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  #196  
Παλιά 12-08-07, 09:08
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Τελευταία φορά Online: 12-11-16 10:12
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Raining Perseids
Credit & Copyright: Fred Bruenjes

Explanation: Tonight is a good night to see meteors. Comet dust will rain down on planet Earth, streaking through dark skies in the annual Perseid meteor shower. While enjoying the anticipated space weather, astronomer Fred Bruenjes recorded a series of many 30 second long exposures spanning about six hours on the night of 2004 August 11/12 using a wide angle lens. Combining those frames which captured meteor flashes, he produced this dramatic view of the Perseids of summer. Although the comet dust particles are traveling parallel to each other, the resulting shower meteors clearly seem to radiate from a single point on the sky in the eponymous constellation Perseus. The radiant effect is due to perspective, as the parallel tracks appear to converge at a distance. Bruenjes notes that there are 51 Perseid meteors in the composite image, including one seen nearly head-on. This year, the Perseids Meteor Shower is expected to peak after midnight tonight, in the moonless early morning hours of August 12.

Tomorrow's picture: triple hot

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  #197  
Παλιά 13-08-07, 08:53
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The Trifid Nebula in Stars and Dust
Credit & Copyright: R. Jay GaBany (Cosmotography.com)

Explanation: Unspeakable beauty and unimaginable bedlam can be found together in the Trifid Nebula. Also known as M20, this photogenic nebula is visible with good binoculars towards the constellation of Sagittarius. The energetic processes of star formation create not only the colors but the chaos. The red-glowing gas results from high-energy starlight striking interstellar hydrogen gas. The dark dust filaments that lace M20 were created in the atmospheres of cool giant stars and in the debris from supernovae explosions. Which bright young stars light up the blue reflection nebula is still being investigated. The light from M20 we see today left perhaps 3000 years ago, although the exact distance remains unknown. Light takes about 50 years to cross M20.

Tomorrow's picture: grand teton sky

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  #198  
Παλιά 14-08-07, 08:27
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A Spectacular Sky Over the Grand Tetons
Credit & Copyright: Wally Pacholka (Astropics.com); Image Processing: Tony Hallas

Explanation: Behold the breathtaking beauty of Earth and sky together. In the foreground is the Teton Mountain Range of Wyoming, USA. The Grand Tetons are a relatively isolated set of high peaks that are part of the Rocky Mountains. On the far left, vast clouds of bright stars and dark dust are visible in the nearly vertical plane of our Milky Way Galaxy. Our Galactic Plane appears to crash into the Tetons, but is actually far more distant. On the left, just to the left of the southernmost Teton peak, the planet Jupiter is visible. Near the image center is the bright star Arcturus. Scrolling to the far right will bring over the familiar asterism of the Big Dipper. Last month it took five images, later digitally fused, to capture the majesty of this panoramic view.

Tomorrow's picture: open space

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  #199  
Παλιά 15-08-07, 08:41
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Mysterious Streaks Over Turkey
Credit & Copyright: Tunc Tezel

Explanation: What are they? Five streaks near the bottom of the above image taken near Ankara, Turkey on Sunday would be identified at first glance as meteors from the Perseids meteor shower peaking just that night. Unexpectedly, however, these streaks do not point back to the Perseids radiant in Perseus. Their origin is therefore somewhat unclear. The above image was captured over the time span of 40 minutes. Other visible celestial icons include the constellation Orion and the Pleiades star cluster. One hypothesis is that the streaks are part of a microburst from a much less active meteor shower known as the Alpha Ursae Majorids. Another possibility is that they are parts of a satellite that broke up as it re-entered the Earth's atmosphere. A discussion of these possibilities can be found here. This year's Perseids meteor shower was a good one, as it was particularly active and corresponded with the dark skies that come with a new moon.

Tomorrow's picture: no moon, no clouds

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  #200  
Παλιά 16-08-07, 08:01
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Moonless Perseid Sky
Credit & Copyright: John Chumack

Explanation: Last weekend, dark, moonless night skies brought many sightings of Perseid meteors to skygazers all over planet Earth. Early Sunday morning astronomer John Chumack's camera captured this Perseid meteor streak with a flare near the end of its track over Yellow Springs, Ohio. The single, four minute long exposure looks toward the constellation of Taurus and the eastern horizon. The meteor streak points back to the annual meteor shower's radiant in Perseus off the upper left corner of the picture. Of course, the view includes the well-known Pleiades Star cluster (near top center) with a bright yellowish planet Mars below it. Also seen with a yellowish tint but not quite as bright as Mars, the giant star Aldebaran anchors the V-shaped Hyades star cluster left of center, above the trees.

Tomorrow's picture: moonview

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  #201  
Παλιά 17-08-07, 08:09
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The Tail of a Wonderful Star
Credit: NASA, JPL-Caltech, GALEX, C. Martin (Caltech), M. Seibert(OCIW)

Explanation: To seventeenth century astronomers, Omicron Ceti or Mira was known as a wonderful star, a star whose brightness could change dramatically in the course of about 11 months. Mira is now seen as the archetype of an entire class of long-period variable stars. Surprisingly, modern astronomers have only recently discovered another striking characteristic of Mira -- an enormous comet-like tail nearly 13 light-years long. The discovery was made using ultraviolet image data from the Galaxy Evolution Explorer (GALEX) satellite. Billions of years ago Mira was likely similar to our Sun, but has now become a swollen red giant star, its outer layers of material blowing off into interstellar space. Fluorescing in ultraviolet light, the cast off material trails behind the giant star as it plows through the surrounding interstellar medium at 130 kilometers per second. The amount of material in Mira's tail is estimated to be equivalent to 3,000 times the mass of planet Earth. About 400 light-years away toward the constellation Cetus, Mira is presently too faint to be seen by the unaided eye, but will become visible again in mid-November.

Tomorrow's picture: looking up

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  #202  
Παλιά 18-08-07, 07:43
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ISS Over Mont-Megantic Observatory
Credit & Copyright: Guillaume Poulin (Astrolab du Parc du Mont-Megantic)

Explanation: On August 1st, a time exposure created this surreal view that looks up into the early morning sky over southern Quebec. Only the light from a nearly Full Moon brightens the sky and highlights the dome of the 1.6 meter telescope at Mont-Megantic Observatory. Shadowy figures on the catwalk are astronomers who have interrupted their work to glimpse the International Space Station (ISS) streaking overhead. The brightest "star" in the moonlit sky, the ISS was easy to spot moving through a background of stars in the high-flying constellation Pegasus.

Tomorrow's picture: sonic boom

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  #203  
Παλιά 19-08-07, 08:14
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A Sonic Boom
Credit: Ensign John Gay, USS Constellation, US Navy

Explanation: Is this what a sonic boom looks like? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.

Tomorrow's picture: misplaced matter

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  #204  
Παλιά 20-08-07, 08:27
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Cluster Crash Illuminates Dark Matter Conundrum
Credit: X-ray: NASA / CXC/ U. Victoria/ A. Mahdavi et al.
Optical/Lensing: CFHT/ U. Victoria/ A. Mahdavi et al.

Explanation: Huge clusters of galaxies are surely colliding in Abell 520 but astrophysicists aren't sure why the dark matter is becoming separated from the normal matter. The dark matter in the above multi-wavelength image is shown in false blue, determined by carefully detailing how the cluster distorts light emitted by more distant galaxies. Very hot gas, a form of normal matter, is shown in false red, determined by the X-rays detected by the Earth-orbiting Chandra X-ray Observatory. Individual galaxies dominated by normal matter appear yellowish or white. Conventional wisdom holds that dark matter and normal matter are attracted the same gravitationally, and so should be distributed the same in Abell 520. Inspection of the above image, however, shows a surprising a lack of a concentration of visible galaxies along the dark matter. One hypothetical answer is that the discrepancy is caused by the large galaxies undergoing some sort of conventional gravitational slingshots. A more controversial hypothesis holds that the dark matter is colliding with itself in some non-gravitational way that has never been seen before. Further simulations and study of this cluster may resolve this scientific conundrum.

Tomorrow's picture: red dome glowing

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  #205  
Παλιά 21-08-07, 08:02
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A Red Dome Under the Big Dipper
Credit & Copyright: M. Colleen Gino

Explanation: Why would the dome of a telescopic observatory appear translucent red? As one of the telescopes of the Etscorn Observatory of New Mexico Tech waited to inspect small portions of the night sky, playful observers decided to make this unusual image. Tricks needed to create this seemingly impossible shot included opening the observatory dome slightly, using a red light to illuminate the inside of the dome, spinning the dome, and using a long exposure. The open slit in the dome then allowed the camera to incrementally image the inside of the observatory, including the telescope. A fortuitous break in the clouds allowed the stars of the Big Dipper asterism to shine through.

Tomorrow's picture: big tarantula

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  #206  
Παλιά 22-08-07, 08:17
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Tentacles of the Tarantula Nebula
Credit & Copyright: WFI, MPG/ESO 2.2-m Telescope, La Silla, ESO

Explanation: The largest, most violent star forming region known in the whole Local Group of galaxies lays in our neighboring galaxy the Large Magellanic Cloud (LMC). Were the Tarantula Nebula at the distance of the Orion Nebula -- a local star forming region -- it would take up fully half the sky. Also called 30 Doradus, the red and pink gas indicates a massive emission nebula, although supernova remnants and dark nebula also exist there. The bright knot of stars left of center is called R136 and contains many of the most massive, hottest, and brightest stars known. The above image taken with the European Southern Observatory's (ESO's) Wide Field Imager is one of the most detailed ever of this vast star forming region. ESO has made it possible to fly around and into this detailed image by clicking here.

Tomorrow's picture: moonview

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  #207  
Παλιά 23-08-07, 07:56
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Southern Moonscape
Credit & Copyright: Wes Higgins

Explanation: The Moon's south pole is near the top of this sharp telescopic view looking across the southern lunar highlands. Recorded on August 3rd from Tecumseh, Oklahoma, planet Earth, the foreshortened perspective heightens the impression of a dense field of craters and makes the craters themselves appear more oval shaped. The prominent crater in the foreground, Moretus, has a diameter of 114 kilometers and lies just west (left) of the Moon's central meridian. For large lunar craters, Moretus is young and features terraced inner walls and a 2.1 kilometer high, bright central peak, similar in appearance to the more northerly crater Tycho. Just to the right of Moretus is the 95 kilometer diameter crater Curtius. Curtius has older, rounded walls marked by smaller, more recent impact craters.

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  #208  
Παλιά 24-08-07, 07:41
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Astronomer's Moon
Credit & Copyright: Mikhail Abgarian, Konstantin Morozov, Yuri Goryachko (Minsk, Belarus)

Explanation: Jupiter is an astronomer's planet -- its large size and contrasting global cloud belts and zones allow detailed studies with a range of earthbound telescopes. On the other hand, most telescopic views of Jupiter's moons usually show only featureless, tantalizing points of light hovering near the ruling gas giant. But this impressive picture from a small, ground-based telescope reveals a stunning amount of detail on Ganymede, a jovian moon about the same size as Earth's moon but at least 1,500 times farther away. The image was carefully constructed by combining and processing only the 409 sharpest frames from a total of 10,000 recorded at 30 frames per second by a digital camera. Ganymede's radius is about 2,600 kilometers indicating that the surface markings visible are as small as around 900 kilometers across.

Tomorrow's picture: just passing through

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  #209  
Παλιά 26-08-07, 07:44
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A Total Lunar Eclipse Over North Carolina
Credit & Copyright: David Cortner

Explanation: This coming Tuesday, our Moon will appear to disappear. A similar total lunar eclipse is seen above in a time lapse image captured in 2003 over North Carolina, USA. As the Earth moves between the Moon and the Sun, the Earth's shadow fell on the moon, making it quite dark. In the above picture the Earth's rotation, multiple exposures, and digital enhancements are used to create a time-lapse effect that dramatizes how the Moon looked as it faded out and re-appeared during the three hour lunar eclipse. As the Earth's shadow engulfed the Moon, the lunar images became less and less bright, practically disappearing during totality. At this time, the Moon, which normally shines by reflecting direct sunlight, shone only by sunlight refracted through the Earth's atmosphere. The next total lunar eclipse won't be visible from Earth until February 2008.

Tomorrow's picture: empty space

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  #210  
Παλιά 27-08-07, 07:44
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Huge Void Implicated in Distant Universe
Drawing Credit: Bill Saxton, NRAO, AUI, NSF NASA

Explanation: What has created this huge empty volume in the universe? No one is yet sure, and even the extent of the estimated billion-light year void is being researched. The void is not a hole in space like a black hole, but rather a vast region of the universe that appears to be mostly devoid of normal matter and even dark matter. The void is still thought to contain dark energy, though, and is clearly traversable by light. The void's existence is being postulated following scientific curiosity about how unusually cold spots came to appear on WMAP's map of cosmic microwave background (CMB) radiation. One possibility was that this CMB region was not actually very cold but light from the spot somehow became less cosmologically redshifted than normal along the way. Other voids in the universe are known to exist, but this void appears to have an unusually large gravitational effect, and so might possibly be the largest in our entire visible universe. Investigating this, a recent study found an unusually low number of cosmic radio sources between Earth and the CMB cold spot, which led to the inference of this giant void. An artist's depiction of the huge cosmic void is shown above.

Tomorrow's picture: organic mars

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