NASA Astronomy Picture of the Day 2011-1

Fireworks Galaxy NGC 6946

Celebrate the New Year with the Fireworks Galaxy! Also known as NGC 6946, the big, beautiful spiral galaxy is located just 10 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation of Cepheus. From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. In this colorful cosmic portrait, the galaxy's colors change from the yellowish light of old stars in the core to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is bright in infrared light and rich in gas and dust, exhibiting a furious rate of star formation. Nearly 40,000 light-years across, the nearby spiral is fittingly referred to as the Fireworks Galaxy. Over the last 100 years, at least nine supernovae, the death explosions of massive stars, were discovered in NGC 6946. By comparison, the average rate for supernovae in the Milky Way is about 1 per century.

Looking Back at an Eclipsed Earth

Here is what the Earth looks like during a solar eclipse. The shadow of the Moon can be seen darkening part of Earth. This shadow moved across the Earth at nearly 2000 kilometers per hour. Only observers near the center of the dark circle see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon. This spectacular picture of the 1999 August 11 solar eclipse was one of the last ever taken from the Mir space station. The two bright spots that appear on the upper left are thought to be Jupiter and Saturn. Mir was deorbited in a controlled re-entry in 2001.

Winter Hexagon Over Stagecoach Colorado

If you can find Orion, you might be able to find the Winter Hexagon. The Winter Hexagon involves some of the brightest stars visible, together forming a large and easily found pattern in the winter sky of Earth's northern hemisphere. The stars involved can usually be identified even in the bright night skies of a big city, although here they appear over darker Stagecoach, Colorado, USA.. The six stars that compose the Winter Hexagon are Aldebaran, Capella, Castor (and Pollux), Procyon, Rigel, and Sirius. Here, the band of our Milky Way Galaxy runs through the center of the Winter Hexagon, while the Pleiades open star cluster is visible just above. The Winter Hexagon asterism engulfs several constellations including much of the iconic steppingstone Orion. Best Astronomy Images: APOD Editor to speak in Philadelphia and New York City this week

A Green Flash from the Sun

Many think it is just a myth. Others think it is true but its cause isn't known. Adventurers pride themselves on having seen it. It's a green flash from the Sun. The truth is the green flash does exist and its cause is well understood. Just as the setting Sun disappears completely from view, a last glimmer appears startlingly green. The effect is typically visible only from locations with a low, distant horizon, and lasts just a few seconds. A green flash is also visible for a rising Sun, but takes better timing to spot. A dramatic green flash, as well as an even more rare blue flash, was caught in the above photograph recently observed during a sunset visible from Teide Observatory at Tenerife, Cannary Islands, Spain. The Sun itself does not turn partly green or blue -- the effect is caused by layers of the Earth's atmosphere acting like a prism. Best Astronomy Images: APOD Editor to speak in Philadelphia tomorrow night and NYC Friday

Eclipsing the Sun

Skywatchers throughout much of Europe, North Africa, and Central Asia, were treated to the first eclipse of the new year on January 4, a partial eclipse of the Sun. But traveling to the area around Muscat, capital city of Oman, photographer Thierry Legault planned to simultaneously record two eclipses on that date, calculating from that position, for a brief moment, both the Moon and the International Space Station could be seen in silhouette, crossing the Sun. His sharp, 1/5000th second exposure is shown here, capturing planet Earth's two largest satellites against the bright solar disk. As the partial solar eclipse unfolded, the space station (above and left of center) zipped across the scene in less than 1 second, about 500 kilometers from the photographer's telescope and camera. Of course, the Moon was 400 thousand kilometers away. Complete with sunspots, the Sun was 150 million kilometers distant. Best Astronomy Images: APOD Editor to speak in Philadelphia tonight and NYC Friday

Sunrise, Moonrise

For many Europeans, the Sun and New Moon rose together on January 4 in a partial solar eclipse. Arriving close on the heels of the new year, it was the first of a series of four(!) partial solar eclipses due in 2011. This composite image documents the graceful celestial event in colorful morning skies over Graz, Austria. Beginning before sunrise, frames were taken to record the position and progress of the eclipse every 15 minutes. As Sun and Moon rose above the eastern horizon, the town of Graz is seen bathed in warming sunlight only partially blocked by the New Moon, spreading beneath the town's landmark clock tower. Best Astronomy Images: APOD Editor to speak in NYC Friday

Sunset, Moonset

Seen from central and northern Asia, the Sun and New Moon set together on January 4, in a partial solar eclipse. Close to its maximum phase, the eclipse is captured near the moment of sunset in this wintry scene from the bank of the Berd River near Novosibirsk, Siberia, Russia. An evocative view in fading light, the picture looks toward the western horizon across a snowy, frozen landscape. Along with offset Sun and Moon, the dimly lit sky includes an industrial smoke plume and airplane contrail. Best Astronomy Images: APOD Editor to speak in NYC tonight.

NGC 7293: The Helix Nebula

A mere seven hundred light years from Earth, in the constellation Aquarius, a sun-like star is dying. Its last few thousand years have produced the Helix Nebula (NGC 7293), a well studied and nearby example of a Planetary Nebula, typical of this final phase of stellar evolution. A total of 10 hours of exposure time have gone in to creating this remarkably deep view of the nebula. It shows details of the Helix's brighter inner region, about 3 light-years across, but also follows fainter outer halo features that give the nebula a span of well over six light-years. The white dot at the Helix's center is this Planetary Nebula's hot, central star. A simple looking nebula at first glance, the Helix is now understood to have a surprisingly complex geometry.

The Antikythera Mechanism

What is it? It was found at the bottom of the sea aboard an ancient Greek ship. Its seeming complexity has prompted decades of study, although some of its functions remained unknown. Recent X-rays of the device have now confirmed the nature of the Antikythera mechanism, and discovered several surprising functions. The Antikythera mechanism has been discovered to be a mechanical computer of an accuracy thought impossible in 80 BC, when the ship that carried it sank. Such sophisticated technology was not thought to be developed by humanity for another 1,000 years. Its wheels and gears create a portable orrery of the sky that predicted star and planet locations as well as lunar and solar eclipses. The Antikythera mechanism, shown above, is 33 centimeters high and similar in size to a large book.

A Sun Halo Beyond Stockholm

What's happened to the Sun? Sometimes it looks like the Sun is being viewed through a large lens. In the above case, however, there are actually millions of lenses: ice crystals. As water freezes in the upper atmosphere, small, flat, six-sided, ice crystals might be formed. As these crystals flutter to the ground, much time is spent with their faces flat, parallel to the ground. An observer may pass through the same plane as many of the falling ice crystals near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting sunlight into our view and creating phenomena like parhelia, the technical term for sundogs. The above image was taken last year in Stockholm, Sweden. Visible in the image center is the Sun, while two bright sundogs glow prominently from both the left and the right. Also visible is the bright 22 degree halo -- as well as the rarer and much fainter 46 degree halo -- also created by sunlight reflecting off of atmospheric ice crystals.

The Cosmic Web of the Tarantula Nebula

It is the largest and most complex star forming region in the entire galactic neighborhood. Located in the Large Magellanic Cloud, a small satellite galaxy orbiting our Milky Way galaxy, the region's spidery appearance is responsible for its popular name, the Tarantula nebula. This tarantula, however, is about 1,000 light-years across. Were it placed at the distance of Milky Way's Orion Nebula, only 1,500 light-years distant and the nearest stellar nursery to Earth, it would appear to cover about 30 degrees (60 full moons) on the sky. Intriguing details of the nebula are visible in the above image shown in scientific colors. The spindly arms of the Tarantula nebula surround NGC 2070, a star cluster that contains some of the brightest, most massive stars known, visible in blue on the right. Since massive stars live fast and die young, it is not so surprising that the cosmic Tarantula also lies near the site of the closest recent supernova.

The Seagull Nebula

This broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker - The Seagull Nebula. This portrait of the cosmic bird covers a 1.6 degree wide swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major. Of course, the region includes objects with other catalog designations: notably NGC 2327, a compact, dusty emission region with an embedded massive star that forms the bird's head (aka the Parrot Nebula, above center). IC 2177 forms the sweeping arc of the seagull's wings. Dominated by the reddish glow of atomic hydrogen, the complex of gas and dust clouds with bright young stars spans over 100 light-years at an estimated 3,800 light-year distance.

NGC 3521 Close Up

Gorgeous spiral galaxy NGC 3521 is a mere 35 million light-years distant, toward the constellation Leo. Spanning some 50,000 light-years, its central region is shown in this dramatic image, constructed from data drawn from the Hubble Legacy Archive. The close-up view highlights this galaxy's characteristic multiple, patchy, irregular spiral arms laced with dust and clusters of young, blue stars. In contrast, many other spirals exhibit grand, sweeping arms. A relatively bright galaxy in planet Earth's sky, NGC 3521 is easily visible in small telescopes, but often overlooked by amateur imagers in favor of other Leo spiral galaxies, like M66 and M65.

Quadrantids over Qumis

The Quadrantid Meteor Shower is an annual event for planet Earth's northern hemisphere skygazers. It usually peaks briefly in the cold, early morning hours of January 4. The shower is named for its radiant point on the sky within the old, astronomically obsolete constellation Quadrans Muralis. That position is situated near the boundaries of the modern constellations Hercules, Bootes, and Draco. In this haunting time exposure, two quadrantid meteor streaks are captured crossing trails left by rising stars of the constellations Virgo and Corvus, but Saturn leaves the brightest "star" trail. The meteor streaks, one bright and one faint, are nearly parallel above and right of center in the frame. Fittingly, the old cistern structure in the foreground lies above the now buried city of Qumis. Known as a city of many gates, Qumis (in Greek history Hecatompylos), was founded 2300 years ago in ancient Persia.

A Total Eclipse at the End of the World

Would you go to the end of the world to see a total eclipse of the Sun? If you did, would you be surprised to find someone else there already? In 2003, the Sun, the Moon, Antarctica, and two photographers all lined up in Antarctica during an unusual total solar eclipse. Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon. One of the treasures collected was the above picture -- a composite of four separate images digitally combined to realistically simulate how the adaptive human eye saw the eclipse. As the image was taken, both the Moon and the Sun peaked together over an Antarctic ridge. In the sudden darkness, the magnificent corona of the Sun became visible around the Moon. Quite by accident, another photographer was caught in one of the images checking his video camera. Visible to his left are an equipment bag and a collapsible chair.

Globular Star Cluster 47 Tuc

Globular star cluster 47 Tucanae is a jewel of the southern sky. Also known as NGC 104, it roams the halo of our Milky Way Galaxy along with some 200 other globular star clusters. The second brightest globular cluster (after Omega Centauri) as seen from planet Earth, it lies about 13,000 light-years away and can be spotted naked-eye near the Small Magellanic Cloud in the constellation of the Toucan. The dense cluster is made up of several million stars in a volume only about 120 light-years across. Red giant stars on the outskirts of the cluster are easy to pick out as yellowish stars in this sharp telescopic portrait. Globular cluster 47 Tuc is also home to exotic x-ray binary star systems.

Night and Day above Almost Planet Sounio

Has a new planet been discovered? What is pictured above is a remarkable 24 hour mosaic surrounding a spot on Sounio, Greece, right here on planet Earth. Images taken at night compose the top half of the picture, with star trails lasting as long as 11 hours visible. Contrastingly, images taken during the day compose the bottom of the image, with the Sun being captured once every 15 minutes. The image center shows a Little Prince wide angle projection centered on the ground but including gravel, grass, trees, Saint John's church, clouds, crepuscular rays, and even a signature icon of the photographer -- the Temple of Poseidon. Meticulous planning as well as several transition shots and expert digital processing eventually culminated in this image documenting half of the final two days of last year.

Kona Galaxy Garden

How does your galaxy grow? Quite contrary to a typical galaxy, this one needs water to flourish. Pictured above as it appears at the Paleaku Peace Gardens Sanctuary in Kona, Hawaii, USA, a meticulously planned garden spanning about 30 meters provides a relatively accurate map of our Milky Way Galaxy. Different plants depict stars, globular clusters, and even nebulas. Many bright stars visible in Earth's night sky are depicted on leaves surrounding the marked location of the Sun. Plant rows were placed to represent arms of our Galaxy, including the Sun's Orion Arm, the impressive Sagittarius Arm, and the little discussed Norma Arm. A small bar runs through our Galaxy's center, while a fountain has been built to represent the central black hole. What a stellar use of space!

Saturn Storm

Late last year, a new, remarkably bright storm erupted in Saturn's northern hemisphere. Amateur astronomers first spotted it in early December, with the ringed gas giant rising in planet Earth's predawn sky. Orbiting Saturn, the Cassini spacecraft was able to record this close-up of the complex disturbance from a distance of 1.8 million kilometers on December 24th. Over time, the storm has evolved, spreading substantially in longitude, and now stretches far around the planet. Saturn's thin rings are also seen slicing across this space-based view, casting broad shadows on the planet's southern hemisphere.

The Once and Future Stars of Andromeda

The big, beautiful Andromeda Galaxy, aka M31, is a spiral galaxy a mere 2.5 million light-years away. Two space-based observatories have combined to produce this intriguing composite image of Andromeda, at wavelengths outside the visible spectrum. The remarkable view follows the locations of this galaxy's once and future stars. In reddish hues, image data from the large Herschel infrared observatory traces enormous lanes of dust, warmed by stars, sweeping along Andromeda's spiral arms. The dust, in conjunction with the galaxy's interstellar gas, comprises the raw material for future star formation. X-ray data from the XMM-Newton observatory in blue pinpoint Andromeda's X-ray binary star systems. These systems likely contain neutron stars or stellar mass black holes that represent final stages in stellar evolution. More than twice the size of our own Milky Way, the Andromeda Galaxy is over 200,000 light-years across.

Alnitak, Alnilam, Mintaka

Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (left to right) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun. They lie about 1,500 light-years away, born of Orion's well-studied interstellar clouds. In fact, clouds of gas and dust adrift in this region have intriguing and some surprisingly familiar shapes, including the dark Horsehead Nebula and Flame Nebula near Alnitak at the lower left. The famous Orion Nebula itself lies off the bottom of this colorful star field. Recorded last December with a modified digital SLR camera and small telescope, the well-planned, two frame mosaic spans about 4 degrees on the sky.

Polar Ring Galaxy NGC 660

NGC 660 lies near the center of this intriguing skyscape, swimming in the boundaries of the constellation Pisces. Over 20 million light-years away, its peculiar appearance marks it as a polar ring galaxy. A rare galaxy type, polar ring galaxies have a substantial population of stars, gas, and dust orbiting in rings nearly perpendicular to the plane of the galactic disk. The bizarre configuration could have been caused by the chance capture of material from a passing galaxy by the disk galaxy, with the captured debris strung out in a rotating ring. The polar ring component can be used to explore the shape of the galaxy's otherwise unseen dark matter halo by calculating the dark matter's gravitational influence on the rotation of the ring and disk. Broader than the disk, NGC 660's ring spans about 40,000 light-years.

Phobos' South Pole from Mars Express

Where on this moon would you land? The moon pictured above is not Earth's moon but Phobos, the closest moon to the planet Mars. Phobos is so close to Mars that it is expected to break up and crash into the red planet within the next 100 million years. Earlier just this year, however, ESA's Mars Express mission took detailed images of the area surrounding Phobos' South Pole. Visible on the small moon's unusually dark surface are many circular craters, long chains of craters, and strange streaks. Large Stickney Crater, which looms on the far right, was also visible in the corresponding North Polar image taken last year. This and other similar images of Phobos are so detailed, resolving items even 10-meters across, that they are useful for examining proposed landing sites of the future Phobos-Grunt mission. The Russian Phobos-Grunt robotic spacecraft is scheduled to launch toward Phobos later this year and return surface samples in 2014. Vote: Astronomy Picture of the Year 2010

The Rippled Red Ribbons of SNR 0509

What is causing the picturesque ripples of supernova remnant SNR 0509-67.5? The ripples, as well as the greater nebula, were imaged in unprecedented detail by the Hubble Space Telescope in 2006 and again late last year. The red color was recoded by a Hubble filter that left only the light emitted by energetic hydrogen. The precise reason for the ripples remains unknown, with two considered origin hypotheses relating them to relatively dense portions of either ejected or impacted gas. The reason for the broader red glowing ring is more clear, with expansion speed and light echos relating it to a classic Type Ia supernova explosion that must have occurred about 400 years earlier. SNR 0509 currently spans about 23 light years and lies about 160,000 light years away toward the constellation of the dolphinfish (Dorado) in the Large Magellanic Cloud. The expanding ring carries with it another great mystery, however: why wasn't this supernova seen 400 years ago when light from the initial blast should have passed the Earth? Like: Follow APOD on Facebook

The Whirlpool Galaxy in Infrared Dust

How do spiral galaxies form stars? To help find out, the Hubble Space Telescope imaged the nearby photogenic spiral M51 in infrared light to highlight the dust that traces the dense gas that best forms stars. To further isolate the dust, much of the optical light from stars has also been digitally removed. The resulting unique image shows swirling and intricate patterns on the longest scales, while numerous bright clumps of previously hidden open star clusters appear on the smaller scales. To see the detailed optical light image for comparison, run your cursor over the above image. Anyone with a good pair of binoculars can see the Whirlpool toward the constellation of the Hunting Dogs (Canes Venatici). M51 lies about 30 million light years away, while the above imaged area spans about 15,000 light years from top to bottom. Astronomers speculate that M51's spiral structure is primarily due to its gravitational interaction with a neighboring smaller galaxy. Browse: See the latest images submitted to APOD

Hidden Treasures of M78

M78 isn't really hiding in planet Earth's night sky. About 1,600 light-years away and nestled in the nebula rich constellation Orion, the large, bright, reflection nebula is well-known to telescopic skygazers. But this gorgeous image of M78 was selected as the winner of the Hidden Treasures 2010 astrophotography competition. Held by the European Southern Observatory (ESO), the competition challenged amateur astronomers to process data from ESO's astronomical archive in search of cosmic gems. The winning entry shows off amazing details within bluish M78 (center) embraced in dark, dusty clouds, along with a smaller reflection nebula in the region, NGC 2071 (top). Yellowish and even more compact, the recently discovered, variable McNeil's Nebula is prominent in the scene below and right of center. Based on data from ESO's WFI camera and 2.2 meter telescope at La Silla, Chile, this image spans just over 0.5 degrees on the sky. That corresponds to 15 light-years at the estimated distance of M78.

NanoSail-D

Featured in this artist's illustration, NASA's NanoSail-D finally unfurled a very thin, 10 square meter reflective sail on January 20th, becoming the first solar sail spacecraft in low Earth orbit. Often considered the stuff of science fiction, sailing through space was suggested 400 years ago by astronomer Johannes Kepler who observed comet tails blown by the solar wind. Modern solar sail spacecraft designs, like NanoSail-D or the Japanese interplanetary spacecraft IKAROS, rely on the small but continuous pressure from sunlight itself for thrust. Glinting in the sunlight as it circles planet Earth, the NanoSail-D solar sail will periodically be bright and easily visible to the eye. In fact, skygazers are urged to participate in an ongoing contest to capture images of NanoSail-D. The images will help NASA monitor the satellite before it reenters the atmosphere in April or May.

Opportunity at Santa Maria Crater

Celebrating 7 years on the surface of the Red Planet, Mars exploration rover Opportunity now stands near the rim of 90 meter wide Santa Maria crater. Remarkably, Opportunity and its fellow rover Spirit were initially intended for a 3 month long primary mission. Still exploring, the golf cart-sized robot and shadow (far right) appear in the foreground of this panoramic view of its current location. The mosaic was constructed using images from the rover's navigation camera. On its 7 year anniversary, Opportunity can boast traversing a total of 26.7 kilometers along the martian surface. After investigating Santa Maria crater, controllers plan to have Opportunity resume a long-term trek toward Endeavour crater, a large, 22 kilometer diameter crater about 6 kilometers from Santa Maria. The rim of Endeavour is visible in the mosaic on the horizon at the right, just above the shadow of the rover's mast. During coming days, communication with the rover will be more difficult as Mars moves close to alignment with the Sun as seen from planet Earth's perspective.

Gibbous Europa

Although the phase of this moon might appear familiar, the moon itself might not. In fact, this gibbous phase shows part of Jupiter's moon Europa. The robot spacecraft Galileo captured this image mosaic during its mission orbiting Jupiter from 1995 - 2003. Visible are plains of bright ice, cracks that run to the horizon, and dark patches that likely contain both ice and dirt. Raised terrain is particularly apparent near the terminator, where it casts shadows. Europa is nearly the same size as Earth's Moon, but much smoother, showing few highlands or large impact craters. Evidence and images from the Galileo spacecraft, indicated that liquid oceans might exist below the icy surface. To test speculation that these seas hold life, NASA and ESA have started preliminary development of the Europa Jupiter System Mission, a spacecraft proposed for launch around 2020 that would further explore Jupiter and in particular Europa. If the surface ice is thin enough, a future mission might drop hydrobots to burrow into the oceans and search for life. Browse: See the latest images submitted to APOD

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