Creature Aurora Over Norway

Explanation: It was Halloween and the sky looked like a creature. Exactly which creature, the astrophotographer was unsure (but possibly you can suggest one). Exactly what caused the eerie apparition was sure: one of the best auroral displays in recent memory. This spectacular aurora had an unusually high degree of detail. Pictured above, the vivid green and purple auroral colors are caused by high atmospheric oxygen and hydrogen reacting to a burst of incoming electrons. Birch trees in Tromsø, Norway formed an also eerie foreground. Many other photogenic auroras have been triggered by recent energetic flares on the Sun.

Solar Eclipse from Uganda

Explanation: The Sun's disk was totally eclipsed for a brief 20 seconds as the Moon's dark umbral shadow raced across Pokwero in northwestern Uganda on November 3rd. So this sharp telescopic view of totality in clear skies from the central African locale was much sought after by eclipse watchers. In the inspiring celestial scene the Moon just covers the overwhelmingly bright photosphere, the lower, normally visible layer of the Sun's atmosphere. Extending beyond the photosphere, the reddish hydrogen alpha glow of the solar chromosphere outlines the lunar silhouette, fading into the Sun's tenuous, hot, outer atmosphere or corona. Planet-sized prominences reaching beyond the limb of the active Sun adorn the edges of the silhouette, including a cloud of glowing plasma separated from the chromosphere near the 1 o'clock position.

In the shadow of Saturn

Explanation: In the shadow of Saturn, unexpected wonders appear. The robotic Cassini spacecraft now orbiting Saturn drifted in giant planet's shadow earlier this year and looked back toward the eclipsed Sun. Cassini saw a unique and celebrated view. First, the night side of Saturn is seen to be partly lit by light reflected from its own majestic ring system. Next, Saturn's expansive ring system appears as majestic as always even from this odd angle. Ring particles, many glowing only as irregular crescents, slightly scatter sunlight toward Cassini in this natural color image. Several moons and ring features are also discernible. Appearing quite prominently is Saturn's E ring, the ring created by the unusual ice-fountains of the moon Enceladus and the outermost ring visible above. To the upper left, far in the distance, are the planets Mars and Venus. To the lower right, however, is perhaps the most wondrous spectacle of all: the almost invisible, nearly ignorable, pale blue dot of Earth.

One Special Day in the Life of Planet Earth

The cameras on NASA's Cassini spacecraft captured this rare look at Earth and its moon from Saturn orbit on July 19, 2013. Taken while performing a large wide-angle mosaic of the entire Saturn ring system, narrow-angle camera images were deliberately inserted into the sequence in order to image Earth and its moon. This is the second time that Cassini has imaged Earth from within Saturn's shadow, and only the third time ever that our planet has been imaged from the outer solar system.

Earth is the blue point of light on the left; the moon is fainter, white, and on the right. Both are seen here through the faint, diffuse E ring of Saturn. Earth was brighter than the estimated brightness used to calculate the narrow-angle camera exposure times. Hence, information derived from the wide-angle camera images was used to process this color composite.

Both Earth and the moon have been increased in brightness for easy visibility; in addition, brightness of the moon has been increased relative to Earth, and the brightness of the E ring has been increased as well.

Images taken using red, green and blue spectral filters were combined to create this natural color view. (The accompanying wide angle frame can be found at PIA17171.) The images were obtained by the Cassini spacecraft cameras on July 19, 2013 at a distance of approximately 898.414 million miles (1.445858 billion kilometers) from Earth. Image scale on the Earth is 5,382 miles (8,662 kilometers) per pixel. The illuminated areas of neither Earth nor the moon are resolved here. Consequently, the size of each "dot" is the same size that a point of light of comparable brightness would have in the narrow angle camera.

A close-up view of Earth and moon, magnified by a factor of five is available at PIA17170.

The first image of Earth captured from the outer solar system was taken by NASA's Voyager 1 in 1990 and famously titled "Pale Blue Dot" (PIA00452). Sixteen years later, in 2006, Cassini imaged the Earth in the stunning and unique mosaic of Saturn called "In Saturn's Shadow-The Pale Blue Dot" (PIA08329). And, seven years further along, Cassini did it again in a coordinated event that became the first time that Earth's inhabitants knew in advance that they were being imaged from nearly a billion miles (nearly 1.5 billion kilometers) away. It was the also the first time that Cassini's highest-resolution camera was employed so that the Earth and its moon could be captured as two distinct targets.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

 

What's that below the Milky Way?

Explanation: What's that below the Milky Way? First, across the top of the above image, lies the faint band that is our planet's sideways view of the central disk of our home Milky Way Galaxy. The Milky Way band can be seen most clear nights from just about anywhere on Earth with a dark sky. What lies beneath is, by comparison, is a much less common sight. It is the striking peak of Castildetierra, a rock formation located in Bardenas Reales, a natural badlands in northeast Spain. Standing 50 meters tall, the rock spire includes clay and sandstone left over from thousands of years of erosion by wind and water. The astrophotographer waited months for the sky to appear just right -- and then took the 14 exposures that compose the above image in a single night.

the Great Comet of 2007

Explanation: Comet McNaught, the Great Comet of 2007, grew a spectacularly long and filamentary tail. The magnificent tail spread across the sky and was visible for several days to Southern Hemisphere observers just after sunset. The amazing tail showed its greatest extent on long-duration, wide-angle camera exposures. During some times, just the tail itself estimated to attain a peak brightness of magnitude -5 (minus five), was caught by the comet's discoverer in the above image just after sunset in January 2007 from Siding Spring Observatory in Australia. Comet McNaught, the brightest comet in decades, then faded as it moved further into southern skies and away from the Sun and Earth. Within the next two weeks of 2013, rapidly brightening Comet ISON might sprout a tail that rivals even Comet McNaught

Aurora and unusual Clouds Over Iceland

Explanation: What's happening in the sky? On this cold winter night in Iceland, quite a lot. First, in the foreground, lies the largest glacier in Iceland: Vatnajokull. On the far left, bright green auroras appear to emanate from the glacier as if it was a volcano. Aurora light is reflected by the foreground lake Jökulsárlón. On the far right is a long and unusual lenticular cloud tinged with green light emitted from another aurora well behind it. Just above this lenticular cloud are unusual iridescent lenticular clouds displaying a broad spectral range of colors. Far beyond the lenticular is the setting Moon, while far beyond even the Moon are setting stars.

 The above image was captured in late March of 2012.

The Flash Spectrum of the Sun

Explanation: In a flash, the visible spectrum of the Sun changed from absorption to emission on November 3rd, during the brief total phase of a solar eclipse. That fleeting moment is captured by telephoto lens and diffraction grating in this well-timed image from clearing skies over Gabon in equatorial Africa. With overwhelming light from the Sun's disk blocked by the Moon, the normally dominant absorption spectrum of the solar photosphere is hidden. What remains, spread by the diffraction grating into the spectrum of colors to the right of the eclipsed Sun, are individual eclipse images at each wavelength of light emitted by atoms along the thin arc of the solar chromosphere. The brightest images, or strongest chromospheric emission lines, are due to Hydrogen atoms that produce the red hydrogen alpha emission at the far right and blue hydrogen beta emission to the left. In between, the bright yellow emission image is caused by atoms of Helium, an element only first discovered in the flash spectrum of the Sun.

The Jets of NGC1097

Explanation: Enigmatic spiral galaxy NGC 1097 shines in southern skies, about 45 million light-years away in the chemical constellation Fornax. Its blue spiral arms are mottled with pinkish star forming regions in this colorful galaxy portrait. They seem to have wrapped around a small companion galaxy below and left of center, about 40,000 light-years from the spiral's luminous core. That's not NGC 1097's most peculiar feature, though. The very deep exposure hints of faint, mysterious jets, most easily seen to extend well beyond the bluish arms toward the lower right. In fact, four faint jets are ultimately recognized in optical images of NGC 1097. The jets trace an X centered on the galaxy's nucleus, but probably don't originate there. Instead, they could be fossil star streams, trails left over from the capture and disruption of a much smaller galaxy in the large spiral's ancient past. A Seyfert galaxy, NGC 1097's nucleus also harbors a supermassive black hole.