, colorful, image. Spanning about 15,000 light-years or so, it is the most massive of the Milky Way's satellite galaxies and is the home of the closest supernova in modern times, SN 1987A. The prominent patch below center is 30 Doradus, also known as the magnificent Tarantula Nebula, is a giant star-forming region about 1,000 light-years across.

Tomorrow's picture: Puppis A

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Puppis A Supernova Remnant

Puppis A Supernova Remnant: APOD: 2015 August 28 - Puppis A Supernova Remnant



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2015 August 28


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Puppis A Supernova Remnant
Image Credit & Copyright: Don Goldman
Explanation: Driven by the explosion of a massive star, supernova remnant Puppis A is blasting into the surrounding interstellar medium about 7,000 light-years away. At that distance, this colorful telescopic field based on broadband and narrowband optical image data is about 60 light-years across. As the supernova remnant expands into its clumpy, non-uniform surroundings, shocked filaments of oxygen atoms glow in green-blue hues. Hydrogen and nitrogen are in red. Light from the initial supernova itself, triggered by the collapse of the massive star's core, would have reached Earth about 3,700 years ago. The Puppis A remnant is actually seen through outlying emission from the closer but more ancient Vela supernova remnant, near the crowded plane of our Milky Way galaxy. Still glowing across the electromagnetic spectrum Puppis A remains one of the brightest sources in the X-ray sky.

Tomorrow's picture: seagull nebula

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The Seagull Nebula

The Seagull Nebula: APOD: 2015 August 29 - The Seagull Nebula



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2015 August 29


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The Seagull Nebula
Image Credit & Copyright: Dieter Willasch (Astro-Cabinet)
Explanation: A broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker - The Seagull Nebula. This portrait of the cosmic bird covers a 1.6 degree wide swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major. Of course, the region includes objects with other catalog designations: notably NGC 2327, a compact, dusty emission region with an embedded massive star that forms the bird's head (aka the Parrot Nebula, above center). Dominated by the reddish glow of atomic hydrogen, the complex of gas and dust clouds with bright young stars spans over 100 light-years at an estimated 3,800 light-year distance.

Tomorrow's picture: ancient stars

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M31: The Andromeda Galaxy

M31: The Andromeda Galaxy:

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2015 August 30


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Explanation: What is the nearest major galaxy to our own Milky Way Galaxy? Andromeda. In fact, 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 million years for light to reach us from there. Although visible without aid, the above image of M31 is a digital mosaic of 20 frames taken with a small telescope. Much about M31 remains unknown, including exactly how long it will before it collides with our home galaxy.

Pluto in Enhanced Color

Pluto in Enhanced Color: APOD: 2015 August 31 - Pluto in Enhanced Color



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2015 August 31


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Pluto in Enhanced Color
Image Credit: NASA, Johns Hopkins Univ./APL, Southwest Research Inst.
Explanation: Pluto is more colorful than we can see. Color data and images of our Solar System's most famous dwarf planet, taken by the robotic New Horizons spacecraft during its flyby in July, have been digitally combined to give an enhanced view of this ancient world sporting an unexpectedly young surface. The featured enhanced color image is not only esthetically pretty but scientifically useful, making surface regions of differing chemical composition visually distinct. For example, the light-colored heart-shaped Tombaugh Regio on the lower right is clearly shown here to be divisible into two regions that are geologically different, with the leftmost lobe Sputnik Planum also appearing unusually smooth. New Horizons now continues on beyond Pluto, will continue to beam back more images and data, and will soon be directed to change course so that it can fly past asteroid 2014 MU69 in 2019 January.

Pluto Images with Brief Explanations: APOD Pluto Search
Tomorrow's picture: through the earth

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Distant Neutrinos Detected Below Antarctic Ice

Distant Neutrinos Detected Below Antarctic Ice:

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2015 September 1


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Explanation: From where do these neutrinos come? The IceCube Neutrino Observatory near the South Pole of the Earth has begun to detect nearly invisible particles of very high energy. Although these rarely-interacting neutrinos pass through much of the Earth just before being detected, where they started remains a mystery. Pictured here is IceCube's Antarctic lab accompanied by a cartoon depicting long strands of detectors frozen into the crystal clear ice below. Candidate origins for these cosmic neutrinos include the violent surroundings of supermassive black holes at the centers of distant galaxies, and tremendous stellar explosions culminating in supernovas and gamma ray bursts far across the universe. As IceCube detects increasingly more high energy neutrinos, correlations with known objects may resolve this cosmic conundrum -- or we may never know.

The Flare and the Galaxy

The Flare and the Galaxy:

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2015 September 2
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Explanation: Is this person throwing a lightning bolt? No. Despite appearances, this person is actually pointing in the direction of a bright Iridium flare, a momentary reflection of sunlight off of a communications satellite in orbit around the Earth. As the Iridium satellite orbits, reflective antennas became aligned between the observer and the Sun to create a flash brighter than any star in the night sky. Iridium flares typically last several seconds, longer than most meteors. Also unlike meteors, the flares are symmetric and predictable. The featured flare involved Iridium satellite 15 and occurred over southern Estonia last week. In this well-planned image, a spectacular night sky appears in the background, complete with the central band of our Milky Way Galaxy running vertically up the image center.

Arp 159 and NGC 4725

Arp 159 and NGC 4725: APOD: 2015 September 3 - Arp 159 and NGC 4725



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2015 September 3


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Arp 159 and NGC 4725
Image Credit & Copyright: Stephen Leshin
Explanation: Pointy stars and peculiar galaxies span this cosmic snapshot, a telescopic view toward the well-groomed constellation Coma Berenices. Bright enough to show off diffraction spikes, the stars are in the foreground of the scene, well within our own Milky Way. But the two prominent galaxies lie far beyond our own, some 41 million light-years distant. Also known as NGC 4747, the smaller distorted galaxy at left is the 159th entry in the Arp Atlas of Peculiar Galaxies, with extensive tidal tails indicative of strong gravitational interactions in its past. At about a 100,000 light-years across, its likely companion on the right is the much larger NGC 4725. At first glance NGC 4725 appears to be a normal spiral galaxy, its central region dominated by the yellowish light of cool, older stars giving way to younger hot blue star clusters along dusty spiral outskirts. Still, NGC 4725 does look a little odd with only one main spiral arm.

Tomorrow's picture: in southern skies

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Milky Way with Airglow Australis

Milky Way with Airglow Australis: APOD: 2015 September 4 - Milky Way with Airglow Australis



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2015 September 4


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Milky Way with Airglow Australis
Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory)
Explanation: After sunset on September 1, an exceptionally intense, reddish airglow flooded this Chilean winter night skyscape. Above a sea of clouds and flanking the celestial Milky Way, the airglow seems to ripple and flow across the northern horizon in atmospheric waves. Originating at an altitude similar to aurorae, the luminous airglow is instead due to chemiluminescence, the production of light through chemical excitation. Commonly captured with a greenish tinge by sensitive digital cameras, this reddish airglow emission is from OH molecules and oxygen atoms at extremely low densities and has often been present in southern hemisphere nights during the last few years. On this night it was visible to the eye, but seen without color. Antares and the central Milky Way lie near the top, with bright star Arcturus at left. Straddling the Milky Way close to the horizon are Vega, Deneb, and Altair, known in northern nights as the stars of the Summer Triangle.

Tomorrow's picture: Atlas V with plume noctilucent

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Atlas V Rising

Atlas V Rising:

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2015 September 5


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Explanation: Early morning risers along Florida's Space Coast, planet Earth, were treated to a launch spectacle on September 2nd. Before dawn an Atlas V rocket rose into still dark skies carrying a US Navy communications satellite from Cape Canaveral Air Force Station into Earth orbit. This minutes long exposure follows the rocket's arc climbing eastward over the Atlantic. As the rocket rises above Earth's shadow, its fiery trail becomes an eerie, noctilucent exhaust plume glinting in sunlight. Of course, the short, bright startrail just above the cloud bank is Venus rising, now appearing in planet Earth's skies as the brilliant morning star.

Earthrise

Earthrise: APOD: 2015 September 6 - Earthrise



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2015 September 6


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Earthrise
Image Credit: Apollo 8, NASA
Explanation: What's that rising over the edge of the Moon? Earth. About 47 years ago, in December of 1968, the Apollo 8 crew flew from the Earth to the Moon and back again. Frank Borman, James Lovell, and William Anders were launched atop a Saturn V rocket on December 21, circled the Moon ten times in their command module, and returned to Earth on December 27. The Apollo 8 mission's impressive list of firsts includes: the first humans to journey to the Earth's Moon, the first to fly using the Saturn V rocket, and the first to photograph the Earth from deep space. As the Apollo 8 command module rounded the farside of the Moon, the crew could look toward the lunar horizon and see the Earth appear to rise, due to their spacecraft's orbital motion. Their famous picture of a distant blue Earth above the Moon's limb was a marvelous gift to the world.

Tomorrow's picture: large predator

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Distorted Green Flash Sunset over Italy

Distorted Green Flash Sunset over Italy: APOD: 2015 September 8 - Distorted Green Flash Sunset over Italy



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2015 September 8


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Distorted Green Flash Sunset over Italy
Image Credit & Copyright: Paolo Lazzarotti
Explanation: This was one strange sunset. For one thing, the typically round Sun appeared distorted, geometrically, and multiply layered. For another, some of these layers appeared unusually green. The Sun, of course, was just fine -- its odd appearance was caused entirely by its light refracting in the Earth's atmosphere. When layers of the Earth's atmosphere are unusually warm, layers of the Sun may appear distorted or even seen multiple times. The effect is most strong nearest sunrise and sunset when terrestrial inversion layers occupy distinct altitudes above the horizon. Different colors of the Sun may also become deflected by significantly different amounts, so that the uppermost superior image may appear momentarily green -- a phenomenon known as a green flash. The featured image was taken in February from Porto Venere, Italy, with San Pietro church situated in the foreground.

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Tomorrow's picture: galaxy wreckage

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NGC 4372 and the Dark Doodad

NGC 4372 and the Dark Doodad:

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2015 September 10


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Explanation: The delightful Dark Doodad Nebula drifts through southern skies, a tantalizing target for binoculars in the constellation Musca, The Fly. The dusty cosmic cloud is seen against rich starfields just south of the prominent Coalsack Nebula and the Southern Cross. Stretching for about 3 degrees across this scene the Dark Doodad is punctuated at its southern tip (lower left) by globular star cluster NGC 4372. Of course NGC 4372 roams the halo of our Milky Way Galaxy, a background object some 20,000 light-years away and only by chance along our line-of-sight to the Dark Doodad. The Dark Doodad's well defined silhouette belongs to the Musca molecular cloud, but its better known alliterative moniker was first coined by astro-imager and writer Dennis di Cicco in 1986 while observing Comet Halley from the Australian outback. The Dark Doodad is around 700 light-years distant and over 30 light-years long.

A Giant Squid in the Flying Bat

A Giant Squid in the Flying Bat: APOD: 2015 September 11 - A Giant Squid in the Flying Bat



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2015 September 11


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A Giant Squid in the Flying Bat
Image Credit & Copyright: Steve Cannistra (StarryWonders)
Explanation: Very faint but also very large on planet Earth's sky, a giant Squid Nebula cataloged as Ou4, and Sh2-129 also known as the Flying Bat Nebula, are both caught in this scene toward the royal constellation Cepheus. Composed with a total of 20 hours of broadband and narrowband data, the telescopic field of view is almost 4 degrees or 8 Full Moons across. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula's alluring bipolar shape is distinguished here by the telltale blue-green emission from doubly ionized oxygen atoms. Though apparently completely surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, a recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, Ou4 would represent a spectacular outflow driven by HR8119, a triple system of hot, massive stars seen near the center of the nebula. If so, the truly giant Squid Nebula would physically be nearly 50 light-years across.

Tomorrow's picture: two for one

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A Partial Solar Eclipse over Texas

A Partial Solar Eclipse over Texas:

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2015 September 13


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Explanation: It was a typical Texas sunset except that most of the Sun was missing. The location of the missing piece of the Sun was not a mystery -- it was behind the Moon. Featured here is one of the more interesting images taken of a partial solar eclipse that occurred in 2012, capturing a temporarily crescent Sun setting in a reddened sky behind brush and a windmill. The image was taken about 20 miles west of Sundown, Texas, USA, just after the ring of fire effect was broken by the Moon moving away from the center of the Sun. Today a new partial solar eclipse of the Sun will be visible from Earth. Unfortunately for people who live in Texas, today's eclipse can only be seen from southern Africa and Antarctica.

A Spiral Aurora over Iceland

A Spiral Aurora over Iceland:

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2015 September 15
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Explanation: What's happened to the sky? Aurora! Captured late last month, this aurora was noted by Icelanders for its great brightness and quick development. The aurora resulted from a solar storm, with high energy particles bursting out from the Sun and through a crack in Earth's protective magnetosphere a few days later. Although a spiral pattern can be discerned, creative humans might imagine the complex glow as an atmospheric apparition of any number of common icons. In the foreground of the featured image is the Ölfusá River, while the lights illuminate a bridge in Selfoss City. Just beyond the low clouds is a nearly full Moon. The liveliness of the Sun -- and the resulting auroras on Earth -- is slowly diminishing as the Sun emerges from a Solar maximum of surface activity and evolves towards a historically more quite period in its 11-year cycle. In fact, solar astronomers are waiting to see if the coming Solar minimum will be as unusually quiet as the last one, where sometimes months would go by with no discernible sunspots or other active solar phenomena.

Pickering's Triangle in the Veil

Pickering's Triangle in the Veil: APOD: 2015 September 17 - Pickering's Triangle in the Veil



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2015 September 17


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Pickering's Triangle in the Veil
Image Credit & Copyright: J-P Metsävainio (Astro Anarchy)
Explanation: Chaotic in appearance, these filaments of shocked, glowing gas break across planet Earth's sky toward the constellation of Cygnus, as part of the Veil Nebula. The Veil Nebula itself is a large supernova remnant, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Blasted out in the cataclysmic event, the interstellar shock waves plow through space sweeping up and exciting interstellar material. The glowing filaments are really more like long ripples in a sheet seen almost edge on, remarkably well separated into the glow of ionized hydrogen and sulfur atoms shown in red and green, and oxygen in blue hues. Also known as the Cygnus Loop, the Veil Nebula now spans nearly 3 degrees or about 6 times the diameter of the full Moon. While that translates to over 70 light-years at its estimated distance of 1,500 light-years, this field of view spans less than one third that distance. Identified as Pickering's Triangle for a director of Harvard College Observatory and cataloged as NGC 6979, the complex of filaments might be more appropriately known as Williamina Fleming's Triangular Wisp.

Tomorrow's picture: where Cthulhu sleeps

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A Plutonian Landscape

A Plutonian Landscape: APOD: 2015 September 18 - A Plutonian Landscape



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2015 September 18


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A Plutonian Landscape
Image Credit: NASA, Johns Hopkins Univ./APL, Southwest Research Institute
Explanation: This shadowy landscape of majestic mountains and icy plains stretches toward the horizon of a small, distant world. It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft's closest approach on July 14. The dramatic, low-angle, near-twilight scene follows rugged mountains still popularly known as Norgay Montes from foreground left, and Hillary Montes along the horizon, giving way to smooth Sputnik Planum at right. Layers of Pluto's tenuous atmosphere are also revealed in the backlit view. With a strangely familiar appearance, the frigid terrain likely includes ices of nitrogen and carbon monoxide with water-ice mountains rising up to 3,500 meters (11,000 feet). That's comparable in height to the majestic mountains of planet Earth. This Plutonian landscape is 380 kilometers (230 miles) across.

Tomorrow's picture: solarsaurus

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A Prominence on the Sun

A Prominence on the Sun:

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2015 September 19


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Explanation: This eerie landscape of incandescent plasma suspended in looping and twisted magnetic fields stretched toward the Sun's eastern horizon on September 16. Captured through a backyard telescope and narrowband filter in light from ionized hydrogen, the scene finds bright plages near dark sunspots and a gigantic prominence lofted above the solar limb. Some 600,000 kilometers across, the magnetized plasma wall would dwarf worlds of the Solar System. Ruling gas giant Jupiter can only boast a diameter of 143,000 kilometers or so, while planet Earth's diameter is less than 13,000 kilometers. Known as a hedgerow prominence for its appearance, the enormous structure is far from stable though, and such large solar prominences often erupt.

Global Ocean Suspected on Saturns Enceladus

Global Ocean Suspected on Saturns Enceladus:

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2015 September 20



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Explanation: Do some surface features on Enceladus roll like a conveyor belt? A leading interpretation of images taken of Saturn's most explosive moon indicate that they do. This form of asymmetric tectonic activity, very unusual on Earth, likely holds clues to the internal structure of Enceladus, which may contain subsurface seas where life might be able to develop. Pictured above is a composite of 28 images taken by the robotic Cassini spacecraft in 2008 just after swooping by the ice-spewing orb. Inspection of these images show clear tectonic displacements where large portions of the surface all appear to move all in one direction. On the image right appears one of the most prominent tectonic divides: Labtayt Sulci, a canyon about one kilometer deep. The magnitude of Enceladus' wobble as it orbits Saturn might indicate damping by a globally extending underground ocean layer.