Explanation: If you saw a total solar eclipse, would you do a double-take? One astrophotographer did just that -- but it took a lake and a bit of planning. Realizing that the eclipse would be low on the horizon, he looked for a suitable place along the thin swath of South America that would see, for a few minutes, the Moon completely block the Sun, both directly and in reflection. The day before totality, he visited a lake called La Cuesta Del Viento (The Slope of the Wind) and, despite its name, found so little wind that the lake looked like a mirror.  Perfect. Returning the day of the eclipse, though, there was a strong breeze  churning up the water -- enough to ruin the eclipse reflection shot. Despair. But wait! Strangely, about an hour before totality, the wind died down. This calmness may have been related to the eclipse itself, because eclipsed ground heats the air less and reduces the amount rising warm air -- which can dampen and even change the wind direction. The eclipse came, his tripod and camera were ready, and so was the lake. The featured image of this double-eclipse came from a single exposure lasting just one fifteenth of a second. Soon after totality, the winds returned and the water again became choppy. No matter -- this double-image of the 2019 July total solar eclipse had been captured forever.

Explanation: Twenty-one years agoresults werefirst presented indicating that most of the energy in our universe is not in stars or galaxies but is tied to space itself.   In the language of cosmologists, a largecosmological constant -- dark energy -- was directly implied by new distantsupernova observations.   Suggestions of acosmological constant werenot new -- they have existed since the advent ofmodern relativistic cosmology. Such claims were not usually popular with astronomers, though, because dark energy was so unlike knownuniverse components, because dark energy's abundance  appeared limited by other observations, and because less-strange cosmologies without a signficant amount of dark energy had previously done well in explaining the data. What was exceptional here was the seemingly direct and reliable method of the observations and the good reputations of thescientists conductingthe investigations. Over the two decades, independent teams of astronomers have continued to accumulate data that appears to confirm the existence ofdark energy and the unsettling result of a presentlyaccelerating universe. In 2011, the team leaders were awarded the Nobel Prize in Physics for their work.   Thefeatured picture of a supernova that occurred in1994on the outskirts of aspiral galaxywas taken by one of these collaborations.

Explanation: Peering from the shadows, the Saturn-facing hemisphere of Mimas lies in near darkness alongside adramatic sunlit crescent. The mosaic was captured near the Cassinispacecraft's finalclose approach on January 30, 2017. Cassini's camera was pointed in a nearly sunward direction only 45,000 kilometers from Mimas. The result is one of the highest resolution views of the icy, crater-pocked,400 kilometer diameter moon. An enhanced version better reveals the Saturn-facing hemisphere of the synchronously rotating moon lit by sunlight reflected from Saturn itself. To see it, slide your cursor over the image (orfollow this link). Other Cassini images of Mimas include the small moon's large and ominousHerschel Crater.

Explanation: A small constellation hiding near thesouth celestial pole, The Chamaeleon boasts no bright stars. Stars are forming within its constellation boundaries though, in a complex of dark, dusty molecular clouds. Some 500 light-years distant, theChamaeleon II dark nebula inhabits this view where the cosmic dust clouds standout mostly in silhouette against the starry southern sky.The telescopic frame is about the angular size of a Full Moon and so spans about 5 light-years at the dark cloud's estimated distance. Scattered near center a telltale reddish glow from identifiedHerbig-Haro objects is seen in the sharp image, jets of shocked glowing gasemanating from recently formed stars.

Explanation: Massive stars spend their brief lives furiously burning nuclear fuel.Through fusionat extreme temperatures and densities surrounding the stellar core, nuclei of light elements ike Hydrogen and Helium are combined to heavierelements likeCarbon, Oxygen, etc. in a progression which ends with Iron. So a supernova explosion, a massive star's inevitable and spectacular demise, blasts back into space debrisenriched inheavier elements to be incorporated into other stars and planets andpeople). This detailed false-color x-ray image from the orbiting Chandra Observatory shows such a hot, expanding stellar debris cloud about 36 light-years across. Cataloged asG292.0+1.8, this young supernova remnant is about 20,000 light-years distant toward the southern constellation Centaurus. Light from the inital supernova explosion reached Earth an estimated 1,600 years ago. Bluish colors highlight filaments of the mulitmillion degree gas which are exceptionallyrich in Oxygen, Neon, and Magnesium.This enriching supernova also produced a pulsar in its aftermath, a rotating neutron star remnant of the collapsed stellar core. The stunning image was released as part of the 20th anniversary celebration ofthe Chandra X-ray Observatory.

Explanation: To some, this nebula looks like the head of a fish. However, this colorful cosmic portrait really featuresglowing gas and obscuring dust clouds in IC 1795, a star forming region in the northern constellation Cassiopeia. The nebula's colors were created by adopting theHubble color palettefor mapping narrow emission from oxygen, hydrogen, and sulfur atoms to blue, green and red colors, and further blending the data with images of the region recorded through broadband filters. Not far on the sky from the famous Double Star Cluster in Perseus, IC 1795 is itself located next to IC 1805, the Heart Nebula, as part of acomplex of star forming regions that lie at the edge of a large molecular cloud. Located just over 6,000 light-years away, the larger star forming complex sprawls along the Perseus spiral arm of our Milky Way Galaxy. At that distance, this picture would span about 70 light-years across IC 1795.

Explanation: What's happening in the Statue of Liberty nebula? Bright stars and interesting molecules are forming and being liberated. Thecomplex nebula resides in the star forming region called RCW 57, and besides the iconic monument, to some looks like a flying superhero or aweeping angel. By digitally removing the stars, this image showcases dense knots of dark interstellar dust, fields of glowing hydrogen gas ionized by these stars, and great loops of gas expelled by dying stars. A detailed study of NGC 3576, also known as NGC 3582 and NGC 3584, uncovered at least 33 massive stars in the end stages of formation, and the clear presence of the complex carbon molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs are thought to be created in the cooling gas of star forming regions, and their development in the Sun's formation nebula five billion years ago may have been an important step in the development of life on Earth.

Explanation:  Have you ever watched a lightning storm in awe?   Join the crowd. Details of what causes  lightning are still  being researched, but it is known that  inside some clouds, internal updrafts cause collisions  between ice and snow that slowly  separate charges between cloud tops and bottoms  The  rapid electrical discharges that are  lightning soon result.  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.   On average, around the world, about  6,000 lightning bolts occur between clouds and the  Earth every minute. Pictured earlier this month in a two-image composite, lightning stems from communication antennas near the top of  Volcán de Agua  (Volcano of Water) in  Guatemala.

Explanation: The North America Nebula can do what most North Americans cannot -- form stars. Precisely where in the nebula these stars are forming has been mostly obscured by some of the nebula's thick dust that is opaque to visible light. However, a view of the North America Nebula in infrared light by the orbiting Spitzer Space Telescope has peered through much of the dust and uncovered thousands of newly formed stars. Rolling your cursor over the above scientifically-colored infrared image will bring up a corresponding optical image of the same region for comparison.   The infrared image neatly captures young stars in many stages of formation, from being imbedded in dense knots of gas and dust, to being surrounded by disks and emitted jets, to being clear of their birth cocoons. The North America Nebula (NGC 7000) spans about 50light years and lies about 1,500 light years away toward the constellation of the Swan (Cygnus). Still, of all the stars known in the North America Nebula, which massive stars emit the energetic light that gives the ionized  red glow is still debated.

Explanation: On July 22nd this GSLV (Geosynchronous Satellite Launch Vehicle) MkIII rocket vanished from sight into a cloud bank an instant after thisdramatic snapshot was taken. Launched from India's Satish Dhawan Space Centre it carried theChandrayaan 2mission spacecraft into Earth orbit.The spacecraft's orbiter, lander, and rover are destined for the Moon, though.In the coming weeks it will perform a series of orbit raising maneuvers, eventually transferring tolunar orbit in early September. Carrying the solar-powered rover, the lander is scheduled to separate and attempt its autonomous soft landing at high latitudes near the lunar south pole. It shouldarrive on the lunar nearside near local sunrise and the start of a two Earth-week longlunar day on September 7.

Explanation: Transfusing sunlightthrough a still dark sky, this exceptional display ofnoctilucent clouds was captured earlier this month, reflected in the calm waters of Vallentuna Lake near Stockholm, Sweden. From the edge of space, about 80 kilometers above Earth's surface, theicy cloudsthemselves still reflect sunlight even though the Sun is below the horizon as seen from the ground.Usually spotted at high latitudes in summer months the night shining clouds have made a strong showing so far during the short northernsummer nights. Also known as polar mesopheric clouds theyare understood to formas water vapor driven into the cold upper atmosphere condenses on the fine dust particles supplied by disintegrating meteors or volcanic ash. NASA's AIM mission provides daily projections of noctilucent cloudsas seen from space.

Explanation: In brush strokes of interstellar dust and glowinghydrogen gas, this beautiful skyscape is painted across the plane of ourMilky Way Galaxynear the northern end of the Great Rift and the constellation Cygnus the Swan. Composed with three different telescopes and about 90 hours of image data the widefield mosaic spans an impressive 24 degrees across the sky. Alpha star of Cygnus, bright, hot, supergiantDeneblies near top center. Crowded with stars and luminous gas clouds Cygnus is also home to the dark, obscuring Northern Coal Sack Nebula, extending from Deneb toward the center of the view. The reddish glow of star forming regions NGC 7000, theNorth America Nebula andIC 5070, the Pelican Nebula, are just left of Deneb. The Veil Nebula is a standout below and left of center. A supernova remnant, the Veil is some 1,400 light years away, but many other nebulae and star clusters areidentifiablethroughout the cosmic scene. Of course, Deneb itself is also known to northern hemisphere skygazers for its place in twoasterisms -- marking the top of theNorthern Cross and a vertex of theSummer Triangle.

Explanation: What's that strange light down the road?Dust orbiting the Sun. At certain times of the year, a band of sun-reflecting dust from the inner Solar System appears prominently just after sunset -- or just before sunrise -- and is called zodiacal light. Although the origin of this dust is still being researched, a leading hypothesis holds that zodiacal dust originates mostly from faint Jupiter-family comets and slowly spirals into the Sun. Recent analysis of dust emitted by Comet 67P, visited by ESA's robotic Rosetta spacecraft, bolster this hypothesis. Pictured when climbing a road up to Teide National Park in the Canary Islands of Spain, a bright triangle of zodiacal light appeared in the distance soon after sunset. Captured on June 21, the scene includes bright Regulus, alpha star of Leo, standing above center toward the left. The Beehive Star Cluster (M44) can be spotted below center, closer to the horizon and also immersed in the zodiacal glow

Explanation: Why is the Cigar Galaxy billowing red smoke? M82, as thisstarburst galaxy is also known, was stirred up by arecent pass near largespiral galaxyM81.   This doesn't fully explain the source of the red-glowing outwardlyexpanding gas and dust, however.  Evidence indicates that this gas and dust is being driven out by the combined emergingparticle winds of many stars, together creating a galacticsuperwind.   The dust particles are thought to originate in M82's interstellar medium and are actually similar in size to particles in cigar smoke. The featured photographic mosaic highlights a specific color of red light strongly emitted by ionizedhydrogen gas, showing detailed filaments of this gas and dust.   The filaments extend for over 10,000light years. The 12-million light-year distantCigar Galaxy is the brightest galaxy in the sky in infrared light, and can be seen in visible light with a smalltelescopetowards the constellation of the Great Bear (Ursa Major).

Explanation: What could create such a large circular shadow on the Moon? The Earth. Last week's full Moon -- the Buck Moon -- was so full that it fell almost exactly in a line with the Sun and the Earth. When that happens the Earth casts its shadow onto the Moon. The circularity of the Earth's shadow on the Moon was commented on by Aristotle and so has been noticed since at least the 4th century BC.   What's new is humanity's ability to record this shadow with such high dynamic range (HDR). The featured HDR composite of last week's partial lunar eclipse combines 15 images and include an exposure as short as 1/400th of a second -- so as not to overexpose the brightest part -- and an exposure that lasted five seconds -- to bring up the dimmest part. This dimmest part -- inside Earth's umbra -- is not completely dark because some light is refracted through the Earth's atmosphere onto the Moon. A total lunar eclipse will occur next in 2021 May.

Great pictures....thank you Rocky.

Explanation: Why are there so many moonquakes?   Analyses of seismometers left on the moon by the Apollo moon landings reveals a surprising number of moonquakes occurring within 100 kilometers of the surface.   In fact, 62 moonquakes were detected in data recorded between 1972 and 1977.   Many of these moonquakes are not only strong enough to move furniture in a lunar apartment, but the stiff rock of the moon continues to vibrate for many minutes, significantly longer than the softer rock earthquakes on Earth.   The cause of the moonquakes remains unknown, but a leading hypothesis is the collapse of underground faults. Regardless of the source, future moon dwellings need to be built to withstand the frequent shakings.   Pictured here 50 years ago today, Apollo 11 astronaut Buzz Aldrin stands beside a recently deployed lunar seismometer, looking back toward the lunar landing module.

Explanation: Have you seena panorama from another world lately?Assembled from high-resolution scansof the original film frames, this one sweeps across the magnificent desolation of the Apollo 11 landing siteon the Moon's Sea of Tranquility. The images were taken byNeil Armstronglooking out his window of the Eagle Lunar Modulefifty years ago, shortly after the July 20, 1969 landing. The frame at the far left (AS11-37-5449) is the first picture taken by a person on another world. Toward the south, thruster nozzles can be seen in the foreground on the left, while at the right, the shadow of the Eagle is visible to the west. For scale, the large, shallow crater on the right has a diameter of about 12 meters. Frames taken from the Lunar Module windows about an hour and a half after landing, beforewalking on the lunar surface, were intended to initially document the landing site in case an early departure was necessary.

Explanation: On July 20, 1969 the Apollo 11 lunar module Eaglesafely touched down on the Moon. It landed near the southwestern corner of the Moon's Mare Tranquillitatis at alanding site dubbedTranquility Base.This panoramic view of Tranquility Base was constructed from the historic photos takenfrom the lunar surface. On the far left astronaut Neil Armstrong casts a long shadow with Sun is at his back and the Eagle resting about 60 meters away (AS11-40-5961). He stands near the rim of 30 meter-diameter Little West crater seen here to the right (AS11-40-5954). Also visible in the foreground is the top of the camera intended for taking stereo close-ups of the lunar surface.

Explanation: On July 16 the Moon celebrated the 50th anniversary of thelaunch of Apollo 11with a lunar eclipse visible from much of planet Earth. In this view part of the lunar disk is immersed in Earth's dark, reddenedumbral shadow. Near the maximum eclipse phase, it just touches down along a mountain ridge. The rugged Tyrolean nightscape was recorded after moonrise south of Innsbruck, Austria with a dramatically lit communication tower along the ridgeline. Of course eclipses rarely travel alone.This partial lunar eclipsewas at the Full Moon following July 2nd's New Moon and totaleclipse of the Sun.

Explanation: Have you ever experienced a really dark night sky? One common and amazing feature is the glowing band of our Milky Way galaxy stretching from horizon to horizon. If you live in or near a big city, though, you might not know this because city lights reflecting off the Earth's atmosphere could only allow you to see the Moon and a few stars. Today, however, being UNESCO's International Day of Light, the International Astronomical Union is asking people to Turn on the Night by trying to better understand, and in the future better reduce, light pollution. You can practice even now by going to the main APOD website at NASA and hovering your cursor over the <a href="https://apod.nasa.gov/apod/image/1905/TotnBefore_Dai_3000.jpg" Before image. The After picture that comes up is a panorama of four exposures taken with the same camera and from the same location, showing what happened recently in China when people in Kaihua County decided to turn down many of their lights. Visible in the Before picture are the stars Sirius (left of center) and Betelgeuse, while visible in the After picture are thousands of stars with the arching band of our Milky Way Galaxy. Humanity has lived for millennia under a dark night sky, and connecting to it has importance for both natural and cultural heritage

Explanation: On May 20, a nearly Full Moon and Jupiter shared this telephoto field of view. Captured when a passing cloud bank dimmed the moonlight, the single exposure reveals the familiar face of our fair planet's own large natural satellite, along with bright Jupiter (lower right) and some of itsGalilean moons. Lined up left to right the tiny pinpricks of light near Jupiter areGanymede,Europa, [Jupiter] andCallisto. (That's not just dust on your screen ...) Closer and brighter, our own natural satellite appears to loom large. But Ganymede, and Callisto are physically larger than Earth's Moon, while water world Europa is only slightly smaller. In fact, of the Solar System's sixlargest planetary satellites, Saturn's moon Titan is missing from the scene and a fourth Galilean moon, Io, is hidden by our ruling gas giant.

Explanation: Everybody saw the Moon. Nobody had ever been there. Humans across planet Earth watched in awe 50 years ago today as a powerful Saturn V rocket attempted to launch humans -- to the Moon. Some in space flight guessed that the machinery was so complex, that so many things had to go right for it to work, that Apollo 11 would end up being another useful dress rehearsal for a later successful Moon-landing mission. But to the Moon they went. The featured video starts by showing astronauts Aldrin, Armstrong, and Collins making their way to the waiting rocket. As the large and mighty Saturn V launched, crowds watched from Cape Canaveral in Florida, USA and on television around the world. The events that unfolded over the next few days, including a dramatic moon walk 50 years ago this Saturday, will forever be remembered as a milestone in human history and an unrivaled demonstration of human ingenuity. This week, many places around the world are planning celebrations of the 50th anniversary of the first humans landing on the Moon.

Explanation: That's no sunspot. It's the International Space Station (ISS) caught passing in front of the Sun.Sunspots, individually, have a dark central umbra, a lighter surrounding penumbra, and no solar panels. By contrast, the ISS is a complex and multi-spired mechanism, one of the largest and most sophisticated machines ever created by humanity.   Also, sunspots occur on the Sun, whereas the ISS orbits the Earth.   Transiting the Sun is not very unusual for the ISS, which orbits the Earth about every 90 minutes, but getting one's timing and equipment just right for a great image is rare. Strangely, besides that fake spot, in this recent two-image composite, the Sun  lacked any real sunspots.   The featured picture combines two images -- one capturing the space station transiting the Sun --  and another taken consecutively capturing details of the Sun's surface. Sunspots have been rare on the Sun since the dawn of the current Solar Minimum, a period of low solar activity. For reasons not yet fully understood, the number of sunspots occurring during both the previous and current solar minima have been unusually low.

Explanation: What's that in the sky? An aurora. A large coronal mass ejection occurred on our Sun five days before this 2012 image was taken, throwing a cloud of fast moving electrons, protons, and ions toward the Earth. Although most of this cloud passed above the Earth, some of it impacted our Earth's magnetosphere and resulted in spectacular auroras being seen at high northern latitudes.Featured here is a particularly photogenic auroral corona captured above Grotfjord, Norway. To some, this shimmering green glow of recombining atmospheric oxygen might appear as a large eagle, but feel free to share what it looks like to you.   Although the Sun is near Solar Minimum, streams of the solar wind continue to impact the Earth and create impressive aurorasvisible even last week.

Explanation: Get out yourred/blue glasses and check out this stereo view from lunar orbit. The 3Danaglyphwas created from two photographs (AS11-44-6633,AS11-44-6634) taken by astronaut Michael Collins during the 1969Apollo 11 mission. It features the lunar module ascent stage, dubbed The Eagle, rising to meet the command module in lunar orbit on July 21. Aboard the ascent stage are Neil Armstrong and Buzz Aldrin, the first towalk on the Moon. The smooth, dark area on the lunar surface is Mare Smythii located just below the equator on the extreme eastern edge of the Moon's near side. Poised beyond the lunar horizon isour fair planet Earth.

Explanation: Irregular galaxy NGC 55 is thought to be similar to the Large Magellanic Cloud (LMC). But whilethe LMC is about 180,000 light-years away and a well-known satellite of our own Milky Way Galaxy, NGC 55 is more like 6 million light-yearsdistant, a member of theSculptor Galaxy Group. Classified as anirregular galaxy, indeep exposures the LMC itself resembles a barred disk galaxy. Spanning about 50,000 light-years, NGC 55 is seen nearly edge-on though, presenting a flattened, narrow profile in contrast with our face-on view of the LMC. Just as large star forming regions createemission nebulaein the LMC, NGC 55 is alsoseen to beproducing new stars. This highly detailedgalaxy portrait highlights a bright core crossed with dust clouds, telltale pinkish star forming regions, and young blue star clusters in NGC 55.

Explanation: Close-up images of NGC 3242 show the cast off shroud of a dying, sun-like star fancifully known as The Ghost of Jupiter nebula. But this deep andwide telescopic view also finds the seldom seen outer halo of the beautiful planetary nebula at the upper left, toward Milky Way stars and background galaxies in the serpentine constellation Hydra. Intense and otherwise invisible ultraviolet radiation from the nebula's central white dwarf star powers its illusive glow in visible light.In fact, planets of NGC 3242's evolved white dwarf star may have contributed to the nebula's symmetric features and shape. Activity beginning in the star's red giant phase, long before it produced a planetary nebula, is likely the cause of the fainter more extensive halo. About a light-year across NGC 3242 is some 4,500light-years away. The tenuous clouds of glowing material at the right could well be interstellar gas,by chance close enough to the NGC 3242's white dwarf to be energized by its ultraviolet radiation.

Explanation: When did Orion become so flashy? This colorful rendition of part of the constellation of Orion comes from red light emitted by hydrogen and sulfur (SII), and blue-green light emitted by oxygen (OIII). Hues on the featured image were then digitally reassigned to be indicative of their elemental origins -- but also striking to the human eye. The breathtaking composite was painstakingly composed from hundreds of images which took nearly 200 hours to collect. Pictured, Barnard's Loop, across the image bottom, appears to cradle interstellar constructs including the intricate Orion Nebula seen just right of center.   The Flame Nebula can also be quickly located, but it takes a careful eye to identify the slight indentation of the dark Horsehead Nebula. As to Orion's flashiness -- a leading explanation for the origin of Barnard's Loop is a supernova blast that occurred about two million years ago.

Explanation: What do birds do during a total solar eclipse? Darkness descends more quickly in a total eclipse than during sunset, but returns just as quickly -- and perhaps unexpectedly  to the avians -- just a few minutes later. Stories about the unusual behavior of birds during eclipses have been told for centuries, but bird reactions were recorded and studied systematically by citizen scientists participating in an eBird project during the total solar eclipse that crossed the USA in 2017 August. Although some unusual behaviors were observed, many observers noted birds acting like it was dusk and either landing or flying low to the ground. Radar confirmed a significant decrease in high-flying birds and insects during and just after totality. Conversely, several sightings of normally nocturnal birds were reported. Pictured, a flock of birds in La Serena, Chile flew through the air together during the total solar eclipse that crossed South America last week. The photographer captured the scene in frames from an eclipse video. The next total solar eclipse in 2020 December will also cross South America, while in 2024 April a total solar eclipse will cross North America from Mexico through New England, USA.