Time once more for one of my favorite holiday traditions: the eighth annual Hubble Space Telescope Advent Calendar. Every day until Friday, December 25, this page will present one new 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, Google+, 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. I also must say how fortunate I feel to have been able to share photo stories with you all year, and I wish a Merry Christmas to those who celebrate it, and peace on Earth to all.

1. A retake of one of the Hubble Space Telescope’s most iconic and popular images: the Eagle Nebula’s Pillars of Creation. This high-definition image shows the pillars as seen in visible light in late 2014 (released in 2015) 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, 25 years after the earlier, more famous 1995 version. 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. The tallest pillar here is about four light years in length, or about 24 trillion miles.
NASA, ESA, Hubble Heritage Team
2. Scientists using the Hubble telescope have produced new maps of Jupiter that show the continuing changes in its famous Great Red Spot. This new image of the atmosphere of the largest planet in our solar system was made on January 19, 2015, during the Outer Planet Atmospheres Legacy (OPAL) program. The images from this program make it possible to determine the speeds of Jupiter’s winds, to identify different phenomena in its atmosphere, and to track changes in its most famous features.
NASA, ESA, A. Simon (GSFC), M. Wong (UC Berkeley), and G. Orton (JPL-Caltech)
3. 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 of this Seyfert II active galaxy. 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
4. The Ring Nebula, the glowing remains of a Sun-like star. The tiny white dot in the center of the nebula is the star's hot core, called a white dwarf. The nebula is about 2,000 light-years away in the constellation Lyra. The structure measures roughly one light-year across. This image from 2011 by Hubble uncovered the detailed structure of the dark, irregular knots of dense gas embedded along the inner rim of the ring. The knots look like spokes in a bicycle. The Hubble images have allowed the research team to match up the knots with the spikes of light around the bright, main ring, which are a shadow effect.
NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA
5. Planetary Nebula NGC 6302. What resemble 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. 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. NGC 6302 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. The “butterfly” stretches more than two light-years across.
NASA, ESA, and the Hubble SM4 ERO Team
6. A starbirth in Galaxy Centaurus A. This Hubble image shows an unprecedented close-up view of a turbulent firestorm of starbirth along a nearly edge-on dust disk girdling Centaurus A, 13 million light years away—the nearest active galaxy to our Milky Way. A vast dark-dust lane girdles the entire elliptical galaxy. This lane has long been considered the dust remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The spiral galaxy deposited its gas and dust into the elliptical galaxy, and the shock of the collision compressed interstellar gas, precipitating a flurry of star formation. Dark filaments of dust mixed with cold hydrogen gas are silhouetted against the incandescent yellow-orange glow from hot gas and stars behind it. Brilliant clusters of young blue stars lie along the edge of the dark-dust rift. Outside the rift the sky is filled with the soft hazy glow of the galaxy's much older resident population of red giant and red dwarf stars.
E.J. Schreier (STScI), and NASA
7. A galactic smile. In the center of this Hubble image are two faint galaxies that seem to be smiling. You can make out two orange eyes and a white button nose. In the case of this “happy face,” the two eyes are the galaxies SDSSCGB 8842.3 and SDSSCGB 8842.4, and the misleading smile lines are actually arcs caused by an effect known as strong gravitational lensing, distorting light from more distant objects. Massive structures in the Universe exert such a powerful gravitational pull that they can warp the spacetime around them and act as cosmic lenses which can magnify, distort, and bend the light behind them. This phenomenon, crucial to many of Hubble’s discoveries, can be explained by Einstein’s theory of general relativity. In this special case of gravitational lensing, a ring—known as an Einstein Ring—is produced from this bending of light when the source, lens and observer are lined up perfectly, resulting in the ring-like structure we see here.
8. This image from Hubble's Advanced Camera for Surveys (ACS) shows a bull's eye pattern of eleven or even more concentric rings, or shells, around the Cat's Eye Nebula (NGC 6543). Each ‘ring’ is actually the edge of a spherical bubble seen projected onto the sky—that's why it appears bright along its outer edge. Observations suggest the star ejected its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, each of which contain as much mass as all of the planets in our solar system combined.
NASA, ESA, HEIC, and The Hubble Heritage Team
9. Warped Galaxy ESO 510-G13. The strong warping of the disk indicates that ESO 510-G13 has recently undergone a collision with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort the structures of the galaxies as their stars, gas, and dust merge together in a process that takes millions of years. Eventually the disturbances will die out, and ESO 510-G13 will become a normal-appearing single galaxy. ESO 510-G13 lies in the southern constellation Hydra, roughly 150 million light-years from Earth.
NASA and The Hubble Heritage Team (STScI/AURA)
10. Surrounded by bright stars, towards the middle-right of the frame we see a small young stellar object (YSO) known as SSTC2D J033038.2+303212. Located in the constellation of Perseus, this star is in the early stages of its life and is still forming into a fully grown star. In this view from Hubble’s Advanced Camera for Surveys it appears to have a murky chimney of material emanating outwards and downwards, framed by bright bursts of gas flowing from the star itself. This fledgling star is actually surrounded by a bright disc of material swirling around it as it forms—a disc that we see edge-on from our perspective. However, this small bright speck is dwarfed by its cosmic neighbor towards the left of the frame, a clump of bright, wispy gas swirling around as it appears to spew dark material out into space. The bright cloud is a reflection nebula known as [B77] 63, a cloud of interstellar gas that is reflecting light from the stars embedded within it. There are actually a number of bright stars within [B77] 63, most notably the emission-line star LkHA 326, and its very near neighbor LZK 18. However, the most dramatic part of the image seems to be a dark stream of smoke piling outwards from [B77] 63 and its stars—a dark nebula called Dobashi 4173. Dark nebulae are incredibly dense clouds of pitch-dark material that obscure the patches of sky behind them, seemingly creating great rips and eerily empty chunks of sky. The stars speckled on top of this extreme blackness actually lie between us and Dobashi 4173.
ESA / Hubble & NASA
11. The peaks of Mystic Mountain. This Hubble image captures the 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. This turbulent cosmic pinnacle lies within a tempestuous stellar nursery called the Carina Nebula, located 7,500 light-years away in the southern constellation of Carina. Scorching radiation and fast winds (streams of charged particles) from super-hot newborn stars in the nebula are shaping and compressing the pillar, causing new stars to form within it. Streamers of hot ionised 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. Long streamers of gas can be seen shooting in opposite directions from the pedestal at the top of the image. Another pair of jets is visible at another peak near the center of the image. These jets, (known as HH 901 and HH 902, respectively, are signposts for new star birth and are launched by swirling gas and dust discs around the young stars, which allow material to slowly accrete onto the stellar surfaces.
NASA, ESA, M. Livio and the Hubble 20th Anniversary Team (STScI)
12. Starburst galaxy Messier 94. Located in the small northern constellation of the Hunting Dogs, about 16 million light-years away. within the bright ring around Messier 94, new stars are forming at a high rate and many young, bright stars are present within it – thanks this feature called a starburst ring. The cause of this peculiarly shaped star-forming region is likely a pressure wave going outwards from the galactic center, compressing the gas and dust in the outer region. The compression of material means the gas starts to collapse into denser clouds. Inside these dense clouds, gravity pulls the gas and dust together until temperature and pressure are high enough for stars to be born.
ESA / Hubble & NASA
13. A pair of one-half light-year long interstellar “twisters”—eerie funnels and twisted-rope structures—in the heart of the Lagoon Nebula (Messier 8) which lies 5,000 light-years away in the direction of the constellation Sagittarius. (Special thanks to RPT)
A. Caulet (ST-ECF, ESA) and NASA
14. A Cosmic Caterpillar. This light-year-long knot of interstellar gas and dust may resembles an enormous caterpillar, but it’s actually a "wanna-be" star with harsh winds from extremely bright nearby stars blasting ultraviolet radiation at it and sculpting its surrounding gas and dust into a 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. 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. 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. The object lies 4,500 light-years away in the constellation of Cygnus.
NASA, ESA, the Hubble Heritage Team (STScI / AURA), and IPHAS
15. A Hubble image of the Antennae galaxies. As this pair of galaxies smash together, billions of stars are born, mostly in groups and clusters of stars. The brightest and most compact of these are called super star clusters. The Antennae galaxies lie about 75 million light years away, in the constellation Corvus.
NASA, ESA, and the Hubble Heritage Team STScI / AURA)-ESA / Hubble Collaboration. Acknowledgement: B. Whitmore and James Long
16. The Twin Jet Nebula, or 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
17. A cosmic lightsaber. In a galaxy not so far away (our own), inside a turbulent birthing ground for new stars known as the Orion B molecular cloud complex, a newborn star shoots twin jets out into space, some 1,350 light-years away from Earth. For more on this image, just released today, see NASA’s article Hubble Sees the Force Awakening in a Newborn Star.
18. A Galactic Collision. ESO 593-8 is an impressive pair of interacting galaxies with a feather-like galaxy crossing a companion galaxy. The two components will probably merge to form a single galaxy in the future. The pair is adorned with a number of bright blue star clusters. ESO 593-8 is located in the constellation of Sagittarius, the Archer, some 650 million light-years away from Earth.
NASA, ESA, the Hubble Heritage Team (STScI / AURA)-ESA / Hubble Collaboration and A. Evans (University of Virginia, Charlottesville / NRAO / Stony Brook University)
19. Globular Cluster 47 Tucanae. Part of the constellation of Tucana (The Toucan) in the southern sky, this is the second-brightest globular cluster in the night sky, hosting tens of thousands of stars. Scientists using Hubble observed the white dwarfs in the cluster. These dying stars migrate from the crowded center of the cluster to its outskirts.
NASA, ESA, and the Hubble Heritage (STScI / AURA)-ESA / Hubble Collaboration Acknowledgment: J. Mack (STScI) and G. Piotto (University of Padova, Italy)
20. The Eskimo Nebula. A planetary nebula, approximately 4,200 light years away from Earth, in the constellation Gemini. Gas surrounds the core of the remnants of a Sun-like star after it has become a red giant, shedding its outer layers.
NASA, ESA, Andrew Fruchter (STScI), and the ERO team (STScI + ST-ECF)
21. The Horsehead Nebula. This Hubble image, released to celebrate the telescope’s 23rd year in orbit, shows part of the sky in the constellation of Orion. Rising like a giant seahorse from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33, a massive complex of gas and dust some 1,500 light years away from Earth. 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 to the nebula’s appearance in visible light.
NASA, ESA, and the Hubble Heritage Team (AURA / STScI)
22. The Loneliest Galaxy. Only two local stars appear in this image, (at top, with visible diffraction spikes). Everything else is a galaxy. In the center, the spiral arms of MCG+01-02-015 seem to wrap around one another, cocooning the galaxy. The scene suggests an abundance of galactic companionship for MCG+01-02-015, but this is a cruel trick of perspective. Instead, MCG+01-02-015’s is a void galaxy, the loneliest of galaxies. The vast majority of galaxies are strung out along galaxy filaments—thread-like formations that make up the large-scale structure of the Universe—drawn together by the influence of gravity into sinuous threads weaving through space. Between these filaments stretch shallow but immense voids; the Universe’s wastelands, where, outside of the extremely rare presence of a galaxy, there is very little matter — about one atom per cubic meter. One such desolate stretch of space is what MCG+01-02-015 calls home. The galaxy is so isolated that if our galaxy, the Milky Way, were to be situated in the same way, we would not have known of the existence of other galaxies until technological advances in telescopes in the 1960s.
ESA / Hubble & NASA and N. Gorin (STScI) Acknowledgement: Judy Schmidt
23. 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)
24. The Hubble Ultra Deep Field. Galaxies, galaxies everywhere - as far as the NASA/ESA Hubble Space Telescope can see. This view of nearly 10,000 galaxies represents a "deep" core sample of the universe, cutting across billions of light-years. The snapshot includes galaxies of various ages, sizes, shapes, and colors. The smallest, reddest galaxies, about 100, may be among the most distant known, existing when the universe was just 800 million years old. The nearest galaxies - the larger, brighter, well-defined spirals and ellipticals - thrived about 1 billion years ago, when the cosmos was 13 billion years old. In vibrant contrast to the rich harvest of classic spiral and elliptical galaxies, there is a zoo of oddball galaxies littering the field. Some look like toothpicks; others like links on a bracelet. A few appear to be interacting. These oddball galaxies chronicle a period when the universe was younger and more chaotic. Order and structure were just beginning to emerge. 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. Located in the constellation Fornax, the region is so empty that only a handful of stars within the Milky Way galaxy can be seen in the image. 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
25. Gravitational Lensing in Abell 2218. This rich galaxy cluster is composed of thousands of individual galaxies. It sits about 2.1 billion light-years from the Earth in the northern constellation of Draco. When used by astronomers as a powerful gravitational lens to magnify distant galaxies, the cluster allows them to peer far into the Universe. However, the strong gravitational forces not only magnify the images of hidden galaxies, but also distort them into long, thin arcs. Multiple distorted images of the same galaxies can be identified by comparing the shape of the galaxies and their color. In addition to the giant arcs, many smaller arclets have been identified.

Merry Christmas everyone! I hope you've enjoyed this year's Hubble calendar. And, here's wishing for a peaceful and joyous New Year. -Alan
NASA, ESA, and Johan Richard (Caltech, USA)Acknowledgement: Davide de Martin & James Long (ESA / Hubble)