CDer:000024255 楼主: jadiyd

[视图资料] Astronomy Picture of the Day 2010-每日天文一图第四季

 楼主| 发表于 2010-03-21 20:53 | 显示全部楼层
2010 March 21

Equinox + 1
Credit & Copyright: Joe Orman
Explanation: Twice a year, at the Spring and Fall equinox, the Sun rises due east. In an emphatic demonstration of this celestial alignment, photographer Joe Orman recorded this inspiring image of the Sun rising exactly along the east-west oriented Western Canal, in Tempe, Arizona, USA. But he waited until one day after the northern Spring equinox, in 2001, to photograph the striking view. Why was the rising Sun due east one day after the equinox? At Tempe's latitude the Sun rises at an angle, arcing southward as it climbs above the horizon. Because the distant mountains hide the true horizon, the Sun shifts slightly southward by the time it clears the mountain tops. Waiting 24 hours allowed the Sun to rise just north of east and arc back to an exactly eastern alignment for the photo. Today is another Equinox + 1 day, with the Sun crossing the celestial equator yesterday at about 17:32 Universal Time.
 楼主| 发表于 2010-03-22 16:14 | 显示全部楼层
2010 March 22

The Nearby Milky Way in Cold Dust
Credit: ESA, Planck HFI Consortium, IRAS
Explanation: What shapes the remarkable dust tapestry of the nearby Milky Way Galaxy? No one knows for sure. The intricate structures, shown above, were resolved in new detail recently in a wide region of the sky imaged in far infrared light by the European Space Agency's Planck satellite. The above image is a digital fusion of three infrared colors: two taken at high resolution by Planck, while the other is an older image taken by the now defunct IRAS satellite. At these colors, the sky is dominated by the faint glow of very cold gas within only 500 light years of Earth. In the above image, red corresponds to temperatures as cold as 10 degrees Kelvin above absolute zero, while white corresponds to gas as warm at 40 Kelvins. The pink band across the lower part of the image is warm gas confined to the plane of our Galaxy. The bright regions typically hold dense molecular clouds that are slowly collapsing to form stars, whereas the dimmer regions are most usually diffuse interstellar gas and dust known as cirrus. Why these regions have intricate filamentary shapes shared on both large and small scales remains a topic of research. Future study of the origin and evolution of dust may help in the understanding the recent history of our Galaxy as well as how planetary systems such as our Solar System came to be born.


 楼主| 发表于 2010-03-23 17:21 | 显示全部楼层
2010 March 23

Reinvigorated Sun and Prominence
Credit & Copyright: Alan Friedman (Averted Imagination)
Explanation: Dramatic prominences can sometimes be seen looming just beyond the edge of the sun. Such was the case last week as a giant prominence, visible above on the right, highlighted a Sun showing increased activity as it comes off an unusually quiet Solar Minimum. A changing carpet of hot gas is visible in the chromosphere of the Sun in the above image taken in a very specific color of light emitted by hydrogen. A solar prominence is a cloud of solar gas held just above the surface by the Sun's magnetic field. The Earth would easily fit below the prominence on the right. Although very hot, prominences typically appear dark when viewed against the Sun, since they are slightly cooler than the surface. A quiescent prominence typically lasts about a month, and may erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar System. The next day, the same prominence looked slightly different.


 楼主| 发表于 2010-03-24 12:41 | 显示全部楼层
2010 March 24

Galaxy Wars: M81 versus M82
Credit & Copyright: Leonardo Orazi
Explanation: On the right, surrounded by blue spiral arms, is spiral galaxy M81. On the left, marked by red gas and dust clouds, is irregular galaxy M82. This stunning vista shows these two mammoth galaxies locked in gravitational combat, as they have been for the past billion years. The gravity from each galaxy dramatically affects the other during each hundred million-year pass. Last go-round, M82's gravity likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms. But M81 left M82 with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays. In a few billion years only one galaxy will remain.


 楼主| 发表于 2010-03-25 15:04 | 显示全部楼层
2010 March 25

NGC 2442: Galaxy in Volans
Image Credit: Data - Hubble Legacy Archive, Processing - Robert Gendler
Explanation: Distorted galaxy NGC 2442 can be found in the southern constellation of the flying fish, (Piscis) Volans. Located about 50 million light-years away, the galaxy's two spiral arms extending from a pronounced central bar have a hook-like appearance in wide-field images. But this mosaicked close-up, constructed from Hubble Space Telescope data, follows the galaxy's structure in amazing detail. Obscuring dust lanes, young blue star clusters and reddish star forming regions surround a core of yellowish light from an older population of stars. The sharp Hubble data also reveal more distant background galaxies seen right through NGC 2442's star clusters and nebulae. The image spans about 75,000 light-years at the estimated distance of NGC 2442.


 楼主| 发表于 2010-03-26 16:53 | 显示全部楼层
2010 March 26

Young Moon and Sister Stars
Image Credit & Copyright: Anna Morris
Explanation: A young crescent Moon shares the western sky with sister stars of the Pleiades cluster in this pretty, evening skyscape recorded on the March equinox from San Antonio, Texas. In the processed digital image, multiple exposures of the celestial scene were combined to show details of the bright lunar surface along with the Pleiades stars. Astronomical images of the well-known Pleiades often show the cluster's alluring blue reflection nebulae, but they are washed-out here in the bright moonlight. Still, during this particular night, skygazers in South and Central America could even watch the 5 day old Moon occult or pass in front of some of the brighter Pleiades stars.
 楼主| 发表于 2010-03-27 14:31 | 显示全部楼层
2010 March 27

Hesiodus Sunrise Ray
Image Credit & Copyright: Stefan Seip (TWAN)
Explanation: Stark shadows of mountains and crater walls stand out along the lunar terminator, or shadow line between night and day, in this telescopic image. Of course, if viewed from the lunar surface near the terminator line, the Sun would be rising and still close to the lunar horizon. But the picture's inset at the left highlights a more elusive lunar sunrise phenomenon. Streaming through a gap in the eastern wall of 45 kilometer wide Hesiodus crater, the low-angle sunlight produces a long sunrise ray playing along the otherwise shadowed crater floor. Sunrise rays are short-lived and can be rewarding to spot for Moon enthusiasts with telescopes. Seen in Hesiodus and other craters, the ray timing can be calculated based on the observer's location. This picture of a first quarter Moon was recorded at 23:45 UT on February 22nd from Stuttgart, Germany. In the inset, the larger crater Pitatus is at the right. For location, Hesiodus and Pitatus are circled at the bottom of the picture.
 楼主| 发表于 2010-03-28 15:03 | 显示全部楼层
2010 March 28

M16: Pillars of Creation
Credit: J. Hester, P. Scowen (ASU), HST, NASA
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 again imaged by the orbiting Chandra X-ray Observatory, and it was found that most EGGS are not strong emitters of X-rays.
 楼主| 发表于 2010-03-29 20:18 | 显示全部楼层
2010 March 29

Moonset Over Pleasant Bay
Credit & Copyright: A. Dunlap-Smith; Drawing Acknowledgement: J. Hevelius
Explanation: It was a sky for the imagination. In the early evening last week, the sky illuminating the unaided eye was perhaps even more illuminating to the mind's eye. The unaided eye saw clouds framing the Moon setting over a calm and reflective bay, spruce trees lining the nearby shores, the Pleiades open star cluster (M45) glowing prominently in the center of the sky, the Andromeda galaxy hovering just over the horizon on the right, and the belt stars of Orion lined up on the left, just below the bright orange star Betelgeuse. The bright star Sirius peeked out of the trees on the far left. The mind's eye might further imagine, however, some of the constellations coming to life, with Orion the Hunter taking up his sword and shield, followed into battle by his Big Dog (Canis Major, whose right eye is Sirius), and watched from across the sky by Cassiopeia, the Queen of Ethiopia, sitting on her Throne. The above image was taken over Pleasant Bay, Maine, USA, and digitally merged with constellations from Uranographicarum, drawn in the 17th century by J. Hevelius.


 楼主| 发表于 2010-03-30 18:17 | 显示全部楼层
本帖最后由 jadiyd 于 2010-3-30 22:38 编辑

2010 March 30
Unusual Starburst Galaxy NGC 1313
Credit & Copyright: Robert Gendler
Explanation: Why is this galaxy so discombobulated? Usually, galaxies this topsy-turvy result from a recent collision with a neighboring galaxy. Spiral galaxy NGC 1313, however, appears to be alone. Brightly lit with new and blue massive stars, star formation appears so rampant in NGC 1313 that it has been labeled a starburst galaxy. Strange features of NGC 1313 include that its spiral arms are lopsided and its rotational axis is not at the center of the nuclear bar. Pictured above, NGC 1313 spans about 50,000 light years and lies only about 15 million light years away toward the constellation of the Reticle (Reticulum). Continued numerical modeling of galaxies like NGC 1313 might shed some light on its unusual nature.
说明:为什么这个星系如此混乱?通常情况下,星系中出现类似这样的混乱状态是因为与其临近星系发生了碰撞造成。但是,旋涡星系NGC1313看上去是孤立的。由新诞生的大质量蓝色恒星照亮, NGC1313内的恒星形成区域看上去很异常猛烈,因此它被标注为星爆星系NGC1313的奇怪特征包括其旋臂是不平衡的,并且它的旋轴并不在星系的中央。上面的影像中,NGC1313覆盖大约5光年,距离我们大约1,500万光年远,位于网罟座内。对类似于NGC1313这样的星系所做的数值模型将说明它的不同特性。
 楼主| 发表于 2010-03-31 16:22 | 显示全部楼层
2010 March 31

Millions of Stars in Omega Centauri
Image Credit & Copyright: Fred Lehman (South Florida Dark Sky Observers)
Explanation: Featured in the sharp telescopic image, globular star cluster Omega Centauri (NGC 5139) is some 15,000 light-years away and 150 light-years in diameter. Packed with about 10 million stars much older than the Sun, Omega Cen is the largest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way.


 楼主| 发表于 2010-04-01 13:21 | 显示全部楼层
本帖最后由 jadiyd 于 2010-4-1 18:58 编辑

2010 April 1

Evidence Mounts for Water on the Moon
Image Courtesy: George Dalisay
Explanation: In 2009, space missions revealed tantalizing signs of water on or near the lunar surface, once thought of as a dry and desolate environment. But researchers are now offering this archival picture as further evidence that humans might one day be able to use the Moon's newly discovered resource to directly quench their thirst. Found in a pile of old Apollo lunar surface photographs, the picture reveals an object at the far left of the frame that appears to be a drinking fountain, surprisingly close to one of the Lunar Module landing struts. When asked why no mention of the object was in their reports, the astronauts replied that they discovered their spacesuit gloves were too bulky to allow them to activate the fountain, so they had simply ignored it during their stay on the lunar surface. Perhaps not coincidentally, this picture was taken exactly 40 years ago, on April Fools Day ...
 楼主| 发表于 2010-04-02 19:57 | 显示全部楼层
2010 April 2

Serene Paraselene
Image Credit & Copyright: Tamas Ladanyi (TWAN)
Explanation: Nestled in the Austrian Alps, frozen Lake Ossiach stretches across the foreground of this serene view. Recorded on March 1, the night sky includes a nearly full Moon and bright planet Saturn seen through thin clouds near picture center. It also includes a remarkably bright and colorful moondog or paraselene at the left. Analogous to a sundog or parhelion, the paraselene is produced by moonlight shining through thin, hexagonal-shaped ice crystals in high cirrus clouds. As determined by the ice crystal geometry, the Moon is 22 degrees from the lovely paraselene.


 楼主| 发表于 2010-04-03 23:18 | 显示全部楼层
2010 April 3

NGC 602 and Beyond
Credit: NASA, ESA, and the Hubble Heritage Team (STScI / AURA) - ESA/Hubble Collaboration
Explanation: Near the outskirts of the Small Magellanic Cloud, a satellite galaxy some 200 thousand light-years distant, lies 5 million year young star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this stunning Hubble image of the region. Fantastic ridges and swept back shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the picture spans about 200 light-years, but a tantalizing assortment of background galaxies are also visible in the sharp Hubble view. The background galaxies are hundreds of millions of light-years or more beyond NGC 602.
 楼主| 发表于 2010-04-04 17:22 | 显示全部楼层
2010 April 4

The Belt of Venus over the Valley of the Moon
Credit & Copyright: Christine Churchill
Explanation: Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink. Called the Belt of Venus, this off-color band between the dark eclipsed sky and the blue sky can be seen in nearly every direction including that opposite the Sun. Straight above, blue sky is normal sunlight reflecting off the atmosphere. In the Belt of Venus, however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus can be seen from any location with a clear horizon. Pictured above, the Belt of Venus was photographed above morning fog in the Valley of the Moon, a famous wine-producing region in northern California, USA. The belt is frequently caught by accident in other photographs.
 楼主| 发表于 2010-04-05 19:01 | 显示全部楼层
2010 April 5

Prometheus Remastered
Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA
Explanation: What does Saturn's shepherd moon Prometheus really look like? The raw images from the robotic Cassini spacecraft's January flyby of the small moon showed tantalizing clues on grainy images, but now that the Cassini team has digitally remastered these images, many more details have come out. Pictured above, Prometheus more clearly shows its oblong shape as well as numerous craters over its 100-kilometer length. In the above image, the bright part of Prometheus is lit directly by the Sun, while much of the dark part is still discernible through sunlight first reflected off of Saturn. These new surface details, together with the moon's high reflectivity, can now help humanity better understand the history of Prometheus and Saturn's rings. Today, Cassini has a planned targeted flyby of Saturn's largest moon Titan, while on Wednesday, Cassini is scheduled to swoop to within 600 kilometers of Dione.
 楼主| 发表于 2010-04-06 17:17 | 显示全部楼层
2010 April 6

A Fox Fur, a Unicorn, and a Christmas Tree
Credit & Copyright: Kerry-Ann Lecky Hepburn (Weather and Sky Photography) & Stefano Cancelli (AstroGarage)
Explanation: What do the following things have in common: a cone, the fur of a fox, and a Christmas tree? Answer: they all occur in the constellation of the unicorn (Monoceros). Pictured above as a star forming region cataloged as NGC 2264, the complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. The wide mosaic spans about 3/4 degree or nearly 1.5 full moons, covering 40 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the Fox Fur Nebula, whose convoluted pelt lies at the upper left, bright variable star S Mon immersed in the blue-tinted haze just below the Fox Fur, and the Cone Nebula at the far right. Of course, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The triangular tree shape traced by the stars appears sideways here, with its apex at the Cone Nebula and its broader base centered near S Mon.

说明:这些接下来的事物有什么共同点? 圆锥,狐皮以及圣诞树?回答是:它们都出现在麒麟座内。上面的影像是一个被编录为NGC2264的恒星诞生区域,复杂的宇宙气体和尘埃距离我们大约2,700光年远,混杂着由高能光激发出来的泛红色的发射星云,这些高能光是由新诞生恒星发出,其中夹杂着黑暗的星际尘埃云。距离年轻炽热的恒星距离较近的模糊尘埃云同样也反射星光,形成了蓝色反射星云。这张广域影像覆盖大约3/4度,接近1.5个满月大小,在NGC2264的估计距离上涵盖约40光年。其中包含的宇宙特征有狐皮星云,它位于影像的左上方,明亮的变星麒麟座S星就位于狐皮星云正下方的泛蓝色薄雾中,锥状星云位于最右侧。当然,NGC2264内的恒星还被称为圣诞树恒星团。三角形的树状结构由恒星分布在两旁,顶点就在锥状星云,而宽阔的底边中央就在麒麟座S附近。

 楼主| 发表于 2010-04-08 11:52 | 显示全部楼层
2010 April 7

Venus and Mercury in the West
Image Credit & Copyright: Manu Arregi Biziola
Explanation: In this twilight skyview, a windmill stands in silent witness to a lovely pairing of planets in the west. The picture was recorded on April 5 from Gallegos del Campo, Zamora, Spain. Venus (left) and Mercury (right) are near their much anticipated conjunction in the early evening sky. But even in the coming days, these two evening stars will remain close in the western sky at sunset. In fact, with brighter Venus as a marker, sky watchers will have an excellent guide for spotting Mercury nearby, a planet often hidden in the Sun's glare.
说明:在这黄昏的天空下,一台风力发电站静静的伫立着目睹了出现在西方天空中的一对行星。影像拍摄于45,地点位于西班牙萨莫拉Gallegos del Campo。金星(左)和水星(右)在傍晚的天空中形成了一次预料之中的“合”。但是在接下来几天里,日落之后两颗昏星仍然会在西方天空中相距很近。事实上,较为明亮的金星即为标志,天空观测者们很容易发现附近的水星,这颗行星经常会淹没在太阳的辉光中。
 楼主| 发表于 2010-04-08 20:17 | 显示全部楼层
2010 April 8

Discovery's Cloud
Image Credit & Copyright: Stefan O'Dougherty and Peter Nguyen
(Acknowledgement: Simone Nageon De Lestang)
Explanation: The space shuttle orbiter Discovery is now docked with the International Space Station, some 350 kilometers above planet Earth. Last Monday, its launch to orbit was a beautiful one as it rose into clear, predawn skies at 6:21am EDT from Kennedy Space Center's pad 39A. Looking east, this time exposure was taken shortly after lift off from a marina about 13 miles west of the launch site in Titusville, Florida. It shows the dawn's emerging colors along the horizon, with wafting rocket contrails at the upper right. The bright streak surrounded by the remarkable, elongated, vapor cloud near the center of the image is the actual track of Discovery, arcing toward the horizon and its orbital rendezvous.


 楼主| 发表于 2010-04-09 15:51 | 显示全部楼层
2010 April 9

Discovery's Dawn
Image Credit & Copyright: Craig Crawford
Explanation: On April 5, visitors to Kennedy Space Center saw these colorful clouds, twisting and drifting through dawn skies. Of course, the clouds were rocket engine plumes from the predawn launch of the space shuttle Discovery on the STS-131 mission to the International Space Station. Their layered colors are created as they reflect the reddened light from the still rising Sun. Fittingly, denizens of the space center's rocket garden are lit in the foreground. At the far left is a 1960s vintage multistage Atlas-Agena rocket. Together on the right, are Mercury-Redstone and Mercury-Atlas rockets.


 楼主| 发表于 2010-04-11 17:39 | 显示全部楼层
2010 April 10

Spitzer's Orion
Credit: NASA, JPL-Caltech, J. Stauffer (SSC/Caltech)
Explanation: Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Spanning about 40 light-years across the region, this new infrared image from the Spitzer Space Telescope was constructed from data intended to monitor the brightness of the nebula's young stars, many still surrounded by dusty, planet-forming disks. Orion's young stars are only about 1 million years old, compared to the Sun's age of 4.6 billion years. The region's hottest stars are found in the Trapezium Cluster, the brightest cluster near picture center. Spitzer's liquid helium coolant ran out in May 2009, so this false color view is from two channels that still remain sensitive to infrared light at warmer operating temperatures.
 楼主| 发表于 2010-04-11 17:39 | 显示全部楼层
2010 April 11

IC 418: The Spirograph Nebula
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgement: R. Sahai (JPL) et al.
Explanation: What is creating the strange texture of IC 418? Dubbed the Spirograph Nebula for its resemblance to drawings from a cyclical drawing tool, planetary nebula IC 418 shows patterns that are not well understood. Perhaps they are related to chaotic winds from the variable central star, which changes brightness unpredictably in just a few hours. By contrast, evidence indicates that only a few million years ago, IC 418 was probably a well-understood star similar to our Sun. Only a few thousand years ago, IC 418 was probably a common red giant star. Since running out of nuclear fuel, though, the outer envelope has begun expanding outward leaving a hot remnant core destined to become a white-dwarf star, visible in the image center. The light from the central core excites surrounding atoms in the nebula causing them to glow. IC 418 lies about 2000 light-years away and spans 0.3 light-years across. This false-color image taken from the Hubble Space Telescope reveals the unusual details.
 楼主| 发表于 2010-04-13 16:07 | 显示全部楼层
2010 April 12

Mercury and Venus Over Paris
Credit & Copyright: Josselin Desmars
Explanation: Go outside tonight and see one of the more interesting planetary conjunctions of recent years. Just after sunset, the planets Mercury and Venus are visible quite near each other. Now Venus, being commonly discernible as one of the brightest objects in the sky, is frequently mistaken for an airplane. (Venus will set quite slowly, though.) Mercury, however, is dimmer and usually harder to find. Recently, though, Mercury can be found just to the right of Venus, appearing increasingly below the brighter planet over the next week. Pictured above, Venus and Mercury were imaged next to the famous Notre Dame Cathedral in Paris, France. A careful inspection of the image will further reveal that the bright object nearly below Venus is iconic Eiffel Tower.


 楼主| 发表于 2010-04-13 16:08 | 显示全部楼层
2010 April 13

Unusual Spiral Galaxy M66 from Hubble
Credit: NASA, ESA, Hubble Heritage, S. Van Dyk (JPL/IPAC), R. Chandar (U. Toledo), D. De Martin & R. Gendler
Explanation: Why isn't spiral galaxy M66 symmetric? Usually density waves of gas, dust, and newly formed stars circle a spiral galaxy's center and create a nearly symmetric galaxy. The differences between M66's spiral arms and the apparent displacement of its nucleus are all likely caused by previous close interactions and the tidal gravitational pulls of nearby galaxy neighbors M65 and NGC 3628. Spiral galaxy M66, pictured above, spans about 100,000 light years, lies about 35 million light years distant, and is the largest galaxy in a group known as the Leo Triplet. Like many spiral galaxies, the long and intricate dust lanes of M66 are seen intertwined with the bright stars and nebulas that light up the spiral arms.


 楼主| 发表于 2010-04-14 15:12 | 显示全部楼层
2010 April 14

A Large Space Station Over Earth
Credit: STS-131 Crew, Expedition 23 Crew, NASA
Explanation: The International Space Station is the largest object ever constructed by humans in space. The station perimeter now extends over roughly the area of a football field, although only a small fraction of this is composed of modules habitable by humans. The station is so large that it could not be launched all at once -- it is being built piecemeal with large sections added continually by flights of the Space Shuttle. To function, the ISS needs huge trusses, some over 15 meters long and with masses over 10,000 kilograms, to keep it rigid and to route electricity and liquid coolants. Pictured above, part of the immense space station was photographed out of a window by a member of the visiting Space Shuttle Discovery STS-131 crew. Visible in the foreground is Japan's Kibo research module, while a large truss is visible toward the left. On the far right, a crescent Earth slices through the blackness of space.
 楼主| 发表于 2010-04-15 19:37 | 显示全部楼层
2010 April 15

NGC 4651: The Umbrella Galaxy
Image Credit & Copyright: R Jay Gabany (Blackbird Obs.), Collaboration: David Martinez-Delgado (MPIA, IAC), et al.
Explanation: Spiral galaxy NGC 4651 is a mere 35 million light-years distant, toward the well-groomed constellation Coma Berenices. About 50 thousand light-years across, this galaxy is seen to have a faint umbrella-shaped structure (right) that seems to extend some 50 thousand light-years farther, beyond the bright galactic disk. The giant cosmic umbrella is now known to be composed of tidal star streams. The streams themselves are extensive trails of stars gravitationally stripped from a smaller satellite galaxy that was eventually torn apart. Placing your cursor over the image will superimpose a simulation of the satellite galaxy's path as it was disrupted and absorbed into NGC 4651. Recent work by a remarkable collaboration of amateur and professional astronomers to image faint structures around bright galaxies suggests that even in nearby galaxies, such tidal star streams are common. The result is predicted by models of galaxy formation, including the formation of our Milky Way.
 楼主| 发表于 2010-04-16 14:20 | 显示全部楼层
本帖最后由 jadiyd 于 2010-4-17 20:05 编辑

2010 April 16

Bright Points on the Quiet Sun
Credit: J. Sanchez Almeida (IAC), et al.
Explanation: Up close, the solar surface is a striking patch work of granules in this very high resolution picture of the quiet Sun. Caused by convection, the granules are hot, rising columns of plasma edged by dark lanes of cooler, descending plasma. But the high-resolution view reveals that the dark lanes are dotted with many small, contrasting bright points. Constantly present on the solar surface, the bright points do not seem to be related to sunspots that come and go with the magnetic solar cycle. Nonetheless, the bright points are regions of concentrated magnetic fields and are bright because the magnetic pressure opens a window to hotter deeper layers below the photosphere. For scale, the white bar at the lower left corresponds to 5,000 kilometers across the Sun's surface. The sharp, narrow-band image was recorded in September, 2007 using the Swedish Solar Telescope on the astronomical island of La Palma.

说明:仔细看这张高清晰影像,可以发现平静的太阳表面出现了壮观的米粒组织。米粒组织由对流造成,它们异常炽热,从柱状电浆中央喷出后,接着从较暗的边缘沉降。然而,这张高分辨率影像还发现在黑色边缘处,点缀着许多细小的亮点,这些亮点出现在太阳表面上,但是这与影响太阳黑子的磁场周期并没有关系。尽管如此,这些亮点是因为磁压力使原本在光球层下的炙热层喷出,造成磁场集合处。规模来说,左下方的白色比例尺相当于太阳表面的5000公里宽。而这张清晰的窄波段影像拍摄于20079月,由拉帕尔马(La Palma)上的瑞典太阳望远镜拍摄。

发表于 2010-04-16 22:10 | 显示全部楼层
 楼主| 发表于 2010-04-17 20:05 | 显示全部楼层
2010 April 17

Damage to Apollo 13
Credit: Apollo 13 Crew, NASA
Explanation: After an oxygen tank exploded and crippled their service module, the Apollo 13 astronauts were forced to abandon plans to make the third manned lunar landing. The extent of the damage is revealed in this grainy, grim photo, taken as the service module was drifting away, jettisoned only hours prior to the command module's reentry and splashdown. An entire panel on the side of the service module has been blown away and extensive internal damage is apparent. Visible below the gutted compartment is a radio antenna and the large, bell-shaped nozzle of the service module's rocket engine. On April 17, 1970 the three astronauts returned safely to Earth.
 楼主| 发表于 2010-04-18 16:18 | 显示全部楼层
2010 April 18

Large Eruptive Prominence Imaged by STEREO
Credit: STEREO Project, NASA
Explanation: What's happened to our Sun? Last week, it produced one of the most power eruptive prominences ever seen. Pictured above, the prominence erupted in only a few hours and was captured in movie form by NASA's twin Sun-orbiting STEREO satellites. A quiescent solar prominence is a cloud of hot solar gas held above the Sun's surface by the Sun's magnetic field. Unpredictably, however, prominences may erupt, expelling hot gas into the Solar System via a Coronal Mass Ejection (CME). As pictured above, many Earths would easily fit under the expanding ribbon of hot gas. 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.
 楼主| 发表于 2010-04-19 18:51 | 显示全部楼层
2010 April 19

Ash and Lightning Above an Icelandic Volcano
Credit & Copyright: Marco Fulle (Stromboli Online)
Explanation: Why did the recent volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well populated areas. The Eyjafjallajökull volcano in southern Iceland began erupting on March 20, with a second eruption starting under the center of small glacier on April 14. Neither eruption was unusually powerful. The second eruption, however, melted a large amount of glacial ice which then cooled and fragmented lava into gritty glass particles that were carried up with the rising volcanic plume. Pictured above two days ago, lightning bolts illuminate ash pouring out of the Eyjafjallajökull volcano.


 楼主| 发表于 2010-04-20 18:29 | 显示全部楼层
本帖最后由 jadiyd 于 2010-4-21 19:49 编辑

2010 April 20

Saturn's Moons Dione and Titan from Cassini
Credit: NASA/JPL/SSI; Color composite: Emily Lakdawalla
Explanation: What would it be like to see a sky with many moons? Such is the sky above Saturn. When appearing close to each other, moons will show a similar phase. A view with two of the more famous moons of Saturn in gibbous phase was captured last month by the robot spacecraft Cassini now orbiting Saturn. Titan, on the left, is among the largest moons in the Solar System and is perpetually shrouded in clouds. In 2005, the Huygens probe landed on Titan and gave humanity its first view of its unusual surface. Dione, on the right, has less than a quarter of Titan's diameter and has no significant atmosphere. The above uncalibrated image was taken on April 10 after Cassini swooped by each moon the previous week.

,影像左方是泰坦(Titan),他是太阳系内最大的卫星,看似在云雾之中。 2005年,惠更斯登陆泰坦,让人类第一次看到这异常的地表。土卫四(Dione)则在影像右方,直径约莫是泰坦的四分之一,没有显著的大气结构。 4月10日卡西尼号太空船掠过卫星时,拍下了这张原始影像
 楼主| 发表于 2010-04-21 16:30 | 显示全部楼层
本帖最后由 jadiyd 于 2010-4-21 19:50 编辑

2010 April 21

Wide Angle: The Cat's Paw Nebula
Credit: ESO, DSS2
Explanation: Nebulae are perhaps as famous for being identified with familiar shapes as perhaps cats are for getting into trouble. Still, no known cat could have created the vast Cat's Paw Nebula visible in Scorpius. At 5,500 light years distant, Cat's Paw is an emission nebula with a red color that originates from an abundance of ionized hydrogen atoms. Alternatively known as the Bear Claw Nebula or NGC 6334, stars nearly ten times the mass of our Sun have been born there in only the past few million years. Pictured above, a wide angle, deep field image of the Cat's Paw nebula was culled from the second Digitized Sky Survey.
因为常闯祸而出名一样。不过,没有能创造出这个位在天蝎座的巨大猫掌星云(Cat's Paw Nebula)。离我们5,500光年远的猫掌星云发射星云,它红色的辉光来自大量被游离氢原。它有另一个名称为熊掌星云NGC 6334,内部有许多质量接近十倍于太阳的恒星,他们是最近的数百万年才从星云诞生出来的。上面这幅猫掌星云末端的广视野深空影像,是取自巡天计画二的资料库。
 楼主| 发表于 2010-04-22 15:41 | 显示全部楼层
本帖最后由 jadiyd 于 2010-4-23 17:12 编辑

2010 April 22
Venus, Mercury, and Moon
Credit & Copyright: Pete Lawrence (Digital-Astronomy)
Explanation: Earlier this month, Venus and Mercury climbed into the western twilight, entertaining skygazers around planet Earth in a lovely conjunction of evening stars. Combining 8 images spanning April 4 through April 15, this composite tracks their progress through skies above Portsmouth, UK. Each individual image was captured at 19:50 UT. The sequential path for both bright planets begins low and to the left. But while Venus continues to swing away from the setting Sun, moving higher above the western horizon, Mercury first rises then falls. Its highest point is from the image taken on April 11. Of course on April 15, Venus and Mercury were joined by a young crescent Moon.
金星和水星出现在薄暮的西方天空中,让地球各地的天文爱好者能欣赏美丽暮星之近合。上面影像,是由在4月4日到4月15日期间,每天拍摄一张世界时19:50 UT时的照片,由八天所拍摄的8张照片所组合出来的。影像呈现了在这段期间,这两颗行星在英国朴次茅斯市(Portsmouth)的天空中如何移动。这两颗明亮行星的轨迹序列起始于左下角,离落渐远的金星逐渐远离的西方地平面,而水星则是先爬升后再下沉;最高点来自4月11日拍摄的影像。在4月15日,新月加入了与金星和水星争辉的行列。
 楼主| 发表于 2010-04-23 17:11 | 显示全部楼层
本帖最后由 jadiyd 于 2010-4-24 15:00 编辑

2010 April 23

SDO: The Extreme Ultraviolet Sun
Credit: NASA / Goddard / SDO AIA Team
Explanation: Don't panic, the Sun has not gone wild. But this wild-looking portrait of the nearest star to planet Earth was made on March 30th by the recently launched Solar Dynamics Observatory (SDO). Shown in false-color, the composite view covers extreme ultraviolet wavelengths and traces hot plasma at temperatures approaching 1 million kelvins. At full resolution, SDO image data is intended to explore solar activity in unprecedented detail. In fact, SDO will send 1.5 terabytes of data back each day, equivalent to a daily download of about half a million MP3 songs. New SDO data releases include a high-resolution movie of the large, eruptive prominence seen along the solar limb at the upper left.

刚升空太阳动态观测站(Solar Dynamics Observatory, SDO)所拍摄,这张远紫外光波段下的假色影像,还可追踪温度接近100万K热等离子。在全解析度下,SDO影像用史无前例的细致程度来探索太阳活动。事实上,SDO每天的观测量是1.5TB,相当于50万首的MP3歌曲。最新发布的SDO资料中,可以看到在太阳左上方边缘的喷发事件,其中还包含了高解析度的动画资料。
 楼主| 发表于 2010-04-24 15:00 | 显示全部楼层
2010 April 24

NGC 1055: Galaxy in a Box
Image Credit & Copyright: Ken Crawford (Rancho Del Sol Obs.), Collaboration: David Martinez-Delgado (MPIA, IAC), et al.
Explanation: Big, beautiful spiral galaxy NGC 1055 is a dominant member of a small galaxy group a mere 60 million light-years away toward the intimidating constellation Cetus. Seen edge-on, the island universe spans about 100,000 light-years, similar in size to our own Milky Way. Colorful, spiky stars in this cosmic portrait of NGC 1055 are in the foreground, well within the Milky Way. But along with a smattering of more distant background galaxies, the deep image also reveals a curious box-shaped inner halo extending far above and below this galaxy's dusty plane. The halo itself is laced with faint, narrow structures, and could represent the mixed and spread out debris from a satellite galaxy disrupted by the larger spiral some 10 billion years ago.
 楼主| 发表于 2010-04-25 17:08 | 显示全部楼层
2010 April 25

Planetary Nebula Mz3: The Ant Nebula
Credit: R. Sahai (JPL) et al., Hubble Heritage Team, ESA, NASA
Explanation: Why isn't this ant a big sphere? Planetary nebula Mz3 is being cast off by a star similar to our Sun that is, surely, round. Why then would the gas that is streaming away create an ant-shaped nebula that is distinctly not round? Clues might include the high 1000-kilometer per second speed of the expelled gas, the light-year long length of the structure, and the magnetism of the star visible above at the nebula's center. One possible answer is that Mz3 is hiding a second, dimmer star that orbits close in to the bright star. A competing hypothesis holds that the central star's own spin and magnetic field are channeling the gas. Since the central star appears to be so similar to our own Sun, astronomers hope that increased understanding of the history of this giant space ant can provide useful insight into the likely future of our own Sun and Earth.
 楼主| 发表于 2010-04-26 17:01 | 显示全部楼层
2010 April 26

Dust Pillar of the Carina Nebula
Credit: NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team (STScI)
Explanation: Inside the head of this interstellar monster is a star that is slowly destroying it. The monster, on the right, is actually an inanimate pillar of gas and dust that measures over a light year in length. The star, not itself visible through the opaque dust, is bursting out partly by ejecting energetic beams of particles. Similar epic battles are being waged all over the star-forming Carina Nebula. The stars will win in the end, destroying their pillars of creation over the next 100,000 years, and resulting in a new open cluster of stars. The pink dots around the image are newly formed stars that have already been freed from their birth monster. The above image was released last week in commemoration of the Hubble Space Telescopes 20th year of operation. The technical name for the stellar jets are Herbig-Haro objects. How a star creates Herbig-Haro jets is an ongoing topic of research, but it likely involves an accretion disk swirling around a central star. A second impressive Herbig-Haro jet occurs diagonally near the image center.


 楼主| 发表于 2010-04-27 16:31 | 显示全部楼层
2010 April 27
The Bloop: A Mysterious Sound from the Deep Ocean
Explanation: What created this strange sound in Earth's Pacific Ocean? Pictured above is a visual representation of a loud and unusual sound, dubbed a Bloop, captured by deep sea microphones in 1997. In the above graph, time is shown on the horizontal axis, deep pitch is shown on the vertical axis, and brightness designates loudness. Although Bloops are some of the loudest sounds of any type ever recorded in Earth's oceans, their origin remains unknown. The Bloop sound was placed as occurring several times off the southern coast of South America and was audible 5,000 kilometers away. Although the sound has similarities to those vocalized by living organisms, not even a blue whale is large enough to croon this loud. The sounds point to the intriguing hypothesis that even larger life forms lurk in the unexplored darkness of Earth's deep oceans. A less imagination-inspiring possibility, however, is that the sounds resulted from some sort of iceberg calving. No further Bloops have been heard since 1997, although other loud and unexplained sounds have been recorded.
 楼主| 发表于 2010-04-28 17:33 | 显示全部楼层
2010 April 28

Sunset on a Golden Sea
Image Credit & Copyright: Pete Lawrence (Digital-Astronomy)
Explanation: On April 17, the sky was clear and the Sun's colour was spectacular as night approached. This striking telescopic view even captures the Sun's swollen and distorted shape from the southern coast of the UK. Reflecting a bright column of sunlight, the sea also appears golden, with the horizon marked by the city of Portsmouth. Were the colours made more intense by volcanic dust? Maybe not. Normally, sunset (and sunrise) colours can be still be very dramatic, especially when the atmosphere is clear and the Sun is viewed very near the horizon, as in this scene. But large dust particles, like those in the airline thwarting ash clouds from the erupting Icelandic volcano Eyjafjallajökull, tend to create diffuse and subdued sunset colours.


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