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Εργαλεία Θεμάτων Τρόποι εμφάνισης
  #1771  
Παλιά 17-08-11, 08:25
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 17

Perseid Below
Credit: Ron Garan, ISS Expedition 28 Crew, NASA
Explanation: Denizens of planet Earth watched this year's Perseid meteor shower by looking up into the moonlit night sky. But this remarkable view captured by astronaut Ron Garan looks down on a Perseid meteor. 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 curving limb of the Earth and a layer of greenish airglow. Out of the frame, the Sun is on the horizon beyond one of the station's solar panel arrays at the upper right. Seen above the meteor near the horizon is bright star Arcturus and a star field that includes the constellations Bootes and Corona Borealis. The image was recorded on August 13 while the space station orbited above an area of China approximately 400 kilometers to the northwest of Beijing.

Poll: Is APOD a blog?
Tomorrow's picture: strange red pillar

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  #1772  
Παλιά 18-08-11, 08:16
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 18

A Sun Pillar Over Ontario
Image Credit & Copyright: Rick Stankiewicz (Peterborough Astronomical Association)
Explanation: What is that on the horizon? No, it's not an alien starship battling distant Earthlings, but rather a sun pillar. When driving across Ontario, Canada in early June, the photographer was surprised to encounter such an "eerie and beautiful" vista, and immediately took pictures. When atmospheric air is cold, ice sometimes forms flat six-sided crystals as it falls from high-level clouds. Air resistance then causes these crystals to lie nearly flat much of the time as they flutter to the ground. If viewed toward a rising or setting Sun, these flat crystals will reflect sunlight and create an unusual column of light -- a sun pillar as seen above. Such columns of light are not uncommon to see, and a retrospective of past APODs that have featured picturesque sun pillars can be found here.

Challenge: Find blogs running longer than APOD.
Tomorrow's picture: open space

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  #1773  
Παλιά 19-08-11, 09:24
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 19

Herschel's Cocoon
Credit: ESA, SPIRE & PACS Consortia, Doris Arzoumanian (CEA Saclay), et al.
Explanation: In this remarkable infrared skyscape of interstellar clouds adrift in the high flying constellation Cygnus, the eye is drawn to the Cocoon Nebula. Also known as IC5146, the dusty star forming region is shown in blue hues in the Herschel Space Observatory false color image, at wavelengths more than 100 times longer than visible red light. And while visible light images show the Cocoon nebula at the end of long dark nebula Barnard 168, Hershel's infrared view finds the cosmic Cocoon punctuating a trail of filamentary clouds of glowing dust. The dusty filaments have widths that suggest they are formed as shockwaves from exploding stars travel through the medium, sweeping up and compressing the interstellar dust and gas. Herschel data also indicate stars are forming along the dusty filaments. The Cocoon Nebula itself is about 15 light-years wide and 4,000 light-years away.

Tomorrow's picture: pixels in space

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  #1774  
Παλιά 20-08-11, 08:34
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 20

Stereo Vesta
Image Credit: NASA, JPL-Caltech, UCLA, MPS, DLR, IDA
Explanation: Get out your red/blue glasses and float next to 4 Vesta. A 500 kilometer diameter world, Vesta lies in the main asteroid belt between the orbits of Mars and Jupiter. This stereo anaglyph was constructed from two separate images recorded on July 24 by the just arrived Dawn spacecraft's framing camera with a resolution of about 500 meters per pixel. The 3D view features Vesta's newly discovered terrain, including long equatorial ridges and troughs and the prominent string of three craters at the upper right dubbed Snowman. Highlighted in 3D, steep sides of many of the craters show streaks of both bright and dark material. Of course, the ion-driven Dawn spacecraft is not marooned off Vesta. After a year exploring the asteroid from orbit, Dawn is scheduled to depart, beginning its journey to Ceres.

Tomorrow's picture: a really tall one

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  #1775  
Παλιά 21-08-11, 08:48
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 21

The Fairy of Eagle Nebula
Image Credit: The Hubble Heritage Team, (STScI/AURA), ESA, NASA
Explanation: The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Pictured above is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. The above image in scientifically re-assigned colors was released in 2005 as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope.

Tomorrow's picture: dark planet

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  #1776  
Παλιά 22-08-11, 08:29
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 22

TrES-2b: Dark Planet
Illustration Credit: David A. Aguilar (CfA), TrES, Kepler, NASA
Explanation: Why is this planet so dark? Planet TrES-2b reflects back less than one percent of the light it receives, making it darker than any known planet or moon, darker even than coal. Jupiter-sized TrES-2b orbits extremely close to a sun-like star 750 light years away, and was discovered producing slight eclipses in 2006 using the modest 10-cm telescopes of the Trans-Atlantic Exoplanet Survey (TrES). The alien world's strange darkness, however, was only uncovered recently by observations indicating its slight reflective glow by the Earth-orbiting Kepler satellite. An artist's drawing of planet is shown above, complete with unsubstantiated speculation on possible moons. Reasons for TrES-2b's darkness remain unknown and are an active topic of research.

Tomorrow's picture: roll cloud

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  #1777  
Παλιά 23-08-11, 09:02
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 23

Aurora Over Greenland
Image Credit: Copyright: Juan Carlos Casado (TWAN)
Explanation: This aurora arched from horizon to horizon. During the current Shelios expedition to observe and learn about the northern lights, the sky last weekend did not disappoint. After sunset and some careful photographic planning, the above image was taken from the expedition's Qaleraliq campsite in southern Greenland. Visible straight through the center of the aurora, found with a careful eye, is the Big Dipper and the surrounding constellation of the Big Bear (Ursa Major). The brightest orb on the far right is the Moon, while Jupiter can be seen even further to the right. The Shelios expedition is scheduled to last until the end of August and include live broadcasts of ongoing auroras.

Tomorrow's picture: not every cloud

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  #1778  
Παλιά 24-08-11, 09:24
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 24

A Pileus Iridescent Cloud Over Ethiopia
Image Credit & Copyright: Esther Havens (Light the World)
Explanation: Yes, but how many dark clouds have a multicolored lining? Pictured, behind this darker cloud, is a pileus iridescent cloud, a group of water droplets that have a uniformly similar size and so together diffract different colors of sunlight by different amounts. The above image was taken just after the picturesque sight was noticed by chance by a photographer in Ethiopia. A more detailed picture of the same cloud shows not only many colors, but unusual dark and wavy bands whose origins are thought related to wave disturbances in the cloud.

Tomorrow's picture: open space


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  #1779  
Παλιά 25-08-11, 08:47
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 25

Portrait of NGC 281
Image Credit & Copyright: J-P Metsävainio (Astro Anarchy)
Explanation: Look through the cosmic cloud cataloged as NGC 281 and it's almost easy to miss stars of open cluster IC 1590. But, formed within the nebula, that cluster's young, massive stars ultimately power the pervasive nebular glow. The eye-catching shapes looming in this portrait of NGC 281 are sculpted columns and dense dust globules seen in silhouette, eroded by intense, energetic winds and radiation from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. Playfully called the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation Cassiopeia. This composite image was made through narrow-band filters, but combines emission from the nebula's hydrogen, sulfur, and oxygen atoms in a visible spectrum palette. It spans over 80 light-years at the estimated distance of NGC 281.

Tomorrow's picture: very cool

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  #1780  
Παλιά 26-08-11, 09:33
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 26

A Young Supernova in the Nearby Pinwheel Galaxy
Image Credit: D. Andrew Howell (LCOGT) et al., Faulkes Telescope North, LCOGT
Explanation: A nearby star has exploded and telescopes all over the world are turning to monitor it. The supernova, dubbed PTF 11kly, was discovered by computer only two days ago as part of the Palomar Transit Factory (PTF) sky survey utilizing the wide angle 1.2-meter Samuel Oschwin Telescope in California. Its rapid recovery makes it one of the supernovas caught most soon after ignition. PTF 11kly occurred in the photogenic Pinwheel galaxy (M101), which, being only about 21 million light years away, makes it one of the closest supernovas seen in decades. Rapid follow up observations have already given a clear indication that PTF 11kly is a Type Ia supernova, a type of white dwarf detonation that usually progresses in such a standard manner than it has helped to calibrate the expansion history of the entire universe. Studying such a close and young Type Ia event, however, may yield new and unique clues. If early indications are correct, PTF 11kly should brighten to about visual magnitude 10 in the coming weeks, making it possible to monitor with even moderately sized telescopes.

Tomorrow's picture: very cool

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  #1781  
Παλιά 27-08-11, 08:08
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 27

Hurricane Irene Forms

Image Credit: GOES 13 satellite, NASA, NOAA
Explanation: How does a hurricane form? Although a complete picture is still being researched, insight into this process might be gleaned by watching the above time lapse movie of the formation of Hurricane Irene, a large storm system currently threatening the eastern seaboard of the USA. Starting as a slight pressure difference visible as nondescript clouds on the lower right, Hurricane Irene is shown growing into large spiraling storm system of low pressure off the coast of South Carolina. A hurricane is powered by evaporating ocean water, and so typically gains strength over warm water and loses strength over land. Besides Earth, other planets that have hurricane-like storm systems include Venus, Saturn, Jupiter, Uranus, and Neptune. Much remains unknown about hurricanes and cyclones, including the exact path they will take.

Tomorrow's picture: big blowtorch

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Σχόλιο : Ότι και να πούμε είναι λίγο, εντυπωσιακό !
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  #1782  
Παλιά 28-08-11, 09:35
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 28

A Jet from Galaxy M87
Image Credit: J. A. Biretta et al., Hubble Heritage Team (STScI /AURA), NASA
Explanation: What's causing a huge jet to emanate from the center of galaxy M87? Although the unusual jet was first noticed early in the twentieth century, the exact cause is still debated. The above picture taken by the Hubble Space Telescope in 1998 shows clear details, however. The most popular hypothesis holds that the jet is created by energetic gas swirling around a massive black hole at the galaxy's center. The result is a 5000 light-year long blowtorch where electrons are ejected outward at near light-speed, emitting eerily blue light during a magnetic spiral. M87 is a giant elliptical galaxy residing only 50 million light-years away in the Virgo Cluster of Galaxies. The faint dots of light surrounding M87's center are large ancient globular clusters of stars.

Tomorrow's picture: galaxies plus


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  #1783  
Παλιά 29-08-11, 09:51
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 29

Hickson 44 in Leo
Image Credit & Copyright: Stephen Leshin
Explanation: Scanning the skies for galaxies, Canadian astronomer Paul Hickson and colleagues identified some 100 compact groups of galaxies, now appropriately called Hickson Compact Groups. The four prominent galaxies seen in this intriguing telescopic skyscape are one such group, Hickson 44, about 100 million light-years distant toward the constellation Leo. The two spiral galaxies in the center of the image are edge-on NGC 3190 with its distinctive, warped dust lanes, and S-shaped NGC 3187. Along with the bright elliptical, NGC 3193 at the right, they are also known as Arp 316. The spiral in the upper left corner is NGC 3185, the 4th member of the Hickson group. Like other galaxies in Hickson groups, these show signs of distortion and enhanced star formation, evidence of a gravitational tug of war that will eventually result in galaxy mergers on a cosmic timescale. The merger process is now understood to be a normal part of the evolution of galaxies, including our own Milky Way. For scale, NGC 3190 is about 75,000 light-years across at the estimated distance of Hickson 44.

Tomorrow's picture: very cool

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  #1784  
Παλιά 30-08-11, 08:25
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 30

The Coldest Brown Dwarf
Credit: NASA, JPL-Caltech, WISE
Explanation: This cosmic snapshot composed with image data from NASA's Wide-field Infrared Survey Explorer (WISE) satellite captures a multitude of faint stars and distant galaxies toward the constellation Lyra at wavelengths longer than visible light. But the object circled at the center is not quite a star. Cataloged as WISE 1828+2650, it lies within 40 light-years of the Sun and is currently the coldest brown dwarf known. A brown dwarf begins like a star, with the gravitational collapse of a dense cloud of gas and dust, but is not massive enough to achieve the core temperatures and densities that trigger hydrogen fusion, the stable source of a star's energy. Instead the failed star ultimately cools and emits most of its light at infrared wavelengths. Remarkably, brown dwarfs are roughly the size of the planet Jupiter. How cold is WISE 1828+2650? While brown dwarfs have measured surface temperatures of up to 1,400 degrees C (2,600 degress F), this brown dwarf , assigned to spectral class Y, has the estimated temperature of a warm room, less than about 27 degrees C (80 degrees F).

Tomorrow's picture: long cloud

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  #1785  
Παλιά 31-08-11, 07:59
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Τελευταία φορά Online: 12-11-16 11:12
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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2011 August 31

Roll Cloud Over Wisconsin
Image Credit: Pierre cb, Wikipedia
Explanation: What kind of cloud is this? A type of arcus cloud called a roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud. When this happens uniformly along an extended front, a roll cloud may form. Roll clouds may actually have air circulating along the long horizontal axis of the cloud. A roll cloud is not thought to be able to morph into a tornado. Unlike a similar shelf cloud, a roll cloud is completely detached from their parent cumulonimbus cloud. Pictured above, a roll cloud extends far into the distance as a storm approached in 2007 in Racine, Wisconsin, USA.

Tomorrow's picture: open space


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