juliensimon/nasa-apod huggingface dataset:
Ring of Fire over Monument Valley (2013-05-09)

As the New Moon continues this season's celestial shadow play, an annular solar eclipse track begins in western Australia at 22:30 UT on May 9 -- near sunrise on May 10 local time. Because the eclipse occurs within a few days of lunar apogee, the Moon's silhouette does not quite cover the Sun during mid-eclipse, momentarily creating a spectacular ring of fire. While a larger region witnesses a partial eclipse, the annular mid-eclipse phase is visible along a shadow track only about 200 kilometers wide but 13,000 kilometers long, extending across the central Pacific. For given locations along it, the ring of fire lasts from 4 to 6 minutes. Near the horizon, the appearance of the May 9/10 annular eclipse (online viewing) is suggested by this dramatic composite from May of 2012. The timelapse sequence depicts an annular eclipse in progress before sunset over Monument Valley in the southwestern United States.

Image credit: Tunç Tezel
Messier 77 (2013-05-10)

Face-on spiral galaxy M77 lies a mere 47 million light-years away toward the aquatic constellation Cetus. At that estimated distance, the gorgeous island universe is about 100 thousand light-years across. Also known as NGC 1068, its compact and very bright core is well studied by astronomers exploring the mysteries of supermassive black holes in active Seyfert galaxies. M77 is also seen at x-ray, ultraviolet, infrared, and radio wavelengths. But this sharp visible light image based on Hubble data follows its winding spiral arms traced by obscuring dust clouds and red-tinted star forming regions close in to the galaxy's luminous core.
Cape York Annular Eclipse (2013-05-11)

This week the shadow of the New Moon fell on planet Earth, crossing Queensland's Cape York in northern Australia ... for the second time in six months. On the morning of May 10, the Moon's apparent size was too small to completely cover the Sun though, revealing a "ring of fire" along the central path of the annular solar eclipse. Near mid-eclipse from Coen, Australia, a webcast team captured this telescopic snapshot of the annular phase. Taken with a hydrogen-alpha filter, the dramatic image finds the Moon's silhouette just within the solar disk, and the limb of the active Sun spiked with solar prominences. Still, after hosting back-to-back solar eclipses, northern Australia will miss the next and final solar eclipse of 2013. This November, a rare hybrid eclipse will track across the North Atlantic and equatorial Africa.

Image credit: MWV Observatory
Clouds, Birds, Moon, Venus (2013-05-12)

Sometimes the sky above can become quite a show. In early September of 2010, for example, the Moon and Venus converged, creating quite a sight by itself for sky enthusiasts around the globe. � From some locations, though, the sky was even more picturesque. In the above image taken in Spain, a crescent Moon and the planet Venus, on the far right, were captured during sunset posing against a deep blue sky. � In the foreground, dark storm clouds loom across the image bottom, while a white anvil cloud shape appears above. Black specks dot the frame, caused by a flock of birds taking flight. Very soon after this picture was taken, however, the birds passed by, the storm ended, and Venus and the Moon set. � Bright Venus again becomes visible just after sunset this 2013 May and will appear near Jupiter toward the end of the month.

Image credit: Isaac Guti�rrez Pascual
(Spain)
Partial Solar Eclipse with Airplane (2013-05-13)

It was just eight minutes after sunrise, last week, and already there were four things in front of the Sun. The largest and most notable was Earth's Moon, obscuring a big chunk of the Sun's lower limb as it moved across the solar disk, as viewed from Fremantle, Australia. This was expected as the image was taken during a partial solar eclipse -- an eclipse that left sunlight streaming around all sides of the Moon from some locations. Next, a band of clouds divided the Sun horizontally while showing interesting internal structure vertically.  The third intervening body might be considered to be the Earth's atmosphere, as it dimmed the Sun from its higher altitude brightness while density fluctuations caused the Sun's edges to appear to shimmer. Although closest to the photographer, the least expected solar occulter was an airplane. Quite possibly, passengers on both sides of that airplane were contemplating the unusual view only visible out the eastern-facing windows.   Cosmonova: APOD editor to speak in Sweden on May 28

Image credit: Phillip Calais
Galaxy Collisions: Simulation vs Observations (2013-05-14)

What happens when two galaxies collide? Although it may take over a billion years, such titanic clashes are quite common. Since galaxies are mostly empty space, no internal stars are likely to themselves collide. Rather the gravitation of each galaxy will distort or destroy the other galaxy, and the galaxies may eventually merge to form a single larger galaxy. Expansive gas and dust clouds collide and trigger waves of star formation that complete even during the interaction process. Pictured above is a computer simulation of two large spiral galaxies colliding, interspersed with real still images taken by the Hubble Space Telescope. Our own Milky Way Galaxy has absorbed several smaller galaxies during its existence and is even projected to merge with the larger neighboring Andromeda galaxy in a few billion years.   Follow APOD on: Facebook (Daily) (Sky) (Spanish) or Google Plus (Daily) (River)
Kepler's Supernova Remnant in X-Rays (2013-05-15)

What caused this mess? Some type of star exploded to create the unusually shaped nebula known as Kepler's supernova remnant, but which type? Light from the stellar explosion that created this energized cosmic cloud was first seen on planet Earth in October 1604, a mere four hundred years ago. The supernova produced a bright new star in early 17th century skies within the constellation Ophiuchus. It was studied by astronomer Johannes Kepler and his contemporaries, without the benefit of a telescope, as they searched for an explanation of the heavenly apparition.  Armed with a modern understanding of stellar evolution, early 21st century astronomers continue to explore the expanding debris cloud, but can now use orbiting space telescopes to survey Kepler's supernova remnant (SNR) across the spectrum.  Recent X-ray data and images of Kepler's supernova remnant taken by the orbiting Chandra X-ray Observatory has shown relative elemental abundances typical of a Type Ia supernova, and further indicated that the progenitor was a white dwarf star that exploded when it accreted too much material from a companion Red Giant star and went over Chandrasekhar's limit. About 13,000 light years away, Kepler's supernova represents the most recent stellar explosion seen to occur within our Milky Way galaxy.   Cosmonova: APOD editor to speak in Sweden on May 28
Four X-class Flares (2013-05-16)

Swinging around the Sun's eastern limb on Monday, a group of sunspots labeled active region AR1748 has produced the first four X-class solar flares of 2013 in less than 48 hours. In time sequence clockwise from the top left, flashes from the four were captured in extreme ultraviolet images from the Solar Dynamics Observatory. Ranked according to their peak brightness in X-rays, X-class flares are the most powerful class and are frequently accompanied by coronal mass ejections (CMEs), massive clouds of high energy plasma launched into space. But CMEs from the first three flares were not Earth-directed, while one associated with the fourth flare may deliver a glancing blow to the Earth's magnetic field on May 18. Also causing temporary radio blackouts, AR1748 is likely not finished. Still forecast to have a significant chance of producing strong flares, the active region is rotating into more direct view across the Sun's nearside.
The Waterfall and the World at Night (2013-05-17)

Above this boreal landscape, the arc of the Milky Way and shimmering aurorae flow through the night. Like an echo, below them lies Iceland's spectacular Godafoss, the Waterfall of the Gods. Shining just below the Milky Way, bright Jupiter is included in the panoramic nightscape recorded on March 9. Faint and diffuse, the Andromeda Galaxy (M31) appears immersed in the auroral glow. The digital stitch of four frames is a first place winner in the 2013 International Earth and Sky Photo Contest on Dark Skies Importance organized by The World at Night. An evocative record of the beauty of planet Earth's night sky, all the contest's winning entries are featured in this video.

Image credit: Stéphane
Vetter
Comet PanSTARRS Anti-Tail (2013-05-18)

Once the famous sunset comet, PanSTARRS (C/2011 L4) is now visible all night from much of the northern hemisphere, bound for the outer solar system as it climbs high above the ecliptic plane. Dimmer and fading, the comet's broad dust tail is still growing, though. This widefield telescopic image was taken against the starry background of the constellation Cepheus on May 15. It shows the comet has developed an extensive anti-tail, dust trailing along the comet's orbit (to the left of the coma), stretching more than 3 degrees across the frame. Since the comet is just over 1.6 astronomical units from planet Earth, that corresponds to a distance of over 12 million kilometers.  In late May Comet PanSTARRS will pass within a few degrees of the north celestial pole.

Image credit: Marco Fulle
Earth's Richat Structure (2013-05-19)

What on Earth is that?  The Richat Structure in the Sahara Desert of Mauritania is easily visible from space because it is nearly 50 kilometers across.  Once thought to be an impact crater, the Richat Structure's flat middle and lack of shock-altered rock indicates otherwise.  The possibility that the Richat Structure was formed by a volcanic eruption also seems improbable because of the lack of a dome of igneous or volcanic rock.  Rather, the layered sedimentary rock of the Richat structure is now thought by many to have been caused by uplifted rock sculpted by erosion.  The above image was captured by the ASTER instruments onboard the orbiting orbiting Terra satellite.  Why the Richat Structure is nearly circular remains a mystery.
Blue Sun Bursting (2013-05-20)

Our Sun is not a giant blueberry. Our Sun can be made to appear similar to the diminutive fruit, however, by imaging it in a specific color of extreme violet light called CaK that is emitted by the very slight abundance of ionized Calcium in the Sun's atmosphere, and then false color-inverting the image. This solar depiction is actually scientifically illuminating as a level of the Sun's chromosphere appears quite prominent, showing a crackly textured surface, cool sunspots appearing distinctly bright, and surrounding hot active regions appearing distinctly dark.  The Sun is currently near the maximum activity level in its 11 year cycle, and has emitted powerful flares over the past week. During times of high activity, streams of energetic particles from Sun may impact the Earth's magnetosphere and set off spectacular auroras.

Image credit: Alan Friedman
The Red Rectangle Nebula from Hubble (2013-05-21)

How was the unusual Red Rectangle nebula created? At the nebula's center is an aging binary star system that surely powers the nebula but does not, as yet, explain its colors. The unusual shape of the Red Rectangle is likely due to a thick dust torus which pinches the otherwise spherical outflow into tip-touching cone shapes. Because we view the torus edge-on, the boundary edges of the cone shapes seem to form an X. The distinct rungs suggest the outflow occurs in fits and starts. The unusual colors of the nebula are less well understood, however, and speculation holds that they are partly provided by hydrocarbon molecules that may actually be building blocks for organic life. The Red Rectangle nebula lies about 2,300 light years away towards the constellation of the Unicorn (Monoceros). The nebula is shown above in great detail as recently reprocessed image from Hubble Space Telescope. In a few million years, as one of the central stars becomes further depleted of nuclear fuel, the Red Rectangle nebula will likely bloom into a planetary nebula.   Cosmonova: APOD editor to speak in Sweden on May 28
Red Sprite Lightning with Aurora (2013-05-22)

What's that in the sky? It is a rarely seen form of lightning confirmed only about 25 years ago: a red sprite. Recent research has shown that following a powerful positive cloud-to-ground lightning strike, red sprites may start as 100-meter balls of ionized air that shoot down from about 80-km high at 10 percent the speed of light and are quickly followed by a group of upward streaking ionized balls. The above image, taken a few days ago above central South Dakota, USA, captured a bright red sprite, and is a candidate for the first color image ever recorded of a sprite and aurora together. Distant storm clouds cross the bottom of the image, while streaks of colorful aurora are visible in the background. Red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side.

Image credit: Walter Lyons 
(FMA Research), 
WeatherVideoHD.TV
Messier 109 (2013-05-23)

Beautiful barred spiral galaxy M109, 109th entry in Charles Messier's famous catalog of bright Nebulae and Star Clusters, is found just below the Big Dipper's bowl in the northern constellation Ursa Major. In telescopic views, its striking central bar gives the galaxy the appearance of the Greek letter "theta", θ, a common mathematical symbol representing an angle. Of course M109 spans a very small angle in planet Earth's sky, about 7 arcminutes or 0.12 degrees. But that small angle corresponds to an enormous 120,000 light-year diameter at the galaxy's estimated 60 million light-year distance. The brightest member of the now recognized Ursa Major galaxy cluster, M109 (aka NGC 3992) is joined by three spiky foreground stars strung out across this frame. The three small, fuzzy bluish galaxies also on the scene, identified left to right as UGC 6969, UGC 6940 and UGC 6923, are possibly satellite galaxies of the larger M109.

Image credit: Bob Franke
Caterpillar Moon (2013-05-24)

A close series of consecutive exposures are combined in this intriguing composite of the Full Moon slowly crawling, across the sky. Beginning on the upper right at 19:42 UT and ending at 22:14 UT on April 25, the sequence follows the Moon from Germany as it passes through Earth's shadow in a partial lunar eclipse. Near the top, the Moon just grazes the southern edge of Earth's dark central shadow, or umbra. But the decreased brightness in the darker part of the outer shadow region, the penumbra, is also apparent on the lunar disk. In fact, the relative size and shape of the Earth's shadow regions and the Moon are easier to see along the segments of this lunar caterpillar. Nearly impossible to follow with the eye though, a penumbral lunar eclipse, the Full Moon passing only through the pale outer penumbral shadow, will begin on May 25.

Image credit: Joerg Kopplin
Lunar Corona over Cochem Castle (2013-05-25)

This bat-like apparition does not shine on clouds passing over Gotham city. Instead, the cloud bank in silhouette against a colorful lunar corona was spotted on the evening of May 18 over Cochem, Germany from the banks of the river Moselle. The lunar corona is formed as bright moonlight is diffracted by water droplets in thin clouds drifting in front of the lunar disk. Below it lies the region's historic Cochem Castle dating from the 11th century, and not Wayne Manor. Still, regardless of your location on planet Earth it is well worth scanning the evening skies this weekend, as a Full Moon rises and bright planets gather in the west.

Image credit: Babak Tafreshi
PanSTARRS Anti-Tail Grows (2013-05-26)

As planet Earth approached the plane of the Comet PanSTARRS (C/2011 L4) orbit on May 23rd, comet watchers were treated to this view of its magnificent anti-tail. The long, narrow anti-tail stretches to the right across this frame for nearly 4 degrees or about 8 times the angular size of the full Moon. Dust forming the anti-tail trails along the comet's orbit as it leaves the inner solar system behind. An almost edge-on perspective from near the outbound comet's orbital plane enhances the view of the anti-tail and makes it seem to point in the sunward direction, only apparently contrary to the behavior of comet dust tails pushed outward by the pressure of sunlight. Sweeping far north in planet Earth's skies, the comet is up all night for most of the northern hemisphere, but now bright moonlight interferes with its visibility. PanSTARRS anti-tail is one of the longest since the appearance of Comet Arend-Roland in 1957.   Cosmonova: APOD editor to speak in Stockholm on Tuesday at 6 pm

Image credit: Joseph Brimacombe
Bird Sun Dog (2013-05-27)

Have you ever seen a little rainbow off to the side of the Sun? Rare but rewarding to see, such spectacles are known as sundogs, mock suns or parhelia.  Sundogs are just sunlight refracting through hexagonal falling ice crystals in the Earth's atmosphere. When thin ice crystals flitter down nearly horizontally, they best refract sunlight sideways and create sundogs.  Alternatively, randomly oriented ice crystals may create a complete circular sun halo. Sundogs occur 22 degrees to each side of a setting or rising Sun, although sometimes nearby clouds can block one or both. The above image was taken through a polarizing filter during October 2012 in M�rida, Spain.

Image credit: Juan Manuel P�rez Rayego
The Large Cloud of Magellan (2013-05-28)

The 16th century Portuguese navigator Ferdinand Magellan and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two fuzzy cloud-like objects easily visible to southern hemisphere skygazers are known as the Clouds of Magellan, now understood to be satellite galaxies of our much larger, spiral Milky Way galaxy. About 160,000 light-years distant in the constellation Dorado, the Large Magellanic Cloud (LMC) is seen here in a remarkably deep, colorful, and annotated composite image. Spanning about 15,000 light-years or so, it is the most massive of the Milky Way's satellite galaxies and is the home of the closest supernova in modern times, SN 1987A.  The prominent patch just left of center is 30 Doradus, also known as the magnificent Tarantula Nebula, is a giant star-forming region about 1,000 light-years across.

Image credit: L. Comolli, 
L. Fontana, G. Ghioldi & E. Sordini
NGC 6960: The Witch's Broom Nebula (2013-05-29)

Ten thousand years ago, before the dawn of recorded human history, a new light would have suddenly have appeared in the night sky and faded after a few weeks.  Today we know this light was from a supernova, or exploding star, and record the expanding debris cloud as the Veil Nebula, a supernova remnant.  This sharp telescopic view is centered on a western segment of the Veil Nebula cataloged as NGC 6960 but less formally known as the Witch's Broom Nebula.  Blasted out in the cataclysmic explosion, the interstellar shock wave plows through space sweeping up and exciting interstellar material. Imaged with narrow band filters, the glowing filaments are like long ripples in a sheet seen almost edge on, remarkably well separated into atomic hydrogen (red) and oxygen (blue-green) gas. The complete supernova remnant lies about 1400 light-years away towards the constellation Cygnus. This Witch's Broom actually spans about 35 light-years. The bright star in the frame is 52 Cygni, visible with the unaided eye from a dark location but unrelated to the ancient supernova remnant.

Image credit: Martin Pugh
One-Armed Spiral Galaxy NGC 4725 (2013-05-30)

While most spiral galaxies, including our own Milky Way, have two or more spiral arms, NGC 4725 has only one. In this sharp color composite image, the solo spira mirabilis seems to wind from a prominent ring of bluish, newborn star clusters and red tinted star forming regions. The odd galaxy also sports obscuring dust lanes a yellowish central bar structure composed of an older population of stars. NGC 4725 is over 100 thousand light-years across and lies 41 million light-years away in the well-groomed constellation Coma Berenices. Computer simulations of the formation of single spiral arms suggest that they can be either leading or trailing arms with respect to a galaxy's overall rotation. Also included in the frame, a more traditional looking spiral appears as a smaller background galaxy.
The Eagle and The Swan (2013-05-31)

The Eagle Nebula and the Swan Nebula span this broad starscape, a telescopic view of the Sagittarius spiral arm toward the center of our Milky Way galaxy. The Eagle, also known as M16, is left, above center, and the Swan, or M17 at the lower right. The deep, wide-field image shows the cosmic clouds as brighter regions of active star-formation. They lie along the spiral arm suffused with reddish emission charactistic of atomic hydrogen gas, and dusty dark nebulae. In fact, the center of both nebulae are locations of well-known close-up images of star formation from the Hubble Space Telescope. M17, also called the Omega Nebula, is about 5500 light-years away, while M16 is some 6500 light-years distant. In the frame that covers 3 degrees across the sky, the extended wings of the Eagle Nebula are spread over 120 light-years.

Image credit: Dieter Willasch
The Milky Trail (2013-06-01)

Have you ever hiked the Queen's Garden trail in Bryce Canyon, Utah, USA, planet Earth? Walking along that path in this dark night skyscape, you can almost imagine your journey continues along the pale, luminous Milky Way. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so bright or quite so colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. Four hundred years ago, Galileo turned his telescope on the Milky Way and announced it to be "... a congeries of innumerable stars ..."

Image credit: Wally Pacholka
A Roll Cloud Over Uruguay (2013-06-02)

What kind of cloud is this?  A roll cloud.  These rare long clouds may form near advancing cold fronts.   In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud.  When this happens uniformly along an extended front, a roll cloud may form.  Roll clouds may actually have air circulating along the long horizontal axis of the cloud.  A roll cloud is not thought to be able to morph into a tornado.  Unlike a similar shelf cloud, a roll cloud, a type of Arcus cloud, is completely detached from their parent  cumulonimbus cloud.  Pictured above, a roll cloud extends far into the distance in 2009 January above Las Olas Beach in Maldonado, Uruguay.
Curiosity: Wheels on Mars (2013-06-03)

Could life ever have existed on Mars? To help find out, humanity landed the Curiosity rover on Mars last August. To make sure the car-sized explorer survived the interplanetary trip and dramatic landing intact, the above image and others was taken peering at, under, and around Curiosity. Pictured above in this unusual vista are three of Curiosity's six wheels, each measuring about half a meter across.  In recent months, Curiosity has been exploring the surroundings of an area dubbed Yellowknife Bay. Analyses of data taken by Curiosity's cameras and onboard laboratories has provided strong new evidence that Mars could once have supported life. In the distance is part of the slope to the central peak inside Gale Crater that Curiosity is scheduled to attempt to climb -- Mt. Sharp.