本帖最后由 人与自然 于 2012-4-1 13:10 编辑
首先解释一下什么叫做“Advent Calendar”，更多内容参阅维基百科：
http://en.wikipedia.org/wiki/Advent_calendar
“Advent Calendar”有点类似中国人进入腊月就开始做过年的准备的这一段时间。西方人过圣诞，也提前一个月。圣诞节前的四个星期是Christmas Advent。advent是降临来临的意思，这个节也称为“降临节”。从倒数第四个周日起，人们就正式进入了兴奋的等待。
Advent Calendar是这一段时间极具代表性的一部分。这是一种可以吃的日历。盒子封面是圣诞老人，共有24个小格子，标了数字，里面有一块巧克力,有的做成圣诞老人，有的做成袜子，有的做成雪撬，有的做的驯鹿，还有蝴蝶节，礼物包，圣诞树等各种不同的形状。小孩子每天打开一格，吃掉一块巧克力，全部吃完了以后，就是圣诞了，大包小包的巧克力糖果接踵而来。
从每年距11月30日最近的一个星期日开始，一直到12月24日圣诞节之前，这大约4周的时间都是“降临节”。这段时间是基督徒们准备和等待基督复活的日子。可能是德国的路德宗教徒最晚于19世纪初首先引入了Advent Calendar的概念，而他们的具体做法，就是发明了Advent Calendar，即“降临节日历”。为此，19世纪初就有人开始想法倒数圣诞节前的日子，比如用粉笔画线，每天挂一小幅跟耶稣有关的图画，或者每天点一根蜡烛等。第一个手工制作的Advent Calendar产生于1851年，20世纪初，开始印刷Advent Calendar，现在，Advent Calendar已经成为圣诞的传统之一。制作和相互寄送贺卡，也成为这一时间的商家赚钱和和人们表达祝福的主要内容。
由于西方圣诞节的类似于中国人过年，居于这样的认识，哈伯望远镜的“Advent Calendar”，其实相当于中国人的“年画”，是著名的“The Big Picture”精选出来的哈伯望远镜照片集合而成，送给全世界的天文爱好者和哈伯迷的圣诞大礼，共25张，极具观赏和科学价值。本贴先贴出2008年度的，2009-2011年度将逐步推出！（原网站图片更大一些，大家可进入原网站欣赏）
鉴于本人的天文学专业翻译水平不足，对这些熟悉的照片也就不再一一翻译；对一些不太熟悉的照片，有兴趣的坛友可以看看英文解释，基本内容应该是可以清晰理解的。
Hubble Space Telescope Advent Calendar 2009 Once more, we enter the month of December and the traditional western Holiday Season, and once again, I'd like to present a Hubble Space Telescope imagery Advent Calendar for 2009. Keep checking this page, because every day, for the next 25 days, a new photo will be revealed here from the Hubble Space Telescope, some old and some new. I have felt extremely fortunate to have been able to share photographs and stories with you all this year, and I wish for a Happy Holiday to all those who will celebrate, and for Peace on Earth to everyone. - Alan (25 photos total - eventually) [previously: the 2008 calendar]
The spectacular structure of Planetary nebula NGC 2818 contains the outer layers of a star that were expelled into interstellar space. The glowing gaseous shrouds in the nebula were shed by the central star after it ran out of fuel to sustain the nuclear reactions in its core. This Hubble image was taken in November 2008 with the Wide Field Planetary Camera 2. The colors in the image represent a range of emissions coming from the clouds of the nebula: red represents nitrogen, green represents hydrogen, and blue represents oxygen. (NASA, ESA, and the Hubble Heritage Team, STScI/AURA) More (see this on Google Sky)
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This composite color infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years. This view combines the sharp imaging of the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey to make the sharpest infrared picture ever made of the Galactic core. The core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust. At this distance - 26,000 light-years away - Hubble reveals details in objects as small as 20 times the size of our own solar system. (NASA, ESA, Q.D. Wang (UMass, Amherst), JPL, and S. Stolovy (Spitzer Science Center/Caltech)) More (see this on Google Sky) #
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On February 24, 2009, the Hubble Space Telescope took a photo of four moons of Saturn passing in front of their parent planet. In this view, the giant orange moon Titan casts a large shadow onto Saturn's north polar hood. Below Titan, near the ring plane and to the left is the moon Mimas, casting a much smaller shadow onto Saturn's equatorial cloud tops. Farther to the left, and off Saturn's disk, are the bright moon Dione and the fainter moon Enceladus. These pictures were taken with Hubble's Wide Field Planetary Camera 2 when Saturn was at a distance of roughly 1.25 billion km (775 million mi) from Earth. (NASA, ESA, and the Hubble Heritage Team, STScI/AURA) More #
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UGC 8335 is a strongly interacting pair of spiral galaxies. The interaction has united the galaxies via a bridge of material and has yanked two strongly curved tails of gas and stars from the outer parts of their bodies . Both galaxies show dust lanes in their centers. UGC 8335 is located in the constellation of Ursa Major, the Great Bear, about 400 million light-years from Earth. It is the 238th galaxy in Arp's Atlas of Peculiar Galaxies. (NASA, ESA, the Hubble Heritage, STScI/AURA-ESA/Hubble Collaboration, and A. Evans, University of Virginia, Charlottesville/NRAO/Stony Brook University) More (see this on Google Sky) #
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The NASA/ESA Hubble Space Telescope caught scattered light from the Boomerang Nebula in images taken with the Advanced Camera for Surveys in early 2005. This reflecting cloud of dust and gas has two nearly symmetric lobes of matter that are being ejected from a central star. Each lobe of the nebula is nearly one light-year in length, making the total length of the nebula half as long as the distance from our Sun to our nearest neighbors - the alpha Centauri stellar system, located roughly 4 light-years away. The Boomerang Nebula resides 5,000 light-years from Earth. Hubble's sharp view is able to resolve patterns and ripples in the nebula very close to the central star that are not visible from the ground. (NASA, ESA and The Hubble Heritage Team STScI/AURA) More (see this on Google Sky) #
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Stars burst to life in the chaotic Carina Nebula in this image of a huge pillar taken in visible and in infrared light by NASA's Hubble Space Telescope. Composed of gas and dust, the nebula resides 7,500 light-years away in the southern constellation Carina. This image, taken in visible light, shows the tip of the 3-light-year-long pillar, bathed in the glow of light from hot, massive stars off the top of the image. Scorching radiation and fast winds (streams of charged particles) from these stars are sculpting the pillar and causing new stars to form within it. Streamers of gas and dust can be seen flowing off the top of the structure. Nestled inside this dense structure are fledgling stars. They cannot be seen in this image because they are hidden by a wall of gas and dust. Although the stars themselves are invisible, one of them is providing evidence of its existence. Thin puffs of material can be seen traveling to the left and to the right of a dark notch in the center of the pillar. The matter is part of a jet produced by a young star. Farther away, on the left, the jet is visible as a grouping of small, wispy clouds. A few small clouds are visible at a similar distance on the right side of the jet. Astronomers estimate that the jet is moving at speeds of up to 850,000 miles an hour. The jet's total length is about 10 light-years. (NASA, ESA, and the Hubble SM4 ERO Team) More (see this on Google Sky) #
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VV 705, or Markarian 848, consists of two galaxies that seem to be embracing each other. Two long, highly curved arms of gas and stars emerge from a central region with two cores. One arm, curving clockwise, stretches to the top of the image where it makes a U-turn and interlocks with the other arm that curves up counter-clockwise from below. The two cores are 16,000 light-years apart. The pair is thought to be midway through a merger. Markarian 848 is located in the constellation of Bootes, the Bear Watcher, and is approximately 550 million light-years away from Earth. (NASA, ESA, the Hubble Heritage STScI/AURA-ESA/Hubble Collaboration, and A. Evans, University of Virginia, Charlottesville/NRAO/Stony Brook University) More (see this on Google Sky) #
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The core of the spectacular globular cluster Omega Centauri glitters with the combined light of 2 million stars. The entire cluster contains 10 million stars, and is among the biggest and most massive of some 200 globular clusters orbiting the Milky Way Galaxy. Omega Centauri lies 17,000 light-years from Earth. Image acquired in June of 2002. (NASA, ESA, and the Hubble Heritage Team, STScI/AURA) More (see this on Google Sky) #
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Messier 104 (M104), the Sombrero galaxy. has a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. At a relatively bright magnitude of +8, M104 is just beyond the limit of naked-eye visibility and is easily seen through small telescopes. The Sombrero lies at the southern edge of the rich Virgo cluster of galaxies and is one of the most massive objects in that group, equivalent to 800 billion suns. The galaxy is 50,000 light-years across and is located 28 million light-years from Earth. X-ray emission suggests that there is material falling into the compact core, where a 1-billion-solar-mass black hole resides. In the 19th century, some astronomers speculated that M104 was simply an edge-on disk of luminous gas surrounding a young star, which is prototypical of the genesis of our solar system. But in 1912, astronomer V. M. Slipher discovered that the hat-like object appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that the Sombrero was really another galaxy, and that the universe was expanding in all directions. (NASA and The Hubble Heritage Team, STScI/AURA) More (see this on Google Sky) #
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The Hubble Space Telescope caught the eerie, wispy tendrils of a dark interstellar cloud being destroyed by the passage of one of the brightest stars in the Pleiades star cluster. Like a flashlight beam shining off the wall of a cave, the star is reflecting light off the surface of pitch black clouds of cold gas laced with dust. These are called reflection nebulae. (NASA/ESA and The Hubble Heritage Team, STScI/AURA, George Herbig and Theodore Simon, University of Hawaii) More (see this on Google Sky) #
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What resemble dainty butterfly wings are actually roiling cauldrons of gas heated to more than 36,000 degrees Fahrenheit. The gas is tearing across space at more than 600,000 miles an hour - fast enough to travel from Earth to the Moon in 24 minutes! A dying star that was once about five times the mass of the Sun is at the center of this fury. It has ejected its envelope of gases and is now unleashing a stream of ultraviolet radiation that is making the cast-off material glow. The Wide Field Camera 3 (WFC3), installed by NASA astronauts in May 2009, snapped this image of the planetary nebula, catalogued as NGC 6302, which lies within our Milky Way galaxy, roughly 3,800 light-years away in the constellation Scorpius. The glowing gas is the star's outer layers, expelled over about 2,200 years. NGC 6302 was imaged on July 27, 2009, with Hubble's Wide Field Camera 3 in ultraviolet and visible light. Filters that isolate emissions from oxygen, helium, hydrogen, nitrogen, and sulfur from the planetary nebula were used to create this composite image. (NASA, ESA, and the Hubble SM4 ERO Team) More (see this on Google Sky) #
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An international team of astronomers using the NASA/ESA Hubble Space Telescope has discovered a ghostly ring of dark matter that was formed long ago during a titanic collision between two massive galaxy clusters. It is the first time that a dark matter distribution has been found that differs substantially from the distribution of ordinary matter. This image shows the galaxy cluster Cl 0024+17 (ZwCl 0024+1652) as seen by Hubble's Advanced Camera for Surveys. The image displays faint faraway background galaxies that had their light bent by the cluster's strong gravitational field. By mapping the distorted light and using it to deduce how dark matter is distributed in the cluster, astronomers spotted the ring of dark matter. One of the background galaxies is located about two times further away than the yellow cluster galaxies in the foreground, and has been multiple-imaged into five separate arc-shaped components, seen in blue. (NASA, ESA, M.J. Jee and H. Ford, Johns Hopkins University) More #
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The planetary nebula, IC 4593, lies in the northern constellation Hercules, about 7,000 light-years away from Earth. Its colorful, intricate shape reveals how the glowing gas ejected by a dying Sun-like star evolved dramatically over time. Over thousands of years, the clouds of gas expand away and the nebula becomes larger. Energetic ultraviolet light from the star penetrates more deeply into the gas, causing the hydrogen and oxygen to glow more prominently. This snapshot was taken with Hubble's Wide Field Planetary Camera 2 in February 2007. (NASA, ESA, and The Hubble Heritage Team STScI/AURA) More (see this on Google Sky) #
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A peculiar system of interacting galaxies known as Arp 194 contains several galaxies, along with a "cosmic fountain" of stars, gas, and dust that stretches over 100,000 light-years. The northern (left) component of Arp 194 appears as a haphazard collection of dusty spiral arms, bright blue star-forming regions, and at least two galaxy nuclei that appear to be connected and in the early stages of merging. A third, relatively normal, spiral galaxy appears off to the right. The southern (lower) component of the galaxy group contains a single large spiral galaxy with its own blue star-forming regions. However, the most striking feature of this galaxy troupe is the impressive blue stream of material extending from the northern component. This "fountain" contains complexes of super star clusters, each one of which may contain dozens of individual young star clusters. The blue color is produced by the hot, massive stars which dominate the light in each cluster. Overall, the "fountain" contains many millions of stars. These young star clusters probably formed as a result of the interactions between the galaxies in the northern component of Arp 194. The compression of gas involved in galaxy interactions can enhance the star-formation rate and give rise to brilliant bursts of star formation in merging systems. Arp 194, located in the constellation Cepheus, resides approximately 600 million light-years away from Earth. (NASA, ESA, and the Hubble Heritage Team STScI/AURA) More (see this on Google Sky) #
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This image shows the edge of a giant gaseous cavity within the star-forming region called NGC 3324. The glowing nebula has been carved out by intense ultraviolet radiation and stellar winds from several hot, young stars. A cluster of extremely massive stars, located well outside this image in the center of the nebula, is responsible for the ionization of the nebula and excavation of the cavity. The image also reveals dramatic dark towers of cool gas and dust that rise above the glowing wall of gas. The dense gas at the top resists the blistering ultraviolet radiation from the central stars, and creates a tower that points in the direction of the energy flow. The high-energy radiation blazing out from the hot, young stars in NGC 3324 is sculpting the wall of the nebula by slowly eroding it away. Located in the Southern Hemisphere, NGC 3324 is at the northwest corner of the Carina Nebula (NGC 3372), home of the Keyhole Nebula and the active, outbursting star Eta Carinae. The entire Carina Nebula complex is located at a distance of roughly 7,200 light-years, and lies in the constellation Carina. (NASA, ESA, and The Hubble Heritage Team STScI/AURA) More (see this on Google Sky) #
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This portrait of Stephan's Quintet, also known as Hickson Compact Group 92, was taken by the new Wide Field Camera 3 (WFC3) aboard NASA's Hubble Space Telescope. Stephan's Quintet, as the name implies, is a group of five galaxies. The name, however, is a bit of a misnomer. Studies have shown that group member NGC 7320, at lower right, is actually a foreground galaxy about seven times closer to Earth than the rest of the group. NGC 7320 is 40 million light-years from Earth. The other members of the quintet reside 290 million light-years away in the constellation Pegasus. WFC3 observed the quintet in July and August 2009. (NASA, ESA, and the Hubble SM4 ERO Team) More (see this on Google Sky) #
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This very deep image taken with the NASA/ESA Hubble Space Telescope shows the spiral galaxy NGC 4921 along with a spectacular backdrop of more distant galaxies. It was created from a total of 80 separate pictures through yellow and near-infrared filters. (NASA, ESA and K. Cook, Lawrence Livermore National Laboratory, USA) More (see this on Google Sky) #
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Huge waves are sculpted in NGC 6537, the Red Spider Nebula, a two-lobed nebula some 3000 light-years away in the constellation of Sagittarius. This warm planetary nebula harbours one of the hottest stars known and its powerful stellar winds generate waves 100 billion kilometres high. The waves are caused by supersonic shocks, formed when the local gas is compressed and heated in front of the rapidly expanding lobes. The atoms caught in the shock emit the spectacular radiation seen in this image. (ESA & Garrelt Mellema, Leiden University, the Netherlands) More (see this on Google Sky) #
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A small region inside the massive globular cluster Omega Centauri which boasts nearly 10 million stars. The stars in Omega Centauri are about about 16,000 light-years from Earth, and are between 10 billion and 12 billion years old. The majority of the stars in the image are yellow-white, like our Sun. These are adult stars that are shining by hydrogen fusion. Toward the end of their normal lives, the stars become cooler and larger. These late-life stars are the orange dots in the image. Even later in their life cycles, the stars continue to cool down and expand in size, becoming red giants. These bright red stars swell to many times larger than our Sun's size and begin to shed their gaseous envelopes. After ejecting most of their mass and exhausting much of their hydrogen fuel, the stars appear brilliant blue. Only a thin layer of material covers their super-hot cores. These stars are desperately trying to extend their lives by fusing helium in their cores. At this stage, they emit much of their light at ultraviolet wavelengths. When the helium runs out, the stars reach the end of their lives. Only their burned-out cores remain, and they are called white dwarfs (the faint blue dots in the image). White dwarfs are no longer generating energy through nuclear fusion and have gravitationally contracted to the size of Earth. They will continue to cool and grow dimmer for many billions of years until they become dark cinders. All of the stars in the image are cozy neighbors. The average distance between any two stars in the cluster's crowded core is only about a third of a light-year, roughly 13 times closer than our Sun's nearest stellar neighbor, Alpha Centauri. Although the stars are close together, WFC3's sharpness can resolve each of them as individual stars. If anyone lived in this globular cluster, they would behold a star-saturated sky that is roughly 100 times brighter than Earth's sky. Hubble observed Omega Centauri on July 15, 2009, in ultraviolet and visible light. (NASA, ESA, and the Hubble SM4 ERO Team) More (see this on Google Sky) #
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This image from NASA's Hubble Space Telescope shows the diverse collection of galaxies in the cluster Abell S0740 that is over 450 million light-years away in the direction of the constellation Centaurus. The giant elliptical ESO 325-G004 looms large at the cluster's center. The galaxy is as massive as 100 billion of our suns. Hubble resolves thousands of globular star clusters orbiting ESO 325-G004. At the galaxy's distance they appear as pinpoints of light contained within the diffuse halo. Other fuzzy elliptical galaxies dot the image. Some have evidence of a disk or ring structure that gives them a bow-tie shape. Several spiral galaxies are also present. The starlight in these galaxies is mainly contained in a disk and follows along spiral arms. This image was created by combining Hubble science observations taken in January 2005 with Hubble Heritage observations taken a year later to form a 3-color composite. The filters that isolate blue, red and infrared light were used with the Advanced Camera for Surveys aboard Hubble. (NASA, ESA, and The Hubble Heritage Team, STScI/AURA) More #
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This portrait is the most detailed view of the largest stellar nursery in our local galactic neighborhood. The massive, young stellar grouping, called R136, is only a few million years old and resides in the 30 Doradus Nebula, a turbulent star-birth region in the Large Magellanic Cloud, a satellite galaxy of our Milky Way located some 170,000 light-years away. Many of the diamond-like icy blue stars are among the most massive stars known. Several of them are over 100 times more massive than our Sun. The image, taken by Hubble on October 20-27, 2009, spans about 100 light-years across. (NASA, ESA, and F. Paresce, R. O'Connell, and the Wide Field Camera 3 Science Oversight Committee) More #
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Hubble's Advance Camera for Surveys (ACS) recently took this image of galaxy NGC 4522 in the Virgo Cluster. Backdropped by many other more distant galaxies, the impression given by NGC 4522 is that it is flying apart. A phenomenon called ram pressure stripping is mangling the galaxy as it hurtles through a region of hot x-ray emitting gas at 10 million kilometers per hour- stripping away its own gas content. NGC 4522 is some 60 million light years away. More #
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The star cluster Pismis 24 lies in the core of the large emission nebula NGC 6357 that extends one degree on the sky in the direction of the Scorpius constellation. Part of the nebula is ionised by the youngest (bluest) heavy stars in Pismis 24. The intense ultraviolet radiation from the blazing stars heats the gas surrounding the cluster and creates a bubble in NGC 6357. The presence of these surrounding gas clouds makes probing into the region even harder. One of the top candidates for the title of "Milky Way stellar heavyweight champion" was, until now, Pismis 24-1, a bright young star that lies in the core of the small open star cluster Pismis 24 (the bright stars in the Hubble image) about 8,000 light-years away from Earth. Pismis 24-1 was thought to have an incredibly large mass of 200 to 300 solar masses. New NASA/ESA Hubble measurements of the star, have, however, resolved Pismis 24-1 into two separate stars, and, in doing so, have "halved" its mass to around 100 solar masses. (NASA, ESA and Jesoes Maz Apellyniz, Instituto de astrofisica de Andalucia, Spain, Davide De Martin, ESA/Hubble) More (see this on Google Sky) #
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The photographer itself - a crew member aboard the Space Shuttle Atlantis captured this still image of the Hubble Space Telescope above the Earth, as the two spacecraft continued their relative separation on May 19, 2009 after having been linked together for the better part of a week during the STS-125 mission. During the week five spacewalks were performed to complete the final servicing mission for the orbital observatory. More #
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In 2004, Hubble created the deepest visible-light image of the Universe and now, with its brand-new camera, it is seeing even farther in the same region. This image, taken by the HUDF09 team with the new WFC3/infrared camera on Hubble in late August 2009, during a total of four days of pointing for 173,000 seconds of total exposure time, is the deepest image of the universe ever taken in near-infrared light. Nearly every smudge and bit of light in this image is a separate galaxy made up of billions of stars. The faintest and reddest objects in the image are galaxies that formed 600 million years after the Big Bang. No galaxies have been seen before at such early times. The image was taken in the same region as the Hubble Ultra Deep Field (2004), and is roughly 2.4 arcminutes wide. Again, I invite you to step outside some dark night in the future and gaze up at the sky, knowing that every bit of apparent darkness above is really filled with the faint light of these billions of faraway galaxies. Best wishes to all, and a Happy New Year - Alan. (NASA, ESA, G. Illingworth, UCO/Lick Observatory and the University of California, Santa Cruz, R. Bouwens, UCO/Lick Observatory and Leiden University and the HUDF09 Team) More #
More links and information
Hubble Advent Calendar 2008 - The Big Picture
Hubblesite - official site
ESA Spacetelescope - ESA home for NASA/ESA Hubble
Hubble Space Telescope - Wikipedia entry |
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