Explanation: On February 2nd early morning risers saw Saturn near an old Moon low on the eastern horizon. On that date bright planet, sunlit crescent, and faint lunar night side were captured in this predawn skyscape from Bursa, Turkey. Of course the Moon's ashen glow isearthshine, earthlight reflected from the Moon's night side. A description of earthshine, in terms of sunlight reflected by Earth's oceans illuminating the Moon's dark surface, was written over 500 years ago byLeonardo da Vinci. On May 2nd an old Moon also rose in the predawn twilight. On that date its ashen glow shared the sky with Venus, the brilliant morning star. May 2nd also marked the 500th anniversaryof Leonardo'sdeath in 1519.

Explanation: The Large Magellanic Cloud (LMC) is an alluring sight in southern skies.But this deep and detailed telescopic view, over 10 months in the making, goes beyond what is visible to mostcircumnavigators of planet Earth. Spanning over 5 degrees or 10 full moons, the 4x4 panel mosaic was constructed from 3900 frames with a total of 1,060 hours of exposure time in both broadband and narrowband filters. The narrowband filters are designed to transmit only light emitted by sulfur, hydrogen, and oxygen atoms. Ionized by energetic starlight, the atoms emit their characteristic light as electrons are recaptured and the atoms transition to a lower energy state. As a result, in this image the LMC seems covered with its own clouds of ionized gassurrounding its massive, young stars. Sculpted by the strong stellar winds and ultraviolet radiation, the glowing clouds, dominated by emission from hydrogen, are known asH II(ionized hydrogen) regions. Itself composed of many overlapping H II regions, the Tarantula Nebulais the large star forming region at the left. The largest satellite of our Milky Way Galaxy, the LMC is about 15,000 light-years across and lies a mere 160,000 light-years away toward the constellation Dorado.

Explanation: Orbiting 400 kilometers above Quebec, Canada, planet Earth, the International Space StationExpedition 59 crew captured this snapshot of the broad St. Lawrence River and curiously circular Lake Manicouagan on April 11. Right of center, the ring-shaped lake is amodern reservoir within the eroded remnant of an ancient 100 kilometer diameter impact crater. The ancient crater is veryconspicuous from orbit, a visible reminder that Earth is vulnerable torocks from space. Over 200 million years old, the Manicouagan crater was likely caused by the impact of a rocky body about 5 kilometers in diameter.Currently, there is no known asteroid with a significant probability of impacting Earth in the next century.But a fictional scenario to helppractice for an asteroid impact ison goingat the 2019 IAA Planetary Defense Conference.

Explanation: To some it looks like a cat's eye. To others, perhaps like a giant cosmic conch shell. It is actually one of brightest and most highly detailed planetary nebula known, composed of gas expelled in the brief yet glorious phase near the end of life of a Sun-like star.This nebula's dying central star may have produced the outer circular concentric shellsby shrugging offouterlayers in a series of regular convulsions. The formation of the beautiful, complex-yet-symmetric inner structures, however, is not well understood. The featured image is a composite of a digitally sharpened Hubble Space Telescope image with X-ray light captured by the orbiting Chandra Observatory. The exquisite floating space statue spans over half a light-year across. Of course,gazing into this Cat's Eye, humanity may well be seeing the fate of our sun, destined to enter its ownplanetary nebula phase of evolution ... in about 5 billion years.

Explanation: The galaxy was never in danger. For one thing, the Triangulum galaxy (M33), pictured, is much bigger than the tiny grain of rock at the head of the meteor. For another, the galaxy is much farther away -- in this instance 3 million light years as opposed to only about 0.0003 light seconds. Even so, the meteor's path took it angularly below the galaxy. Also the wind high in Earth's atmosphere blew the meteor's glowing evaporative molecule train away from the galaxy, in angular projection. Still, the astrophotographer was quite lucky to capture both a meteor and a galaxy in a single exposure -- which was subsequently added to two other images of M33 to bring up the spiral galaxy's colors. At the end, the meteor was gone in a second, but the galaxy will last billions of years.

Explanation: Massive stars, abrasive winds, mountains of dust, and energetic light sculpt one of the largest and most picturesque regions of star formation in the Local Group of Galaxies.   Known as N11, the region is visible on the upper right of many images of its home galaxy, the Milky Way neighbor known as the Large Magellanic Clouds (LMC).   The featured image was taken for scientific purposes by the Hubble Space Telescope and reprocessed for artistry by an amateur to win a Hubble's Hidden Treasures competition.   Although the section imaged above is known as NGC 1763, the entire N11 emission nebula is second in LMC size only to the Tarantula Nebula.   Compact globules of dark dust housing emerging young stars are also visible around the image. A new study of variable stars in the LMC with Hubble has helped to recalibrate the distance scale of the  observable universe, but resulted in a slightly different scale than found using the pervasive cosmic microwave background.

Explanation: They say Orionalways comes up sideways, and he does seem to on this cold December night. The bright stars of the familiar northern winter constellation lie just above the snowy tree tops surrounding a cozy cottage near the town of Ustupky in the Czech Republic. But Gemini's meteors also seem to rain on the wintry landscape. The meteor streaks are captured in exposures made near last Friday's peak of the annualGeminid meteor shower. They stream away from the shower's radiant above the trees, near the two bright stars of the zodiacal constellation of the Twins. Comet Wirtanen, a visitor to planet Earth's skies, is visible too. Look for its telltalegreenish coma nearthe stars of the seven sisters.

Explanation: Bright elliptical galaxyMessier 87 (M87) is home to the supermassive black hole captured by planet Earth'sEvent Horizon Telescopein the first ever image of a black hole. Giant of the Virgo galaxy cluster about 55 million light-years away, M87 is the large galaxy rendered in blue hues in this infraredimage from the Spitzer Space telescope.   Though M87 appears mostly featureless and cloud-like, the Spitzer image does record details of relativistic jets blasting from the galaxy's central region. Shown in the inset at top right, the jets themselves span thousands of light-years.The brighter jet seen on the right is approaching and close to our line of sight. Opposite, the shock created by the otherwise unseen receding jet lights up a fainter arc of material. Inset at bottom right, thehistoric black hole image is shown in context, at the center of giant galaxy and relativistic jets. Completely unresolved in the Spitzer image, the supermassive black hole surrounded by infalling material is the source of the enormous energy driving the relativistic jets from thecenter of active galaxy M87.

Explanation: Tracking alongthe southern Milky Way this beautiful celestial mosaic was recorded under dark Brazilian skies. Spanning some 20 degrees it actually starts with the dark expanse ofthe Coalsack nebula at the lower left, tucked under an arm of the Southern Cross. That compact constellation is topped by bright yellowishGamma Crucis, a cool giant star a mere 88 light-years distant. A line from Gamma Crucis through the blue star at the bottom of the cross, Alpha Crucis, points toward the South Celestial Pole. Follow the Milky Way to the right and your gaze will sweep across IC 2948, popularly known as theRunning Chicken nebula, before it reachesEta Carinae and the Carina Nebula near the right edge of the frame. About 200 light-years across, the Carina Nebula is a star forming region much larger than the more northerly stellar nursery the Orion Nebula. The Carina Nebula lies around 7,500 light-years from Earth along the planeof the Milky Way.

Explanation: Ridges of glowing interstellar gas and dark dust clouds inhabit theturbulent, cosmic depths of the Lagoon Nebula. Also known as M8, the bright star forming region is about 5,000 light-years distant. But it still makes for a popular stop ontelescopic tours of the constellation Sagittarius, toward the center of our Milky Way Galaxy. Dominated by the telltale red emission of ionized hydrogen atoms recombining with stripped electrons, this stunning view of the Lagoon is over 100 light-years across. At its center, the bright, compact, hourglass shape is gas ionized and sculpted by energetic radiation and extreme stellar winds from amassive young star. In fact, the many bright stars of open cluster NGC 6530 drift within the nebula,just formed in the Lagoon several million years ago. Broadband image data from Pan-STARRS(Panoramic Survey Telescope & Rapid Response System) was combined with narrowband data from amateur telescopes to create this wide and deep portrait of the Lagoon Nebula.

Explanation: The symmetric, multi-legged appearanceof the Southern Crab Nebula is certainly distinctive. About 7,000 light-years distant toward the southern sky constellation Centaurus, its glowing nested hourglass shapes are produced by the remarkable symbiotic binary star system at its center. The nebula'sdramatic stellar duo consists of a hot white dwarf star and cool, pulsating red giant star shedding outer layers that fall onto the smaller, much hotter companion. Embedded in a disk of material, outbursts from the white dwarf cause an outflow of gas driven away both above and below the disk resulting in thebipolar hourglass shapes. The bright central shape is about half a light-year across.This new Hubble Space Telescope imagecelebrates the 29th anniversary of Hubble's launch on April 24, 1990 on board the Space ShuttleDiscovery.

Explanation: Meteor showers are caused by streams of solid particles, dust size and larger, moving as a group through space. In most cases, the orbits of these meteor streams can be identified with dust expelled from a comet. When the Earth passes through a stream, the particles leave brilliant trails through the night sky as they disintegrate in Earth's atmosphere. The meteor paths are all parallel to each other, but, like train tracks, the effect of perspective causes them to appear to originate from a radiant point in the distance. The featured image composite was taken during January's Quadrantid meteor shower from La Palma, one of Spain's Canary Islands, off the northwest coast of Africa.The Quadrantids radiant is visible just below the handle of the Big Dipper. A careful eye will also discern the faint green coma of Comet Wirtanen. Tonight is the peak of the modest Lyrid meteor shower, with several meteors per hour visible from dark locations with clear skies.

Explanation: Cosmic dust clouds and young, energetic starsinhabit this telescopic vista, less than 500 light-years away toward the northern boundary ofCorona Australis, the Southern Crown. The dust clouds effectively block light from more distant background stars in theMilky Way. But the striking complex of reflection nebulae cataloged asNGC 6726, 6727, and IC 4812 produce a characteristic color as blue light from the region's young, hot stars isreflected by the cosmic dust. The dustalso obscures from view starsstill in the processof formation. At top right, smaller yellowish nebula NGC 6729 bends around young variable starR Coronae Australis. Near it, glowing arcs and loopsshocked by outflows from embedded newborn stars are identified as Herbig-Haro objects. On the sky this field of view spans about 1 degree. That corresponds to almost 9 light-years at the estimated distance of the nearby star forming region.

Explanation: Admire the beauty but fear the beast. The beauty is the aurora overhead, here taking the form of great green spiral, seen between picturesque clouds with the bright Moon to the side and stars in the background. The beast is the wave of charged particles that creates the aurora but might, one day, impair civilization. In 1859, following notable auroras seen all across the globe, a pulse of charged particles from a coronal mass ejection (CME) associated with a solar flare impacted Earth's magnetosphere so forcefully that they created the Carrington Event. A relatively direct path between the Sun and the Earth might have been cleared by a preceding CME. What is sure is that the Carrington Event compressed the Earth's magnetic field so violently that currents were created in telegraph wires so great that many wires sparked and gave telegraph operators shocks. Were a Carrington-class event to impact the Earth today, speculation holds that damage might occur to global power grids and electronics on a scale never yet experienced. The featured aurora was imaged in 2016 over Thingvallavatn Lake in Iceland, a lake that partly fills a fault that divides Earth's large Eurasian and North American tectonic plates.

Explanation: Twenty seven Merlin rocket engines are firing in thisclose-up of the launch of a Falcon Heavy rocket. Derived from threeFalcon 9first stage rockets with nine Merlin rocket engines each, the Falcon Heavy left NASA's Kennedy Space Center launch pad 39A on April 11. This second launch of aFalcon Heavy rocketcarried the Arabsat 6A communications satellite to space. In February of 2018, the first Falcon Heavy launch carriedStarman and a Tesla Roadster. Designed to be reusable, both booster stages and the central core returned safely to planet Earth, the boosters to Cape Canaveral Air Force Station landing zones. The core stage landed off shore on autonomous spaceport drone shipOf Course I Still Love You.

Explanation: A postcard from planet Earth, this springtime night skyscape looks over Alandan lake in the Alborz mountains.Taken after local midnighton April 17, the central Milky Way is rising over the region's southeast horizon. Its luminous track of stars and nebulae along the plane of our galaxy are reflected in the mirror-like lake. The brightest celestial beacon mingled with the diffuse galactic starlight is Jupiter. Slightly dimmer, Saturn is below and left just above the mountains. As spring brought leaves to the trees and the galactic center to the northern night the photographer found it alsogave frogs their voices, heard like a melody across the calm water.

Explanation: Still bright in evening skies,Mars was just past oppositionand closest to Earth on July 31, a mere 57.6 million kilometers away. Captured only a week later, this remarkable image shows theRed Planet's disknear its maximum size in earthbound telescopes, but still less than 1/74th the apparent diameter of a Full Moon. Broad regional surface shadings are starting to reappear in thetantalizingview as the latest planet-widedust storm subsides. With the bright south polar cap at the bottom, the Valles Marineris extends along the center of the disk.Just below it lies the roughly circular Solis Lacus region sometimes known as theEye of Mars. In a line, three prominent dark spots left of center are the volcanic Tharsis Montes.

https://apod.nasa.gov/apod/ap190415.html

Explanation: Similarin size to large, bright spiral galaxies in our neighborhood,IC 342is a mere 10 million light-yearsdistant in the long-necked, northern constellation Camelopardalis. A sprawling island universe, IC 342 would otherwise be a prominent galaxy in our night sky, but it is hidden from clear view and only glimpsed through the veil of stars, gas and dust clouds along the plane of our own Milky Way galaxy. Even though IC 342's light is dimmed and reddened by interveningcosmic clouds, thissharp telescopic image traces the galaxy's own obscuring dust, young star clusters, and glowing pink star forming regions along spiral arms that wind far fromthe galaxy's core. IC 342 may have undergone a recent burst ofstar formation activity and is close enough to have gravitationally influenced the evolution of thelocal groupof galaxies and the Milky Way

Explanation: Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, theexpansive corona, thesun's outer atmosphere, is an alluring sight. But the subtle details andextreme ranges in the corona's brightness, although discernible to the eye, are notoriously difficult to photograph.Pictured here, however, using over 120 images and meticulous digital processing, is a detailed wide-angle image of the Sun's corona taken during theGreat American Eclipse in 2017 August. Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields. Hundreds of stars as faint as 11th magnitude are visible behind the Moon and Sun, with Mars appearing in red on the far right. The next total eclipse of the Sun will occur on July 2 and be visible during sunset from a thin swath across Chile and Argentina.

Explanation: Sometimes Saturn disappears. It doesn't really go away, though, it just disappears from view when our Moon moves in front. Such a Saturnian eclipse was visible along a small swath of Earth -- from Brazil to Sri Lanka -- near the end of last month. The featured color image is a digital fusion of the clearest images captured by successive videos of the event taken in red, green, and blue, and taken separately for Saturn and the comparative bright Moon. The exposures were taken from South Africa just before occultation -- and also just before sunrise. When Saturn re-appeared on the other side of the Moon almost two hours later, the Sun had risen. This year, eclipses of Saturn by the Moon occur almost monthly, but, unfortunately, are visible only to those with the right location and with clear and dark skies.

Explanation: What's happening in the sky? The atmosphere over northern Norway appeared quite strange for about 30 minutes last Friday when colorful clouds, dots, and plumes suddenly appeared. The colors were actually created by the NASA-funded Auroral Zone Upwelling Rocket Experiment (AZURE) which dispersed gas tracers to probe winds in Earth's upper atmosphere.AZURE's tracers originated from two short-lived sounding rockets launched from the Andøya Space Center in Norway. The harmless gases, trimethylaluminum and a barium/strontium mixture, were released into the ionosphere at altitudes of 115 and 250 km. The vapor trails were observed dispersing from several ground stations. Mapping how AZURE's vapors dispersed should increase humanity's understanding of how the solar wind transfers energy to the Earth and powers aurora.

Explanation: Just two weeks ago, dark skies over the desert in northern Iran held this alluring celestial vista. The dramatic digital mosaic finds the Moon and Mars alongside the Milky Way's dusty rifts, stars, and nebulae. Captured through a series of exposures to cover a range in brightness, that night's otherwise Full Moon is immersed in Earth's shadow. It actually appears fainterand redder than the Red Planet itself during the widely watched total lunar eclipse.For cosmic tourists, the skyscape also includes theLagoon (M8) and Trifid (M20)nebulae and planet Saturn shining against the Milky Way's pale starlight. The Moon isn't quite done withits shadow play, though.Today, the New Moonpartially eclipses the Sun for much of northern planet Earth.

https://apod.nasa.gov/apod/ap190407.html

Explanation: After sunset on March 28, the International Space Station climbed above the western horizon, as seen from  Wallasey, England at the mouth of the River Mersey. Still glinting in the sunlight some400 kilometers above planet Earth, the fast moving ISS was followed by hand with a small backyard telescope and high frame rate digital camera. A total of 2500 frames were recorded during the 7 minute long visible ISS passage and 100 of them captured images of the space station. These are the four best frames showing remarkable details of the ISS in low Earth orbit.Near the peak of its track, about 60 degrees above the horizon, the ISS was brighter than the brightest star in the sky and as close as 468 kilometers to the Wallasey backyard.

Explanation: This astronomical skyspanning view is a mosaic from the Pan-STARRS observatory. The images were recorded with its 1.8 meter telescope at the summit ofHaleakala on planet Earth's island of Maui. In fact, Earth's north celestial pole is centered in this across-the-sky projection. A declinationof -30 degrees, the southern horizon limit as seen from the Hawaiian Valley Isle, defines the circular outer edge.Crowded starfieldsand cosmic dust clouds along the plane of our Milky Way galaxy stretch across the scene with the bright bulge of the galactic center at the bottom. Compiled over four years, the image data represent the second edition of data from Pan-STARRS (Panoramic Survey Telescope & Rapid Response System), currentlythe planet's largest digital sky survey. In 2017 Pan-STARRS was used to first recognize the interstellar voyage of'Oumuamua, visitor to our Solar System.

Explanation: After the Crab Nebula, M1, this giant star cluster is the second entry in 18th century astronomer Charles Messier's famous list of things with are not comets. M2 is one of the largest globular star clusters now known to roam the halo of our Milky Way galaxy. Though Messier originally described it a nebula without stars, thisstunning Hubble image resolves stars across the central 40 light-years of M2.Its populationof stars numbers close to 150,000, concentrated within a total diameter of around 175 light-years. About 55,000 light-years distant toward the constellation Aquarius, this ancient denizen of the Milky Way, alsoknown as NGC 7089, is 13 billion years old.

Explanation: The famous Horsehead Nebula in Orion is not alone.   A deep exposure shows that thedark familiar shaped indentation, visible just below center, is part of avast complex of absorbingdust andglowing gas.   To bring out details of the  Horsehead's pasture, an amateur astronomer used a backyard telescope in Austriato accumulate and artistically combine 7.5 hours of images in the light of Hydrogen (red), Oxygen (green), and Sulfur (blue). The resulting spectacular picture details an intricate tapestry of gaseous wisps and dust-laden filaments that were created andsculpted over eons by stellar winds and ancient supernovas.   The Flame Nebula is visible just to the left of the Horsehead, while the bright star on the upper left is Alnilam, the central star in Orion's Belt. The Horsehead Nebula lies 1,500 light years distant towards the constellation of Orion.

Explanation: Score three points for NASA.   With time running out late in Apollo 15's mission to the Moon in 1971, Astronaut David Scott prepared to split the uprightsand bring about yet another dramatic end-of-the-mission victory for NASA.   Scott used a special  lunar football designed for the rugged games held on the Moon.   R1-D1, a predecessor to R2-D2, cheered from the sideline.   Happy April Fools' Day from the folks at APOD.   In reality, Astronaut Scott placed a drill that measured how temperature changed with lunar depth. The foreground device actually detectedhigh-energy particles that escaped from the Sun.

Explanation: Across the heart of theVirgo Cluster of Galaxieslies a striking string of galaxies known as Markarian's Chain.   The chain,pictured here, is highlighted on the right with two large but featurelesslenticular galaxies,M84 andM86. Prominent to their lower left is a pair of interacting galaxies known asThe Eyes. The home Virgo Cluster is the nearestcluster of galaxies, contains over 2000 galaxies, and has a noticeable gravitational pull on the galaxies of theLocal Group of Galaxies surrounding ourMilky Way Galaxy.   The center of theVirgo Cluster is located about 70 millionlight years away toward the constellation of Virgo.   At least seven galaxies in the chain   appear to move coherently, although others appear to be superposed by chance.