科普 神奇的宇宙----图片(每天更新中)

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White Ridges on Mars

Explanation: What created these white ridges on Mars? The images showing the white ridges, including some of the highest resolution images ever taken from Martian orbit, were recorded last year by the Mars Reconnaissance Orbiter (MRO). A current leading hypothesis is that the white ridges formed as water flowed through underground cracks and bleached and hardened the edges of surrounding rocks. Over millions of years, surface winds eroded the darker rock leaving the raised white ridges. Such water-created light-colored markings are well known here on Earth. The hypothesis is particularly interesting as underground water could have helped to support microbial life on the red world. The above image resolves surface features as small as one meter across in Candor Chasma region of huge Valles Marineris on Mars.

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M16: Pillars of Creation

Explanation: It has become one of the most famous images of modern times. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillars' end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away. The pillars of creation were imaged recently by the orbiting Chandra X-ray Observatory, and it was found that most EGGS are not strong emitters of X-rays.

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Stereo Eros

Explanation: Get out your red/blue glasses and float next to asteroid 433 Eros, now over 220 million kilometers away! Orbiting the Sun once every 1.8 earth-years, asteroid Eros is a diminutive 40 x 14 x 14 kilometer world of undulating horizons, craters, boulders and valleys. Its unsettling scale and bizarre shape are emphasized in this picture - a mosaic of images from the NEAR Shoemaker spacecraft processed to yield a stereo anaglyphic view. Along with dramatic chiaroscuro, NEAR's 3-D imaging provided important measurements of the asteroid's landforms and structures, and clues to the origin of this city-sized chunk of solar system. The smallest features visible here are about 30 meters across. After spending a year in orbit around Eros, the historic Near Shoemaker spacecraft made the first ever landing on an asteroid's surface February 12, 2001.

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Polar Ring Galaxy NGC 2685

Explanation: NGC 2685 is a confirmed polar ring galaxy - a rare type of galaxy with stars, gas and dust orbiting in rings perpendicular to the plane of a flat galactic disk. The bizarre configuration could be caused by the chance capture of material from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable. In this fascinating view of the peculiar system also known as Arp 336 or the Helix galaxy, the strange, perpendicular rings are easy to trace as they pass in front of the galactic disk, along with other disturbed outer structures. NGC 2685 is about 50,000 light-years across and 40 million light-years away in the constellation Ursa Major.

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Planetary Nebula NGC 2440

Explanation: Planetary nebula NGC 2440 has an intriguing bow-tie shape in this stunning view from space. The nebula is composed of material cast off by a dying sun-like star as it enters its white dwarf phase of evolution. Details of remarkably complex structures are revealed within NGC 2440, including dense ridges of material swept back from the nebula's central star. Near the center of the view, the star itself is one of the hottest known, with a surface temperature of about 200,000 kelvins. About 4,000 light-years from planet Earth toward the nautical constellation Puppis, the nebula spans over a light-year and is energized by ultraviolet light from the central star. The false-color image was recorded earlier this month using the Hubble's Wide-Field Planetary Camera 2(WFPC2), demonstrating still impressive imaging capabilities following the failure of the Advanced Camera for Surveys.

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The Rosette Nebula

Explanation: Would the Rosette Nebula by any other name look as sweet? The bland New General Catalog designation of NGC 2237 doesn't appear to diminish the appearance of the this flowery emission nebula. Inside the nebula lies an open cluster of bright young stars designated NGC 2244. These stars formed about four million years ago from the nebular material and their stellar winds are clearing a hole in the nebula's center, insulated by a layer of dust and hot gas. Ultraviolet light from the hot cluster stars causes the surrounding nebula to glow. The Rosette Nebula spans about 100 light-years across, lies about 5000 light-years away, and can be seen with a small telescope towards the constellation of Monoceros.

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Vela Supernova Remnant in Visible Light

Explanation: The explosion is over but the consequences continue. About eleven thousand years ago a star in the constellation of Vela could be seen to explode, creating a strange point of light briefly visible to humans living near the beginning of recorded history. The outer layers of the star crashed into the interstellar medium, driving a shock wave that is still visible today. A roughly spherical, expanding shock wave is visible in X-rays. The above image captures much of that filamentary and gigantic shock in visible light, spanning almost 100 light years and appearing twenty times the diameter of the full moon. As gas flies away from the detonated star, it decays and reacts with the interstellar medium, producing light in many different colors and energy bands. Remaining at the center of the Vela Supernova Remnant is a pulsar, a star as dense as nuclear matter that completely rotates more than ten times in a single second.

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Io: The Prometheus Plume

Explanation: What's happening on Jupiter's moon Io? Two sulfurous eruptions are visible on Jupiter's volcanic moon Io in this color composite image from the robotic Galileo spacecraft that orbited Jupiter from 1995 to 2003. At the image top, over Io's limb, a bluish plume rises about 140 kilometers above the surface of a volcanic caldera known as Pillan Patera. In the image middle, near the night/day shadow line, the ring shaped Prometheus plume is seen rising about 75 kilometers above Io while casting a shadow below the volcanic vent. Named for the Greek god who gave mortals fire, the Prometheus plume is visible in every image ever made of the region dating back to the Voyager flybys of 1979 - presenting the possibility that this plume has been continuously active for at least 18 years. The above digitally sharpened image was originally recorded in 1997 on June 28 from a distance of about 600,000 kilometers.

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Stars of the Galactic Center

Explanation: The center of our Milky Way Galaxy is hidden from the prying eyes of optical telescopes by clouds of obscuring dust and gas. But in this stunning vista, the Spitzer Space Telescope's infrared cameras, penetrate much of the dust revealing the stars of the crowded galactic center region. A mosaic of many smaller snapshots, the detailed, false-color image shows older, cool stars in bluish hues. Reddish glowing dust clouds are associated with young, hot stars in stellar nurseries. The galactic center lies some 26,000 light-years away, toward the constellation Sagittarius. At that distance, this picture spans about 900 light-years.

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Ptolemaeus, Alphonsus and Arzachel

Explanation: These three ancient, large impact craters lie on the north eastern shores of Mare Nubium, the lunar Sea of Clouds. Along the top of the stark mosaic (left to right) are the namesakes of Ptolemaeus, Alphonsus and Arzachel. The picture offers a remarkably detailed view of the well-studied region with shadows emphasizing the large crater central peaks and slumping walls. Careful examination also reveals the 110 kilometer long Straight Wall, a fault 200-300 meters high, and the intriguing Davy crater chain. Overall, the striking moonscape is similar to the final images recorded by the Ranger 9 spacecraft, before it crashed into the 108 kilometer wide crater Alphonsus in March of 1965.

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Galaxies Away

Explanation: This stunning group of galaxies is far, far away - about 450 million light-years from planet Earth - cataloged as galaxy cluster Abell S0740. Dominated by the cluster's large central elliptical galaxy (ESO 325-G004), this sharp Hubble view takes in a remarkable assortment of galaxy shapes and sizes with only a few spiky foreground stars scattered through the field. The giant elliptical galaxy spans over 100,000 light years and contains about 100 billion stars, comparable in size to our own spiral Milky Way. The Hubble data reveal a wealth of detail in even these distant galaxies, including magnificent arms and dust lanes, star clusters, ring structures, and gravitational lensing arcs.

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Liquid Lakes on Saturn's Titan

Explanation: Why would some regions on Titan reflect very little radar? The leading explanation is that these regions are lakes, possibly composed of liquid methane. The above image is a false-color synthetic radar map of a northern region of Titan taken during a flyby of the cloudy moon by the robotic Cassini spacecraft last July. On this map, which spans about 150 kilometers across, dark regions reflect relatively little of the broadcast radar signal. Images like this show Titan to be only the second body in the Solar System to possess liquids on the surface. Future observations from Cassini during Titan flybys will further test the methane lake hypothesis, as comparative wind effects on the regions are studied.

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Sun Storm: A Coronal Mass Ejection

Explanation: What's happening to our Sun? Another Coronal Mass Ejection (CME)! The Sun-orbiting SOHO spacecraft has imaged many erupting filaments lifting off the active solar surface and blasting enormous bubbles of magnetic plasma into space. Direct light from the sun is blocked in the inner part of the above image, taken in 2002, and replaced by a simultaneous image of the Sun in ultraviolet light. The field of view extends over two million kilometers from the solar surface. While hints of these explosive events, called coronal mass ejections or CMEs, were discovered by spacecraft in the early 70s, this dramatic image is part of a detailed record of this CME's development from the presently operating SOHO spacecraft. Near the minimum of the solar activity cycle CMEs occur about once a week, but near solar maximum rates of two or more per day are typical. Strong CMEs may profoundly influence space weather. Those directed toward our planet can have serious effects.

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Shadow of a Martian Robot

Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity and sister robot Spirit have been probing the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured above, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Opportunity and Spirit have now spent over three years exploring the red world, find new clues into the wet ancient past of our Solar System's second most habitable planet.

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Alborz Mountains in Moonlight

Explanation: On January 25th, light from a first quarter Moon illuminated this dreamlike landscape looking across the rugged, snow-covered peaks of the Alborz Mountain Range in northern Iran. The stunning sky is filled with stars, including the yellow-tinged Betelgeuse at the shoulder of Orion. Sirius, alpha star of Canis Major and the brightest star in planet Earth's night, stands above and left of picture center. The eerie glow along the Haraz valley in the foreground is light from cars traveling a highway leading from Tehran to the Caspian Sea.

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Flame Nebula Close-Up

Explanation: Of course, the Flame Nebula is not on fire. Also known as NGC 2024, the nebula's suggestive reddish color is due to the glow of hydrogen atoms at the edge of the giant Orion molecular cloud complex some 1,500 light-years away. The hydrogen atoms have been ionized, or stripped of their electrons, and glow as the atoms and electrons recombine. But what ionizes the hydrogen atoms? In this close-up view, a dark lane of absorbing interstellar dust stands out in silhouette against the hydrogen glow and actually hides the true source of the Flame Nebula's energy from optical telescopes. Behind the dark lane lies a cluster of hot, young stars, seen at infrared wavelengths through the obscuring dust. A young, massive star in that cluster is the likely source of energetic ultraviolet radiation that ionizes the hydrogen gas in the Flame Nebula.

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A Tail of Two Hemispheres

Explanation: By January 19/20 Comet McNaught's magnificent dust tail stretched for about 150 million kilometers (~1 AU), requiring images from both southern and northern hemispheres of planet Earth to take it all in. Two such views - from Cerro Paranal in Chile (left) and the Carnic Alps in Italy - are combined in this unique graphic that also outlines a perspective view of the comet's orbit (dotted line) and relative position of the Sun. Driven by solar radiation pressure the dust tail initially points away from the Sun, but also trails outside the comet's orbit. Astronomers try to account for the complex structure along the tail, including the pronounced striations, by considering forces acting on the dust (e.g. gravity, solar wind and radiation) as well as the release time and size of the dust grains. In the diagram, the modeled location of dust grains released at approximately the same time relative to perihelion passage, synchrones, are shown as dashed lines. The location of grains of similar size, syndynes, are shown as solid lines.

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Cassini Crosses Saturn's Ring Plane

Explanation: What would the rings of Saturn look like if you passed right through the ring plane? To find out, NASA aimed cameras from the Cassini spacecraft right at Saturn's rings as the robotic explorer passed from the sunlit side of the rings to the shadowed side. Resulting images from a vantage point outside the rings and most moons, but inside the orbit of Titan, have been gathered together in the above time-lapse movie. The dramatic movie demonstrates that ring particle density and reflectivity makes some parts of the shadowed side nearly the photographic negative of the sunlit side, but nearly empty regions remain continually dark. Visible also are Saturn-orbiting moons Enceladus, Mimas, Janus, Epimetheus, Prometheus, and Pandora. The extreme thinness of Saturn's rings can be appreciated from frames taken near the crossing time.

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Thor's Helmet from CFHT

Explanation: NGC 2359 is a striking emission nebula with an impressive popular name - Thor's Helmet Sure, its suggestive winged appearance might lead some to refer to it as the "duck nebula", but if you were a nebula which name would you choose? By any name NGC 2359 is a bubble-like nebula some 30 light-years across, blown by energetic winds from an extremely hot star seen near the center and classified as a Wolf-Rayet star. Wolf-Rayet stars are rare massive blue giants which develop stellar winds with speeds of millions of kilometers per hour. Interactions with a nearby large molecular cloud are thought to have contributed to this nebula's more complex shape and curved bow-shock structures. NGC 2359 is about 15,000 light-years distant toward the constellation Canis Major.

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Saturn's Hyperion: A Moon with Odd Craters

Explanation: What lies at the bottom of Hyperion's strange craters? Nobody knows. To help find out, the robot Cassini spacecraft now orbiting Saturn swooped past the sponge-textured moon in late 2005 and took an image of unprecedented detail. That image, shown above in false color, shows a remarkable world strewn with strange craters and a generally odd surface. The slight differences in color likely show differences in surface composition. At the bottom of most craters lies some type of unknown dark material. Inspection of the image shows bright features indicating that the dark material might be only tens of meters thick in some places. Hyperion is about 250 kilometers across, rotates chaotically, and has a density so low that it might house a vast system of caverns inside.