Explanation: The firstFull Moon of northern springrises behind four distant towers in thistelescopic view. In an image captured from some 40 kilometers west of the city of Madrid, this moonrise also represents a near coincidence of the full lunar phase withlunar perigee and theMarch equinox. Close to the horizon, the Full Moon's strangely rippled and distorted shape has more to do with the long sight-line through alayered atmosphere, though. Tantalizing visible effects of the substantial atmospheric refraction include the appearance of a thin floating sliver just above the lunar disk. The remarkable optical mirage is related to the more commonly witnessedgreen flashof the setting Sun.

Explanation: Despite the cold,a chance to view the shimmering northern lights coaxed this skygazer onto the frozen surface of Lake Superior on the west coast of the Keweenaw Peninusla and offered this nocturnal crescendo as a reward. A northern late winter night sky also plays across thepanoramic composition of images made between 10pm and 1am on the night of February 28/March 1. At left, a faint band of Zodiacal light rises sharply from the horizon crossing Mars and the Pleides star cluster. Both the distant galaxy M31 and our own Milky Way shine above the greenishauroral arc. Navigationalnorth pole star Polaris is centered above and accompanied on the right by the northern night's most recognizable asterism,the Big Dipper. Terrestrial lights include markers for two breakwaters on the the horizon near the center of the scene.

Explanation: Stars trail and theSun rises in this night and day composite panorama made on March 19. The view looks toward the eastern horizon from La Nava de Santiago, Spain. To create it, a continuous series of digital frames was recorded for about two hours and combined to trace the concentric motion of the stars through the night sky.A reflectionof the Earth's rotation, star trails curve around the north celestial pole toward upper left and the south celestial pole toward the lower right.Of course onthat day the Sunwas near the celestial equator, a diagonal straight line in the wide-angle projection. A dense dimming filter was used to capture the Sun's image every two minutes. Superimposed on the star trails it rose due east in the morning sky. In the scene, foreground landscape and alocal prehistoric monumentwere illuminated byfull moonlight, though. The monument's corridor faces nearly to the east and the equinox sunrise.

Explanation: The five naked-eye planets, Mercury, Venus, Mars, Jupiter and Saturn, have been seen since ancient times to wander the night skies of planet Earth. So it could be remarkable that on this night, standing at the side of a clear, calm lake, six planets can be seen with the unaided eye.Have a look.Very bright and easy to spot for skygazers, yellowish Mars is left of a pale Milky Way. Saturn is immersed in the glow of the Milky Way's diffuse starlight. Jupiter is very near the horizon on the right, shining beyond the trees against the glow of distant city lights. Last weekend, while admiring this night time view across beautiful, high-altitude Lake Tenaya in Yosemite National Park, athoughtful and reflective observer could probablysee three planets more.

Explanation: Sometimes, regions of planet Earth light up with fire. Since fire is the rapid acquisition of oxygen, and since oxygen is a key indicator of life, fire on any planet would be an indicator of life on that planet. Most of the Earth's land has been scorched by fire at some time in the past. Although causing many a tragedy, for many places on Earth fire is considered part of a natural ecosystem cycle.   Large forest fires on Earth are usually caused either by humans or lightning and can be visible from orbit.Featured from the year 2000, stunned elk avoid a fire sweeping through Montana's Bitterroot Valley by standing in a river.

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Explanation: The dark Horsehead Nebula and the glowingOrion Nebula are contrasting cosmic vistas. Adrift 1,500 light-years away in one of the night sky'smost recognizableconstellations, they appear in opposite corners of the abovestunning two-panel mosaic. The familiar Horseheadnebula appears as a dark cloud on the lower left, a small silhouettenotched against the glow of hydrogen (alpha) gas, here tinted orange. Alnitak is the easternmost star inOrion's belt and can be found to the left of theHorsehead. Below Alnitak is theFlame Nebula, with clouds of bright emission anddramatic dark dust lanes. The magnificent emission region, theOrion Nebula (aka M42), lies at the upper right, surrounded by the blue glow of reflecting dust. Immediately to its left is a prominent reflection nebula sometimes called the Running Man. Pervasive tendrilsof glowing hydrogen gas are easilytracedthroughout the region.

Explanation: What's happening at the center of spiral galaxy M106? A swirling disk of stars and gas, M106's appearance is dominated by blue spiral arms and red  dust lanes near the nucleus, as shown in the featured image.   The core of M106 glows brightly in radio waves and X-rays where twin jets have been found running the length of the galaxy.   An unusual central glow makes M106 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole.  M106, also designated NGC 4258, is a relatively close 23.5 million light years away, spans 60 thousand light years across, and can be seen with a small telescope towards the constellation of the Hunting Dogs (Canes Venatici).

Explanation: The best knownasterism in northern skies hangs over the Canadian Rockies in this mountain and night skyscape taken last week from Banff National Park. But most remarkable is the amazing greenish airglow. With airglow visible to the eye, but not in color,the scene was captured in two exposures with a single camera, one exposure made while tracking the stars and one fixed to a tripod. Airglow emission is predominately from atmospheric oxygen atoms at extremely low densities. Commonly recorded in color by sensitive digital cameras the eerie, diffuse light is seen here inwaves acrossthe northern night. Originating at an altitude similar to aurorae, the luminous airglow isdue to chemiluminescence, the production of light through chemical excitation and radiative decay. Energy for the chemical excitation is provided during daytime by the Sun's extremeultraviolet radiation. Unlike aurorae which are limited tohigh latitudes, airglow can be foundaround the globe.

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Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely notone of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way galaxy. M101 was also one of the originalspiral nebulae observed by Lord Rosse's large19th century telescope, the Leviathan of Parsontown.M101 sharesthis modern telescopic field of view with more distant background galaxies, foreground stars within the Milky Way, and a companiondwarf galaxy NGC 5474 (lower right). The colors of the Milky Waystars can also be found in the starlight from the large island universe. Its core is dominated by light from cool yellowish stars.Alongits grand design spiral arms are the blue colors of hotter, young stars mixed with obscuring dust lanes and pinkish star forming regions. Also known as thePinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major,about 23 million light-years away. Its companion NGC 5474 has likely been distorted by its past gravitational interactions with the dominant M101.

Explanation: Mars exploration roverOpportunity's parting panoramafrom Perseverance Valley spans 360 degrees in this false color mosaic.The scene is composedof 354 individual images recorded through 3 different color filters by the rover's panoramic camera from May 13 throughJune 10, 2018. A few frames remain in black and white at the lower left though. Those were obtained through only one filter just before a dust storm engulfed Mars in June 2018, ultimately ending the solar-powered rover's trailblazing 15 year mission. Just right of center, the annotation identifies Opportunity's entry point to Perseverance Valley along the Endeavor crater's western rim. The rover's tracks begin there, extending from over the horizon toward the far right and its final resting spot on the Red Planet.

Explanation: That's not a young crescent Moonpoised above the hills along the western horizon at sunset. It's Venus in a crescent phase. About 54 million kilometers away and less than 20 percent illuminated, it was captured by telescope and camera on September 30 near Bacau, Romania. The bright celestial beacon is now languishing in the evening twilight, its days as the Evening Star in 2018 coming to a close. But it also grows larger in apparent size and becomes an ever thinner crescent intelescopic views. Heading toward aninferior conjunction (non-judgmental), the inner planet will be positioned between Earth and Sun on October 26 and lost from view in the solar glare. At month's end a crescent Venus will reappear in the east though, rising just before the Sun as the brilliantMorning Star.

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Explanation: What does Venus look like beneath its thick clouds? These clouds keep the planet's surface hidden from even the powerful telescopic eyes of Earth-bound astronomers. In the early 1990s, though, using imaging radar, NASA's Venus-orbiting Magellan spacecraft was able to lift the veil from the face of Venus and produced spectacular high resolution images of the planet's surface. Colors used in this computer generated picture of Magellan radar data are based on color images from the surface of Venus transmitted by the Soviet  Venera 13 and 14 landers. The bright area running roughly across the middle represents the largest highland region of Venus known as Aphrodite Terra. Venus, on the left, is about the same size as our Earth, shown to the right for comparison.

Explanation: Are galaxies giant magnets? Yes, but the magnetic fields in galaxies are typically much weaker than onEarth's surface, as well as more complex and harder to measure. Recently, though, the HAWC+ instrument onboard the airborne (747) SOFIA observatory has been successful in detailing distant magnetic fields by observing infrared light polarized by reflection from dust grains. Featured here, HAWC+ observations of the M82, the Cigar galaxy, show that the central magnetic field is perpendicular to the disk and parallel to the strong supergalactic wind. This observation bolsters the hypothesis that M82's central magnetic field helps its wind transport the mass of millions of stars out from the central star-burst region. The featured image shows magnetic field lines superposed on top of an optical light (gray) and hydrogen gas (red) image from Kitt Peak National Observatory, further combined with <a www.esa.int="" our_activities="" space_science="" herschel="" why_the_infrared"="">infrared images (yellow) from SOFIA and the Spitzer Space Telescope. The Cigar Galaxy is about 12 million light years distant and visible with binoculars towards the constellation of the Great Bear.

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Explanation: How can the Moon rise through a mountain?   It cannot -- what wasphotographed here is amoonrise through theshadow of a largevolcano.   The volcano is Mauna Kea,Hawai'i,USA, a frequent spot forspectacularphotographssinceitisone ofthepremierobservinglocationsonplanetEarth. The Sun has just set in theopposite direction, behind the camera. Additionally, theMoon has just passed fullphase -- were it precisely atfull phase it would rise, possiblyeclipsed, at the very peak of the shadow. The Moon is actually rising in the triangular shadow cone of the volcano, a corridor of darkness  that tapers off in the distance like converging train tracks. The Moon is too large and too far away to be affected by the shadow of the volcano.Refraction of moonlight through theEarth's atmosphere makes theMoon appear slightly oval.  Cinder cones from old volcanic eruptions are visible in the foreground.

Explanation: Peering from the shadows, the Saturn-facing hemisphere of tantalizinginner moon Enceladus poses in this Cassini spacecraft image.North is up inthe dramatic scene captured during November 2016 as Cassini's camera was pointed in a nearly sunward direction about 130,000 kilometers from the moon's bright crescent. In fact, the distant world reflects over 90 percent of the sunlight it receives, giving its surface about the same reflectivity asfresh snow. A mere 500 kilometers in diameter,Enceladus is a surprisingly active moon. Data collected during Cassini's flybys and years of images have revealed the presence of remarkable south polargeysers and a possibleglobal ocean of liquid water beneath an icy crust.

Explanation: Normally faint and elusive, the Jellyfish Nebula is caught inthis alluringtelescopic field of view. The entire scene is a two panel mosaic constructed using narrowband image data, with emission from sulfur, hydrogen and oxygen atoms shown in red, green and blue hues. It's anchored right and left by two bright stars,Mu andEtaGeminorum, at the foot of thecelestial twin. The Jellyfish Nebula itself is right of center, the brighter arcing ridge of emission with dangling tentacles. In fact, the cosmic jellyfish is part of bubble-shapedsupernova remnant IC 443, the expanding debris cloud from amassive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin inastrophysical waters theCrab Nebulasupernova remnant, the Jellyfish Nebula isknown to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged asSharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across.

Explanation: Where have all the sunspots gone? Last month the total number of spots that crossed our Sun was ... zero. Well below of the long term monthly average, the Sun's surface has become as unusually passive this solar minimum just like it did 11 years ago during the last solar minimum. Such passivity is not just a visual spectacle, it correlates with the Sun being slightly dimmer, with holes in the Sun's corona being more stable, and with a reduced intensity in the outflowing solar wind. The reduced wind, in turn, cools and collapses Earth's outer atmosphere (the thermosphere), causing reduced drag on many Earth-orbiting satellites. Pictured in inverted black & white on the left, the Sun's busy surface is shown near solar maximum in 2012, in contrast to the image on the right, which shows the Sun's surface last August, already without spots (for a few days), as solar minimum was setting in. Effects of this unusually static solar minimum are being studied.

Explanation: What created these huge galactic superbubbles? Two of these unusual bubbles, each spanning thousands of light-years, were recently discovered near the center of spiral galaxy NGC 3079.The superbubbles, shown in purple on the image right, are so hot they emit X-rays detected by NASA's Earth-orbiting Chandra X-Ray Observatory. Since the bubbles straddle the center of NGC 3079, a leading hypothesis is that they were somehow created by the interaction of the central supermassive black hole with surrounding gas. Alternatively, the superbubbles might have been created primarily by the energetic winds from many young and hot stars near that galaxy's center. The only similar known phenomenon is the gamma-ray emitting Fermi bubbles emanating from the center of our Milky Way Galaxy, discovered 10 years ago in images taken by NASA's Fermi satellite. Research into the nature of the NGC 3079 superbubbles will surely continue, as well as searches for high-energy superbubbles in other galaxies.

Explanation: Why are bullets of gas shooting out of the Orion Nebula? Nobody is yet sure.   First discovered in 1983, each bullet is actually about the size of our Solar System, and moving at about 400 km/sec from a central source dubbed IRc2.   The age of the bullets, which can be found from their speed and distance from IRc2, is very young -- typically less than 1,000 years. As the bullets expand out the top of the Kleinmann-Low section of the Orion Nebula, a small percentage of iron gas causes the tip of each bullet to glow blue, while each bullet leaves a tubular pillar that glows by the light of heated hydrogen gas.   The detailed image was created using the 8.1 meter Gemini South telescope in Chile with an adaptive optics system (GeMS).GeMS usesfive laser generated guide stars to help compensate for the blurring effects of planet Earth's atmosphere.

Explanation: The bright clusters and nebulae of planet Earth's night sky are often named for flowers orinsects. Though its wingspan covers over 3 light-years,NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the dying central star of this particularplanetary nebulahas become exceptionally hot, shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. This sharp close-up was recorded by the Hubble Space Telescope in 2009. The Hubble image data is reprocessed here, showing off the remarkable details of the complex planetary nebula. Cutting across a bright cavity of ionized gas, the dusttorussurrounding the central star is near the center of this view, almost edge-on to the line-of-sight.Molecular hydrogen  has been detected in the hot star's dusty cosmic shroud.NGC 6302lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius).

Explanation: Still racingacross planet Earth's night skies, Comet Iwamoto (C/2018 Y1) shares this pretty telescopic field of view with stars and nebulae of northern constellation Auriga, the Charioteer.Captured onFebruary 27, Iwamoto's greenish coma and faint tail appear between a complex of reddish emission nebulae and open star cluster M36 (bottom right). The reddish emission is light from hydrogen gas ionized by ultraviolet radiation from hot stars near the region's giant molecular cloud some 6,000 light-years distant. The greenish glow from thecomet, less than 5 light-minutes away, is predominantly emission from diatomic carbon molecules fluorescing in sunlight. M36, one ofAuriga's more familiar star clusters, is also a background object far beyond the Solar System, about 4,000 light-years away. Comet Iwamoto passed closest to Earth on February 12 and is outward bound in a highly elliptical orbit that will carry it beyond the Kuiper belt. With an estimated orbital period of 1,317 yearsit should return to the inner Solar System in 3390 AD.

Explanation: On January 1, New Horizons swooped to within 3,500 kilometers of theKuiper Belt world known as Ultima Thule. That's about 3 times closer than its July 2015 closest approach to Pluto. The spacecraft's unprecedented feat of navigational precision, supported by data from ground and space-based observing campaigns, was accomplished 6.6 billion kilometers (over 6 light-hours) from planet Earth. Six and a half minutes before closest approach to Ultima Thule it captured the nine frames used in this composite image.The most detailed picture possibleof the farthest object ever explored, the image has a resolution of about 33 meters per pixel, revealing intriguing bright surface features and dark shadows near the terminator. A primitive Solar System object, Ultima Thule's two lobes combine to span just 30 kilometers. The larger lobe, referred to as Ultima, isrecently understood to be flattenedlike a fluffy pancake, while the smaller, Thule, has a shape that resembles a dented walnut.

Explanation: Can magnetism affect how stars form?Recent analysis of Orion data from the HAWC+ instrument on the airborne SOFIA observatory indicate that, at times, it can. HAWC+ is able to measure the polarization of far-infrared light which can reveal the alignment of dust grains by expansive ambient magnetic fields. In the featured image, these magnetic fields are shown as curvy lines superposed on an infrared image of the Orion Nebula taken by a Very Large Telescope in Chile. Orion's Kleinmann-Low Nebula is visible slightly to the upper right of the image center, while bright stars of the Trapezium cluster are visible just to the lower left of center. The Orion Nebula at about l300 light years distant is the nearest major star formation region to the Sun.

Explanation: Dark shapes with bright edges winging their way through dusty NGC 6188 are tens of light-years long. The emission nebula is found near the edge of an otherwise dark large molecular cloud in the southernconstellation Ara, about 4,000 light-years away.Born inthat region only a few million years ago, the massive youngstars of the embedded AraOB1 associationsculpt the fantastic shapes and power the nebular glow with stellar winds and intense ultraviolet radiation. The recentstar formation itself was likely triggered by winds and supernova explosions, from  previous generations of massive stars, that swept up and compressed the molecular gas. With image data from theChilescope Observatory, a false-color Hubble palettewas used to create this gorgeous wide-field image and shows emission from sulfur, hydrogen, and oxygen atoms in red, green, and blue hues. The field of view spans about four full Moons, corresponding to about 150 light years at the estimated distanceof NGC 6188.

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Explanation: What are those red filaments in the sky? It is a rarely seen form of lightning confirmed only about 30 years ago: red sprites. Recent research has shown that following a powerful positivecloud-to-ground lightning strike,red sprites may start as 100-meter balls ofionized air that shoot down from about 80-km high at 10 percent the speed of light and arequickly followedby a group of upward streaking ionized balls. The featured image, taken just over a week ago inKununurra, Western Australia, captured some red sprites while shooting a time-lapse sequence of a distant lightning storm. Pictured, green trees cover the foreground, dark mountains are seen on the horizon, ominous storm clouds hover over the distant land, while red sprites appear in front of stars far in the distance. Red sprites take only a fraction of a second to occur and are best seen whenpowerful thunderstorms are visible from the side.