Time once more for one of my favorite holiday traditions, the 10th annual Hubble Space Telescope Advent Calendar. Every day until Monday, December 25, this page will present one new incredible image  of our universe from NASA's Hubble telescope. Be sure to bookmark this calendar and come back every day until the 25th, or follow on Twitter (@TheAtlPhoto), 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. Again, I want to say how fortunate I feel to have been able to share photo stories with you all year, and how happy I am to put together the 10th edition of this calendar. Wishing you a merry Christmas, happy holidays, and peace on Earth.

1. The Bubble Nebula, also known as NGC 7635, is an emission nebula located 8,000 light years away in the Cassiopeia constellation. The bubble is created by stellar wind pushing out from a massive hot central star, visible here just left of the center of the image, a purple star partly obscured by blue gas clouds. The nebula is seven light years across—about one-and-a-half times the distance from our sun to its nearest stellar neighbor, Alpha Centauri. This stunning image was observed by the NASA/ESA Hubble Space Telescope to celebrate its 26th year in space.
NASA, ESA, Hubble Heritage Team
2. Dark Nebulae in a Young Star Cluster. Seen here is a section of an open star cluster in the Eagle Nebula that formed about 5.5 million years ago, approximately 6,500 light-years from Earth. NGC 6611 is a very young cluster, containing many hot, blue stars, whose fierce ultraviolet glow make the surrounding nebula glow brightly. Dark patches can also be spotted, punctuating the stellar landscape at right. These dark areas are very dense regions of gas and dust, which obstruct light from passing through. Many of these may be hiding the sites of the early stages of star formation, before the fledgling stars clear away their surroundings and burst into view.
ESA / Hubble & NASA
3. Backlit Dust Lanes. The giant galaxy NGC 7049 lies 100 million light years away from Earth in the constellation of Indus, in the southern sky. It measures approximately 150,000 light-years across, or about 1.5 times wider than the Milky Way. The dust lanes, which appear as a lacy web, are dramatically backlit by the millions of stars in the halo of NGC 7049.
NASA, ESA and W. Harris - McMaster University, Ontario, Canada
4. Turbulence in Sh2-106. This emission nebula is a compact star-forming region about 2,000 light-years from Earth in the constellation Cygnus. A newly-formed star called S106 IR is shrouded in dust at the center of the image, and is responsible for the surrounding gas cloud’s hourglass-like shape and the turbulence visible within. Light from glowing hydrogen is colored blue in this image. The image combines observations from the Hubble Space Telescope (in the center) with images from the National Astronomical Observatory of Japan’s Subaru Telescope to extend the field of view around the edges of the image.
NASA, ESA, the Hubble Heritage Team, STScI / AURA, and NAOJ
5. Peering Into Pandora's Cluster. This image of giant galaxy cluster Abell 2744 was the first to come from Hubble's Frontier Fields observing program, which used gravitational lensing, a magnifying phenomenon especially evident near enormous galaxy clusters, to peer deep into the distant Universe. Abell 2744, nicknamed Pandora's Cluster, is thought to have a very violent history, having formed from a cosmic pile-up of multiple galaxy clusters.Nearly every object visible in this image is a separate galaxy, each composed of billions of stars.
NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, & the HFF Team
6. A Caterpillar in the Carina Nebula. Scattered across the enormous Carina nebula are numerous dense clumps of cosmic gas and dust called Bok globules, including this one, which resembles a huge glowing caterpillar. First described by by astronomer Bart Bok, the globules are relatively small, dark, and cold regions made up of molecular hydrogen, carbon oxides, helium, and dust. The glowing edge of the caterpillar indicates that it is being photoionized by the hottest stars in the surrounding cluster. It has been hypothesized that stars may form inside these dusty cocoons.
NASA, ESA, N. Smith, University of California, Berkeley, and The Hubble Heritage Team. STScI/AURA
7. Spiral Arms in the Dorado Group. Located approximately 40 million light-years away in the constellation of Dorado (the Dolphinfish). the galaxy NGC 1566 is an intermediate spiral galaxy, meaning that while it does not have a well defined bar-shaped region of stars at its center—like barred spirals—it is not quite an unbarred spiral either. It is the brightest and most dominant member of the Dorado Group, a loose concentration of galaxies that together comprise one of the richest galaxy groups of the southern hemisphere.
ESA / Hubble & NASA, Flickr user Det58
8. A Violent Birth Announcement. Cloaked in a haze of golden gas and dust is IRAS 14568-6304, an infant star, about 2,500 light-years away. It appears to be embedded within an intriguing swoosh of dark sky, which curves through the image and obscures the sky behind. This dark region is known as the Circinus molecular cloud. This cloud has a mass around 250,000 times that of the Sun, and it is filled with gas, dust and young stars. IRAS 14568-6304 is special because it is driving a protostellar jet, which appears here as the "tail" below the star. This jet is the leftover gas and dust that the star took from its parent cloud in order to form. While most of this material forms the star and its accretion disc—the disc of material surrounding the star, which may one day form planets—at some point in the formation process the star began to eject some of the material at supersonic speeds through space. This phenomenon is not only beautiful, but can also provide us with valuable clues about the process of star formation.
ESA / Hubble & NASA Acknowledgements: R. Sahai / JPL, Serge Meunier
9. A Festive Portrait of a Stellar Nursery. Hundreds of brilliant blue stars wreathed by warm, glowing clouds—R136 is the largest stellar nursery in our local galactic neighborhood. The massive, young stellar grouping 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. 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 brilliant stars are carving deep cavities in the surrounding material by unleashing a torrent of ultraviolet light, and hurricane-force stellar winds (streams of charged particles), which are etching away the enveloping hydrogen gas cloud in which the stars were born.
NASA, ESA, and F. Paresce, INAF-IASF, Bologna, R. O'Connell, University of Virginia, Charlottesville, and the Wide Field Camera 3 Science Oversight Committee
10. A Violent Galactic Merger. NGC 7714 is a spiral galaxy 100 million light-years from Earth—a relatively close neighbor in cosmic terms. The galaxy has witnessed some violent and dramatic events in its recent past. Tell-tale signs of this brutality can be seen in NGC 7714's strangely shaped arms, and in the smoky golden haze that stretches out from the galactic center—caused by an ongoing merger with its smaller galactic companion NGC 7715, which is out of the frame of this image.
ESA, NASA, A. Gal-Yam, Weizmann Institute of Science
11. The Red Spider Nebula. Huge waves are sculpted in this two-lobed nebula some 3,000 light-years away in the constellation of Sagittarius. This warm planetary nebula harbors one of the hottest stars known and its powerful stellar winds generate waves 100 billion kilometers 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
12. Infrared Horsehead Nebula. Rising like a giant seahorse from turbulent waves of dust and gas in the constellation of Orion is the Horsehead Nebula, otherwise known as Barnard 33. This image shows the region in infrared light, which has longer wavelengths than visible light and can pierce through the dusty material that usually obscures the nebula’s inner regions. The result is a rather ethereal and fragile-looking structure, made of delicate folds of gas—very different from the nebula’s appearance in visible light. The nebula lies 1,300 light-years away from Earth.
NASA, ESA, and the Hubble Heritage Team, AURA / STScI
13. Galaxy with a Glowing Heart. Nearby spiral galaxy NGC 1433 lies about 32 million light-years from Earth. It is a type of very active galaxy known as a Seyfert galaxy—a classification that accounts for 10% of all galaxies. They have very bright, luminous centers comparable to that of our galaxy, the Milky Way. Galaxy cores are of great interest to astronomers. The centers of most, if not all, galaxies are thought to contain a supermassive black hole, surrounded by a disc of infalling material.
Space Scoop / ESA / Hubble & NASA, D. Calzetti, UMass and the LEGU.S. Team
14. Amazing Alignment Reveals an Einstein Ring. The galaxy circled at center is one of a group of galaxies called Luminous Red Galaxies that have unusually large mass, containing about ten times the mass of the Milky Way. The blue semi-circle that appears to surround the red galaxy is the real prize in this image. This blue horseshoe is a distant galaxy that has been magnified and warped into a nearly complete ring by the strong gravitational pull of the massive foreground Luminous Red Galaxy. To see such a so-called Einstein Ring required the fortunate alignment of the foreground and background galaxies, making this object’s nickname “the Cosmic Horseshoe” particularly apt. The Cosmic Horseshoe gives us a tantalizing view of the early Universe: the blue galaxy’s redshift—a measure of how the wavelength of its light has been stretched by the expansion of the cosmos—is approximately 2.4. This means we see it as it was about 3 billion years after the Big Bang. The Universe is now 13.7 billion years old.
ESA / Hubble & NASA
15. Mystic Mountain. In 2010, Hubble peered deep into the Carina Nebula, 7,500 light-years from Earth, capturing this image of chaotic activity atop a pillar of gas and dust, three light-years tall, which is being eaten away by the brilliant light from nearby bright stars. The pillar 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. Streamers of hot ionized gas can be seen flowing off the ridges of the structure, and wispy veils of gas and dust, illuminated by starlight, float around its towering peaks. The denser parts of the pillar are resisting being eroded by radiation.
NASA, ESA, M. Livio and the Hubble 20th Anniversary Team, STScI
16. A Menagerie of Galaxies. Located 4 billion light-years away in the constellation Cetus, galaxy cluster Abell 370 contains an astounding assortment of several hundred galaxies tied together by the mutual pull of gravity. The brightest and largest galaxies in the cluster are the yellow-white, massive, elliptical galaxies containing many hundreds of billions of stars each. Spiral galaxies—like our Milky Way—have younger populations of stars and are bluish. Entangled among the galaxies are mysterious-looking arcs of blue light. These are actually distorted images of remote galaxies behind the cluster. These far-flung galaxies are too faint for Hubble to see directly. Instead, the cluster acts as a huge lens in space that magnifies and stretches images of background galaxies like a funhouse mirror.
NASA, ESA, and J. Lotz and the HFF Team, STScI
17. An Enormous Swirl of Dusty Filaments. NGC 4696 is the largest galaxy in the Centaurus Cluster, and lies 145 million light-years away from Earth. This image shows the dusty filaments surrounding the center of this huge galaxy in greater detail than ever before. These filaments loop and curl inwards in an intriguing spiral shape, swirling around the supermassive black hole at such a distance that they are dragged into and eventually consumed by the black hole itself.
NASA, ESA / Hubble, A. Fabian
18. A Giant Galactic Hybrid. The galaxy UGC 12591 sits somewhere between a lenticular and a spiral galaxy. It lies just under 400 million light-years away from us in the westernmost region of the Pisces–Perseus Supercluster, a long chain of galaxy clusters that stretches out for hundreds of light-years—one of the largest known structures in the cosmos. UGC 12591 is also extraordinarily massive. The galaxy and its halo together contain several hundred billion times the mass of the Sun, or four times the mass of the Milky Way. It also whirls round extremely quickly, rotating at speeds of up to 1.8 million kilometers per hour.
ESA / Hubble & NASA
19. My God, It’s Full of Stars. In 2006, Hubble was pointed toward the center of our galaxy, 26,000 light-years away, searching for other planetary systems. For a full week it imaged nearly 200,000 of the millions of stars crammed together in a dense collection in the Milky Way galaxy's ancient central hub. The region surveyed represents one entire field of the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) program.Sixteen candidate planets were discovered.
ESA / A. Calamida and K. Sahu, STScI and the SWEEPS Science Team / NASA
20. The Twin Jet Nebula. Situated about 4,000 light-years from Earth, PN M2-9 is a striking example of a bipolar planetary nebula. Bipolar planetary nebulae are formed when the central object is not a single star, but a binary system. Studies have shown that the nebula’s size increases with time, and measurements of this rate of increase suggest that the stellar outburst that formed the lobes occurred just 1,200 years ago.
ESA, Hubble & NASA, Acknowledgement: Judy Schmidt
21. Galaxies, Galaxies, Everywhere. Every object in this image (save for two nearby stars) is a separate galaxy made up of billions of stars. This is a detail of the "Hubble Ultra Deep Field," a larger image filled with nearly 10,000 galaxies--the deepest visible-light image of the cosmos. This galaxy-studded view represents a "deep" core sample of the universe, cutting across billions of light-years. In vibrant contrast to the rich harvest of classic spiral and elliptical galaxies, there exists a zoo of oddball galaxies littering the field. Some look like toothpicks; others like links on a bracelet. Peering into the Ultra Deep Field is like looking through a 2.5-meter-long soda straw. In ground-based photographs, the patch of sky in which the galaxies reside (just one-tenth the diameter of the full Moon) is largely empty. The image required 800 exposures taken over the course of 400 Hubble orbits around Earth. The total amount of exposure time was 11.3 days, taken between September 24, 2003, and January 16, 2004.
NASA, ESA, and S. Beckwith (STScI) and the HUDF Team
22. Gazing Into The Ring. Messier 57, otherwise known as The Ring Nebula, lies 2,500 light-years away. From Earth’s perspective, the nebula looks like a simple elliptical shape with a shaggy boundary. However, new observations show that the nebula is shaped like a distorted doughnut. This doughnut has a rugby-ball-shaped region of lower-density material slotted into in its central “gap”, stretching towards and away from us. The central star, once a massive red giant, is now very faint, having ejected most of its outer layers and exhausted its hydrogen fuel supply, on its way to becoming a white dwarf.
NASA, ESA, and C. Robert O’Dell, Vanderbilt University
23. A Cosmic Merger. NGC 5256 is a pair of galaxies 350 million light-years away viewed in their final chaotic stage of merging. The pair was previously observed by Hubble as part of a collection of 59 images of merging galaxies, released on Hubble’s 18th anniversary on April 24, 2008. New data makes the gas and dust being whirled around inside and outside the galaxy more visible than ever before.
ESA / Hubble, NASA
24. Galaxies Among the Stars. A detail from a closeup view of open star cluster NGC 6791, filled with stars estimated to be 8 billion years old. The cluster is in our own galaxy, some 13,000 light-years away. At upper left, two distant background galaxies can be seen through the spaces between the stars.
NASA, ESA, and L. Bedin (STScI)
25. The Pillars of Creation. The Eagle Nebula's four-light-year-tall pillars are seen here seen in a visible light image, capturing the multi-colored glow of gas clouds, wispy tendrils of dark cosmic dust, and the rust-colored elephants’ trunks of the nebula’s famous pillars. The nebula lies 7,000 light-years away. The dust and gas in the pillars is seared by the intense radiation from young stars and eroded by strong winds from massive nearby stars. Merry Christmas everyone, and many thanks to all of the scientists and engineers who designed, built and have used this amazing orbiting instrument that so magnifies the heavens.
NASA, ESA / Hubble and the Hubble Heritage Team