Shell Game in the LMC

An alluring sight in southern skies, the Large Magellanic Cloud (LMC) is seen here through narrowband filters. The filters are designed to transmit only light emitted by ionized sulfur, hydrogen, and oxygen atoms. Ionized by energetic starlight, the atoms emit their characteristic light as electrons are recaptured and the atom transitions to a lower energy state. As a result, this false color image of the LMC seems covered with shell-shaped clouds of ionized gas surrounding massive, young stars. Sculpted by the strong stellar winds and ultraviolet radiation, the glowing clouds, dominated by emission from hydrogen, are known as H II (ionized hydrogen) regions. Itself composed of many overlapping shells, the Tarantula Nebula is the large star forming region at top center. A satellite of our Milky Way Galaxy, the LMC is about 15,000 light-years across and lies a mere 180,000 light-years away in the constellation Dorado. via NASA http://ift.tt/2iIpJL2

Curiosity Surveys Lower Mount Sharp on Mars

If you could stand on Mars -- what might you see? If you were the Curiosity rover, then just last month you would have contemplated the featured image -- a breathtaking panorama of the lower portion of Mount Sharp. The colors have been adjusted to mimic lighting familiar to Earthlings. Surveyed here was a rocky plain before increasingly high rolling hills. The rounded hills in the middle distance, called the Sulfate Unit, are Curiosity's highest currently planned destination. One reason these hills are interesting is because sulfates are an energy source for some micro-organisms. The immediate path forward, though, was toward the southeast on the left part of the image. via NASA http://ift.tt/2hosYXb

The Magnificent Horsehead Nebula

Sculpted by stellar winds and radiation, a magnificent interstellar dust cloud by chance has assumed this recognizable shape. Fittingly named the Horsehead Nebula, it is some 1,500 light-years distant, embedded in the vast Orion cloud complex. About five light-years "tall", the dark cloud is cataloged as Barnard 33 and is visible only because its obscuring dust is silhouetted against the glowing red emission nebula IC 434. Stars are forming within the dark cloud. Contrasting blue reflection nebula NGC 2023, surrounding a hot, young star, is at the lower left. The gorgeous color image combines both narrowband and broadband images recorded using three different telescopes. via NASA http://ift.tt/2i5mZbE

An Airplane Glory

Looking out the window of an airplane, you might be lucky enough to see "the glory" in the direction directly opposite the Sun. Before airplanes, the phenomenon, known to some as the heiligenschein or the Specter of the Brocken, was sometimes seen from mountaintops. There, when conditions were right, one could look away from the Sun and see what appeared to be the shadow of a giant surrounded by a bright halo. The giant turns out to be the observer, as in the modern version a silhouette of an plane frequently occupies the glory's center. This bright glory was photographed two weeks ago over Michigan from an airplane on approach to O'Hare International Airport. The cause of the glory is still being researched and is relatively complex. Surely, small droplets of water in some way reflect, refract, and diffract sunlight backwards towards the Sun. The phenomenon has similar counterparts in other branches of science including astronomy, where looking out from the Earth in the direction opposite the Sun yields a bright spot called the gegenschein. via NASA http://ift.tt/2hVAYR2

Sharpless 308: Star Bubble

Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a full moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue. via NASA http://ift.tt/2gXLXYn

Sharpless 308: Star Bubble

Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a full moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue. via NASA http://ift.tt/2gXLXYn

Southern Jupiter from Perijove 3

Southern Jupiter looms some 37,000 kilometers away in this JunoCam image from December 11. The image data was captured near Juno's third perijove or closest approach to Jupiter, the spacecraft still in its 53 day long looping orbit. With the south polar region on the left, the large whitish oval toward the right is massive, counterclockwise rotating storm system. Smaller than the more famous Great Red Spot, the oval storm is only about half the diameter of planet Earth, one of a string of white ovals currently in the southern hemisphere of the Solar System's, ruling gas giant. via NASA http://ift.tt/2hZSClv

Seagull to Sirius

This broad, beautiful mosaic spans almost 20 degrees across planet Earth's sky. The nebula-rich region lies near the edge of the Orion-Eridanus superbubble, filled with looping, expanding shells of gas and dust embedded in molecular clouds near the plane of the Milky Way Galaxy. Recognizable at the left is the expansive Seagull Nebula, composed of emission nebula NGC 2327, seen as the seagull's head, with the more diffuse IC 2177 as the wings and body. Some 3,800 light-years away, the wings of the Seagull Nebula spread about 240 light-years, still within our local spiral arm. The bluish light of Sirius, alpha star of Canis Major and brightest star in the night, easily dominates the scene at right but shines from a distance of only 8.6 light-years. Study the big picture and you should also be rewarded with star cluster Messier 41, also known as NGC 2287, not to mention the mighty Thor's Helmet. via NASA http://ift.tt/2hRIH1m

The Lagoon Nebula in High Definition

Stars are battling gas and dust in the Lagoon Nebula but the photographers are winning. Also known as M8, this photogenic nebula is visible even without binoculars towards the constellation of Sagittarius. The energetic processes of star formation create not only the colors but the chaos. The red-glowing gas results from high-energy starlight striking interstellar hydrogen gas. The dark dust filaments that lace M8 were created in the atmospheres of cool giant stars and in the debris from supernovae explosions. The light from M8 we see today left about 5,000 years ago. Light takes about 50 years to cross this section of M8. Data used to compose this image was taken with the wide-field camera OmegaCam of the ESO's VLT Survey Telescope (VST). via NASA http://ift.tt/2hEMAur

Meteors over Four Girl Mountains

On some nights it rains meteors. Peaking over the next two nights, asteroid dust is expected to rain down on Earth during the annual Geminids meteor shower. This year, unfortunately, fainter Geminids will be harder to see because of the brightness of the Long Nights Full Moon, which occurs Wednesday. Pictured, an image from this year's Perseids meteor shower in August captured multiple streaks over Four Girls Mountain in central China. The bright Pleaides open star cluster appears toward the upper right, while numerous emission nebulas are visible in red, many superposed on the diagonal band of the Milky Way. via NASA http://ift.tt/2gHbmsn

Over Saturns Turbulent North Pole

The Cassini spacecraft's Grand Finale at Saturn has begun. The Grand Finale will allow Cassini to explore Saturn and some of Saturn's moons and rings in unprecedented detail. The first phase started two weeks ago when a close flyby of Titan changed Cassini's orbit into one that passes near Saturn's poles and just outside of Saturn's outermost F-ring. Featured here is an image taken during the first of Cassini's 20 week-long F-ring orbits around Saturn. Visible are the central polar vortex on the upper left, a hexagonal cloud boundary through the image center, and numerous light-colored turbulent storm systems. In 2017 April, Cassini will again use the gravity of Titan to begin a new series of 22 Proximal orbits -- trajectories that will take Cassini inside of Saturn's rings for the first time. Cassini's new science adventure is scheduled to end on 2017 September 17, though, when the robotic spacecraft will be directed into a dramatic mission-ending dive into Saturn's atmosphere. via NASA http://ift.tt/2hlvVLX

The Lunar X

The striking X appearing in this lunarscape is easily visible in binoculars or a small telescope. Yet, not too many have seen it. The catch is this lunar X is fleeting, only apparent in the hours before the Moon's first quarter phase. At the terminator, or shadow line between lunar day and night, the X illusion is produced by a configuration of the craters Blanchinus, La Caille and Purbach. Near the Moon's first quarter phase, an astronaut standing close to the craters' position would see the slowly rising Sun very near the horizon. Temporarily, the crater walls would be in sunlight while the crater floors were still in darkness. Seen from planet Earth, contrasting sections of bright walls against the dark floors by chance look remarkably like an X. This sharp image of the Lunar X was captured at approximately 16:45 UT on December 6, 2016. For extra credit, sweep your gaze along the lunar terminator and you can also spot the Lunar V. via NASA http://ift.tt/2hg43Ja

Aurora over Jupiters South Pole from Juno

Why is there a glowing oval over Jupiter's South Pole? Aurora. Near the closest part of its first pass near Jupiter in August, NASA's robotic spacecraft Juno captured this dramatic infrared image of a bright auroral ring. Auroras are caused by high energy particles from the Sun interacting with a planet's magnetic field, and ovals around magnetic poles are common. Data from Juno are giving preliminary indications that Jupiter's magnetic field and aurorae are unexpectedly powerful and complex. Unfortunately, a computer glitch caused Juno to go into safe mode during its last pass near the Jovian giant in September. That glitch has now been resolved, making Juno ready for its next pass over Jupiter's cloud tops this coming Sunday. via NASA http://ift.tt/2h2oM3h

Lightning over Colorado

Have you ever watched a lightning storm in awe? Join the crowd. Oddly, nobody knows exactly how lightning is produced. What is known is that charges slowly separate in some clouds causing rapid electrical discharges (lightning), but how electrical charges get separated in clouds remains a topic of much research. Lightning usually takes a jagged course, rapidly heating a thin column of air to about three times the surface temperature of the Sun. The resulting shock wave starts supersonically and decays into the loud sound known as thunder. Lightning bolts are common in clouds during rainstorms, and on average 44 lightning bolts occur on the Earth every second. Pictured, over 60 images were stacked to capture the flow of lightning-producing storm clouds in July over Colorado Springs, Colorado, USA. via NASA http://ift.tt/2ha4WUe

Galaxies in Pegasus

This wide, sharp telescopic view reveals galaxies scattered beyond the stars of the Milky Way at the northern boundary of the high-flying constellation Pegasus. Prominent at the upper right is NGC 7331. A mere 50 million light-years away, the large spiral is one of the brighter galaxies not included in Charles Messier's famous 18th century catalog. The disturbed looking group of galaxies at the lower left is well-known as Stephan's Quintet. About 300 million light-years distant, the quintet dramatically illustrates a multiple galaxy collision, its powerful, ongoing interactions posed for a brief cosmic snapshot. On the sky, the quintet and NGC 7331 are separated by about half a degree. via NASA http://ift.tt/2g4uUXq

A Triple Star is Born

A triple star system is forming, enshrouded within this dusty natal disk some 750 light-years away in the Perseus molecular cloud. Imaged at millimeter wavelengths by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the extreme close-up shows two protostars separated by a mere 61 AU (1 AU is the Earth-Sun distance) with a third 183 AU from the central protostar. The ALMA image also reveals a clear spiral structure indicating instability and fragmentation led to the multiple protostellar objects within the disk. Astronomers estimate that the system, cataloged as L1448 IRS3B, is less than 150,000 years old. Captured at an early phase, the starforming scenario is likely not at all uncommon, since almost half of all sun-like stars have at least one companion. via NASA http://ift.tt/2fOoNI1