juliensimon/nasa-apod huggingface dataset:
Conjunction Over Reunion Island (2012-03-07)

You don't have to be on Reunion Island to see this week's planetary conjunction. Only if you want to see this picturesque seascape as well.  To see the conjunction from just about anywhere in the world, look to the west after sunset. The first planet you may notice is Venus, the brightest object in the western sky. Above Venus, the second brightest object is Jupiter. The hardest planet to spot is Mercury, which is visible only briefly after sunset as a faint dot just above the horizon.  Picturesque rocks leading out from Reunion Island to the Indian Ocean populate the foreground of the above picture.  Taken last week, the distant planets Venus and Jupiter were joined by a bright crescent Moon, which has now moved away.   Students (of all ages): See free astronomy lectures online

Image credit: Luc Perrot
The Seagull Nebula (2012-03-08)

A broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker - The Seagull Nebula. This portrait of the cosmic bird covers a 1.6 degree wide swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major. Of course, the region includes objects with other catalog designations: notably NGC 2327, a compact, dusty emission region with an embedded massive star that forms the bird's head (aka the Parrot Nebula, above center). IC 2177 forms the sweeping arc of the seagull's wings. Dominated by the reddish glow of atomic hydrogen, the complex of gas and dust clouds with bright young stars spans over 100 light-years at an estimated 3,800 light-year distance.

Image credit: Harel Boren
NGC 1579: Trifid of the North (2012-03-09)

Colorful NGC 1579 resembles the better known Trifid Nebula, but lies much farther north in planet Earth's sky, in the heroic constellation Perseus. About 2,100 light-years away and 3 light-years across, NGC 1579 is, like the Trifid, a study in contrasting blue and red colors, with dark dust lanes prominent in the nebula's central regions. In both, dust reflects starlight to produce beautiful blue reflection nebulae. But unlike the Trifid, in NGC 1579 the reddish glow is not emission from clouds of glowing hydrogen gas excited by ultraviolet light from a nearby hot star. Instead, the dust in NGC 1579 drastically diminishes, reddens, and scatters the light from an embedded, extremely young, massive star, itself a strong emitter of the characteristic red hydrogen alpha light.

Image credit: Adam Block
Lick Observatory Moonrise (2012-03-10)

As viewed from a well chosen location at sunset, the gorgeous Full Moon rose behind Mount Hamilton, east of San Jose, California on March 7. The lunar disk frames historic Lick Observatory perched on the mountain's 4,200 foot summit. Both observatory and Moon echo the warm color of sunlight (moonlight is reflected sunlight) filtered by a long path through the atmosphere. Substantial atmospheric refraction contributes the Moon's ragged, green rim. Of course, the March Full Moon is also known as the Full Worm Moon. In the telescopic photo, Lick's 40 inch Nickel Telescope dome is on the left. The large dome on the right houses Lick's Great 36 inch Refractor.

Image credit: Rick
Baldridge
The Sombrero Galaxy in Infrared (2012-03-11)

This floating ring is the size of a galaxy.  In fact, it is part of the photogenic Sombrero Galaxy, one of the largest galaxies in the nearby Virgo Cluster of Galaxies.  The dark band of dust that obscures the mid-section of the Sombrero Galaxy in optical light actually glows brightly in infrared light.  The above image, digitally sharpened, shows the infrared glow, recently recorded by the orbiting Spitzer Space Telescope, superposed in false-color on an existing image taken by NASA's Hubble Space Telescope in optical light. The Sombrero Galaxy, also known as M104, spans about 50,000 light years across and lies 28 million light years away.  M104 can be seen with a small telescope in the direction of the constellation Virgo.
The Scale of the Universe - Interactive (2012-03-12)

What does the universe look like on small scales? On large scales?  Humanity is discovering that the universe is a very different place on every proportion that has been explored. For example, so far as we know, every tiny proton is exactly the same, but every huge galaxy is different. On more familiar scales, a small glass table top to a human is a vast plane of strange smoothness to a dust mite -- possibly speckled with cell boulders. Not all scale lengths are well explored -- what happens to the smallest mist droplets you sneeze, for example, is a topic of active research -- and possibly useful to know to help stop the spread of disease. The above interactive flash animation, a modern version of the classic video Powers of Ten, is a new window to many of the known scales of our universe.  By moving the scroll bar across the bottom, you can explore a diversity of sizes, while clicking on different items will bring up descriptive information.

Image credit: Cary & Michael Huang
The M81 Galaxy Group Through the Integrated Flux Nebula (2012-03-13)

Large galaxies and faint nebulae highlight this deep image of the M81 Group of galaxies.  First and foremost in the wide-angle 12-hour exposure is the grand design spiral galaxy M81, the largest galaxy visible in the image.  M81 is gravitationally interacting with M82 just below it, a big galaxy with an unusual halo of filamentary red-glowing gas.  Around the image many other galaxies from the M81 Group of galaxies can be seen, as well as a lucky satellite glint streaking across the image left. Together with other galaxy congregates including our Local Group of galaxies and the Virgo Cluster of galaxies, the M81 Group is part of the expansive Virgo Supercluster of Galaxies.  This whole galaxy menagerie is seen through the faint glow of an Integrated Flux Nebula, a little studied complex of diffuse gas and dust clouds in our Milky Way Galaxy.

Image credit: Nicol�s Villegas
Angry Sun Erupting (2012-03-14)

It's one of the baddest sunspot regions in years. Active Region 1429 may not only look, to some, like an angry bird -- it has thrown off some of the most powerful flares and coronal mass ejections of the current solar cycle. The extended plumes from these explosions have even rained particles on the Earth's magnetosphere that have resulted in colorful auroras. Pictured above, AR 1429 was captured in great detail in the Sun's chromosphere three days ago by isolating a color of light emitted primarily by hydrogen. The resulting image is shown in inverted false color with dark regions being the brightest and hottest. Giant magnetically-channeled tubes of hot gas, some longer than the Earth, are known as spicules and can be seen carpeting the chromosphere. The light tendril just above AR 1429 is a cool filament hovering just over the active sunspot region. As solar maximum nears in the next few years, the increasingly wound and twisted magnetic field of the Sun may create even more furious active regions that chirp even more energetic puffs of solar plasma into our Solar System.   Gallery: See images of the latest planetary conjunction

Image credit: Alan Friedman
(Averted Imagination)
Solar Flare in the Gamma-ray Sky (2012-03-15)

What shines in the gamma-ray sky? The answer is usually the most exotic and energetic of astrophysical environments, like active galaxies powered by supermassive black holes, or incredibly dense pulsars, the spinning remnants of exploded stars. But on March 7, a powerful solar flare, one of a series of recent solar eruptions, dominated the gamma-ray sky at energies up to 1 billion times the energy of visible light photons. These two panels illustrate the intensity of that solar flare in all-sky images recorded by the orbiting Fermi Gamma-ray Space Telescope. On March 6, as on most days, the Sun was almost invisible to Fermi's imaging detectors. But during the energetic X-class flare, it became nearly 100 times brighter than even the Vela Pulsar at gamma-ray energies. Now faded in Fermi's view, the Sun will likely shine again in the gamma-ray sky as the solar activity cycle approaches its maximum.
Bright Planets at McMath-Pierce Solar Telescope (2012-03-16)

Bright planets Venus and Jupiter are framed by the National Solar Observatory's McMath-Pierce Solar Telescope in this very astronomical scene. The photo was taken at Kitt Peak National Observatory on March 9. A heliostat sits atop the 100 foot high solar telescope tower to focus the Sun's rays down a long diagonal shaft that reaches underground to the telescope's primary mirror. Of course, after sunset shadows were cast and the structure illuminated by light from the nearly full rising Moon. Opened to begin the night's work, the dome housing Kitt Peak's 2.1 meter reflector is included in the frame, while the Pleiades star cluster shines above the heliostat tower. The angular McMath-Pierce was commissioned 50 years ago to study the Sun, but has also made many observations of these two bright planets. On this night it was conducting observations of sodium atoms in the tenuous lunar atmosphere.
NGC 2683: Edge-On Spiral Galaxy (2012-03-17)

This elegant island universe is cataloged as NGC 2683. It lies a mere 16 million light-years distant toward the northern constellation Lynx. A spiral galaxy comparable to our own Milky Way, NGC 2683 is seen nearly edge-on in the cosmic vista. Blended light from a large population of old, yellowish stars forms the remarkably bright galactic core. Their starlight silhouettes the dust lanes along winding spiral arms, dotted with NGC 2683's young blue star clusters. The sharp image was recorded through the lens of a refracting telescope that shows brighter foreground Milky Way stars as colorful and round, lacking diffraction spikes characteristic of images from reflecting telescopes with internal supports. The many more distant galaxies scattered through the background appear as fuzzy, extended sources.

Image credit: Dietmar Hager
Jupiter and Venus from Earth (2012-03-18)

It was visible around the world. The sunset conjunction of Jupiter and Venus was visible last week almost no matter where you lived on Earth.  Anyone on the planet with a clear western horizon at sunset could see them. This week the two are still notable, even though Jupiter has sunk below the brighter Venus. And if you look higher in the sky you can see Mars as well. Pictured above, a creative photographer traveled away from the town lights of Szubin, Poland to image a near closest approach of the two planets almost a week ago. The bright planets were separated only by three degrees and his daughter striking a humorous pose. A faint red sunset still glowed in the background. Although this conjunction is drawing to a close, another conjunction between Venus and Jupiter will occur next May.    Gallery: See more images of this planetary conjunction from around the world
Sunspot Group 1429 and the Distant Sun (2012-03-19)

What's that on the Sun? Over the past two weeks, one of the most energetic sunspot regions of recent years crossed the face of the Sun. Active Region 1429, visible above as the group of dark spots on the Sun's upper right, blasted out several solar flares and coronal mass ejections since coming around the edge of the Sun almost a month ago. Fast moving particles from these solar explosions have impacted the Earth and been responsible for many colorful auroras seen over the past two weeks. The picturesque foreground features trees and birds near Merida, Spain, where the above image was taken about a week ago.  Although AR 1429 has continued to rotate to the right and gone around the limb of the Sun -- as seen from the Earth -- monitoring of the region will be continued by one of the STEREO satellites, however, which is orbiting the Sun well ahead of the Earth.

Image credit: Juan Manuel P�rez Rayego
Evolution of the Moon (2012-03-20)

What is the history of the Moon? The Moon was likely created from debris expelled when a Mars-sized object violently impacted the Earth about 4.5 billion years ago. Just after gravitationally condensing, as imagined above, the glowing-hot surface of the Moon cooled and cracked. Rocks large and small continued to impact the surface, including a particularly large impact that created Aitken Basin about 4.3 billion years ago. A Heavy Bombardment period then continued for hundreds of millions of years, creating large basins all over the lunar surface. Over the next few billion years lava flowed into Earth-side basins, eventually cooling into the dark maria we see today.  As always, relentless impacts continued, forming the craters we see today, slowly diminishing over the past billion years. Today the cooled Moon we know and love is as dark as coal and always keeps the same face toward Earth. Exactly how the Moon formed initially, and why lunar maria are only on the Earth side, remain active topics of research.   Vernal Equinox: This day and night are equal over all planet Earth
Aurora Over Iceland (2012-03-21)

If you see a sky like this -- photograph it. Three nights ago in Iceland, an  adventurous photographer (pictured) chanced across a sky full of aurora and did just that. Afterwards, by stitching together five smaller photographs, the entire aurora-lit sky was recreated in this 180-degree panorama taken from Vatnaj�kull glacier. Auroras are sparked by energetic particles from the Sun impacting the magnetic environment around the Earth.  Resultant energetic particles such as electrons and protons rain down near the Earth's poles and impact the air.  The impacted air molecules obtain excited electrons, and when electrons in oxygen molecules fall back to their ground state, they emit green light.  Auroras are known to have many shapes and colors.   News Flash -- Supernova in M95: See recent images

Image credit: Daniel Lopez
(El Cielo de Canarias)
M95 with Supernova (2012-03-22)

Barred spiral galaxy M95 is about 75,000 light-years across, comparable in size to our own Milky Way and one of the larger galaxies of the Leo I galaxy group. In fact, it is part of a not quite so famous trio of Leo galaxies with neighbors M96 and M105, about 38 million light-years distant. In this sharp and colorful cosmic portrait, a bright, compact ring of star formation surrounds the galaxy's core. Surrounding the prominent yellowish bar are tightly wound spiral arms traced by dust lanes, young blue star clusters, and telltale pinkish star forming regions. As a bonus, follow along the spiral arm unwinding down and to the right and you'll soon get to M95's latest supernova SN 2012aw, discovered on March 16 and now identified as the explosion of a massive star. A good target for small telescopes, the supernova stands out in this video feature (vimeo) comparing the recent image with a deep image of M95 without supernova taken in 2009.

Image credit: Adam Block
Messier 9 Close-up (2012-03-23)

Renown 18th century astronomer Charles Messier described this 9th entry in his famous astronomical catalog as "Nebula, without star, in the right leg of Ophiuchus ...". But Messier 9 (M9) does have stars, known to modern astronomers as a globular cluster of over 300,000 stars within a diameter of about 90 light-years. It lies some 25,000 light-years distant, near the central bulge of our Milky Way galaxy. This Hubble Space Telescope close-up resolves the dense swarm of stars across the cluster's central 25 light-years. At least twice the age of the Sun and deficient in heavy elements, the cluster stars have colors corresponding to their temperatures, redder stars are cooler, bluer stars are hotter. Many of the cluster's cool red giant stars show a yellowish tint in the sharp Hubble view.
The New Moon in the Old Moon's Arms (2012-03-24)

Also known as the Moon's ashen glow, Earthshine is Earthlight illuminating the Moon's night side. Taken on Nowruz, the March 20 equinox, from Esfahan, Iran, planet Earth, this telescopic image captures strong Earthshine from an old Moon. The darker earthlit disk is in the arms of a bright sunlit crescent. But the view from the Moon would have been enchanting too. When the Moon appears in Earth's sky as a slender crescent, a dazzlingly bright, nearly full Earth would be seen from the lunar surface. The Earth's brightness due to reflected sunlight is known to be strongly influenced by cloud cover. Still, a description of Earthshine, in terms of sunlight reflected by Earth's oceans in turn illuminating the Moon's dark surface, was written 500 years ago by Leonardo da Vinci.

Image credit: M. Taha Ghouchkanlu
Barred Spiral Galaxy NGC 1300 (2012-03-25)

Big, beautiful, barred spiral galaxy NGC 1300 lies some 70 million light-years away on the banks of the constellation Eridanus. This Hubble Space Telescope composite view of the gorgeous island universe is one of the largest Hubble images ever made of a complete galaxy. NGC 1300 spans over 100,000 light-years and the Hubble image reveals striking details of the galaxy's dominant central bar and majestic spiral arms. In fact, on close inspection the nucleus of this classic barred spiral itself shows a remarkable region of spiral structure about 3,000 light-years across. Unlike other spiral galaxies, including our own Milky Way, NGC 1300 is not presently known to have a massive central black hole.
M82: Galaxy with a Supergalactic Wind (2012-03-26)

What's lighting up the Cigar Galaxy?  M82, as this irregular galaxy is also known, was stirred up by a recent pass near large spiral galaxy M81.  This doesn't fully explain the source of the red-glowing outwardly expanding gas, however.  Recent evidence indicates that this gas is being driven out by the combined emerging particle winds of many stars, together creating a galactic superwind..  The above photographic mosaic highlights a specific color of red light strongly emitted by ionized hydrogen gas, showing detailed filaments of this gas.  The filaments extend for over 10,000 light years. The 12-million light-year distant Cigar Galaxy is the brightest galaxy in the sky in infrared light, and can be seen in visible light with a small telescope towards the constellation of the Great Bear (Ursa Major).
Unusual Hollows Discovered on Planet Mercury (2012-03-27)

What are those unusual features on planet Mercury? The slightly bluish tinge of features dubbed hollows has been exaggerated on the above image by the robotic MESSENGER spacecraft currently orbiting Mercury. The rounded depressions appear different than impact craters and nothing like them has been noted on Earth's Moon or anywhere else in the Solar System. The above image is a section of the floor of Raditladi impact basin about 40 kilometers wide that includes the mountains of the central peak.  One progenitor hypothesis is that the hollows formed from the sublimation of material exposed and heated during the violent impact that created the Raditladi basin. NASA's MESSENGER is the first spacecraft ever to orbit Mercury, and is currently scheduled to explore the Solar System's innermost planet into 2013.
Earthshine and Venus Over Sierra de Guadarrama (2012-03-28)

What just above that ridge? The Moon. Specifically, the Earth's Moon was caught just above the horizon in a young crescent phase. The familiar Moon might look a bit odd as the exposure shows significant Earthshine -- the illumination of the part of the Moon hidden from direct sunlight by the sun-reflecting Earth. Also captured in the image is the bright planet Venus on the right.  Venus and Jupiter passed only three degrees from each other last week during a photogenic planetary conjunction. The above image was taken two days ago near Madrid, Spain. The foreground horizon silhouette includes some of the Seven Peaks of the Sierra de Guadarrama mountain range. Just a few minutes after this picture was taken, the Moon set.  Conjunction Gallery: See images of the Moon, Venus, and Jupiter together over the past month.
Rocket Trails in the Milky Way (2012-03-29)

On March 27, five sounding rockets leapt into early morning skies from NASA's Wallops Flight Facility in Virginia. Part of the Anomalous Transport Rocket EXperiment (ATREX), begining at 4:58 am EDT the rockets launched consecutively at 80 second intervals. Releasing a chemical tracer they created luminous white clouds within Earth's ionosphere at altitudes above 60 to 65 miles, swept along by the poorly understood high-altitude jet stream. (Not the same jet stream that airliners fly through at altitudes of 5 to 6 miles.) Seen along the mid-atlantic region of the United States, the clouds drifted through starry skies, captured in this clear photograph from East Point, New Jersey.  Looking south toward the launch site, the tantalizing celestial background includes the stars of Sagittarius, Scorpius, and the more permanent faint, white, luminous clouds of the Milky Way.

Image credit: Catching the Light
The Grand Canyon in Moonlight (2012-03-30)

In this alluring night skyscape recorded on March 26, a young Moon stands over the distant western horizon in conjunction with brilliant planet Venus. In the foreground, the Colorado River glistens in moonlight as it winds through the Grand Canyon, seen from the canyon's southern rim at Lipan Point. Of course, the Grand Canyon is known as one of the wonders of planet Earth. Carved by the river, the enormous fissure is about 270 miles (440 kilometers) long, up to 18 miles (30 kilometers) wide and approaches 1 mile (1.6 kilometers) deep. On this date, wonders of the night sky included the compact Pleiades and V-shaped Hyades star clusters poised just above the Moon. Bright planet Jupiter is below the closer Moon/Venus pairing, near the western horizon.

Image credit: Malcolm Park
Paris by Night (2012-03-31)

Do you recognize the lights of Paris in this picture? In the cityscape taken on March 25 from the top of the 210 meter tall Montparnasse skyscraper, many will spot the looming Eiffel Tower, or the large domed structure of Les Invalides (right), or the colorfully lit elevated Metro train line gently curving toward picture center. You can even pick out the Arc de Triomphe close to the horizon on the right. But regardless of your location, the celestial lights near the western horizon should look very familiar. The lovely triple conjuntion of brilliant Venus (top), Jupiter, and a young crescent Moon was visible in evening skies around planet Earth.

Image credit: Serge Brunier
Dad Quiets Omicron Ceti (2012-04-01)

The Omicron Cetians have been silenced.  After alien-like monsters were reported to disturb his daughter's sleep for four nights in a row, this father took action.  When last questioned, the daughter seemed to indicate that the hullabaloo might have come from a planetary system possibly sounding like "Omicron Ceti".  Getting to the root of the problem, the dad then took his daughter outside and used a powerful laser to blast the alien's home world.  Humorously, the parent star Omicron Ceti now shows itself to be unstable and is dramatically increasing its brightness.  Happy April Fool's Day from the folks at APOD.  In actuality, the star being pointed out is Mira, a famous variable star expected to reach its maximum brightness again in late August.  The father in question was actually pointing out, to his daughter, the star that shares her name.

Image credit: Tamas Ladanyi
Tungurahua Erupts (2012-04-02)

Volcano Tungurahua sometimes erupts spectacularly.  Pictured above, molten rock so hot it glows visibly pours down the sides of the 5,000-meter high Tungurahua, while a cloud of dark ash is seen being ejected toward the left.  Wispy white clouds flow around the lava-lit peak, while a star-lit sky shines in the distance.  The above image was captured in 2006 as ash fell around the adventurous photographer.  Located in Ecuador, Tungurahua has become active roughly every 90 years for the last 1,300 years.

Image credit: Patrick