科普 神奇的宇宙----图片(每天更新中)

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Barred Spiral Galaxy NGC 1672

Explanation: Many spiral galaxies have bars across their centers. Even our own Milky Way Galaxy is thought to have a modest central bar. Prominently barred spiral galaxy NGC 1672, pictured above, was captured in spectacular detail in this recently released image taken by the orbiting Hubble Space Telescope. Visible are dark filamentary dust lanes, young clusters of bright blue stars, red emission nebulas of glowing hydrogen gas, a long bright bar of stars across the center, and a bright active nucleus that likely houses a supermassive black hole. Light takes about 60 million years to reach us from NGC 1672, which spans about 75,000 light years across. NGC 1672, which appears toward the constellation of the Swordfish (Dorado), is being studied to find out how a spiral bar contributes to star formation in a galaxy's central regions.

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Long Stem Rosette

Explanation: The Rosette Nebula (aka NGC 2237) is not the only cosmic cloud of gas and dust to evoke the imagery of flowers. But it is the one most often suggested as a suitable astronomy image for Valentine's Day. Of the many excellent Rosette Nebula pictures submitted to APOD editors, this view seemed most appropriate, with a long stem of glowing hydrogen gas in the region included in the composition. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals of this rose are actually a stellar nursery whose lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young stars. The stars in the energetic cluster, cataloged as NGC 2244, are only a few million years old, while the central cavity in the Rosette Nebula is about 50 light-years in diameter. Happy Valentine's Day!

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Elliptical Galaxy NGC 1132

Explanation: NGC 1132 is one smooth galaxy -- but how did it form? As an elliptical galaxy, NGC 1132 has little dust and gas, and few stars have formed in it recently. Although many elliptical galaxies are in clusters of galaxies, NGC 1132 appears as a large, isolated galaxy toward the constellation of the River (Eridanus). To probe the history of this intriguing trillion-star ball, astronomers imaged NGC 1132 in both visible light with the Hubble Space Telescope and X-ray light with the Chandra X-ray Observatory. In this composite false-color image, visible light is white, while the X-ray light is blue and indicates the unusual presence of very hot gas. The X-ray light also likely traces out the location of dark matter. One progenitor hypothesis is that NGC 1132 is the result of a series of galaxy mergers in what once was a small group of galaxies. NGC 1132 is over 300 million light years away, so the light we see from it today left before dinosaurs roamed the Earth. Many fascinating background galaxies can be seen far in the distance.

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Echoes from RS Pup

Explanation: This dusty reflection nebula surrounds pulsating star RS Pup, some 10 times more massive than the Sun and on average 15,000 times more luminous. In fact, RS Pup is a Cepheid type variable star; a class of stars whose brightness is used to estimate distances to nearby galaxies as one of the first steps in establishing the cosmic distance scale. As RS Pup pulsates over a period of about 40 days, its regular changes in brightness are also seen along the nebula delayed in time, effectively a light echo. The otherwise overwhelming light from RS Pup itself is hidden behind the dark central stripe in the color image. Using new measurements of the time delay and angular size of the nebula, the known speed of light allows astronomers to geometrically determine the distance to RS Pup to be 6,500 light-years, with a remarkably small error of plus or minus 90 light-years. An impressive achievement for stellar astronomy, the echo-measured distance also more accurately establishes the true brightness of RS Pup, and by extension other Cepheid stars, improving the knowledge of distances to galaxies beyond the Milky Way.

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Saturn's Moon Epimetheus from the Cassini Spacecraft

Explanation: How did Epimetheus form? No one is yet sure. To help answer that question, this small moon has recently been imaged again in great detail by the robot spacecraft Cassini now orbiting Saturn. Epimetheus sometimes orbits Saturn in front of Janus, another small satellite, but sometimes behind. The above image, taken last December, shows a surface covered with craters indicating great age. Epimetheus spans about 115 kilometers across. Epimetheus does not have enough surface gravity to restructure itself into a sphere. The flattened face of Epimetheus shown above might have been created by a single large impact.

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Abell 2218: A Galaxy Cluster Lens

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Explanation: Gravity can bend light, allowing huge clusters of galaxies to act as telescopes. Almost all of the bright objects in this Hubble Space Telescope image are galaxies in the cluster known as Abell 2218. The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it. As a result, multiple images of these background galaxies are distorted into long faint arcs -- a simple lensing effect analogous to viewing distant street lamps through a glass of wine. The cluster of galaxies Abell 2218 is itself about three billion light-years away in the northern constellation of the Dragon (Draco). The power of this massive cluster telescope has allowed astronomers to detect a galaxy at redshift 5.58, the most distant galaxy yet measured. This young, still-maturing galaxy is faintly visible to the lower right of the cluster core.

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Atlantis on Pad 39A

Explanation: An intricate network of lighting plays across the 130 foot high Rotating Service Structure (RSS) in this dramatic night view of the Space Shuttle Atlantis on the Kennedy Space Center's launch pad 39A. Small human figures visible in silhouette emphasize the structure's enormous scale. Seen here after rolling back before Thursday's shuttle launch, the RSS provides pre-launch access to the orbiter and its payload. For this mission to the International Space Station, STS-122, Atlantis' payload is the European Space Agency's Columbus science laboratory. During the mission, three space walks are planned to attach the Columbus lab. Atlantis is expected to dock with the space station today.

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The Bay of Rainbows

Explanation: Dark, smooth regions that cover the Moon's familiar face are called by Latin names for oceans and seas. The naming convention is historical, though it may seem a little ironic to denizens of the space age who recognize the Moon as a mostly dry and airless world, and the smooth, dark areas as lava-flooded impact basins. For example, this elegant lunar vista, a careful mosaic of telescopic images, looks across the expanse of the northwestern Mare Imbrium, or Sea of Rains, into the Sinus Iridum - the Bay of Rainbows. Ringed by the Jura Mountains (montes), the bay is about 250 kilometers across, bounded at the bottom of the rugged arc by Cape (promontorium) Laplace. The cape's sunlit face towers nearly 3,000 meters above the bay's surface. At the top of the arc is Cape Heraclides, at times seen as a moon maiden.

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NGC 4013 and the Tidal Stream

Explanation: Nearly 50 million light-years away in the constellation Ursa Major, NGC 4013 was long considered an isolated island universe. Seen edge-on, the gorgeous spiral galaxy was known for its flattened disk and central bulge of stars, cut by silhouetted dust lanes. But this deep color image of the region reveals a previously unknown feature associated with NGC 4013, an enormous, faint looping structure extending (above and toward the left) over 80 thousand light-years from the galaxy's center. A detailed exploration of the remarkable structure reveals it to be a stream of stars originally belonging to another galaxy, likely a smaller galaxy torn apart by gravitational tides as it merged with the larger spiral. Astronomers argue that the newly discovered tidal stream also explains a warped distribution of neutral hydrogen gas seen in radio images of NGC 4013 and offers parallels to the formation of our own Milky Way galaxy.

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Sunspot in the New Solar Cycle

Explanation: A new cycle has begun on our Sun. Over the past year, the Sun's magnetic field has reset and now a new 11 year period is beginning. Pictured above in a specific color of light emitted by hydrogen is sunspot 10982, one of the first sunspots of the new solar cycle. The two dark lines visible just above and to either side of the bright sunspot are cool filaments held aloft by the Sun's magnetic field. Hot and cold regions are shown as regions of relative light and dark, respectively. A solar cycle is caused by the changing magnetic field, and varies from solar maximum, when sunspot, coronal mass ejection, and flare phenomena are most frequent, to solar minimum, when such activity is relatively infrequent. Solar minimums occurred in 1996 and 2007, while the last solar maximum occurred in 2001. Of course, tomorrow's annular solar eclipse is mostly for penguins.

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Three Month Composite of Comet Holmes
Explanation: How has Comet Holmes changed? Since brightening unexpectedly by nearly one million fold in late October, the last three months have found the coma of Comet 17P/Holmes both expanding and fading. This spectacular composite image shows how the coma and tail of Comet Holmes have changed. Due to Earth's changing vantage point, Comet Holmes, out beyond the orbit of Mars, was seen in November nearly head-on, but in recent months is seen more from the side. Additionally, the comet's motion, when combined with Earth's changing perspective, has caused the comet to have shifted relative to the background stars. The curved path of Comet Holmes shows it to be undergoing apparent retrograde motion as the Earth orbits quickly in front of it. The extent of the coma currently makes Comet Holmes over five times the physical size of our Sun. Anecdotal evidence holds that the comet is hard to see without long photographic exposures, but on such exposures the comet may still be an impressive sight.

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Light Echoes from V838 Mon

Explanation: What caused this outburst of V838 Mon? For reasons unknown, star V838 Mon's outer surface suddenly greatly expanded with the result that it became the brightest star in the entire Milky Way Galaxy in January 2002. Then, just as suddenly, it faded. A stellar flash like this has never been seen before -- supernovas and novas expel matter out into space. Although the V838 Mon flash appears to expel material into space, what is seen in the above image from the Hubble Space Telescope is actually an outwardly moving light echo of the bright flash. In a light echo, light from the flash is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star. V838 Mon lies about 20,000 light years away toward the constellation of the unicorn (Monoceros), while the light echo above spans about six light years in diameter.

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Water Claimed in Evaporating Planet HD 209458b

Explanation: Planet HD 209458b is evaporating. It is so close to its parent star that its heated atmosphere is simply expanding away into space. Some astronomers studying this distant planetary system now believe they have detected water vapor among the gases being liberated. This controversial claim, if true, would mark the first instance of planetary water beyond our Solar System, and indicate anew that life might be sustainable elsewhere in the universe. HD 209458b is known as a hot Jupiter type system because it involves a Jupiter-type planet in a Mercury-type orbit. Although spectroscopic observations from the Hubble Space Telescope are the basis for the water detection claim, the planetary system is too small and faint to image. Therefore, an artist's impression of the HD 209458b system is shown above. Research into the atmospheric composition of HD 209458b and other extrasolar planets is continuing.

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MWC 922: The Red Square Nebula

Explanation: What could cause a nebula to appear square? No one is quite sure. The hot star system known as MWC 922, however, appears to be imbedded in a nebula with just such a shape. The above image combines infrared exposures from the Hale Telescope on Mt. Palomar in California, and the Keck-2 Telescope on Mauna Kea in Hawaii. A leading progenitor hypothesis for the square nebula is that the central star or stars somehow expelled cones of gas during a late developmental stage. For MWC 922, these cones happen to incorporate nearly right angles and be visible from the sides. Supporting evidence for the cone hypothesis includes radial spokes in the image that might run along the cone walls. Researchers speculate that the cones viewed from another angle would appear similar to the gigantic rings of supernova 1987A, possibly indicating that a star in MWC 922 might one day itself explode in a similar supernova.

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M3: Inconstant Star Cluster

Explanation: Star clusters appear constant because photographs of them are frozen in time. In reality, though, cluster stars swarm the center and frequently fluctuate in brightness. Although the time it takes for stars to cross a cluster is about 100,000 years, the time it takes for a star to fluctuate noticeably can be less than one night. In fact, the above time lapse movie of bright globular cluster M3 was taken over a single night. Most of the variable stars visible above are RR Lyrae stars, stars that can quickly double their brightness while becoming noticeably bluer. Furthermore, RR Lyrae stars vary their light in a distinctive pattern that allows unique identification. Lastly, since RR Lyrae stars all have the same intrinsic brightness, identifying them and measuring how dim they appear tells how far they are, since faintness means farness. These distances, in turn, help calibrate the scale of the entire universe.

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Venus by the Lake

Explanation: Finding Venus in the night sky is not too hard these days. Now appearing as the evening star, Venus rules as the brightest celestial beacon in west just after sunset. And if you can find Venus tonight, you can also easily find the lovely Pleiades star cluster (aka M45) close by. In this serene skyview, recorded on Tuesday near Bolu, Turkey, Venus and the Pleiades are on the right, with brilliant Venus reflected in the calm waters of the small lake in the foreground. Left of Venus, the bright star Aldebaran anchors the V-shaped Hyades star cluster. Farther left are stars of the familiar constellation Orion with Rigel, at the foot of Orion, also reflected in the lake. Meanwhile, Sirius, in Canis Major, is the brightest star on the left side of the view. But the bright terrestrial light below Sirius is not a reflection, it's just a light near the lake shore.

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Seven Dusty Sisters

Explanation: Hurtling through a cosmic dust cloud a mere 400 light-years away, the lovely Pleiades or Seven Sisters star cluster is well-known in astronomical images for its striking blue reflection nebulae. At visible wavelengths, the starlight is scattered and reflected by the dust, but in this portrait in infrared light by the Spitzer Space Telescope, the dust itself glows. The false color image spans about 1 degree or seven light-years at the distance of the Pleiades, with the densest regions of the dust cloud shown in yellow and red hues. Exploring this young, nearby cluster, the Spitzer data have revealed many cool, low mass stars, brown dwarfs or failed stars, and possible planetary debris disks. Want to see the Pleiades tonight? Look near Venus, the brilliant evening star in the west just after sunset.

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The Cone Nebula Neighborhood

Explanation: Cosmic clouds of hydrogen gas and dust abound in this gorgeous skyscape, stretching through Monoceros in the neighborhood of The Cone Nebula. A dark, obscuring dust cloud, the simple, sculpted shape of the Cone Nebula is near the lower left edge. Surrounded by the red glow of hydrogen gas, the cone points up, toward bright, blue-white S Monocerotis, a quadruple system of very massive, hot stars. S Mon itself is also surrounded by intriguing red emission nebulae characteristic of star forming regions while above and to the right of S Mon, expansive dark markings on the sky are silhouetted by a larger region of fainter emission. Yellowish open star cluster Trumpler 5 is below picture center, with the striking blue reflection nebula, IC 2169 near the center right edge. The curious compact cometary shape near the bottom edge is Hubble's Variable Nebula. Over 31 hours of exposure time went into this truly remarkable, 2.5 degree wide, color mosaic.

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The Arms of NGC 4258

Explanation: Better known as M106, bright spiral galaxy NGC 4258 is about 30 thousand light years across and 21 million light years away toward the northern constellation Canes Venatici. The yellow and red hues in this composite image show the galaxy's sweeping spiral arms as seen in visible and infrared light. But x-ray and radio data (blue and purple) reveal two extra spiral arms -- arms that don't align with the more familiar tracers of stars, gas, and dust. In fact, an analysis of the x-ray and radio data suggests that the anamolous arms are composed of material heated by shock waves. Detected at radio wavelengths, powerful jets originating in the galaxy's core likely drive the shocks into the disk of NGC 4258.

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Aurora Over Alaska

Explanation: Higher than the highest mountain, higher than the highest airplane, lies the realm of the aurora. Aurora rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from solar shockwave causing energetic electrons and protons to striking molecules in the Earth's atmosphere. Frequently, when viewed from space, a complete aurora will appear as a circle around one of the Earth's magnetic poles. The above digitally enhanced photograph was taken in 2005 January shows a spectacular aurora borealis above the frozen landscape of Bear Lake, Alaska, USA. The above image was voted Wikipedia Commons Picture of the Year for 2006.