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Explanation: In one of the brightest parts of Milky Way lies a nebula where some of the oddest things occur. NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebulas. The Keyhole Nebula (NGC 3324), the bright structure just above the image center, houses several of these massive stars and has itself changed its appearance. The entire Carina Nebula spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky...

Explanation: Why would the sky glow like a giant repeating rainbow? Airglow. Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water. The long-duration exposure nearly along the vertical walls of airglow likely made the undulating structure particularly visible. OK, but where do the colors originate? The deep red glow likely originates from OH molecules about 87-kilometers high, excited by...

Explanation: What's happened to the sky? Moonlight illuminates a snowy scene in this night land and skyscape made on 2013 January from Lower Miller Creek, Alaska, USA. Overexposed near the mountainous western horizon is the first quarter Moon itself, surrounded by an icy halo and flanked left and right by moondogs. Sometimes called mock moons, a more scientific name for the luminous apparitions is paraselenae (plural). Analogous to a sundog or parhelion, a paraselene is produced by moonlight refracted through thin, hexagonal, plate-shaped ice crystals. As determined by the crystal geometry, paraselenae are seen at an angle of 22 degrees...

Explanation: What's that at the end of the road? The Sun. Many towns have roads that run east - west, and on two days each year, the Sun rises and sets right down the middle. Today is one of those days: an equinox. Not only is today a day of equal night (("aequus"-"nox") and day time, but also a day when the sun rises precisely to the east and sets due west. Featured here is a picturesque road in northwest Illinois, USA that runs approximately east -west. The image was taken one year ago today, during the March Equinox of...

Explanation: Get out your red/blue glasses and gaze across Ceres at mysterious mountain Ahuna Mons. Shown in a 3D anaglyph perspective view, the mosaicked image data was captured in December of 2015, taken from the Dawn spacecraft's low-altitude mapping orbit about 385 kilometers above the surface of the dwarf planet. A remarkable dome-shaped feature on Ceres, with steep, smooth sides Ahuna Mons is about 20 kilometers (12 miles) in diameter at its base, rising on average 4 kilometers to a flattened summit. Similar in size to mountains found on planet Earth, no other Cerean surface feature is so tall and...

Explanation: A familiar, zigzag, W pattern in northern constellation Cassiopeia is traced by five bright stars in this colorful and broad mosaic. Stretching about 15 degrees across rich starfields, the celestial scene includes dark clouds, bright nebulae, and star clusters along the Milky Way. In yellow-orange hues Cassiopeia's alpha star Shedar is a standout though. The yellowish giant star is cooler than the Sun, over 40 times the solar diameter, and so luminous it shines brightly in Earth's night from 230 light-years away. A massive, rapidly rotating star at the center of the W, bright Gamma Cas is about 550...

Explanation: Sporting a surprisingly bright, lovely green coma Comet 252P/Linear poses next to the Large Magellanic Cloud in this southern skyscape. The stack of telephoto exposures was captured on March 16 from Penwortham, South Australia. Recognized as a Jupiter family periodic comet, 252P/Linear will come close to our fair planet on March 21, passing a mere 5.3 million kilometers away. That's about 14 times the Earth-Moon distance. In fact, it is one of two comets that will make remarkably close approaches in the next few days as a much fainter Comet Pan-STARRS (P/2016 BA14) comes within 3.5 million kilometers (9...

Explanation: All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet night last September, much of that night's auroras had died down. Suddenly though, a new burst of particles streamed down from space, lighting up the Earth's atmosphere once again. This time, unexpectedly, pareidoliacally, they created an amazing shape reminiscent of a giant phoenix. With camera equipment at the ready, two quick sky images were taken, followed immediately by a third of the land. The mountain in the background is Helgafell, while the small foreground river is called Kaldá, both located about 30...

Explanation: What would you do if you saw the Sun disappear? Quite possibly: cheer. That's what many exuberant sky watchers did across Indonesia during a total eclipse of the Sun last week. There and then, the land and sky went dark during the day as our Sun disappeared for a few minutes behind our Moon. Many people watching knew they were witnessing a rare event, and their joyous exclamations can be heard on the featured video. What a far cry this reaction is from centuries ago, when more typical eclipse reactions derived from fear and worry. The video shows first...

Explanation: Sometimes even the dark dust of interstellar space has a serene beauty. One such place occurs toward the constellation of Taurus. The filaments featured here can be found on the sky between the Pleiades star cluster and the California Nebula. This dust is not known not for its bright glow but for its absorption and opaqueness. Several bright stars are visible with their blue light seen reflecting off the brown dust. Other stars appear unusually red as their light barely peaks through a column of dark dust, with red the color that remains after the blue is scattered away....

Explanation: If seen in the right light, Saturn glows like a neon sign. Although Saturn has comparatively little of the element neon, a composite image false-colored in three bands of infrared light highlights features of the giant ringed planet like a glowing sign. At the most blue band of the infrared light featured, false-colored blue in the above image, Saturn itself appears dark but Saturn's thin rings brightly reflect light from our Sun. Conversely, Saturn's B ring is so thick that little reflected light makes it through, creating a dark band between Saturn's A and C rings. At the most...

Explanation: In a flash, the visible spectrum of the Sun changed from absorption to emission on March 9 during the total solar eclipse. That fleeting moment, at the beginning the total eclipse phase, is captured by telephoto lens and diffraction grating in this image from clearing skies over Ternate, Indonesia. At left, the overwhelming light from the Sun is just blocked by the lunar disk. 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. The...

Explanation: This snapshot from deep space captures planet Earth on March 9. The shadow of its large moon is falling on the planet's sunlit hemisphere. Tracking toward the east (left to right) across the ocean-covered world the moon shadow moved quickly in the direction of the planet's rotation. Of course, denizens of Earth located close to the shadow track centerline saw this lunar shadow transit as a brief, total eclipse of the Sun. From a spacebased perspective between Earth and Sun, the view of this shadow transit was provided by the Deep Space Climate Observatory (DSCOVR) spacecraft's Earth Polychromatic Imaging...

Explanation: A dark Sun hangs in the clearing sky over a volcanic planet in this morning sea and skycape. It was taken during this week's total solar eclipse, a dramatic snapshot from along the narrow path of totality in the dark shadow of a New Moon. Earth's Indonesian isle of Ternate, North Maluku lies in the foreground. The sky is still bright near the eastern horizon though, beyond the region's flattened volcanic peaks and outside the Moon's umbral shadow. In fact, near the equator the dark lunar umbra is rushing eastward across Earth's surface at about 1,700 kilometers (1,100 miles)...

Explanation: Why is this galaxy so thin? Many disk galaxies are actually just as thin as NGC 5866, pictured above, but are not seen edge-on from our vantage point. One galaxy that is situated edge-on is our own Milky Way Galaxy. Classified as a lenticular galaxy, NGC 5866 has numerous and complex dust lanes appearing dark and red, while many of the bright stars in the disk give it a more blue underlying hue. The blue disk of young stars can be seen extending past the dust in the extremely thin galactic plane, while the bulge in the disk center...

Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA). Acknowledgment: R. Sahai and J. Trauger (Jet Propulsion Laboratory) ------------------------------------------------------------------------------------------------------------------------------------------------ This is a final act of celestial beauty before the long fade into cosmic history. Invisibly buried in the centre of this colourful swirl of gas is a dying star, roughly the same mass as the sun. As a star ages, the nuclear reactions that keep it shining begin to falter. This uncertain energy generation causes the stars to pulsate in an irregular way, casting off its outer layers into space. As the star sheds these outer gases, the super-hot core...

Explanation: The total solar eclipse of March 8/9 will be the only total eclipse in 2016. Crossing the international date line, the New Moon's dark shadow traces a limited, narrow path for viewing the total phase, making landfall in Indonesia and mostly tracking across the Pacific Ocean. A much larger region will be witness to a partially eclipsed Sun though, during morning hours on March 9 for southeast Asia and northeast Australia, and before sunset March 8 for Hawaii and Alaska. Safely viewing the eclipse can actually be very easy. One technique is demonstrated in this shoe group portrait from...

Explanation: What is that changing object in a cold hydrocarbon sea of Titan? Radar images from the robotic Cassini spacecraft orbiting Saturn have been recording the surface of the cloud-engulfed moon Titan for years. When imaging the flat -- and hence radar dark -- surface of the methane and ethane lake called Ligeia Mare, an object appeared in 2013 July just was not there in 2007. Subsequent observations in 2014 August found the object remained -- but had changed. In an image released last week, the mystery object seems to have disappeared in 2015 January. The featured false-color image shows...

Explanation: One of the most spectacular solar sights is an erupting prominence. In 2011, NASA's Sun-orbiting Solar Dynamic Observatory spacecraft imaged an impressively large prominence erupting from the surface. The dramatic explosion was captured in ultraviolet light in the above time lapse video covering 90 minutes, where a new frame was taken every 24 seconds. The scale of the prominence is huge -- the entire Earth would easily fit under the flowing curtain of hot gas. A solar prominence is channeled and sometimes held above the Sun's surface by the Sun's magnetic field. A quiescent prominence typically lasts about a...

Explanation: Looking toward the south from an altitude of 400 kilometers, this stunning snapshot from orbit finds bright lights of Tokyo and cities across central and southern Japan, planet Earth shining upward through broken clouds. The spacefaring perspective was captured last July by astronaut Scott Kelly during his stay on board the International Space Station. Thin stripes of airglow follow the curve of the planet's dark limb, while beyond lie stars of the constellation Centaurus and the southern sky. Their solar panels extended, a docked Soyuz (bottom) and Progress spacecraft are posed in the foreground. Kelly returned to planet Earth...