科普 神奇的宇宙----图片(每天更新中)

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Saturn from Below

Explanation: Swooping below Saturn, the Cassini spacecraft spied several strange wonders. Visible in the distance are some of the many complex rings that orbit the Solar System's second largest planet. In the foreground looms the gigantic world itself, covered with white dots that are clouds high in Saturn's thick atmosphere. Saturn's atmosphere is so thick that only clouds are visible. At the very South Pole of Saturn lies a huge vortex that is a hurricane-like storm showing no sign of dissipating. The robotic Cassini spacecraft took the above image in January from about one million kilometers out, resolving details about 50 kilometers across.

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The View from Everest

Explanation: What would it be like to stand atop the tallest mountain on Earth? To see a full panoramic vista from there, scroll right. Visible are snow peaked mountains near and far, tremendous cliffs, distant plateaus, the tops of clouds, and a dark blue sky. Mt. Everest stands 8.85 kilometers above sea level, roughly the maximum height reached by international airplane flights, but much less than the 300 kilometers achieved by a space shuttle. Hundreds of people have tried and failed to climb the behemoth by foot, a feat first accomplished successfully in 1953. About 1000 people have now made it to the summit. Roddy Mackenzie, who climbed the mountain in 1989, captured the above image. Mt. Everest lies in the Himalayan mountains in the country of Nepal. In the native language of Nepal, the mountain's name is "Sagarmatha" which means "forehead of the sky."

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Three Years of Saturn

Explanation: Using an image recorded just last month as a base, this composite illustration tracks the motion of bright Saturn as it wanders through planet Earth's night sky. Starting at the upper right, Saturn's position is shown about every two weeks beginning in August 2005 and projected through September 2008. Over the three year period, Saturn actually appears to reverse its general eastward (leftward) drift, tracing out three flattened curves. The periodic backwards or retrograde motion with respect to the background stars is a reflection of the motion of the Earth itself. Retrograde motion can be seen each time Earth overtakes and laps planets orbiting farther from the Sun, the Earth moving more rapidly through its own closer-in orbit. The Beehive star cluster in Cancer lies near the track at the upper right. Stars along the "backward question mark" at the head of Leo are in the left half of the frame. Saturn's position this month is near the right hand limit of the middle curve. Click on the picture to download and view the gif animation.

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Four Years of Saturn

Explanation: Saturn and its magnificent ring system can offer even casual astronomers the most memorable of telescopic sights. Wandering between Leo and Cancer this month, a bright Saturn is well placed for viewing in evening skies. But from our earthbound perspective, the tilt of Saturn's rings does change with time. In 1995 and 1996 the broad rings were edge-on and nearly invisible, gradually opening to a spectacular maximum tilt of about 27 degrees by 2003. This frame from a series of Saturn images beginning a year later, in 2004, and ending just last month shows the steady decrease in apparent tilt as the rings head toward another edge-on presentation in 2009. Saturn's south pole is toward the bottom. Click on the picture to view the sharp, color gif movie.

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Asteroid and Galaxy

Explanation: Apollo class asteroid 2006 VV2 flashed past planet Earth in late March, approaching to within 3.4 million kilometers or about 8.8 times the Earth-Moon distance. Due to the proximity of its orbit to Earth and its estimated diameter of over 1 kilometer, 2006 VV2 is classified as a Potentially Hazardous Asteroid. Telescopes large and small were trained on the much anticipated flyby, the closest for a known asteroid of comparable size until the year 2036. This composite telescopic view is from a series of images recorded over a period of about an hour on Mar. 28 from Vado, New Mexico. The asteroid begins near the center of the field and tracks down and to the left, apparently passing very near galaxy M81. Of course, along with its companion galaxy M82 on the right, M81 is really 12 million light years away, compared to the asteroid's range of a mere 15 light seconds.

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New Horizons at Io

Explanation: Spewed from a volcano, a complex plume rises over 300 kilometers above the horizon of Jupiter's moon Io in this image from cameras onboard the New Horizons spacecraft. The volcano, Tvashtar, is marked by the bright glow (about 1 o'clock) at the moon's edge, beyond the terminator or night/day shadow line. The shadow of Io cuts across the plume itself. Also capturing stunning details on the dayside surface, the high resolution image was recorded when the spacecraft was 2.3 million kilometers from Io. Later it was combined with lower resolution color data by astro-imager Sean Walker to produce this sharp portrait of the solar system's most active moon. Outward bound at almost 23 kilometers per second, the New Horizons spacecraft should cross the orbit of Saturn in June next year, and is ultimately destined to encounter Pluto in 2015.

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A Mysterious Hexagonal Cloud System on Saturn

Explanation: Why would clouds form a hexagon on Saturn? Nobody is yet sure. Originally discovered during the Voyager flybys of Saturn in the 1980s, nobody has ever seen anything like it anywhere else in the Solar System. If Saturn's South Pole wasn't strange enough with its rotating vortex, Saturn's North Pole might now be considered even stranger. The bizarre cloud pattern is shown above in a recent infrared image taken by the Saturn-orbiting Cassini spacecraft. The images show the stability of the hexagon even 20 years after Voyager. Movies of Saturn's North Pole show the cloud structure maintaining its hexagonal structure while rotating. Unlike individual clouds appearing like a hexagon on Earth, the Saturn cloud pattern appears to have six well defined sides of nearly equal length. Four Earths could fit inside the hexagon. Although full explanations are not yet available, planetary scientists are sure to continue to study this most unusual cloud formation for quite some time.

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An Active Sunspot Viewed Sideways

Explanation: Why are there dark spots on the sun? Although noted for thousands of years, sunspots have been known for decades to be regions of the Sun that are slightly depressed and cooled by the Sun's complex and changing magnetic field. High resolution pictures like the above image from Japan's new Sun-watching Hinode satellite, however, are helping to increase modern understanding. In the center of the above image is a sunspot, but not seen in the usual orientation --this sunspot is seen sideways. Of particular interest is erupting glowing gas that shows how the Sun's magnetic field comes right out of the spot center, but curves markedly around the spot edges. Better understanding of how the Sun ejects particles into space may result in more accurate predictions of solar storms that affect satellites, astronauts, and even power grids on Earth.

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Americans Defeat Russians in First Space Quidditch Match

Explanation: A historic first Space Quidditch match came to a spectacular conclusion last night as astronaut Michael Lopez-Alegria caught the Golden Snitch to give the Americans a hard fought victory over the Russians. "The Russians used brilliant strategy, but only NASA had the T2KQMU (Thunderbolt 2000 Quidditch Maneuvering Unit)," commented Lopez-Alegria, pictured above squeezing the elusive Golden Snitch in his left hand. Happy April Fools Day from the folks at APOD. In reality, Astronauts Jeff Wisoff and Lopez-Alegria are shown space-walking in 2001 October during a space shuttle mission to help build the International Space Station.

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Hale-Bopp: The Great Comet of 1997

Explanation: Ten short years ago, Comet Hale-Bopp rounded the Sun and offered a dazzling spectacle in planet Earth's night. This stunning view, recorded shortly after the comet's perihelion passage on April 1, 1997, features the memorable tails of Hale-Bopp -- a whitish dust tail and blue ion tail. Here, the ion tail extends well over ten degrees across the northern sky, fading near the double star clusters in Perseus, while the head of the comet lies near Almach, a bright star in the constellation Andromeda. Do you remember Hale-Bopp? The photographer's sons do, pictured in the foreground at ages 12 and 15. In all, Hale-Bopp was reported as visible to the naked eye from roughly late May 1996 through September 1997.

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Three Galaxies and a Comet

Explanation: Diffuse starlight and dark nebulae along the southern Milky Way arc over the horizon and sprawl diagonally through this gorgeous nightscape. The breath-taking mosaic spans a wide 100 degrees, with the rugged terrain of the Patagonia, Argentina region in the foreground. Along with the insider's view of our own galaxy, the image features our outside perspective on two irregular satellite galaxies - the Large and Small Magellanic Clouds. Recorded on January 28, the scene also captures the broad tail and bright coma of Comet McNaught, The Great Comet of 2007.

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NGC 1365: Majestic Island Universe

Explanation: Barred spiral galaxy NGC 1365 is truly a majestic island universe some 200,000 light-years across. Located a mere 60 million light-years away toward the chemical constellation Fornax, NGC 1365 is a dominant member of the well-studied Fornax galaxy cluster. This impressively sharp color image shows intense star forming regions at the ends of the bar and along the spiral arms, as well as details of dust lanes cutting across the galaxy's bright core. At the core lies a supermassive black hole. Astronomers think NGC 1365's prominent bar plays a crucial role in the galaxy's evolution, drawing gas and dust into a star-forming maelstrom and ultimately feeding material into the central black hole.

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Enceladus Creates Saturn's E Ring

Explanation: The active moon Enceladus appears to be making Saturn's E ring. An amazing picture showing the moon at work was taken late last year by the Saturn-orbiting Cassini spacecraft and is shown above. Enceladus is the dark spot inside the bright flare, right near the center of Saturn's E ring. Streams of ice and water vapor can be seen pouring off Enceladus into the E ring. The above bright image of the normally faint E-ring was made possible by aligning Cassini so that Saturn blocked the Sun. From that perspective, small ring particles reflect incoming sunlight more efficiently. Cassini has now been orbiting Saturn for almost three years, and is scheduled to swoop by the unexpectedly cryovolcanic Enceladus at least several more times.

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Bullet Pillars in Orion

Explanation: Why are bullets of gas shooting out of the Orion Nebula? Nobody is yet sure. First discovered in 1983, each bullet is actually about the size of our Solar System, and moving at about 400 km/sec from a central source dubbed IRc2. The age of the bullets, which can be found from their speed and distance from IRc2, is very young -- typically less than 1,000 years. As the bullets rip through the interior of the Orion Nebula, a small percentage of iron gas causes the tip of each bullet to glow blue, while each bullet leaves a tubular pillar that glows by the light of heated hydrogen gas. Pictured above, the Orion bullets were captured in unprecedented detail by the adaptive optics technology of the Gemini North telescope. M42, the Orion Nebula, is the closest major star forming region to us and filled with changing dust, gas, and bright stars. The Orion Nebula, is located about 1,500 light years away and can be seen with the unaided eye toward the constellation of Orion.

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Lisbon Moonset

Explanation: Brilliant Venus, a slender crescent Moon, and lights along the Ponte 25 de Abril glow against the western twilight in this lovely moonset scene from Lisbon, Portugal, recorded on March 20. In fact, such serene views were enjoyed across planet Earth this week, as the young Moon remained near the setting Sun following a partial solar eclipse, and Venus ruled as the evening star. Because of strong Earthshine - light from the sunlit Earth - even the Moon's night side is clearly visible in the picture. The Ponte 25 de Abril is a 2.3 kilometer long suspension bridge across the Tagus river, often compared to the Golden Gate bridge in San Francisco, USA.

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Touran Sunrise

Explanation: Clouds covered the eastern horizon on Monday, when the Sun rose over the expansive Touran Wildlife Reserve in northeastern Iran. Of course, on that day the Moon rose with the Sun, creating a widely enjoyed partial solar eclipse. Along with a mountainous horizon, the cloud cover lent a dramatic aspect to this eclipse sunrise and made it possible for astronomer Babak Tafreshi to record these telephoto images without using a filter. Advancing north in planet Earth's sky, the Sun itself was also approaching the equinox, the astronomical marker for the first day of northern hemisphere spring and the beginning of Norouz, the Persian New Year.

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Goa Silhouettes

Explanation: On Moonday, March 19, shortly before the equinox, locations in Asia and the Arctic were favoured by the New Moon's shadow during a partial solar eclipse. Although the view from Goa, India found the eclipsed Sun near the horizon, photographer Joerg Schoppmeyer was still able to capture this lovely image, combining celestial with terrestrial silhouettes. The next eclipse season will begin in late August this year, featuring a total lunar eclipse on August 28, and another partial solar eclipse on September 11. Compared to the March 19th eclipse, the September 11th eclipse will be seen on the other side of our fair planet, from parts of South America and Antarctica.

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Molecular Cloud Barnard 163

Explanation: It may look to some like a duck, but it lays stars instead of eggs. In the center of the above image lies Barnard 163, a nebula of molecular gas and dust so thick that visible light can't shine through it. With a wing span measured in light years, Barnard 163's insides are surely colder than its exterior, allowing conditions where gas can clump and eventually form stars. Barnard 163 lies about 3,000 light years from Earth toward the constellation of Cepheus the King. The red glow in the background results from IC 1396, a large emission nebula that houses the Elephant's Trunk Nebula. Finding Barnard 163 in an image of its greater emission nebula IC 1396 can be a challenge, but it's possible.

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A Blue Crescent Moon from Space

Explanation: What's happening to the Moon? Drifting around the Earth in 2006 July, astronauts from the International Space Station (ISS) captured a crescent Moon floating far beyond the horizon. The captured above image is interesting because part of the Moon appears blue, and because part of the moon appears missing. Both effects are created by the Earth's atmosphere. Air molecules more efficiently scatter increasingly blue light, making the clear day sky blue for ground observers, and the horizon blue for astronauts. Besides reflecting sunlight, these atmospheric molecules also deflect moonlight, making the lower part of the moon appear to fade away. As one looks higher in the photograph, the increasingly thin atmosphere appears to fade to black.

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Galaxy Group Hickson 44

Explanation: Galaxies, like stars, frequently form groups. A group of galaxies is a system containing more than two galaxies but less than the tens or hundreds typically found in a cluster of galaxies. A most notable example is the Local Group of Galaxies, which houses over 30 galaxies including our Milky Way, Andromeda, and the Magellanic Clouds. Pictured above is nearby compact group Hickson 44. This group is located about 60 million light-years away toward the constellation of Leo. Also known as the NGC 3190 Group, Hickson 44 contains several bright spiral galaxies and one bright elliptical galaxy on the upper left. The bright source on the upper right is a foreground star. Many galaxies in Hickson 44 and other compact groups are either slowly merging or gravitationally pulling each other apart.