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  #601  
Παλιά 25-07-08, 08:45
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Τελευταία φορά Online: 12-11-16 11:12
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Spitzer's M101
Credit: NASA, JPL-Caltech, K. Gordon (STScI) et al.

Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way Galaxy. M101 was also one of the original spiral nebulae observed by Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. Recorded at infrared wavelengths by the Spitzer Space telescope, this 21st century view shows starlight in blue hues while the galaxy's dust clouds are in red. Examining the dust features in the outer rim of the galaxy, astronomers have found that organic molecules present throughout the rest of M101 are lacking. The organic molecules tracked by Spitzer's instruments are called polycyclic aromatic hydrocarbons (PAHs). Of course, PAHs are common components of dust in the Milky Way and on planet Earth are found in soot. PAHs are likely destroyed near the outer edges of M101 by energetic radiation in intense star forming regions. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.

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  #602  
Παλιά 26-07-08, 08:32
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Τελευταία φορά Online: 12-11-16 11:12
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Central IC 1805
Credit & Copyright: Keith Quattrocchi

Explanation: Cosmic clouds seem to form fantastic shapes in the central regions of emission nebula IC 1805. Of course, the clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster (aka Melotte 15). About 1.5 million years young, the cluster stars appear on the right in this colorful skyscape, along with dark dust clouds silhouetted against glowing atomic gas. A composite of narrow and broad band telescopic images, the view spans about 15 light-years and includes emission from hydrogen in green, sulfur in red, and oxygen in blue hues. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - The Heart Nebula. IC 1805 is located about 7,500 light years away toward the constellation Cassiopeia.

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  #603  
Παλιά 27-07-08, 08:14
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IC 4406: A Seemingly Square Nebula
Credit: C. R. O'Dell (Vanderbilt U.) et al., Hubble Heritage Team, NASA

Explanation: How can a round star make a square nebula? This conundrum comes to light when studying planetary nebulae like IC 4406. Evidence indicates that IC 4406 is likely a hollow cylinder, with its square appearance the result of our vantage point in viewing the cylinder from the side. Were IC 4406 viewed from the top, it would likely look similar to the Ring Nebula. This representative-color picture is a composite made by combining images taken by the Hubble Space Telescope in 2001 and 2002. Hot gas flows out the ends of the cylinder, while filaments of dark dust and molecular gas lace the bounding walls. The star primarily responsible for this interstellar sculpture can be found in the planetary nebula's center. In a few million years, the only thing left visible in IC 4406 will be a fading white dwarf star.

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  #604  
Παλιά 28-07-08, 08:43
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SDSSJ1430: A Galaxy Einstein Ring
Credit: A. Bolton (UH/IfA) for SLACS and NASA/ESA

Explanation: What's large and blue and can wrap itself around an entire galaxy? A gravitational lens mirage. Pictured above on the left, the gravity of a normal white galaxy has gravitationally distorted the light from a much more distant blue galaxy. More normally, such light bending results in two discernable images of the distant galaxy, but here the lens alignment is so precise that the background galaxy is distorted into a nearly complete ring. Since such a lensing effect was generally predicted in some detail by Albert Einstein over 70 years ago, such rings like SDSSJ1430 are now know as Einstein Rings. SDSSJ1430 was discovered during the Sloan Lens Advanced Camera for Surveys (SLACS) campaign, an observation program that inspected lens candidates found by the Sloan Digital Sky Survey (SDSS) with the Hubble Space Telescope's ACS. Strong gravitational lenses like SDSSJ1440 are more than oddities -- their multiple properties allow astronomers to determine the mass and dark matter content of the foreground galaxy lenses. Given these determinations, SLACS data has now been used, for example, to show that dark matter fraction increases with overall galaxy mass. The inset images on the right depict, from top to bottom, a computer reconstructed image of what the background blue galaxy really looks like, just the white foreground galaxy, and just the lensed blue background galaxy.

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  #605  
Παλιά 29-07-08, 07:50
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The Milky Way Over Ontario
Credit & Copyright: Kerry-Ann Lecky Hepburn (Weather and Sky Photography)

Explanation: Sometimes, after your eyes adapt to the dark, a spectacular sky appears. Such was the case earlier this month over Ontario, Canada, when part of a spectacular sky also became visible in a reflection off a lake. To start, the brightest objects visible are bright stars and the planet Jupiter, seen as the brightest spot on the upper left. A distant town appears as a diffuse glow over the horizon. More faint still, the disk of the Milky Way Galaxy becomes apparent as a dramatic diffuse band across the sky that seems to crash into the horizon far in the distance. In the foreground, a picturesque landscape includes trees, a lake, and a stone wall. Finally, on this serene night in July when the lake water was unusually clam, reflections appear. Visible in the lake are not only reflections of several bright stars, but part of the Milky Way band itself. Careful inspection of the image will reveal, however, that bright stars leave small trails in the lake reflections that do not appear in the sky above. The reason for this is because the above image is actually a digital composite of time-consecutive exposures from the same camera. In the first set of exposures, sky images were co-added with slight rotations to keep the stars in one place.

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  #606  
Παλιά 30-07-08, 09:08
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The International Space Station Transits the Sun
Credit & Copyright: Martin Wagner

Explanation: That's no sunspot. It's the International Space Station (ISS) caught by chance passing in front of the Sun. Sunspots, individually, have a dark central umbra, a lighter surrounding penumbra, and no solar panels. By contrast, the ISS is a complex and multi-spired mechanism, one of the largest and most sophisticated machines ever created by humanity. Also, sunspots occur on the Sun, whereas the ISS orbits the Earth. Transiting the Sun is not very unusual for the ISS, which orbits the Earth about every 90 minutes, but getting one's timing and equipment just right for a great image is rare. Strangely, besides that fake spot, the Sun, last week, lacked any real sunspots. Sunspots have been rare on the Sun since the dawn of the current Solar Minimum, a period of low solar activity. Although fewer sunspots have been recorded during this Solar Minimum than for many previous decades, the low solar activity is not, as yet, very unusual.

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  #607  
Παλιά 31-07-08, 07:20
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Galaxies on a String
Credit & Copyright: Acquisition - Martin Winder, Processing - Warren Keller

Explanation: Galaxies NGC 5216 (top right) and NGC 5218 really do look like they are connected by a string. Of course, that string is a cosmic trail of gas, dust, and stars about 22,000 light-years long. Also known as Keenan's system (for its discoverer) and Arp 104, the interacting galaxy pair is some 17 million light-years away in the constellation Ursa Major. The debris trail that joins them, along with NGC 5218's comma-shaped extension and the distorted arms of NGC 5216 are a consequence of mutual gravitational tides that disrupt the galaxies as they repeatedly swing close to one another. Drawn out over billions of years, the encounters will likely result in their merger into a single galaxy of stars. Such spectacular galactic mergers are now understood to be a normal part of the evolution of galaxies, including our own Milky Way.

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  #608  
Παλιά 01-08-08, 08:42
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Moon Games
Credit & Copyright: Laurent Laveder (PixHeaven.net / TWAN)

Explanation: The Moon's measured diameter is around 3,476 kilometers (2,160 miles). But apparent angular size, or the angle covered by an object, can also be important to Moon enthusiasts. Angular size depends on distance, the farther away an object is, the smaller an angle it covers. Since the Moon is 400,000 kilometers away, its angular size is only about 1/2 degree, a span easily covered by the tip of your finger held at arms length, or a measuring tape held in the distance by a friend. Of course the Sun is much larger than the Moon, 400 times larger in fact, but today the New Moon will just cover the Sun. The total solar eclipse can be seen along a track across northern Canada, the Arctic, Siberia, and northern China. (A partial eclipse is visible from a broader region). Solar eclipses illustrate the happy coincidence that while the Sun is 400 times the diameter of the Moon, it is also 400 times farther away giving the Sun and Moon exactly the same angular size.

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  #609  
Παλιά 02-08-08, 08:25
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Τελευταία φορά Online: Σήμερα 15:05
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Eclipse Shirt
Credit & Copyright: Philippe Haake

Explanation: Of course, everyone is concerned about what to wear to a solar eclipse. No need to worry though, nature often conspires to project images of the eclipse so that stylish and appropriate patterns adorn many visible surfaces - including clothing - at just the right time. Most commonly, small gaps between leaves on trees can act as pinhole cameras and generate multiple recognizable images of the eclipse. In Madrid to view the 2005 October 3rd annular eclipse of the Sun, astronomer Philippe Haake met a friend who had another inspiration. The result, a grid of small holes in a kitchen strainer produced this pattern of images on an 'eclipse shirt'. While Yesterday's solar eclipse was total only along a narrow path beginning in northern Canada, extending across the Arctic, and ending in China, a partial eclipse could be seen from much of Europe and Asia.

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  #610  
Παλιά 03-08-08, 09:07
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Τελευταία φορά Online: Σήμερα 15:05
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Open Cluster NGC 290: A Stellar Jewel Box
Credit: ESA & NASA; Acknowledgement: E. Olszewski (U. Arizona)

Explanation: Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color. The photogenic cluster, pictured above, was captured recently by the orbiting Hubble Space Telescope. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars. NGC 290 lies about 200,000 light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC). The open cluster contains hundreds of stars and spans about 65 light years across. NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve, since all the open cluster's stars were born at about the same time.

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  #611  
Παλιά 04-08-08, 09:04
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X-Rays from the Cat's Eye Nebula
Credit: X-ray: NASA/CXC/SAO; Optical: NASA/STScI

Explanation: Haunting patterns within planetary nebula NGC 6543 readily suggest its popular moniker -- the Cat's Eye nebula. Starting in 1995, stunning false-color optical images from the Hubble Space Telescope detailed the swirls of this glowing nebula, known to be the gaseous shroud expelled from a dying sun-like star about 3,000 light-years from Earth. This composite picture combines the latest Hubble optical image of the Cat's Eye with new x-ray data from the orbiting Chandra Observatory and reveals surprisingly intense x-ray emission indicating the presence of extremely hot gas. X-ray emission is shown as blue-purple hues superimposed on the nebula's center. The nebula's central star itself is clearly immersed in the multimillion degree, x-ray emitting gas. Other pockets of x-ray hot gas seem to be bordered by cooler gas emitting strongly at optical wavelengths, a clear indication that expanding hot gas is sculpting the visible Cat's Eye filaments and structures. Gazing into the Cat's Eye, astronomers see the fate of our sun, destined to enter its own planetary nebula phase of evolution ... in about 5 billion years.

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  #612  
Παλιά 05-08-08, 07:59
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Τελευταία φορά Online: Σήμερα 15:05
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A Total Solar Eclipse Over China
Credit & Copyright: Bill Buckingham

Explanation: What's that black dot over the Sun? The Moon. This past weekend, the Sun went dark during the day as the Moon completely covered it. The total solar eclipse was visible over a thin swath of Earth extending from northern Canada to China. As shown above, many sky enthusiasts gathered to witness the total or partial solar eclipse, which lasted only a few minutes. The above image was taken during totality near Barkol in Xinjiang, China, with the Barkol Shan mountain range visible on the horizon. Although the brightest parts of the Sun are covered, the normally invisible corona of hot gas surrounding the Sun became prominent. Just to the upper left of the Moon darkened Sun are planets Mercury and Venus. The increased darkening of the sky toward the right indicates the darkened atmosphere created by the passing shadow cone of the total solar eclipse. The next total solar eclipse will occur next July and be visible in parts of India and China.

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  #613  
Παλιά 06-08-08, 08:58
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Τελευταία φορά Online: Σήμερα 15:05
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(Για μεγαλύτερη ανάλυση, κάνετε κλικ στην εικόνα)

NGC 1818: A Young Globular Cluster
Credit: Diedre Hunter (Lowell Obs.) et al., HST, NASA

Explanation: Globular clusters once ruled the Milky Way. Back in the old days, back when our Galaxy first formed, perhaps thousands of globular clusters roamed our Galaxy. Today, there are perhaps 200 left. Many globular clusters were destroyed over the eons by repeated fateful encounters with each other or the Galactic center. Surviving relics are older than any Earth fossil, older than any other structures in our Galaxy, and limit the universe itself in raw age. There are few, if any, young globular clusters in our Milky Way Galaxy because conditions are not ripe for more to form. Things are different next door, however, in the neighboring LMC galaxy. Pictured above is a "young" globular cluster residing there: NGC 1818. Observations show it formed only about 40 million years ago - just yesterday compared to the 12 billion year ages of globular clusters in our own Milky Way

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  #614  
Παλιά 07-08-08, 09:18
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(Για ολόκληρη τη φωτογραφία, κάντε κλικ στην εικόνα)


At the Sun's Edge
Credit & Copyright: Catalin Beldea (Descopera Magazine)

Explanation: A train trip on the Trans-Siberian railway to Novosibirsk resulted in this stunning view along the edge of the Sun recorded during the August 1st total solar eclipse. The picture is a composite of two images taken at special moments in the eclipse sequence, corresponding to the very beginning and the very end of the total eclipse phase. Those times are known to eclipse chasers as 2nd and 3rd contact. Bright beads around the Moon's dark silhouette are rays of sunlight shining through lunar valleys at the edge of the lunar disk. But the composite view also captures solar prominences, looping structures of hot plasma suspended in magnetic fields, extending beyond the Sun's edge.

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  #615  
Παλιά 08-08-08, 07:17
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The Crown of the Sun
Credit & Copyright: Hartwig Luethen

Explanation: During a total solar eclipse, the Sun's extensive outer atmosphere, or corona, is an inspirational sight. The subtle shades and shimmering features of the corona that engage the eye span a brightness range of over 10,000 to 1, making them notoriously difficult to capture in a single picture. But this composite of 28 digital images ranging in exposure time from 1/1000 to 2 seconds comes close to revealing the crown of the Sun in all its glory. The telescopic views were recorded near Kochenevo, Russia during the August 1 total solar eclipse and also show solar prominences extending just beyond the edge of the eclipsed sun. Remarkably, features on the dark near side of the New Moon can also be made out, illuminated by sunlight reflected from a Full Earth.

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