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2013 Hubble Space Telescope Advent Calendar

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It's time for my favorite holiday tradition: the 2013 Hubble Space Telescope Advent Calendar. Every day until Wednesday, December 25, this page will present an amazing new image of our universe from NASA's Hubble telescope. Be sure to bookmark this calendar and come back every day until Christmas, or follow on Twitter (@in_focus), Google+, Facebook, or Tumblr for daily updates. I hope you enjoy these amazing and awe-inspiring images and the efforts of the science teams who have brought them to Earth. Merry Christmas, and Peace on Earth to all. (Also, choosing the "1280px" viewing option below, if you can support it, is always a good option.) [25 photos]

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This year's first image: A composite image of visible-light observations by NASA's Hubble Space Telescope, combined with infrared data from the ground-based Large Binocular Telescope in Arizona to assemble a dramatic view of the well-known Ring Nebula. The Ring Nebula is the glowing remains of a Sun-like star, the smoldering core, called a white dwarf, is the tiny white dot in the center of the Nebula. The object is tilted toward Earth so that astronomers see the ring face-on. The Hubble observations reveal that the nebula's shape is more complicated than astronomers thought. The blue gas in the nebula's center is actually a football-shaped structure that pierces the red doughnut-shaped material. Hubble also uncovers the detailed structure of the dark, irregular knots of dense gas embedded along the inner rim of the ring. The faint, scallop-shaped material surrounding the ring was expelled by the star during the early stages of the planetary nebula formation. Most Sun-like stars become planetary nebulae at the end of their lives. Once a star consumes all of its hydrogen, the nuclear fuel that makes it shine, it expands to a red giant. The bloated star then expels its outer layers, exposing its hot core. Ultraviolet radiation from the core illuminates the discarded material, making it glow. The Ring Nebula is about 2,000 light-years away in the constellation Lyra. The nebula measures roughly one light-year across. (NASA, ESA, C.R. O'Dell, Vanderbilt University, and D. Thompson, Large Binocular Telescope Observatory)
This year's first image: A composite image of visible-light observations by NASA's Hubble Space Telescope, combined with infrared data from the ground-based Large Binocular Telescope in Arizona to assemble a dramatic view of the well-known Ring Nebula. The Ring Nebula is the glowing remains of a Sun-like star, the smoldering core, called a white dwarf, is the tiny white dot in the center of the Nebula. The object is tilted toward Earth so that astronomers see the ring face-on. The Hubble observations reveal that the nebula's shape is more complicated than astronomers thought. The blue gas in the nebula's center is actually a football-shaped structure that pierces the red doughnut-shaped material. Hubble also uncovers the detailed structure of the dark, irregular knots of dense gas embedded along the inner rim of the ring. The faint, scallop-shaped material surrounding the ring was expelled by the star during the early stages of the planetary nebula formation. This outer material was imaged by the Large Binocular Telescope. Most Sun-like stars become planetary nebulae at the end of their lives. Once a star consumes all of its hydrogen, the nuclear fuel that makes it shine, it expands to a red giant. The bloated star then expels its outer layers, exposing its hot core. Ultraviolet radiation from the core illuminates the discarded material, making it glow. The Ring Nebula is about 2,000 light-years away in the constellation Lyra. The nebula measures roughly one light-year across. (NASA, ESA, C.R. O'Dell, Vanderbilt University, and D. Thompson, Large Binocular Telescope Observatory)
The gravitational field surrounding this massive cluster of galaxies, Abell 68, acts as a natural lens in space to brighten and magnify the light coming from very distant background galaxies. Like a funhouse mirror, lensing creates a fantasy landscape of arc-like images and mirror images of background galaxies. The foreground cluster is 2 billion light-years away, and the lensed images come from galaxies far behind it. In this photo, the image of a spiral galaxy at upper left has been stretched and mirrored into a shape similar to that of an alien from the classic 1970s computer game Space Invaders! A second, less distorted image of the same galaxy appears to the left of the large, bright elliptical galaxy. In the upper right of the photo is another striking feature of the image that is unrelated to gravitational lensing. What appears to be purple liquid dripping from a galaxy is a phenomenon called ram-pressure stripping. The gas clouds within the galaxy are being stripped out and heated up as the galaxy passes through a region of denser intergalactic gas. (NASA, ESA, and the Hubble Heritage/ESA-Hubble Collaboration) #
This light-year-long knot of interstellar gas and dust resembles a massive caterpillar. Harsh winds from extremely bright stars are blasting ultraviolet radiation at this "wanna-be" star and sculpting the gas and dust into its long shape. The culprits are 65 of the hottest, brightest known stars, classified as O-type stars, located 15 light-years away from the knot, towards the right edge of the image. These stars, along with 500 less bright, but still highly luminous B-type stars make up what is called the Cygnus OB2 association. Collectively, the association is thought to have a mass more than 30,000 times that of our Sun. The caterpillar-shaped knot, called IRAS 20324+4057, is a protostar in a very early evolutionary stage. It is still in the process of collecting material from an envelope of gas surrounding it. However, that envelope is being eroded by the radiation from Cygnus OB2. Protostars in this region should eventually become young stars with final masses about one to ten times that of our Sun, but if the eroding radiation from the nearby bright stars destroys the gas envelope before the protostars finish collecting mass, their final masses may be reduced. (NASA, ESA, the Hubble Heritage Team - STScI/AURA, and IPHAS) #
This interacting galaxy duo is collectively called Arp 142. The pair contains the disturbed, star-forming spiral galaxy NGC 2936, along with its elliptical companion, NGC 2937 at left. Once part of a flat, spiral disk, the orbits of the galaxy's stars have become scrambled due to gravitational tidal interactions with the other galaxy. This warps the galaxy's orderly spiral, and interstellar gas is strewn out into giant tails like stretched taffy. Gas and dust drawn from the heart of NGC 2936 becomes compressed during the encounter, which in turn triggers star formation. These bluish knots are visible along the distorted arms that are closest to the companion elliptical. The reddish dust, once within the galaxy, has been thrown out of the galaxy's plane and into dark veins that are silhouetted against the bright starlight from what is left of the nucleus and disk. The companion elliptical, NGC 2937, is a puffball of stars with little gas or dust present. The stars contained within the galaxy are mostly old, as evidenced by their reddish color. There are no blue stars that would be evidence of recent star formation. While the orbits of this elliptical's stars may be altered by the encounter, it's not apparent that the gravitational pull by its neighboring galaxy is having much of an effect. Arp 142 lies 326 million light-years away in the southern constellation Hydra. (NASA, ESA, and the Hubble Heritage Team - STScI/AURA) #
The stellar nursery of the Carina Nebula. What appears to be a craggy mountaintop enshrouded by wispy clouds, is actually a three-light-year-tall pillar of gas and dust that is being eaten away by the brilliant light from nearby bright stars. The pillar, some 7,500 light-years distant, is also being assaulted from within, as infant stars buried inside it fire off jets of gas that can be seen streaming from towering peaks. Nestled inside this dense mountain are fledgling stars. Long jets of gas can be seen shooting in opposite directions off the pedestal at the top of the image. The jets are launched by swirling disks around the young stars, which allow material to slowly accrete onto the stars' surfaces. (NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team, STScI) #
The beautiful, petal-like shells of galaxy PGC 6240 are captured here in intricate detail by the NASA/ESA Hubble Space Telescope, set against a sky full of distant background galaxies. PGC 6240 is an elliptical galaxy approximately 350 million light years away in the southern constellation of Hydrus, the Water Snake. It is orbited by a number of globular clusters that contain both young and old stars - thought to be a result of a galactic merger in the recent past. The background is dotted with dozens of other more distant galaxies. (ESA/Hubble and NASA) #
A photo illustration of the magnificent spiral galaxy M106. Astrophotographer Robert Gendler retrieved archival Hubble images of M106 to assemble a mosaic of the center of the galaxy. He then used his own and fellow astrophotographer Jay GaBany's observations of M106 to combine with the Hubble data in areas where there was less coverage, and finally, to fill in the holes and gaps where no Hubble data existed. This portrait of M106 contains only the inner structure around the halo and nucleus. Large amounts of gas from the galaxy are thought to be falling into and fueling a supermassive black hole contained in the nucleus. Also known as NGC 4258, M106 lies 23.5 million light-years away, in the constellation Canes Venatici. (NASA, ESA, the Hubble Heritage Team - STScI/AURA, and R. Gendler for the Hubble Heritage Team) #
Globular cluster Messier 15 is located some 35,000 light-years away in the constellation of Pegasus (The Winged Horse). It is one of the oldest clusters known, with an age of around 12 billion years. Both very hot blue stars and cooler golden stars can be seen swarming together in the image, becoming more concentrated towards the cluster's bright center. Messier 15 is one of the densest globular clusters known, with most of its mass concentrated at its core. As well as stars, Messier 15 was the first cluster known to host a planetary nebula, and it has been found to have a rare type of black hole at its centre. This image is made up of observations from Hubble's Wide Field Camera 3 and Advanced Camera for Surveys in the ultraviolet, infrared, and optical parts of the spectrum. (NASA, ESA) #
The iconic Horsehead Nebula has graced astronomy books ever since its discovery over a century ago. In this Hubble Space Telescope view, the nebula appears in a new light, as seen in infrared wavelengths. The nebula, shadowy in optical light, appears transparent and ethereal when seen in the infrared, represented here with visible shades. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that are easily seen in infrared light. The backlit wisps along the Horsehead's upper ridge are being illuminated by Sigma Orionis, a young five-star system just off the top of the Hubble image. A harsh ultraviolet glare from one of these bright stars is slowly evaporating the nebula. Along the nebula's top ridge, two fledgling stars peek out from their now-exposed nurseries. Gas clouds surrounding the Horsehead have already dissipated, but the tip of the jutting pillar contains a slightly higher density of hydrogen and helium, laced with dust. This casts a shadow that protects material behind it from being photo-evaporated, and a pillar structure forms. Astronomers estimate that the Horsehead formation has about five million years left before it too disintegrates. (NASA, ESA, and the Hubble Heritage Team - STScI/AURA) #
A snapshot of MyCn18, a young planetary nebula, reveals that the object has an hourglass shape with an intricate pattern of "etchings" in its walls. A planetary nebula is the glowing relic of a dying, Sun-like star. The results are of great interest because they shed new light on the poorly understood ejection of stellar matter that accompanies the slow death of Sun-like stars. (Raghvendra Sahai and John Trauger, JPL, the WFPC2 science team, and NASA) #
Galaxy group Stephan's Quintet is 290 million light-years away, in the constellation Pegasus. Four of these five galaxies are actually close enough to be locked in a vast intricate dance. Galaxy NGC 7320, the brighter galaxy at lower left, appears to be part of the group, but is in fact 250 million light years closer than the others. (NASA, ESA, and the Hubble SM4 ERO Team) #
Hubble caught Jupiter's moon Ganymede just before it ducked behind the giant planet. Ganymede completes an orbit around Jupiter every seven days. Because Ganymede's orbit is tilted nearly edge-on to Earth, it routinely can be seen passing in front of and disappearing behind its giant host, only to reemerge later. Composed of rock and ice, Ganymede is the largest moon in our solar system. It is even larger than the planet Mercury. But Ganymede looks like a dirty snowball next to Jupiter, the largest planet in our solar system. Jupiter is so big that only part of its Southern Hemisphere can be seen in this image. Hubble's view is so sharp that astronomers can see features on Ganymede's surface, most notably the white impact crater, Tros, and its system of rays, bright streaks of material blasted from the crater. Tros and its ray system are roughly the width of Arizona. (NASA, ESA, and E. Karkoschka, University of Arizona) #
Comet ISON, before it broke apart as it rounded the Sun. Here, ISON floats against a seemingly infinite backdrop of numerous galaxies and a handful of foreground stars. Discovered in 2012, the tiny ball of ice and rock (about 2 km in diameter), hurtled toward the Sun for a very close visit -- passing approximately 1,165,000 km (724,000 mi) above the Sun's surface at a relative speed of 1,359,900 kph (845,000 mph). The speed, gravitational forces, and extreme radiation were too much for ISON, which broke apart as it passed behind our star. (NASA, ESA, and the Hubble Heritage Team, STScI/AURA) #
Light echoes of the star V838 Monocerotis. This image shows the dramatic illumination of surrounding dusty cloud structures, called a light echo, that built in brilliance for several years after the star suddenly brightened for several weeks in early 2002. The illumination of interstellar dust comes from the red supergiant star at the middle of the image, which gave off a pulse of light three years before, somewhat similar to setting off a flashbulb in a darkened room. The dust surrounding V838 Mon may have been ejected from the star during a previous explosion, similar to the 2002 event. (NASA, ESA, and The Hubble Heritage Team, STScI/AURA) #
Abell 2261. The giant elliptical galaxy in the center of this image is the most massive and brightest member of the galaxy cluster Abell 2261. Spanning a little more than one million light-years, the galaxy is about 10 times the diameter of our Milky Way galaxy. The bloated galaxy is a member of an unusual class of galaxies with a diffuse core filled with a fog of starlight. Normally, astronomers would expect to see a concentrated peak of light around a central black hole. The Hubble observations revealed that the galaxy's puffy core, measuring about 10,000 light-years, is the largest yet seen. The gravitational effect on the light traveling from background galaxies can cause images to appear stretched or smudged, something called gravitational lensing. (NASA, ESA, M. Postman, STScI, T. Lauer, NOAO, and the CLASH team) #
The Antennae Galaxies. Known as NGC 4038 and NGC 4039, these two galaxies are locked in a deadly embrace. Once normal, sedate spiral galaxies like the Milky Way, the pair have spent the past few hundred million years in a clash so violent that stars have been ripped from their host galaxies to form a streaming arc between the two. Clouds of gas are seen in bright pink and red, surrounding the bright flashes of blue star-forming regions - some of which are partially obscured by dark patches of dust. The rate of star formation is so high that the Antennae Galaxies are said to be n a state of starburst, a period in which all of the gas within the galaxies is being used to form stars. (ESA/Hubble, NASA) #
IRAS 23166+1655 is an unusual pre-planetary nebula, a celestial spiral around the star LL Pegasi. The spiral pattern suggests a regular periodic origin for the nebula's shape. The material forming the spiral is moving outwards a speed of about 50.000 km/hour and, by combining this speed with the distance between layers, astronomers calculate that the shells are each separated by about 800 years. The spiral is thought to arise because LL Pegasi is a binary system, with the star that is losing material and a companion star orbiting each other. (ESA/NASA, R. Sahai) #
Spiral galaxy NGC 634 was discovered back in the nineteenth century by French astronomer Édouard Jean-Marie Stephan. It is about about 120,000 light years across, and lies 250 million light years away in the Triangulum constellation. Other, more distant galaxies can be seen in the background as well as through the galaxy. (ESA/Hubble, NASA) #
A small section of the Carina Nebula, a star-forming region about 7,500 light-years from Earth in the southern constellation of Carina. Infant stars blaze with a ferocity so severe that the radiation emitted carves away at the surrounding gas, sculpting it into strange structures. The dust clumps towards the upper right of the image, looking like ink dropped into milk, were formed in this way. It has been suggested that they are cocoons for newly forming stars. The brightest stars in the image are in the much closer to us, and are not actually part of the Carina Nebula. (ESA/Hubble, NASA ) #
The Luminous Red Galaxy in the center of the bullseye here has an unusually large mass, containing about ten times the mass of the Milky Way. The blue horseshoe shape is a distant galaxy that has been magnified and warped into a nearly complete ring by the strong gravitational pull of the massive foreground galaxy. This "Cosmic Horseshoe" is one of the best examples of an Einstein Ring -- gravitational lensing where the alignment is perfect, allowing the light from distant galaxies to warp around nearer massive galaxies into a circular shape. The distant blue galaxy is about 10 billion light years away. (ESA/Hubble, NASA) #
Planetary nebula NGC 6302, better known as the Butterfly Nebula, is made up of roiling cauldrons of gas heated to nearly 20,000 degrees Celsius. The gas is tearing across space at more than 950 000 kilometres per 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. Roughly 3,800 light-years distant, the central star itself cannot be seen, because it is hidden within a doughnut-shaped ring of dust, which appears as a dark band pinching the nebula in the center. (NASA, ESA and the Hubble SM4 ERO Team) #
An animation, showing the light echoes bouncing around variable star RS Puppis over a period of five weeks. as the star grows brighter and dimmer as it pulsates. These pulsations have created a stunning example of a phenomenon known as a light echo, where light appears to reverberate through the murky environment around the star. RS Puppis is a type of variable star known as a Cepheid variable, with a fairly long period, varying in brightness by almost a factor of five every 40 or so days. (NASA, ESA, and the Hubble Heritage Team) #
Disk galaxy NGC 5866, viewed edge-on, about 50 million light years away from Earth. A dust disk runs along the edge of the galaxy, past which you can see its structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo. Background galaxies that are millions to billions of light-years farther away are also seen through the halo. (NASA, ESA, and The Hubble Heritage Team) #
In February of 1997, the Hubble Space Telescope begins its separation from the Space Shuttle Discovery following its release after a servicing mission. This 13.2 m (43.5 ft), 11,110 kg (24,500 lb) telescope has been in low Earth orbit for nearly 24 years now, returning thousands of images and priceless data to scientists here on Earth. barring any major trouble, engineers believe Hubble could remain operational for years, possibly past the launch the James Webb Space Telescope, scheduled for launch in 2018. (NASA) #
The Hubble Ultra Deep Field. Almost none of the objects visible in this image are within our own galaxy, the Milky Way. Instead, practically every smudge, dot or spiral you see here is an entire galaxy, each composed of billions of stars. In late 2003, scientists pointed Hubble at a relatively dim patch of sky, and just opened up the shutter, leaving it open for more than one million seconds (just over 11 days). The result was the Ultra Deep Field, a snapshot of more than 10,000 previously unknown galaxies visible within a tiny patch of our night sky. No other image has ever demonstrated so powerfully the unimaginable vastness of our universe, or the wonders yet to be discovered. (NASA, ESA, S. Beckwith, STScI and the HUDF Team)

Thanks so much for being a part of this year's Hubble Advent Calendar! Merry Christmas, Happy New Year, and a heartfelt wish for Peace on Earth in 2014!

-Alan

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