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Εργαλεία Θεμάτων Τρόποι εμφάνισης
  #376  
Παλιά 01-01-08, 11:30
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Τελευταία φορά Online: 12-11-16 11:12
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Σ' αυτό το πιάνο ποιος θα παίξει ;

Rays from an Unexpected Aurora
Credit & Copyright: Lyndon Anderson (Prairie Journal)

Explanation: This aurora was a bit of a surprise. For starters, on this day in 2002, no intense auroral activity was expected at all. Possibly more surprising, however, the aurora appeared to show an usual structure of green rays from some locations. In this view, captured from North Dakota, USA, a picket fence of green rays stretches toward the horizon. Mirroring the green rays is a red band, somewhat rare in its own right. Lights from the cities of Bismarck and Mandan are visible near the horizon.

Note: A German language mirror of APOD is now available.
Tomorrow's picture: pixels in space

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  #377  
Παλιά 02-01-08, 11:08
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A Galaxy is not a Comet
Credit & Copyright: Emiel Kempen

Explanation: This gorgeous galaxy and comet portrait was recorded on December 30th, in the skies over Hoogeveen, The Netherlands. The combined series of 60 x 60 second exposures finds the lovely green coma of Comet 8P/Tuttle near its predicted conjunction with the Triangulum Galaxy. Aligning each exposure with the stars shows the comet as a streak, slowly moving against the background stars and galaxy. An alternative composition with exposures centered on the comet, shows the background stars and galaxy as streaks. The alluring celestial scene would also have been a rewarding one for the influential 18th century comet hunter Charles Messier. While Messier scanned French skies for comets, he carefully cataloged positions of things which were fuzzy and comet-like in appearance but did not move against the background stars and so were definitely not comets. The Triangulum Galaxy, also known as M33, is the 33rd object in his famous not-a-comet catalog. The modern understanding holds that the Triangulum Galaxy is a large spiral galaxy some 3 million light-years distant. Comet 8P/Tuttle, just bright enough to be visible to the unaided eye in dark, northern skies, is about 40 million kilometers (2 light-minutes) away.

The Amateur Astronomers Association of New York Presents:
APOD Editor's Lecture: January 4th - American Museum of Natural History
Tomorrow's picture: 2007 Geminids

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  #378  
Παλιά 04-01-08, 09:45
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The Milky Way at 5000 Meters
Credit & Copyright: Serge Brunier

Explanation: Climb up to 5000 meters (16,500 feet) above sea level, near Cerro Chajnantor in the northern Chilean Andes, and your night sky could encompass this cosmic vista. Recorded from that high and dry locale, the spectacular fish-eye image features the myriad stars and sprawling dust clouds of our Milky Way Galaxy. The direction toward the center of the Galaxy is near the zenith and center of the picture, but the Galactic Center itself is hidden from view, located far behind the obscuring dust. Brilliant Jupiter rules this scene just above the Milky Way's central bulge with the noticeably fainter, yellowish, giant star Antares to its right. Small and faint, near the right edge of the picture is one of the Milky Way's many satellite galaxies, the Small Magellanic Cloud.

The Amateur Astronomers Association of New York Presents:
APOD Editor's Lecture: Tonight - American Museum of Natural History
Tomorrow's picture: light-weekend

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  #379  
Παλιά 06-01-08, 09:48
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upiter's Rings Revealed
Credit: (NOAO), J. Burns (Cornell) et al., Galileo Project, JPL, NASA

Explanation: Why does Jupiter have rings? Jupiter's rings were discovered in 1979 by the passing Voyager 1 spacecraft, but their origin was a mystery. Data from the Galileo spacecraft that orbited Jupiter from 1995 to 2003 later confirmed that these rings were created by meteoroid impacts on small nearby moons. As a small meteoroid strikes tiny Adrastea, for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit. Pictured above is an eclipse of the Sun by Jupiter, as viewed from Galileo. Small dust particles high in Jupiter's atmosphere, as well as the dust particles that compose the rings, can be seen by reflected sunlight.

Note: Meet astronomy bloggers and APOD editor RN in Austin this Tuesday night.
Tomorrow's picture: majestic spiral

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  #380  
Παλιά 07-01-08, 11:19
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Quadrantid Meteors and Aurora from the Air
Credit: Jeremie Vaubaillon et al., Caltech, NASA

Explanation: Where do meteor showers originate? To help answer this question, astronomers studied in some detail the Quadrantid meteor shower that occurred over this past weekend. In particular, astronomers with specialized cameras flew as part of the Quadrantid's Multi-Instrument Aircraft Campaign (MAC) aboard a NASA DC-8 aircraft above northern Canada over the past few days and studied the Quadrantid meteor shower in unprecedented detail. Pictured above is a composite image combining many short exposures. Visible in the image are the tail of the airplane reflecting a red beacon on the left, green aurora most prominent on the image right, and numerous meteor streaks throughout. Preliminary indications are that the meteor stream is quite stable in time but variable in meteor abundance. Over 100 meteors per hour were visible at the peak from the MAC aircraft. Meteor data from around the world will continue to be analyzed to try to verify Peter Jenniskens's recent hypothesis that minor planet 2003 EH1 is an intermittently active comet and the parent body of the annual Quadrantid meteor shower.

Note: Meet astronomy bloggers and APOD editor RN in Austin this Tuesday night.
Tomorrow's picture: jupiter io

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  #381  
Παλιά 08-01-08, 10:23
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Κάντε κλικ για μεγάλη ανάλυση φωτογραφίας

A Jupiter-Io Montage from New Horizons
Credit: NASA, Johns Hopkins U. APL, SWRI

Explanation: As the New Horizons spacecraft sweeps through the Solar System, it is taking breathtaking images of the planets. In February of last year, New Horizons passed Jupiter and the ever-active Jovian moon Io. In this montage, Jupiter was captured in three bands of infrared light making the Great Red Spot look white. Complex hurricane-like ovals, swirls, and planet-ringing bands are visible in Jupiter's complex atmosphere. Io is digitally superposed in natural color. Fortuitously, a plume was emanating from Io's volcano Tvashtar. Frost and sulfuric lava cover the volcanic moon, while red-glowing lava is visible beneath the blue sunlight-scattering plume. The robotic New Horizons spacecraft is on track to arrive at Pluto in 2015.

Note: Meet sky enthusiasts, astro bloggers, and APOD editor RN in Austin tonight.
Tomorrow's picture: majestic spiral

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  #382  
Παλιά 09-01-08, 09:37
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Hidden Galaxy IC 342 from Kitt Peak
Credit & Copyright: T. Rector (U. Alaska Anchorage), H. Schweiker, WIYN, NOAO, AURA, NSF

Explanation: Beautiful nearby spiral galaxy IC 342 could be more famous if it wasn't so hidden. A sprawling island universe, IC 342 would be a prominent galaxy in our night sky, but it is almost hidden from view behind the veil of stars, gas and dust clouds in the plane of our Milky Way galaxy. Similar in size to other large, bright spiral galaxies IC 342 is a mere 7 million light-years distant in the long-necked, northern constellation of the Giraffe (Camelopardalis). Even though IC 342's light is dimmed by intervening cosmic clouds, this remarkably sharp telescopic image traces the galaxy's own obscuring dust, blue star clusters, and glowing pink star forming regions along spiral arms that wind far from the galaxy's core. IC 342 may have undergone a recent burst of star formation activity and is close enough to have gravitationally influenced the evolution of the local group of galaxies and the Milky Way.

Note: Astronomy lectures by an APOD editor are now available as a free podcast.
Tomorrow's picture: pixels in space

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  #383  
Παλιά 10-01-08, 09:22
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Active Galaxy Centaurus A
Credit: X-ray - NASA, CXC, R.Kraft (CfA), et al.;
Radio - NSF, VLA, M.Hardcastle (U Hertfordshire) et al.; Optical - ESO, M.Rejkuba (ESO-Garching) et al.

Explanation: A mere 11 million light-years away, Centaurus A is a giant elliptical galaxy - the closest active galaxy to Earth. This remarkable composite view of the galaxy combines image data from the x-ray ( Chandra), optical(ESO), and radio(VLA) regimes. Centaurus A's central region is a jumble of gas, dust, and stars in optical light, but both radio and x-ray telescopes trace a remarkable jet of high-energy particles streaming from the galaxy's core. The cosmic particle accelerator's power source is a black hole with about 10 million times the mass of the Sun coincident with the x-ray bright spot at the galaxy's center. Blasting out from the active galactic nucleus toward the upper left, the energetic jet extends about 13,000 light-years. A shorter jet extends from the nucleus in the opposite direction. Other x-ray bright spots in the field are binary star systems with neutron stars or stellar mass black holes. Active galaxy Centaurus A is likely the result of a merger with a spiral galaxy some 100 million years ago.

Tomorrow's picture: behind Polaris

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  #384  
Παλιά 11-01-08, 09:39
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Polaris Dust Nebula
Image Credit & Copyright: Steve Mandel (Hidden Valley Observatory)
Research Collaboration: Adolf Witt (University of Toledo) et al.

Explanation: Centered on North Star Polaris, this 4 degree wide field of view covers part of a complex of relatively unfamiliar, diffuse dust clouds soaring high above the plane of our Milky Way Galaxy. The combined light of the Milky Way stars are reflected by the dusty, galactic cirrus, the reflected starlight having the same blue tint characteristic of better known reflection nebulae. But this deep color image also records a faint reddish luminescence from the dust grains as they convert invisible stellar ultraviolet radiation to visible red light. Dubbed extended red emission, the dim cosmic glow is thought to be caused by complex organic molecules known as PAHs (polycyclic aromatic hydrocarbons), common constituents interstellar dust. On planet Earth, PAHs are widely encountered as the sooty products of combustion.

Tomorrow's picture: light-weekend

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  #385  
Παλιά 12-01-08, 10:09
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Mercury Chases the Sunset
Image Credit & Copyright: Doug Zubenel

Explanation: This colorful view of the western sky at sunset features last Wednesday's slender crescent Moon. Of course, when the Moon is in its crescent phase it can never be far from Sun in the sky. Also always close to the Sun in Earth's sky is innermost planet Mercury, seen here below and right of center against the bright orange glow along the horizon. Mercury is usually difficult to glimpse because of the overwhelming sunlight, but increasingly better views of the small planet near sunset will be possible as it wanders farther east of the Sun in the coming days. On January 14th, NASA's MESSENGER spacecraft will have a good view too, as it makes its first Mercury flyby.

Tomorrow's picture: from above

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  #386  
Παλιά 13-01-08, 10:59
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Hurricane Ivan from the Space Station
Credit: Expedition 9 Crew, International Space Station, NASA

Explanation: Ninety percent of the houses on Grenada were damaged by the destructive force of Hurricane Ivan. At its peak, Ivan was a Category 5 hurricane, the highest power category on the Saffir-Simpson Scale, and created sustained winds in excess of 200 kilometers per hour. Ivan was the largest hurricane to strike the US in 2004, and, so far, the 10th most powerful in recorded history. As it swirled in the Atlantic Ocean, the tremendous eye of Hurricane Ivan was photographed from above by the orbiting International Space Station. The name Ivan has now been retired from Atlantic Ocean use by the World Meteorological Organization.

Note: Astronomy lectures by an APOD editor are now available as a free podcast.
Tomorrow's picture: colorful cocoon

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  #387  
Παλιά 14-01-08, 09:56
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The Cocoon Nebula from CFHT
Credit & Copyright: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT

Explanation: What creates the colors of the Cocoon Nebula? The Cocoon Nebula, cataloged as IC 5146, is a strikingly beautiful nebula located about 4,000 light years away toward the constellation of the Swan (Cygnus). Inside the Cocoon Nebula is a newly developing open cluster of stars. Like other stellar nurseries, the Cocoon Nebula holds, at the same time, a bright red emission nebula, blue reflection nebulas, and dark absorption nebulas. Given different mixtures, these three processes create a host of colors in this image taken recently by the Canada-France-Hawaii Telescope (CFHT) in Hawaii, USA. Speculation based on recent measurements holds that the massive star towards the left of the picture opened a hole in an existing molecular cloud through which much of the glowing material flows. The same star, which formed about 100,000 years ago, now provides the energy source for much of the emitted and reflected light from this nebula.

Tomorrow's picture: open space

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  #388  
Παλιά 15-01-08, 09:22
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Double Supernova Remnants DEM L316
Credit & Copyright: Gemini Observatory, GMOS-South, NSF

Explanation: Are these two supernova shells related? To help find out, the 8-meter Gemini Telescope located high atop a mountain in Chile was pointed at the unusual, huge, double-lobed cloud dubbed DEM L316. The resulting image, shown above, yields tremendous detail. Inspection of the image as well as data taken by the orbiting Chandra X-Ray Observatory indicate how different the two supernova remnants are. In particular, the smaller shell appears to be the result of Type Ia supernova where a white dwarf exploded, while the larger shell appears to be the result of a Type II supernova where a massive normal star exploded. Since those two stellar types evolve on such different time scales, they likely did not form together and so are likely not physically associated. Considering also that no evidence exists that the shells are colliding, the two shells are now hypothesized to be superposed by chance. DEM L316 lies about 160,000 light years away in the neighboring Large Magellanic Cloud (LMC) galaxy, spans about 140 light-years across, and appears toward the southern constellation of the Swordfish (Dorado).

Tomorrow's picture: open space

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  #389  
Παλιά 16-01-08, 10:51
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MESSENGER Approaches Mercury
Credit: MESSENGER Teams, JHU APL, NASA

Explanation: Two days ago, the MESSENGER spacecraft became only the second in human history to swoop past Mercury. The last spacecraft to visit the Sun's closest planet was Mariner 10 over 35 years ago. Mariner 10 was not able to photograph Mercury's entire surface, and the images it did send back raised many questions. Therefore, much about planet Mercury remains unknown. This week's MESSENGER flyby was only the first of three. Over the next few years MESSENGER will swing past Mercury twice more and finally orbit in 2011, but MESSENGER is currently moving too fast to enter orbit around Mercury now. This image was taken by MESSENGER two days ago upon approach to Mercury. Many detailed images of Mercury are expected to be sent back over the next few days. The data acquired by MESSENGER will help better understand how Mercury's surface was formed, and why it is so dense.

Tomorrow's picture: pixels in space

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  #390  
Παλιά 17-01-08, 09:55
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Thor's Emerald Helmet
Credit & Copyright: Robert Gendler

Explanation: This helmet-shaped cosmic cloud with wing-like appendages is popularly called Thor's Helmet. Heroically sized even for a Norse god, Thor's Helmet is about 30 light-years across. In fact, the helmet is actually more like an interstellar bubble, blown as a fast wind from the bright, massive star near the bubble's center sweeps through a surrounding molecular cloud. Known as a Wolf-Rayet star, the central star is an extremely hot giant thought to be in a brief, pre-supernova stage of evolution. Cataloged as NGC 2359, the nebula is located about 15,000 light-years away in the constellation Canis Major. The sharp image captures striking details of the nebula's filamentary structures and also records an almost emerald color from strong emission due to oxygen atoms in the glowing gas.

Tomorrow's picture: Star Wars in NGC 2770

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