科普 神奇的宇宙----图片(每天更新中)

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Steep Cliffs on Mars

Explanation: Vertical cliffs of nearly two kilometers occur near the North Pole of Mars. Also visible in the above image of the Martian North Polar Cap are red areas of rock and sand, white areas of ice, and dark areas of unknown composition but hypothesized to be volcanic ash. The cliffs are thought to border volcanic caldera. Although the sheer drop of the Martian cliffs is extreme, the drop is not as deep as other areas in our Solar System, including the 3.4-kilometer depth of Colca Canyon on Earth and the 20 kilometer depth of Verona Rupes on Uranus' moon Miranda. The above image, digitally reconstructed into a perspective view, was taken by the High Resolution Stereo Camera on board the ESA's robotic Mars Express spacecraft currently orbiting Mars.

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Jumbled Galaxy Centaurus A

Explanation: At the center of this sharp skyscape, Centaurus A seems to be a fantastic jumble of old yellow stars, young blue star clusters, and imposing dark dust lanes. Spanning over 60,000 light-years, the peculiar elliptical galaxy is apparently the result of a collision of two otherwise normal galaxies. The left over cosmic debris is steadily being consumed by a black hole with a billion times the mass of the Sun which lies at the center of Centaurus A. It's likely that such black hole central engines generate the radio, X-ray, and gamma-ray energy radiated by Centaurus A and other active galaxies. For an active galaxy Centaurus A is close, a mere 10 million light-years away, and is well-studied by earthbound astronomers.

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Cat's Eye Wide and Deep

Explanation: The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its more familiar outlines are seen in the brighter central region of this impressive wide-angle view. But the composite image also combines many short and long exposures to reveal the nebula's extremely faint halo. At an estimated distance of 3,000 light-years, the faint outer halo is over 5 light-years across. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. More recently, some planetary nebulae are found to have halos like this one, likely formed of material shrugged off during earlier episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years. Visible on the right, some 50 million light-years beyond the Cat's Eye, lies spiral galaxy NGC 6552.

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A Visit from Atlantis

Explanation: This remarkable image of the space shuttle orbiter Atlantis docked with the International Space Station (ISS) was taken at a range of 190 nautical miles. To record the fast moving pair, last week astronomers at Clay Center Observatory, near Boston, Massachusetts, planet Earth, used a satellite tracking system and 25-inch diameter telescope in combination with a digital video camera. In the sharp picture, Atlantis is below and left of center. The aft view shows three main engines just below its vertical tail glinting in the sunlight. With the Sun shining from below, the body of the orbiter casts a long shadow across the ISS itself and impressive details of the ISS solar arrays used for power generation are easily visible. The large set of solar arrays installed at the lower right was delivered during this visit from Atlantis.

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Neon Saturn

Explanation: If seen in the right light, Saturn glows like a neon sign. Although Saturn has comparatively little of the element neon, a composite image false-colored in three bands of infrared light highlights features of the giant ringed planet like a glowing sign. At the most blue band of the infrared light featured, false-colored blue in the above image, Saturn itself appears dark but Saturn's thin rings brightly reflect light from our Sun. Conversely, Saturn's B ring is so thick that little reflected light makes it through, creating a dark band between Saturn's A and C rings. At the most red band of the infrared, false-colored red above, Saturn emits a surprisingly detailed thermal glow, indicating planet-wide bands, huge hurricane-like storms, and a strange hexagon-shaped cloud system around the North Pole. In the middle infrared band, false-colored green, the sunlit side of Saturn's atmosphere reflects brightly. The above image was obtained in late February by the robotic Cassini spacecraft orbiting about 1.6 million kilometers out from Saturn.

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Wisps of the Iris Nebula

Explanation: Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged as NGC 7023, this is not the only nebula in the sky to evoke the imagery of flowers. Still, this beautiful digital image shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a massive, hot, young star in its formative years. Central filaments of cosmic dust glow with a reddish photoluminescence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Yet the dominant color of the central nebula is blue, characteristic of dust grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are present on the left of the image, and lead the eye to see other convoluted and fantastic shapes. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. As shown here, the bright blue portion of the Iris Nebula is about six light-years across.

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The International Space Station Expands Again

Explanation: The developing International Space Station (ISS) has changed its appearance again. During the past week, the Space Shuttle Atlantis visited the ISS and added pieces of the Integrated Truss Structure that mirrored those added in September 2006, including a second impressively long array of solar panels. The entire array of expansive solar panels are visible at the edges of the above image taken by the Shuttle Atlantis Crew after leaving the ISS to return to Earth. The world's foremost space outpost can be seen developing over the past several years by comparing the above image to past images. Also visible above are many different types of modules, a robotic arm, another impressive set of solar panels, and a supply ship. Construction began on the ISS in 1998.

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All the Colors of the Sun

Explanation: It is still not known why the Sun's light is missing some colors. Shown above are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device. The above spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our yellow-appearing Sun emits light of nearly every color, it does indeed appear brightest in yellow-green light. The dark patches in the above spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below. Since different types of gas absorb different colors of light, it is possible to determine what gasses compose the Sun. Helium, for example, was first discovered in 1870 on a solar spectrum and only later found here on Earth. Today, the majority of spectral absorption lines have been identified - but not all.

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3D Barringer Meteorite Crater

Explanation: Barringer Meteorite Crater, near Winslow, Arizona, is one of the best known impact craters on planet Earth. View this color stereo anaglyph with red/blue glasses to get a dramatic sense of the crater's dimensions -- one mile wide, and up to 570 feet deep. (A cross-eyed stereo pair is available here.) Historically, this crater is the first recognized to be caused by an impact rather than a volcanic eruption. Modern research indicates that the impactor responsible, a 300,000 ton nickel-iron meteor, struck some 50,000 years ago. Estimates suggest that it was about 130 feet across and was traveling over 26,000 miles per hour. For comparison, the asteroid or comet impactor that created the Chicxulub crater 65 million years ago, and is thought to have caused the extinction of the dinosaurs, was 6 to 12 miles across.

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Small Worlds Ceres and Vesta

Explanation: Ceres and Vesta are, respectively, only around 950 kilometers and 530 kilometers in diameter - about the size of Texas and Arizona. But they are two of the largest of over 100,000 minor bodies orbiting in the main asteroid belt between Mars and Jupiter. These remarkably detailed Hubble Space Telescope images show brightness and color variations across the surface of the two small worlds. The variations could represent large scale surface features or areas of different compositon. The Hubble image data will help astronomers plan for a visit by the asteroid-hopping Dawn spacecraft, scheduled for launch on July 7 and intended to orbit first Vesta and then Ceres after a four year interplanetary cruise. Though Shakespeare might not have been impressed, nomenclature introduced by the International Astronomical Union in 2006 classifies nearly spherical Ceres as a dwarf planet.

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Stars and the Solstice Sun

Explanation: If you could turn off the atmosphere's ability to scatter overwhelming sunlight, today's daytime sky might look something like this ... with the Sun surrounded by the stars of the constellations Taurus and Gemini. Of course, today is the Solstice. Traveling along the ecliptic plane, the Sun is at its northernmost position in planet Earth's sky, marking the astronomical beginning of summer in the north. Accurate for the exact time of today's Solstice, this composite image also shows the Sun at the proper scale (about the angular size of the Full Moon). Open star cluster M35 is to the Sun's left, and the other two bright stars in view are Mu and Eta Geminorum. Digitally superimposed on a nighttime image of the stars, the Sun itself is a composite of a picture taken through a solar filter and a series of images of the solar corona recorded during the solar eclipse of February 26, 1998 by Andreas Gada.

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A Daylight Eclipse of Venus

Explanation: Something was about to happen. Just two days ago, two of the three celestial objects easily visible during the day appeared to collide. But actually, Earth's Moon passed well in front of the distant planet Venus. The occultation was caught from Switzerland in the hours before sunset. Moments after this image was taken, the Moon, visible as the crescent on the right of the above image, eclipsed Venus, appearing near half phase on the lower left. Clouds that once threatened to obscure the whole event, were visible on the far left. About 90 minutes later, Venus re-appeared just to the right of the bright crescent.

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Eris: More Massive than Pluto

Explanation: Eris, a dwarf planet currently orbiting the Sun at about twice Pluto's distance, has been measured to have about 27 percent more mass than Pluto. The mass was calculated by timing the orbit of Eris' moon Dysnomia. Images taken with a ground-based Keck telescope, when combined with existing images taken by Hubble Space Telescope, show that Dysnomia has a nearly circular orbit lasting about 16 days. Cataloged as 2003 UB313 only a year ago, infrared images also showed previously that Eris is actually larger in diameter than Pluto. The plane of Eris' orbit is well out of the plane of the Solar System's planets. In the above drawing, a scientific artist has imagined Eris and Dysnomia orbiting our distant Sun. No space missions are currently planned to Eris, although the robotic New Horizons spacecraft bound for Pluto has recently passed Jupiter.

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Monitoring M2-9

Explanation: Exploring the myriad shapes found in the cosmic zoo of planetary nebulae, some astronomers have focused on the intriguing example of M2-9. About 2,100 light-years away and over one light-year across, M2-9 is known as a twin jet or butterfly nebula in reference to its striking bipolar symmetry. Monitoring M2-9 over many years from ground based telescopes has revealed the dramatic west to east (left to right) progression of features illustrated in this collage. The apparent motion could well be caused by an energetic rotating beam sweeping across the nebular material. Astronomers argue that the beam is collimated by interacting stellar winds in a double star system at the center of M2-9. The binary system of a giant star and hot white dwarf star orbit each other about once every 120 years. Click on the image to watch an animated gif of M2-9.

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Analemma over Ukraine

Explanation: If you took a picture of the Sun at the same time each day, would it remain in the same position? The answer is no, and the shape traced out by the Sun over the course of a year is called an analemma. The Sun's apparent shift is caused by the Earth's motion around the Sun when combined with the tilt of the Earth's rotation axis. The Sun will appear at its highest point of the analemma during summer and at its lowest during winter. Analemmas created from different Earth latitudes would appear at least slightly different, as well as analemmas created at a different time each day. The analemma pictured to the left was built up by Sun photographs taken from 1998 August through 1999 August from Ukraine. The foreground picture from the same location was taken during the early evening in 1999 July.

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Lunar Orbiter Views Crater Copernicus

Explanation: To prepare for the Apollo landings, five Lunar Orbiter spacecraft were launched during 1966 and 1967 to gather detailed images of our fair planet's large, natural satellite. Dramatic views returned by the spacecraft cameras included this stark moonscape. The mosaic of 93 kilometer wide impact crater Copernicus features central peaks rising above the crater floor and rugged crater walls.

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Messier 96

Explanation: Dust lanes seem to swirl around the core of Messier 96 in this colorful, detailed portrait of the beautiful island universe. Of course M96 is a spiral galaxy, and counting the faint arms extending beyond the brighter central region it spans 100 thousand light-years or so, about the size of our own Milky Way. M96 is known to be 38 million light-years distant, a dominant member of the Leo I galaxy group. Background galaxies and smaller Leo I group members can be found by examining the picture, but accomplished astro-imager Adam Block notes he is most intrigued by the edge-on spiral galaxy that apparently lies behind the outer spiral arm near the 10 o'clock position. The edge-on spiral appears to be about 1/5 the size of M96. If the spiral is similar in actual size to M96, then it lies about 5 times farther away.

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Warped Sky: Star Trails Panorama

Explanation: What's happened to the sky? A time warp, of sorts, and a digital space warp too. The time warp occurs because the above image captured in a single frame a four hour exposure of the night sky. Prominent and picturesque star trails are visible. The space warp occurs because the above image is actually a full 360 degree panorama, horizontally compressed to fit your browser. As the Earth rotated, stars appeared to circle both the South Celestial Pole, on the left, and the North Celestial Pole, which occurs just below the horizon on the right. The above image captured the sky over Mudgee, New South Wales, Australia, including the domes of two large telescopes artificially lit by red light. A horizontally unwarped image is visible by clicking on the above image.

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vdB 152: Reflection Nebula in Cepheus

Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula vdB 152 really is very faint. It lies about 1400 light-years away, along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of cosmic dust in the region block light from background stars or scatter light from the embedded bright star (top) giving parts of the nebula a characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through interstellar space is very different from the cloud's velocity. This deep telescopic image spans about 7 light-years at the estimated distance of vdB 152.

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Shuttle Plume

Explanation: What kind of cloud is that? Not a naturally occurring one. Pictured above is the drifting smoke plume left over from last Friday's launch of the Space Shuttle Atlantis. The twisted plume was captured shortly after launch high above NASA's massive Vehicle Assembly Building, the largest single story building in the world. Rockets frequently create picturesque plumes during launch. The Space Shuttle is currently visiting the International Space Station and delivering a new backbone truss segment to the continually developing and occupied spaceport. This trip, officially labeled STS-117, is the 118th space shuttle flight overall and the 28th for the Atlantis Orbiter.