科普 神奇的宇宙----图片(每天更新中)

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Shoreline Terrain on Saturn's Titan

Explanation: What could have created this unusual terrain on Saturn's moon Titan? The robotic Cassini spacecraft now orbiting Saturn swooped once again, earlier this month, past the Solar System's most enigmatic moon and radar imaged a rich but unusual region that appears to be some sort of shoreline. The choppy, light-colored, high regions on the left appears to be have channels cut by a moving fluid, while the smoother dark regions on the right appear to outline bays. Results from the Huygens probe that landed on Titan earlier this year imply that fluids, possibly liquid methane and not water, might only occupy some of these channels and bays intermittently. The radar image shown above spans about 200 kilometers.

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Portrait of RY Tauri

Explanation: A star emerges from its natal cloud of gas and dust in this tantalizing portrait of RY Tauri, a small stellar nursery at the edge of the Taurus molecular cloud, a mere 450 light-years away. Illuminating a region that spans about 2/3 of a light-year, the youthful, central star is large, cool, and known to vary in brightness. Still collapsing, in a few million years the star's winds will likely clear out the gas and dust clouds, as it settles down to become a steady main sequence star like the Sun. What remains could well include a planetary system. The image data for RY Tauri is from the Gemini Observatory, on Mauna Kea, Hawaii -- based on observations proposed by the Astronomy Club of Dorval, Quebec.

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Approaching Asteroid Itokawa

Explanation: What are asteroids made of? To help find out, Japan's JAXA space agency launched the Hayabusa mission to rendezvous with asteroid Itokawa. Last week, the small robotic Hayabusa spacecraft arrived at asteroid Itokawa and stationed itself only 20 kilometers away. Although a long term goal is to find out how much ice, rock and trace elements reside on the asteroid's surface, a shorter term goal is to determine the mass of the asteroid by measuring the attraction of the drifting Hayabusa spacecraft. During the next few months, Hayabusa will also image and map asteroid Itokawa as it orbits the Sun. The above time-lapse image sequence was taken by Hayabusa upon final approach, showing the general oblong shape of the asteroid. In November, a small coffee-can sized robot dubbed MINERVA is scheduled for release and is expected to hop around the asteroid taking pictures. Also in November, Hayabusa will fire pellets into asteroid Itokawa and collect some of the debris in a return capsule. In December, Hayabusa will fire its rockets toward Earth and drop the return capsule to Earth in 2007 June.

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The Shadow of Phobos

Explanation: Hurtling through space above the Red Planet, potato-shaped Phobos completes an orbit of Mars in less than eight hours. In fact, since its orbital period is shorter than the planet's rotation period, Mars-based observers see Phobos rise in the west and set in the east - traveling from horizon to horizon in about 5 1/2 hours. These three images from the Mars Global Surveyor (MGS) spacecraft record the oval shadow of Phobos racing over western Xanthe Terra on August 26, 1999. The area imaged is about 250 kilometers across and is seen in panels from left to right as red filter, blue filter, and combined color composite views from the MGS wide-angle camera system. The three dark spots most easily seen in the red filter image are likely small fields of dark sand dunes on crater floors. Standing in the shadow of Phobos, you would see the Martian version of a solar eclipse!

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The Nucleus of Comet Tempel 1

Explanation: Approaching the nucleus of comet Tempel 1 at ten kilometers per second, the Deep Impact probe's targeting camera recorded a truly dramatic series of images. Successive pictures improve in resolution and have been composited here at a scale of 5 meters per pixel -- including images taken within a few meters of the surface moments before the July 4th impact. Analyzing the resulting cloud of debris, researchers are directly exploring the makeup of a comet, a primordial chunk of solar system material. Described as a recipe for primordial soup, the list of Tempel 1's ingredients - tiny grains of silicates, iron compounds, complex hydrocarbons, and clay and carbonates thought to require liquid water to form - might be more appropriate for a cosmic souffle, as the nucleus is apparently porous and fluffy. Seen here, Tempel 1's nucleus is about five kilometers long, with the impact site between the two large craters near the bottom.

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The Boomerang Nebula in Polarized Light

Explanation: Why did the Boomerang Nebula form? The symmetric cloud dubbed the Boomerang appears to have been created by a high-speed wind of gas and dust blowing from an aging central star at speeds of nearly 600,000 kilometers per hour. What confines the wind remains a mystery though -- it may be a central disk of dense gas or a central magnetic field. The rapid expansion itself, however, has cooled molecules in the nebular gas to about one degree above absolute zero - colder than even the cosmic background radiation - making it the coldest known region in the distant Universe. Shining with light from the central star reflected by dust, the frigid Boomerang Nebula is believed to be a star or stellar system evolving toward the planetary nebula phase. To help better understand the Boomerang's origin, astronomers are studying the above image taken in polarized light, color coded by an angular direction associated with the polarization. Different progenitor scenarios create different amounts and patterns of polarized light. The above image was taken by the Hubble Space Telescope's Advanced Camera for Surveys earlier this year. The Boomerang Nebula spans about one light year and lies about 5,000 light years away toward the constellation Centaurus.

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The Colliding Galaxies of NGC 520

Explanation: Is this one galaxy or two? The jumble of stars, gas, and dust that is NGC 520 is now thought to incorporate the remains of two separate galaxies. A combination of observations and simulations indicate the NGC 520 is actually the collision of two disk galaxies. Interesting features of NGC 520 include an unfamiliar looking tail of stars at the image bottom and a perhaps more familiar looking band of dust running diagonally across the image center. A similar looking collision might be expected were our disk Milky Way Galaxy to collide with our large galactic neighbor Andromeda (M31). The collision that defines NGC 520 started about 300 million years ago and continues today. Although the speeds of stars are fast, the distances are so vast that the interacting pair will surely not change its shape noticeably during our lifetimes. NGC 520, at visual magnitude 12, has been noted to be one of the brightest interacting galaxies on the sky, after interacting pairs of galaxies known as the Antennae. NGC 520 was imaged above in spectacular fashion by the Gemini Observatory in Hawaii, USA. Also known as Arp 157, NGC 520 lies about 100 million light years distant, spans about 100 thousand light years, and can be seen with a small telescope toward the constellation of the Fish (Pisces).

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Supernova Survivor

Explanation: Beginning with a full view of beautiful spiral galaxy M81, follow the insets (left, bottom, then right) to zoom in on a real survivor. Seen at the center of the final field on the right is a star identified as the survivor of a cosmic cataclysm -- the supernova explosion of its companion star. Light from the cosmic blast, likely triggered by the core collapse of a star initially more than 10 times as massive as the Sun, first reached Earth over 10 years ago and was cataloged as supernova SN 1993J. Though the supernova itself is no longer visible, light-echoes from dust in the region can still be seen near the companion, the first known survivor of a supernova in a binary star system. Astronomers believe that a substantial transfer of material to the surviving companion star during the last few hundred years before the stellar explosion can explain peculiarities seen in this supernova. After supernova SN 1987A in the Large Magellanic Cloud, SN 1993J in nearby M81 is the brightest supernova seen in modern times.

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IC 1396 in Cepheus

Explanation: Stunning emission nebula IC 1396 mixes glowing cosmic gas and dark dust clouds in the high and far off constellation of Cepheus. Energized by the bright, bluish central star seen here, this star forming region sprawls across hundreds of light-years -- spanning over three degrees on the sky while nearly 3,000 light-years from planet Earth. Among the intriguing dark shapes within IC 1396, the winding Elephant's Trunk nebula lies just below center. The gorgeous color view is a composition of digitized black and white photographic plates recorded through red and blue astronomical filters. The plates were taken using the Samuel Oschin Telescope, a wide-field survey instrument at Palomar Observatory, between 1989 and 1993.

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Fresh Tiger Stripes on Saturn's Enceladus

Explanation: The tiger stripes on Saturn's moon Enceladus might be active. Even today, they may be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Recent evidence for this has come from the robot Cassini spacecraft now orbiting Saturn. Cassini detected a marked increase in particle collisions during its July flyby only 270 kilometers over a South Polar region of Enceladus. Pictured above, a high resolution image of Enceladus is shown from the close flyby. The unusual surface features dubbed tiger stripes are visible on the left in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead.

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Globular Cluster 47 Tucanae from SALT

Explanation: Stars come in bunches. Of the over 200 globular star clusters that orbit the center of our Milky Way Galaxy, 47 Tucanae is the second brightest globular cluster, behind Omega Centauri. Known to some affectionately as 47 Tuc or NGC 104, it is only visible from Earth's Southern Hemisphere. It was therefore a fitting target for first light observations of the gigantic new 10-meter diameter Southern African Large Telescope (SALT) this past week. The resulting image is shown above. Light takes about 20,000 years to reach us from 47 Tuc which can be seen near the Small Magellanic Cloud toward the constellation of Tucana. The dynamics of stars near the center of 47 Tuc are not well understood, particularly why there are so few binary systems there.

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Comet Hale-Bopp Over Val Parola Pass

Explanation: Comet Hale-Bopp became much brighter than any surrounding stars. It was seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind struck expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

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X-Ray Portrait of Trumpler 14

Explanation: A wonder of planet Earth's southern sky, star cluster Trumpler 14 lies about nine thousand light-years away in the Carina complex -- a rich star forming region at the edge of a giant molecular cloud. This false-color x-ray portrait of Trumpler 14 from the orbiting Chandra Observatory spans over 40 light-years and reveals stunning details of a cluster with one of the highest concentrations of massive stars in the Galaxy. Profoundly affecting their environment, the hot cluster stars are themselves a mere one million years old. Energetic winds from the stars have cleared out a cavity in the dense cloud, filling it with shock heated, x-ray emitting gas. Still to come, the next few million years will see these stellar prodigies rapidly exhaust their nuclear fuel and explode in violent supernovae, flooding their cosmic neighborhood with gas enriched in heavy elements.

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One-Armed Spiral Galaxy NGC 4725

Explanation: While most spiral galaxies, including our own Milky Way, have two or more spiral arms, peculiar galaxy NGC 4725 has only one. In this false-color Spitzer Space Telescope infrared image, the galaxy's solo spira mirabilis is seen in red, highlighting the emission from dust clouds warmed by newborn stars. The blue color is light from NGC 4725's population of old stars. Also sporting a prominent ring and a central bar, this galaxy is over 100 thousand light-years across and lies 41 million light-years away in the well-groomed constellation Coma Berenices. Computer simulations of the formation of single spiral arms suggest that they can be either leading or trailing arms with respect to a galaxy's overall rotation.

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Crepuscular Rays Over Utah

Explanation: What could cause such rays of dark? Dark sky rays were caught in spectacular fashion earlier this month above Utah, USA. The cause is something surprisingly familiar: shadows. Clouds near the horizon can block sunlight from reflecting off air, making columns outward from the Sun appear unusually dark. Cloud shadows can be thought of as the complement of the more commonly highlighted crepuscular rays, also visible above, where sunlight pours though cloud holes. Sometimes, on the opposite side of the sky, anticrepuscular rays can also be seen.

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Albireo: A Bright and Beautiful Double

Explanation: Sometimes, even a small telescope can help unlock a hidden beauty of the heavens. Such is the case of the bright double star Albireo. Seen at even slight magnification, Albireo unfolds from a bright single point into a beautiful double star of strikingly different colors. At 380 light years distant, the two bright stars of Albireo are comparatively far from each other and take about 75,000 years to complete a single orbit. The brighter yellow star is itself a binary star system, but too close together to be resolved even with a telescope. Albireo, pictured above, is the fifth brightest star system toward the constellation of the Swan (Cygnus) and easily visible to the unaided eye.

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Muon Wobble Possible Door to Supersymmetric Universe

Explanation: How fast do fundamental particles wobble? A surprising answer to this seemingly inconsequential question has come out of Brookhaven National Laboratory in New York, USA and may not only indicate that the Standard Model of Particle Physics is incomplete but also that our universe is filled with a previously undetected type of fundamental particle. Specifically, the muon, a particle with similarities to a heavy electron, has had its relatively large wobble under scrutiny since 1999 in an experiment known as g-2 (gee-minus-two), pictured above. The result has galvanized other experimental groups around the world to confirm it, and pressures theorists to better understand it. The rate of wobble is sensitive to a strange sea of virtual particles that pop into and out of existence everywhere. The unexpected wobble rate may indicate that this sea houses virtual particles that include nearly invisible supersymmetric counterparts to known particles. If so, a nearly invisible universe of real supersymmetric particles might exist all around us.

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Barred Spiral Milky Way

Explanation: A recent survey of stars conducted with the Spitzer Space Telescope is convincing astronomers that our Milky Way Galaxy is not just your ordinary spiral galaxy anymore. Looking out from within the Galaxy's disk, the true structure of the Milky Way is difficult to discern. However, the penetrating infrared census of about 30 million stars indicates that the Galaxy is distinguished by a very large central bar some 27,000 light-years long. In fact, from a vantage point that viewed our galaxy face-on, astronomers in distant galaxies would likely see a striking barred spiral galaxy suggested in this artist's illustration. While previous investigations have identified a small central barred structure, the new results indicate that the Milky Way's large bar would make about a 45 degree angle with a line joining the Sun and the Galaxy's center. DON'T PANIC ... astronomers still place the Sun beyond the central bar region, about a third of the way in from the Milky Way's outer edge.

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NGC 281: The Pacman Nebula

Explanation: NGC 281 is a busy workshop of star formation. Prominent features include a small open cluster of stars, a diffuse red-glowing emission nebula, large lanes of obscuring gas and dust, and dense knots of dust and gas in which stars may still be forming. The open cluster of stars IC 1590 visible around the center has formed only in the last few million years. The brightest member of this cluster is actually a multiple-star system shining light that helps ionize the nebula's gas, causing the red glow visible throughout. The lanes of dust visible left of center are likely homes of future star formation. Particularly striking in the above photograph are the dark Bok globules visible against the bright nebula. The NGC 281 system, dubbed the Pacman nebula for its overall shape, lies about 10 thousand light years distant.

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A Lenticular Cloud Over Hawai'i

Explanation: Can a cloud do that? Actually, pictured above are several clouds all stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance. The above picture was taken near Mauna Kea, Hawaii, USA.