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Εργαλεία Θεμάτων Τρόποι εμφάνισης
  #3121  
Παλιά 05-05-15, 07:50
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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.
2015 May 5

Gravitational Anomalies of Mercury
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 central area is Caloris Basin, a huge impact feature measuring about 1,500 kilometers across. Last week, after completing its mission and running low on fuel, MESSENGER was purposely crashed onto Mercury's surface.
Tomorrow's picture: summer triangles

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  #3122  
Παλιά 06-05-15, 08:59
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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.
2015 May 6

Summer Triangles over Japan
Image Credit & Copyright: Shingo Takei (TWAN)
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 only evident from the direction of Earth -- in actuality the stars are thousands of light years apart in space.
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Tomorrow's picture: open space

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  #3123  
Παλιά 07-05-15, 08:27
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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.
2015 May 7

At the Limit of Diffraction
Image Credit & Copyright: Yuri Beletsky (Las Campanas Observatory, Carnegie Institution)
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 double star system Alpha Centauri. Testing the system at the eyepiece of the 6.5 meter diameter Magellan Clay Telescope at Las Campanas Observatory, astronomer Laird Close is enjoying a historic diffraction limited view (inset) and the wide apparent separation of the close binary star system ... without traveling to low earth orbit.
Tomorrow's picture: pixels in space

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  #3124  
Παλιά 08-05-15, 08:43
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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.
2015 May 8

When Vega is North
Image Credit & Copyright: Miguel Claro | Dark Sky Alqueva
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 your camera is ready now and you don't want to wait 12,000 years for Vega to be the North Star, consider this ingenious demonstration of contemporary star trails (left) versus star trails reminiscent of the year 14000 CE. Both were recorded this April at the Alqueva Dark Sky Reserve in Alentejo, Portugal. To produce the more Vega-centric star trails of the distant future, astronomer Miguel Claro combined the rotation of two startracking camera mounts to create the apparent shift in planet Earth's North Celestial Pole.
Tomorrow's picture: light-weekend

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  #3125  
Παλιά 09-05-15, 08:24
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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.
2015 May 9

Trio Leo
Image Credit & Copyright: Philippe Durville
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 off their spiral structure. Gravitational interactions between galaxies in the group have also left telltale signs, including the warped and inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous view of the region spans about one degree (two full moons) on the sky. The field covers over 500 thousand light-years at the trio's estimated distance of 30 million light-years.
Tomorrow's picture: the sands of time

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  #3126  
Παλιά 10-05-15, 08:33
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Astronomy Picture of the Day

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2015 May 10

MyCn18: An Hourglass Planetary Nebula
Image Credit: R. Sahai and J. Trauger (JPL), WFPC2, HST, NASA
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 the nebula ejection process that are helping to resolve the outstanding mysteries of the complex shapes and symmetries of planetary nebulas.
Tomorrow's picture: volcano universe

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  #3127  
Παλιά 11-05-15, 08:35
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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.
2015 May 11

The Sky from Mauna Kea
Image Credit & Copyright: Shane Black Photography; Rollover Annotation: Judy Schmidt
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 left, while orange lava in the volcanic caldera of Kilauea lights up the clouds just left of center. The summit of an even more distant Hawaiian volcano, Mauna Loa, is visible in dark silhouette near the central horizon. Green airglow is visible above the clouds, caused by air molecules excited by the Sun during the day. The Moon is the bright orb on the right. A diffuse band of light-colored zodiacal light extends up from the far right. Most distant, the dramatic central band of our Milky Way Galaxy appears to rise vertically from Mauna Loa. The person who witnessed and captured this breathtaking panorama stands before you in the image center.
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Tomorrow's picture: unusual mars

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  #3128  
Παλιά 12-05-15, 07:41
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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.
2015 May 12

Two Worlds, One Sun
Left Image Credit & Copyright: Damia Bouic;
Right Image Credit: NASA, JPL-Caltech, MSSS; Digital processing: Damia Bouic
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 the blue hues from Mars is not fully understood, but thought to be related to forward scattering properties of Martian dust. The terrestrial sunset was taken in 2012 March from Marseille, France, while the Martian sunset was captured last month by NASA's robotic Curiosity rover from Gale crater on Mars.
Tomorrow's picture: magnificent horse

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  #3129  
Παλιά 13-05-15, 08:22
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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.
2015 May 13

The Magnificent Horsehead Nebula
Image Credit & Copyright: Data: Giuseppe Carmine Iaffaldano; Processing: Roberto Colombari
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.
Tomorrow's picture: open space

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  #3130  
Παλιά 14-05-15, 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.
2015 May 14

Dwarf Planet, Bright Spot
Image Credit: NASA, JPL-Caltech, UCLA, MPS/DLR/IDA
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 revealed to be made up of smaller spots of reflective material that could be exposed ice glinting in the sunlight. On Saturday, Dawn's ion propulsion system was turned on to spiral the spacecraft into a closer 4,350-kilometer orbit by June 6. Of course another unexplored dwarf planet, Pluto, is expecting the arrival of a visitor from Earth, the New Horizons spacecraft, by mid-July.
Tomorrow's picture: land of giants

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  #3131  
Παλιά 15-05-15, 08:29
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Astronomy Picture of the Day

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2015 May 15

Jupiter, Ganymede, Great Red Spot
Image Credit & Copyright: Damian Peach/SEN
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 giant, is about 143,000 kilometers in diameter at its equator. That's nearly 10 percent the diameter of the Sun.
Tomorrow's picture: blue Mars

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  #3132  
Παλιά 16-05-15, 07:14
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Astronomy Picture of the Day

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2015 May 16

Ares 3 Landing Site: The Martian Revisited
Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA
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 scale Watney's 6-meter-diameter habitat at the site would be about 1/10th the diameter of the large crater. Of course, the Ares 3 landing coordinates are only about 800 kilometers north of the (real life) Carl Sagan Memorial Station, the 1997 Pathfinder landing site.
Tomorrow's picture: white dwarf revisited

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  #3133  
Παλιά 17-05-15, 08:59
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Astronomy Picture of the Day

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2015 May 17

NGC 2440: Pearl of a New White Dwarf
Image Credit: H. Bond (STScI), R. Ciardullo (PSU), WFPC2, HST, NASA; Processing: Forrest Hamilton
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 billion years. The above false color image was captured by the Hubble Space Telescope in 1995. NGC 2440 lies about 4,000 light years distant toward the southern constellation Puppis.
Tomorrow's picture: aurora and ice

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  #3134  
Παλιά 18-05-15, 07:47
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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.
2015 May 18

Auroras and Star Trails over Iceland
Image Credit & Copyright: Vincent Brady
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 were artificially faded.
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Tomorrow's picture: cluster of stars

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  #3135  
Παλιά 20-05-15, 09:39
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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.
2015 May 20

A Cliff Looming on Comet 67P
Image Credit & Licence: ESA, Rosetta, NAVCAM
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 surface location last November. If newly exposed to sunlight, Philae might regain enough energy to again signal Rosetta.
Click Through the Universe: Random APOD Generator
Tomorrow's picture: open space

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