The Antennae galaxies, viewed in the sharpest-yet image of this merging pair of galaxies. During the course of their collision, billions of stars will be formed. The two spiral galaxies, about 45 million light-years from our solar system, started to interact a few hundred million years ago, making the Antennae galaxies one of the nearest and youngest examples of a pair of colliding galaxies. Nearly half of the faint objects in the Antennae image are young clusters containing tens of thousands of stars. The orange blobs are the two cores of the original galaxies and consist mainly of old stars criss-crossed by filaments of dust, which appears brown in the image. The two galaxies are dotted with brilliant blue star-forming regions surrounded by glowing hydrogen gas, appearing in the image in pink. #

The Sombrero galaxy, Messier 104 (M104). The galaxy's hallmark is 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. #

This picture, taken by Hubble’s Wide Field Camera 3, shows NGC 4696, the largest galaxy in the Centaurus Cluster. The new images taken with Hubble show 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. #

The Bubble Nebula is seen in an image captured in February of 2016, by the Hubble Space Telescope's Wide Field Camera 3. The nebula is 7 light-years across - about one-and-a-half times the distance from our sun to its nearest stellar neighbor, Alpha Centauri - and resides 7,100 light-years from Earth in the constellation Cassiopeia. #

This Hubble image unveils a very cluttered-looking universe filled with galaxies near and far. Some are distorted like a funhouse mirror through a warping-of-space phenomenon first predicted by Einstein a century ago. In the center of the image is the immense galaxy cluster Abell S1063, located 4 billion light-years away, and surrounded by magnified images of galaxies much farther. Thanks to Hubble's sharpness, the photo unveils the effect of space warping due to gravity. The huge mass of the cluster distorts and magnifies the light from galaxies that lie far behind it due to an effect called gravitational lensing. This phenomenon allows Hubble to see galaxies that would otherwise be too small and faint to observe. This frontier image provides a sneak peak of the early universe, and gives us a taste of what the James Webb Space Telescope will be capable of seeing in greater detail when it launches in 2018. #

The Horsehead Nebula viewed in infrared wavelengths. The nebula, shadowy in optical light, appears transparent and ethereal when seen in the infrared, represented here with visible shades. 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. The Horsehead Nebula is part of a much larger complex in the constellation Orion. Known collectively as the Orion Molecular Cloud, it also houses other famous objects such as the Great Orion Nebula (M42), the Flame Nebula, and Barnard's Loop. At about 1,500 light-years away, this complex is one of the nearest and most easily photographed regions in which massive stars are being formed. #

The Whirlpool Galaxy. The graceful, winding arms of the majestic spiral galaxy M51 appear like a grand spiral staircase sweeping through space. They are actually long lanes of stars and gas laced with dust. This image, taken in January 2005 with the Advanced Camera for Surveys aboard the NASA/ESA Hubble Space Telescope, illustrates a spiral galaxy's grand design, from its curving spiral arms, where young stars reside, to its yellowish central core, a home of older stars. The galaxy is nicknamed the Whirlpool because of its swirling structure. The Whirlpool's most striking feature is its two curving arms, a hallmark of so-called grand-design spiral galaxies. Many spiral galaxies possess numerous, loosely shaped arms that make their spiral structure less pronounced. These arms serve an important purpose in spiral galaxies. They are star-formation factories, compressing hydrogen gas and creating clusters of new stars. In the Whirlpool, the assembly line begins with the dark clouds of gas on the inner edge, then moves to bright pink star-forming regions, and ends with the brilliant blue star clusters along the outer edge. The Whirlpool is one of astronomy's galactic darlings. Located approximately 25 million light-years away in the constellation Canes Venatici (the Hunting Dogs). #

Two jets of energized gas stream across this image, ejected from the poles of a young star. If the jets (streaming at several hundred kilometers per second) collide with the surrounding gas and dust they can clear vast spaces, and create curved shock waves, seen as knotted clumps called Herbig-Haro objects. This is HH 24, about 1,500 light years distant, in the constellation Orion. #

The Helix Nebula. The Helix is a planetary nebula, the glowing gaseous envelope expelled by a dying, sun-like star. It resembles a simple doughnut as seen from Earth, but looks can be deceiving. New evidence suggests that the Helix consists of two gaseous disks nearly perpendicular to each other. The Helix, located 690 light-years away, is one of the closest planetary nebulae to Earth. #

Io over Jupiter. Jupiter's moon Io, roughly the size of Earth's moon, appears to be skimming Jupiter's cloud tops, but it's actually 310, 000 miles (500,000 kilometers) away. Io zips around Jupiter in 1.8 days, whereas our moon circles Earth every 28 days. The conspicuous black spot on Jupiter is Io's shadow and is about the size of the moon itself (2,262 miles or 3,640 kilometers across). This shadow sails across the face of Jupiter at 38,000 mph (17 kilometers per second). The smallest details visible on Io and Jupiter measure 93 miles (150 kilometers) across, or about the size of Connecticut. #

The Cat's Eye Nebula. This nebula was one of the first planetary nebulae to be discovered, it is one of the most complex seen in space. A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers that form bright nebulae with amazing and intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas. 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. The Cat's Eye lies 3,262 light years distant from our solar system. #

The barred spiral galaxy NGC 1300. Barred spirals differ from normal spiral galaxies in that the arms of the galaxy do not spiral all the way into the center, but are connected to the two ends of a straight bar of stars containing the nucleus at its center. In the core of the larger spiral structure of NGC 1300, the nucleus shows its own distinct "grand-design" spiral structure that is about 3,300 light-years long. Only galaxies with large-scale bars appear to have these grand-design inner disks—a spiral within a spiral. The galaxy lies roughly 69 million light-years away in the direction of the constellation Eridanus. #

A stellar nursery in the Carina Nebula. A billowing cloud of cold interstellar gas and dust rising from a tempestuous stellar nursery located 7,500 light-years away in the southern constellation Carina. This pillar of dust and gas serves as an incubator for new stars and is teeming with new star-forming activity. Hot, young stars erode and sculpt the clouds into this fantasy landscape by sending out thick stellar winds and scorching ultraviolet radiation. The low-density regions of the nebula are shredded while the denser parts resist erosion and remain as thick pillars. In the dark, cold interiors of these columns new stars continue to form. #

A Galactic Penguin. From our perspective, viewed by Hubble, this pair of interacting galaxies bears a resemblance to a penguin guarding its egg. NGC 2936, once a standard spiral galaxy, is warped and pulled by neighboring NGC 2937, a smaller elliptical galaxy. The galaxies lie about 400 million light years distant in the Hydra constellation. #

The Eagle Nebula’s Pillars of Creation. This image shows the pillars as seen in visible light, 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 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 Eagle nebula lies 7,000 light years distant, in the constellation Serpens Cauda. #

Pulses in the the core of the Crab Nebula. While many other images of the famous Crab Nebula nebula have focused on the filaments in the outer part of the nebula, this image shows the very heart of the nebula including the central neutron star — it is the rightmost of the two bright stars near the center of this image. The rapid motion of the material nearest to the central star is revealed by the subtle rainbow of colors in this time-lapse image, the rainbow effect being due to the movement of material over the time between one image and another. The neutron star has about the same mass as the sun but compressed into an incredibly dense sphere that is only a few miles across. Spinning 30 times a second, the neutron star shoots out detectable beams of energy that make it look like it's pulsating. The Crab Nebula lies 6,500 light-years away in the constellation Taurus. #

The Butterfly Nebula. 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. 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 "butterfly" stretches for more than two light-years, which is about half the distance from the Sun to the nearest star, Alpha Centauri. #

Imagine what the night sky would look like if we lived here. The average distance between any two stars in the crowded core of globular cluster Omega Centauri is only about a third of a light-year, The core 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. #

One of the most perfect geometrical forms created in space, this image shows the formation of an unusual pre-planetary nebula, known as IRAS 23166+1655, around the star LL Pegasi in the constellation of Pegasus. The striking picture shows what appears to be a thin spiral pattern of astonishingly regularity winding around the star, which is itself hidden behind thick dust. 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 Retina Nebula. A dying star, IC 4406 exhibits a high degree of symmetry; the left and right halves of the Hubble image are nearly mirror images of the other. If we could fly around IC 4406 in a starship, we would see that the gas and dust form a vast donut of material streaming outward from the dying star. From Earth, we are viewing the donut from the side. This side view allows us to see the intricate tendrils of dust that have been compared to the eye's retina. The nebula lies about 2,000 light-years away, near the southern constellation of Lupus. #

A view of the Monkey Head Nebula. NGC 2174 lies about 6,400 light-years away in the constellation of Orion. The colorful region is filled with young stars embedded within bright wisps of cosmic gas and dust. This portion of the Monkey Head Nebula was imaged in 2014, in the infrared using Hubble's Wide Field Camera 3. #

Spiral galaxy ESO 137-001 plows through space. This galaxy is zooming toward the upper right, in between other galaxies in the Norma cluster located over 200 million light-years away. The road is harsh: intergalactic gas in the Norma cluster is sparse, but so hot at 180 million degrees Fahrenheit that it glows in X-rays. The spiral plows through the seething intra-cluster gas so rapidly--at nearly 4.5 million miles per hour--much of its own gas is caught and torn away. Astronomers call this "ram pressure stripping." The galaxy's stars remain intact due to the binding force of their gravity. Tattered threads of gas, the blue jellyfish-tendrils sported by ESO 137-001 in the image, illustrate the process. Ram pressure has strung this gas away from its home in the spiral galaxy and out over intergalactic space. Once there, these strips of gas have erupted with young, massive stars, which are pumping out light in vivid blues and ultraviolet. #

Giant Twisters in the Lagoon Nebula. This Hubble Space Telescope image reveals a pair of 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. #

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. #

The Hubble Ultra Deep Field. Every object in this image (save for two nearby stars) is a separate galaxy made up of billions of stars. This view of nearly 10,000 galaxies is the deepest visible-light image of the cosmos. Called the Hubble Ultra Deep Field, this view 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. 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. 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 #