科普 神奇的宇宙----图片(每天更新中)

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A Robot's Shadow on Asteroid Itokawa

Explanation: What's that unusual looking spot on asteroid Itokawa? It's the shadow of the robot spacecraft Hayabusa that took the image. Japan's Hayabusa mission arrived at the asteroid in early September and has been imaging and maneuvering around the floating space mountain ever since. The above picture was taken earlier this month. Asteroid Itokawa spans about 300 meters. One scientific goal of the Hayabusa mission is to determine out how much ice, rock and trace elements reside on the asteroid's surface, which should give indications about how asteroids and planets formed in the early Solar System. A can-sized robot MINERVA that was scheduled to hop around the asteroid's surface has not, so far, functioned as hoped. Later this month, Hayabusa is scheduled to descend to asteroid Itokawa and collect surface samples in a return capsule. In December, Hayabusa will fire its rockets toward Earth and drop the return capsule down to Earth's Australian outback in 2007 June.

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M78 and Reflecting Dust Clouds in Orion

Explanation: An eerie blue glow and ominous columns of dark dust highlight M78 and other bright reflection nebula in the constellation of Orion. The dark filamentary dust not only absorbs light, but also reflects the light of several bright blue stars that formed recently in the nebula. Of the two reflection nebulas pictured above, the more famous nebula is M78, on the upper right, while NGC 2071 can be seen to its lower left. The same type of scattering that colors the daytime sky further enhances the blue color. M78 is about five light-years across and visible through a small telescope. M78 appears above only as it was 1600 years ago, however, because that is how long it takes light to go from there to here. M78 belongs to the larger Orion Molecular Cloud Complex that contains the Great Nebula in Orion and the Horsehead Nebula.

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Endeavour to Orbit

Explanation: Birds don't fly as high. Airplanes don't go as fast. The Statue of Liberty weighs less. No species other than human can even comprehend what is going on, nor could any human just a millennium ago. The launch of a rocket bound for space is an event that inspires awe and challenges description. The exhaust column pictured is from the Space Shuttle Endeavour after last week's night launch to visit the International Space Station. Endeavour's rocket engines create the dramatic glow from above the clouds. From a standing start, the two million kilogram rocket ship left to circle the Earth where the outside air is too thin to breathe and where there is little noticeable onboard gravity. Rockets bound for space are now launched from somewhere on Earth about once a week.

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A Taurid Meteor Fireball

Explanation: Have you ever seen a very bright meteor? Unexpected, this year's Taurid meteor shower resulted in numerous reports of very bright fireballs during the nights surrounding Halloween. Pictured above, a fireball that momentarily rivaled the brightness of the full Moon was caught over Cerro Pachon, Chile by a continuous sky monitor on November 1. Several bright Taurid fireballs are identifiable on the sky movie for that night. The above image is a digitally rectangled version of a circular fisheye frame and shows the entire sky, horizon to horizon. The bright meteor was seen swooping between the directions of the Large and Small Magellanic Clouds. The band of the Milky Way Galaxy crosses the horizon behind the dome of the 8-meter Gemini South Telescope. Taurid meteor fireballs are likely pebble sized debris left by Comet Encke. Over the next week the Leonids meteor shower will peak, although they will need to be seen through the glare of a nearly full Moon.

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Surveyor Hops

Explanation: This panorama of the cratered lunar surface was constructed from images returned by the US Surveyor 6 lander. Surveyor 6 was not the first spacecraft to accomplish a soft landing on the Moon ... but it was the first to land and then lift off again! After the spacecraft touched down near the center of the Moon's nearside in November of 1967, NASA controllers commanded it to hop. Briefly firing its rocket engine and lifting itself some 4 meters above the surface, the Surveyor moved about 2.5 meters to one side before setting down again. The hopping success of Surveyor 6 essentially marked the completion of the Surveyor series main mission - to determine if the lunar terrain was safe for the planned Apollo landings.

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Mountains of Creation

Explanation: This fantastic skyscape lies at the eastern edge of giant stellar nursery W5, about 7,000 light-years away in the constellation Cassiopeia. An infrared view from the Spitzer Space Telescope, it features interstellar clouds of cold gas and dust sculpted by winds and radiation from a hot, massive star outside the picture (just above and to the right). Still swaddled within the cosmic clouds, newborn stars are revealed by Spitzer's penetrating gaze, their formation also triggered by the massive star. Fittingly dubbed "Mountains of Creation", these interstellar clouds are about 10 times the size of the analogous Pillars of Creation in M16, made famous in a 1995 Hubble Space Telescope view. W5 is also known as IC 1848 and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae. The Spitzer image spans about 70 light-years at the distance of W5.

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Gravitational Tractor

Explanation: How would you change the course of an Earth-threatening asteroid? One idea - a massive spacecraft that uses gravity as a towline - is illustrated in this dramatic artist's view of a gravitational tractor in action. In the hypothetical scenario worked out by Edward Lu and Stanley Love at NASA's Johnson Space Center, a 20 ton nuclear-electric spacecraft tows a 200 meter diameter asteroid by simply hovering near the asteroid. The spacecraft's ion drive thrusters are canted away from the surface. The steady thrust would gradually and predictably alter the course of the tug and asteroid, coupled by their mutual gravitational attraction. While it sounds like the stuff of science fiction, ion drives do power existing spacecraft and a gravitational tractor would work regardless of the asteroid's structure or surface properties.

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A Solar Prominence from SOHO

Explanation: What happened to the Sun? Nothing very unusual: the strange-looking solar appendage on the lower left is actually just a spectacular looking version of a common solar prominence. A solar prominence is a cloud of solar gas held above the Sun's surface by the Sun's magnetic field. Pictured above in 2002 October, NASA's Sun-orbiting SOHO spacecraft imaged an impressively large prominence hovering over the surface, informally dubbed a flame. Over 40 Earths could line up along the vast length of the fireless flame of hovering hot gas. A quiescent prominence typically lasts about a month, and may erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar System. Although somehow related to the Sun's changing magnetic field, the energy mechanism that creates and sustains a Solar prominence is still a topic of research.

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NGC 7635: The Bubble Nebula

Explanation: It's the bubble versus the cloud. NGC 7635, the Bubble Nebula, is being pushed out by the stellar wind of massive central star BD+602522. Next door, though, lives a giant molecular cloud, visible above to the lower right. At this place in space, an irresistible force meets an immovable object in an interesting way. The cloud is able to contain the expansion of the bubble gas, but gets blasted by the hot radiation from the bubble's central star. The radiation heats up dense regions of the molecular cloud causing it to glow. The Bubble Nebula, pictured above in scientifically mapped colors to bring up contrast, is about 10 light-years across and part of a much larger complex of stars and shells. The Bubble Nebula can be seen with a small telescope towards the constellation of Cassiopeia.

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The Drifts of Mars

Explanation: What would it be like to walk across Mars? The robot Opportunity rover is currently experiencing what it is like to roll across part of the red planet. It's not always easy -- the rover is being instructed to dodge the deeper drifts of dark sand. During its exploration of Erebus Crater, the rover stopped and took the above picture. Inside this part of Erebus Crater, the surface of mars is covered not only by dark sand but also light outcrops of rock. Scattered across the exposed rock are numerous small round pebbles known as blueberries . Typically smaller than marbles, these unexpected and unusual rocks likely formed by accretion in an ancient wet environment. Also visible are some strange protruding edges known as razorbacks. The above image was taken early last month.

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A Sunspot Up Close

Explanation: Why would a small part of the Sun appear slightly dark? Visible above is a close-up picture of a sunspot, a depression on the Sun's face that is slightly cooler and less luminous than the rest of the Sun. The Sun's complex magnetic field creates this cool region by inhibiting hot material from entering the spot. Sunspots can be larger than the Earth and typically last for only a few days. This high-resolution picture also shows clearly that the Sun's face is a bubbling sea of separate cells of hot gas. These cells are known as granules. A solar granule is about 1000 kilometers across and lasts about 10 minutes. After that, many granules end up exploding.

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Aurora from Space

Explanation: From the ground, spectacular auroras seem to dance high above. But the International Space Station (ISS) orbits at nearly the same height as many auroras, sometimes passing over them, and sometimes right through them. Still, the auroral electron and proton streams pose no direct danger to the ISS. In 2003, ISS Science Officer Don Pettit captured the green aurora, pictured above in a digitally sharpened image. From orbit, Pettit reported that changing auroras appeared to crawl around like giant green amoebas. Over 300 kilometers below, the Manicouagan Impact Crater can be seen in northern Canada, planet Earth.

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M78: Stardust and Starlight

Explanation: Interstellar dust clouds and bright nebulae abound in the fertile constellation of Orion. One of the brightest, M78, is just below center in this sharp widefield view, covering an area north of Orion's belt. At a distance of about 1,500 light-years, the bluish nebula itself is about 5 light-years across. Its blue tint is due to dust preferentially reflecting the blue light of hot, young stars in the region. Dark dust lanes and other nebulae can easily be traced through this gorgeous skyscape that also includes the remarkable McNeil's Nebula -- a newly recognized nebula associated with the formation of a sun-like star.

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Possible Pluto Moons

Explanation: In 1930, tiny, icy world Pluto was discovered orbiting in the distant solar system. In 1978, its relatively large companion Charon was detected by ground-based observations. This year, the Hubble Space Telescope may well have detected two further members of the Pluto system. Provisionally designated S/2005 P1 and S/2005 P2, the two potential new moons are seen orbiting in a counterclockwise direction about 44,000 kilometers (27,000 miles) from Pluto in these deep Hubble images recorded only three days apart. The diminutive and faint companions are also apparently detected on Hubble images of Pluto from 2002, but this coming February follow-up observations are planned in an effort to confirm the discovery of the new moons. Compared to Pluto's and Charon's diameters of 2,300 and 1,300 kilometers respectively, these moons are estimated to be between 60 and 200 kilometers across. Well within the Kuiper Belt, an extensive region beyond the orbit of Neptune, the Pluto system could be the first quadruple Kuiper Belt object known.

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Epimetheus and Janus: Interchangeable Moons of Saturn

Explanation: These two moons change places. Epimetheus and Janus, two small moons of Saturn, actually switch positions as they orbit their home planet. The orbital radii of the moons are strangely separated by less than the radii of the moons themselves: about 50 kilometers. One moon orbits Saturn well ahead of the other, at first. As the two moons gravitationally attract, they approach each other and, every few years, actually pass and trade orbits. This strange dance creates speculation that Epimetheus and Janus were once joined and later split from each other. Pictured above, the two moons were photographed rounding their orbits just outside of Saturn's F ring. The above image was taken in early September by the robot Cassini spacecraft, also orbiting Saturn.

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NGC 3242: The Ghost of Jupiter

Explanation: After a star like the Sun completes fusion in its core, it throws off its outer layers in a brief, beautiful cosmic display called a planetary nebula. NGC 3242 is such a planetary nebula, with the stellar remnant white dwarf star visible at the center. This nebula is sometimes called The Ghost of Jupiter for its faint, but similar appearance to our solar system's ruling gas giant planet. NGC 3242 is light-years across however, and much farther away than the measly 40 light-minutes distance to Jupiter. In fact, while watching this ghostly nebula expand over time, astronomers have estimated the distance to NGC 3242 to be about 1,400 light-years. The red FLIERs visible near the edges of the nebula are still a bit mysterious, though.

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4,500 Kilometers Above Dione

Explanation: What does the surface of Saturn's moon Dione look like? To find out, the robot Cassini spacecraft currently orbiting Saturn flew right past the fourth largest moon of the giant planet earlier this month. Pictured above is an image taken about 4,500 kilometers above Dione's icy surface, spanning about 23 kilometers. Fractures, grooves, and craters in Dione's ice and rock are visible. In many cases, surface features are caused by unknown processes and can only be described. Many of the craters have bright walls but dark floors, indicating that fresher ice is brighter. Nearly parallel grooves run from the upper right to the lower left. Fractures sometimes across the bottom of craters, indicating a relatively recent formation. The lip of a 60-kilometer wide crater runs from the middle left to the upper center of the image, while the crater's center is visible on the lower right. Images like this will continue to be studied to better understand Dione as well as Saturn's complex system of rings and moons.

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October Mars

Explanation: This October, Mars has become a bright, yellowish star in planet Earth's sky as it approaches oppositon, the period when Mars and Earth pass close as they orbit the Sun. How close is Mars? A mere 70 million kilometers or so, close enough to allow Earth-bound astronomers excellent views of the alluring Red Planet. For example, this series of sharp Mars images follows the development of a dust storm as the planet rotates from right to left. The telescopic views clearly show details of the martian surface, including the planet's southern ice cap (top) and hood of clouds over the north pole at the bottom edge. The dust storm itself is visible as a light yellowish band across an otherwise dark region in the southern hemisphere. Even if a telescope isn't handy, be sure to check out Mars soon. It will continue to shine brightly in the night over the coming days.

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Supernova Remnant N132D in Optical and X Rays

Explanation: Thousands of years after a star exploded, its expanding remnant still glows brightly across the spectrum. Such is the case with N132D, a supernova remnant located in the neighboring Large Magellanic Cloud (LMC) galaxy. The expanding shell from this explosion now spans 80 light-years and has swept up about 600 Suns worth of mass. N132D was imaged recently in optical light and in great detail with the Hubble Space Telescope. The Hubble image was then combined with a position coincident detailed image in X-ray light taken by the Chandra X-ray Observatory. The combination, shown above in representative colors, shows a nearly spherical expanding shockwave highlighted by pink emission from hydrogen gas and purple emission from oxygen gas. A dense field of unrelated stars also from the LMC populates the image. Studying the image gives an opportunity to study material once hidden deep inside a star. N132D spans about 150 light years and lies about 160,000 light years away toward the constellation of Dorado.

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Angular Sand on Martian Hills

Explanation: Why isn't this sand round? The robotic Spirit rover currently rolling across Mars has found notably angular sand in the Columbia Hills on Mars. Previously, small bits of sand found in the plains of Gusev Crater were significantly more round. The finding indicates that angular hill sand has tumbled less and likely traveled a shorter distance than the corresponding round plain sand. Such tumbling has the general effect of making sand and rocks increasingly round and with fewer sharp edges. Pictured above, as taken last month, are angular sand grains magnified by Spirit's Microscopic Imager. The above frame spans about three centimeters.