Η διαστημική φωτογραφία της ημέρας - Αρχείο

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Unusual Dusty Galaxy NGC 7049
Credit: NASA, ESA and W. Harris (McMaster University)

Explanation: How was this unusual looking galaxy created? No one is sure, especially since spiral galaxy NGC 7049 looks so strange. NGC 7049's strikingly appearance is primarily due to an unusually prominent dust ring seen mostly in silhouette. The opaque ring is much darker than the din of millions of bright stars glowing behind it. Besides the dark dust, NGC 7049 appears similar to a smooth elliptical galaxy, although featuring surprisingly few globular star clusters. NGC 7049 is pictured above as imaged recently by the Hubble Space Telescope. The bright star near the top of NGC 7049 is an unrelated foreground star in our own Galaxy. Not visible here is unusual central polar ring of gas circling out of the plane near the galaxy's center. Since NGC 7049 is the brightest galaxy in its cluster of galaxies, its formation might be fostered by several prominent and recent galaxy collisions. NGC 7049 spans about 150 thousand light years and lies about 100 million light years away toward the constellation of Indus.

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Venus Near Inferior Conjunction
Credit & Copyright: Eddie Guscott

Explanation: This remarkable picture of a slender crescent Venus was made during daylight hours on March 26. Venus was then very near inferior conjunction, its closest approach to a point on a line directly between Earth and the Sun. So, daylight was a good time to carefully record the telescopic view when both Venus and Sun were high in the daytime sky. Near inferior conjunction, Venus is closest to us and at its largest apparent size, but Venus is also strongly backlit by sunlight, presenting its night side partially outlined by a narrow crescent. What makes the image remarkable are the faint arcs extending beyond the sunlit crescent around to the night side of Venus, due to sunlight filtering through the planet's dense atmosphere. Astronomer Eddie Guscott reports from his site in Essex, England that the faint extensions came and went as the Earth's atmospheric blurring changed. His image was constructed from 85 of the sharpest frames chosen from thousands taken with a webcam and telescope.

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ISS and Astronaut
Credit & Copyright: Ralf Vandebergh

Explanation: These two frames, taken with a video camera and a telescope, reveal remarkable details of the International Space Station (ISS) orbiting some 350 kilometers above planet Earth. Recorded during last month's visit by the crew of shuttle orbiter Discovery on mission STS-119, the pictures show extended solar arrays glinting in bright sunlight against a dark sky. They also likely capture the blurred image of a spacewalking astronaut during the mission's EVA-2 (Extravehicular Activity-2)! The astronaut is installing equipment along one of the station's truss assemblies. Astronomer Ralf Vandebergh, who often images the ISS during its favorable passes through Dutch skies, comments that no other bright ISS structures occupy the position indicated in the inset, and that a reflective, white-suited astronaut would be visible against the truss and correspond to the bright blur. Vandebergh notes that the timing and location further suggest the spacewalker is STS-119 astronaut Joseph Acaba.

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Σχόλιο : Κατάλαβε κανείς τι θέλει να πει ο ποιητής εδώ;

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The Big Picture
Credit & Copyright: Dennis di Cicco (TWAN) & Sean Walker, Skyandtelescope.com

Explanation: Intricate, glowing nebulae that shine in planet Earth's night sky are beautiful to look at in deep images made with telescopes and sensitive cameras. But they are faint and otherwise invisible to the naked-eye. That makes their relative location and extent on the sky difficult to appreciate. So, consider this impressive composite image of a wide region of the northern winter sky. With a total exposure time of 40 hours, the painstaking mosaic presents a nebula-rich expanse known as the Orion-Eridanus Superbubble above a house in suburban Boston, USA. Within the wide and deep view are nebulae more often seen in narrower views, including the Great Orion Nebula, the Rosette Nebula, the Seagull Nebula, the California Nebula, and Barnard's Loop. The familiar constellation of Orion itself is just above the foreground house. Brightest star Sirius is left of the roof, and the recognizable Pleiades star cluster is above the tree at the right. A version of the big picture that includes simple constellation guidelines is available here.

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M39: Open Cluster in Cygnus
Credit: Heidi Schweiker, WIYN, NOAO, AURA, NSF

Explanation: Lying just at the limit of human perception is a picturesque starfield containing one of the larger open clusters on the northern sky. Spanning an angle larger than the Moon, M39's relatively few stars lie only about 800 light years distant toward the constellation of Cygnus. The above picture of M39 is a mosaic of 33 images taken by the WIYN telescope on Kitt Peak in Arizona, USA. The stars in M39 are all about 300 million years old, much younger than the 5,000 million years of our Sun. Open clusters, also called galactic clusters, contain fewer and younger stars than globular clusters. Also unlike globular clusters, open clusters are generally confined to the plane of our Galaxy.

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Εδώ θα βρείτε βίντεο σήμερα, αν και ο τίτλος ειναι για φωτογραφία.....

Star Trails over the Canada-France-Hawaii Telescope
Credit & Copyright: Jean-Charles Cuillandre (CFHT)

Explanation: Just fix your camera to a tripod and you too can make an image of graceful trails traced by the stars as planet Earth rotates on its axis. Making a time lapse video like that shown above may require more effort, though. Made on 2006 October 13 from Mauna Kea, Hawaii, USA, this video nicely captured what you might see of the night sky if you could keep your brain from changing your perceived visual image about every hundredth of a second. Starting from a dark sky and point-like stars, the video demonstrates how stars appear to move over the night as the world turns. Near the center of the developing bull's-eye pattern is Polaris, the North Star. Visible in the left foreground is the 3.7-meter aperture Canada-France-Hawaii Telescope (CFHT). The red glow that illuminated the CFHT dome near the beginning of the film was created by a car leaving the volcanic summit. The Moon rose about half way through the video and created a white glow that gradually illuminated most of the CFHT dome. The above remarkable time-lapse video was constructed from about 1,000 consecutive frames taken with a digital camera over nearly nine hours.

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M101: The Pinwheel Galaxy
Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona

Explanation: Why do many galaxies appear as spirals? A striking example is M101, shown above, whose relatively close distance of about 27 million light years allow it to be studied in some detail. Recent evidence indicates that a close gravitational interaction with a neighboring galaxy created waves of high mass and condensed gas which continue to orbit the galaxy center. These waves compress existing gas and cause star formation. One result is that M101, also called the Pinwheel Galaxy, has several extremely bright star-forming regions (called HII regions) spread across its spiral arms. M101 is so large that its immense gravity distorts smaller nearby galaxies.

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Castle and Full Moon
Credit & Copyright: Paolo Tanga, Observatoire de la Cote d'Azur

Explanation: Clouds couldn't hide this bright Full Moon as it rose last week over the medieval castle of Tourrette-Levens near Nice, France. Exactly full on April 9 at 1456 UT, it followed the March equinox, making it the first Full Moon of spring in the north and autumn in the southern hemisphere. Known as the Easter Moon, it fixes the date for the Christian celebration of Easter on the first Sunday after the first Full Moon of northern spring. Also called the Grass Moon or Egg Moon in the north, in the southern hemisphere, following the autumnal equinox, this Full Moon shines throughout the night as a Hunter's Moon.

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Medieval Astronomy from Melk Abbey
Credit: Paul Beck (Univ. Vienna), Georg Zotti (Vienna Inst. Arch. Science)
Copyright: Library of Melk Abbey, Frag. 229

Explanation: Discovered by accident, this manuscript page provides graphical insight to astronomy in medieval times, before the Renaissance and the influence of Nicolaus Copernicus, Tycho de Brahe, Johannes Kepler, and Galileo. The intriguing page is from the lecture notes on astronomy compiled by the monk Magister Wolfgang de Styria before the year 1490 at Melk Abbey in Austria. The top panels clearly illustrate the necessary geometry for a lunar (left) and solar eclipse in the Earth-centered Ptolemaic system. At lower left is a diagram of the Ptolemaic view of the solar system and at the lower right is a chart to calculate the date of Easter Sunday in the Julian calendar. Text at the upper right explains the movement of the planets according to the Ptolemaic system. The actual manuscript page is on view at historic Melk Abbey as part of a special exhibition during the International Year of Astronomy.

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NGC 1333 Stardust
Credit & Copyright: Stephen Leshin

Explanation: NGC 1333 is seen in visible light as a reflection nebula, dominated by bluish hues characteristic of starlight reflected by dust. A mere 1,000 light-years distant toward the heroic constellation Perseus, it lies at the edge of a large, star-forming molecular cloud. This striking close-up view spans about 4 light-years at the estimated distance of NGC 1313. It shows details of the dusty region along with hints of contrasting emission in red jets and glowing gas from recently formed stars. In fact, NGC 1333 contains hundreds of stars less than a million years old, most still hidden from optical telescopes by the pervasive stardust. The chaotic environment may be similar to one in which our own Sun formed over 4.5 billion years ago.

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The View Near a Black Hole
Drawing Credit: April Hobart, CXC

Explanation: In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes. The gas surrounding GRO J1655-40, for example, has been found to display an unusual flickering at a rate of 450 times a second. Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly. What physical mechanisms actually cause the flickering -- and a slower quasi-periodic oscillation (QPO) -- in accretion disks surrounding black holes and neutron stars remains a topic of much research.

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¦-ΊΪί ΆΈώΆ _ΪύΊ __ΪΎή±ά_-ά ήώά Ήίή-Έύ άΊ-ΈΫ_ύ

Flowing Barchan Sand Dunes on Mars
Credit: HiRISE, MRO, LPL (U. Arizona), NASA

Explanation: When does Mars act like a liquid? Although liquids freeze and evaporate quickly into the thin atmosphere of Mars, persistent winds may make large sand dunes appear to flow and even drip like a liquid. Visible on the above image right are two flat top mesas in southern Mars, where the season is changing from Spring to Summer. A light dome topped hill is also visible on the far left of the image. As winds blow from right to left, flowing sand on and around the hills leaves picturesque streaks. The dark arc-shaped droplets of fine sand are called barchans, and are the interplanetary cousins of similar Earth-based sand forms. Barchans can move intact downwind and can even appear to pass through each other. Over the past few weeks, winds on southern Mars have been kicking up dust and are being watched to see if they escalate into another of Mars' famous planet-scale sand storms.

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Global Warming Predictions
Credit & Copyright: Robert A. Rohde, Global Warming Art

Explanation: How much will the Earth's surface warm up over the lives of our children? No one is sure. Compared to the past 100 million years, the Earth is currently enduring a relative cold spell, possibly about four degrees Celsius below average. Over the past 100 years, however, data indicate the average global temperature of the Earth has increased by nearly one degree Celsius. Few disagree that recent global warming is occurring, and the Intergovernmental Panel on Climate Change (IPCC) has concluded that we humans have created a warming surge that is likely to continue. A future temperature increase like that shown on the above predictive map may cause sea levels to rise, precipitation patterns to change, and much pole ice to melt. The result could impact many local agricultures and the global economy. Geoengineering projects that might include artificial cloud creation might reduce the amount of warming sunlight that reaches the Earth's surface.

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Sky Panorama Over Lake Salda
Credit & Copyright: Tunç Tezel (TWAN)

Explanation: As midnight approached, a spectacular sky appeared. Such was the case last month from the shore of Lake Salda in southwestern Turkey. In the above night sky panorama, rocky sand covers the foreground, while building lights are visible across the lake. Looking up, the stars of Orion lie just ahead, while Sirius, the brightest star in the sky, appears to Orion's left. To Orion's right, just above the horizon, lies the Pleiades open star cluster. Arching across the sky is the central band of our Milky Way Galaxy. High in the center, the stars Castor and Pollux are visible. Lake Salda is famous partly for its blue color that is slightly discernable even in the above image.

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Sharpless 308
Credit & Copyright: Don Goldman

Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 308 it lies some 5,200 light-years away in the constellation Canis Major and covers over 2/3 degree on the sky (compared with 1/2 degree for the Full Moon). That corresponds to a diameter of 60 light-years at its estimated distance. The massive star itself, a Wolf-Rayet star, is the bright blue one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the expansive image is dominated by the glow of ionized oxygen atoms mapped to bluish hues.

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