juliensimon/nasa-apod huggingface dataset:
The Gaia Stars of M15 (2019-03-28)

Messier 15 is a 13 billion year old relic of the early formative years of our galaxy, one of about 170 globular star clusters that still roam the halo of the Milky Way.  About 200 light-years in diameter, it lies about 35,000 light years away toward the constellation Pegasus. But this realistic looking view of the ancient globular star cluster is not a photograph. Instead it's an animated gif image constructed from remarkably precise individual measurements of star positions, brightness, and color. The astronomically rich data set used was made by the sky-scanning Gaia satellite which also determined parallax distances for 1.3 billion Milky Way stars. In the animated gif, twinkling stars are M15's identified RR Lyrae stars. Plentiful in M15, RR Lyrae stars are evolved pulsating variable stars whose brightness and pulsation period, typically less than a day, are related.
M104: The Sombrero Galaxy (2019-03-29)

The striking spiral galaxy M104 is famous for its nearly edge-on profile featuring a broad ring of obscuring dust lanes. Seen in silhouette against an extensive central bulge of stars, the swath of cosmic dust lends a broad brimmed hat-like appearance to the galaxy suggesting a more popular moniker, The Sombrero Galaxy. Hubble Space Telescope data have been used to create this sharp view of the well-known galaxy. The processing results in a natural color appearance and preserves details often lost in overwhelming glare of M104's bright central bulge when viewed with smaller ground-based telescopes. Also known as NGC 4594, the Sombrero galaxy can be seen across the spectrum and is host to a central supermassive black hole. About 50,000 light-years across and 28 million light-years away, M104 is one of the largest galaxies at the southern edge of the Virgo Galaxy Cluster.
3D 67P (2019-03-30)

Put on your red/cyan glasses and float next to the jagged and double-lobed nucleus of Churyumov-Gerasimenko, also known as Comet 67P. The stereo anaglyph was created by combining two images from the Rosetta spacecraft's narrow angle OSIRIS camera taken on July 25, 2015 from a distance of 184 kilometers. Numerous jets are emanating from the small solar system world's active surface near its closest approach to the Sun. The larger lobe is around 4 kilometers in diameter, joined to a smaller, 2.5 kilometer diameter lobe by a narrow neck. Rosetta's mission to the comet ended in September 2016 when the spacecraft was commanded to a controlled impact with the comet's surface. Keep those 3D glasses on though. You can check out a new catalog of nearly 1400 stereo anaglyphs created from Rosetta image data on this website.
Markarian's Chain of Galaxies (2019-03-31)

Across the heart of the Virgo Cluster of Galaxies lies a striking string of galaxies known as Markarian's Chain.  The chain, pictured here, is highlighted on the right with two large but featureless lenticular galaxies, M84 and M86. Prominent to their lower left is a pair of interacting galaxies known as The Eyes. The home Virgo Cluster is the nearest cluster of galaxies, contains over 2000 galaxies, and has a noticeable gravitational pull on the galaxies of the Local Group of Galaxies surrounding our Milky Way Galaxy.  The center of the Virgo Cluster is located about 70 million light 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.    Note: APOD now available in Ukrainian

Image credit: Sergio Kaminsky
Astronaut Kicks Lunar Field Goal (2019-04-01)

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 uprights and 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 detected high-energy particles that escaped from the Sun.   No Joke: NASA Plans to Return to the Moon in the Next Five Years
Space Station Silhouette on the Moon (2019-04-02)

What's that unusual spot on the Moon? It's the International Space Station. Using precise timing, the Earth-orbiting space platform was photographed in front of a partially lit gibbous Moon last month. The featured image was taken from Palo Alto, California, USA with an exposure time of only 1/667 of a second. In contrast, the duration of the transit of the ISS across the entire Moon was about half a second.  A close inspection of this unusually crisp ISS silhouette will reveal the outlines of numerous solar panels and trusses.  The bright crater Tycho is visible on the lower left, as well as comparatively rough, light colored terrain known as highlands, and relatively smooth, dark colored areas known as maria.  On-line tools can tell you when the International Space Station will be visible from your area.   Newly Added Venue:  APOD now available on Instagram in Persian

Image credit: Eric Holland
Wisps Surrounding the Horsehead Nebula (2019-04-03)

The famous Horsehead Nebula in Orion is not alone.  A deep exposure shows that the dark familiar shaped indentation, visible just below center, is part of a vast complex of absorbing dust and glowing gas.  To bring out details of the  Horsehead's pasture, an amateur astronomer used a backyard telescope in Austria to 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 and sculpted 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.    Bounce around the Universe: Random APOD Generator

Image credit: Mario Zauner
Messier 2 (2019-04-04)

After the Crab Nebula, M1, this giant star cluster is the second entry in 18th century astronomer Charles Messier's famous list of things that 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 as a nebula without stars, this stunning Hubble image resolves stars across the central 40 light-years of M2. Its population of 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, also known as NGC 7089, is 13 billion years old.
Pan-STARRS Across the Sky (2019-04-05)

This astronomical sky spanning view is a mosaic from the Pan-STARRS observatory. The images were recorded with its 1.8 meter telescope at the summit of Haleakala on planet Earth's island of Maui. In fact, Earth's north celestial pole is centered in this across-the-sky projection. A declination of -30 degrees, the southern horizon limit as seen from the Hawaiian Valley Isle, defines the circular outer edge. Crowded starfields and 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), currently the 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.
ISS from Wallasey (2019-04-06)

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 some 400 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.

Image credit: Richard Addis
A Scorpius Sky Spectacular (2019-04-07)

If Scorpius looked this good to the unaided eye, humans might remember it better.  Scorpius more typically appears as a few bright stars in a well-known but rarely pointed out zodiacal constellation. To get a spectacular image like this, though, one needs a good camera, color filters, and a digital image processor.  To bring out detail, the featured image not only involved long duration exposures taken in several colors, but one exposure in a very specific red color emitted by hydrogen.  The resulting image shows many breathtaking features.  Vertically across the image left is part of the plane of our Milky Way Galaxy.   Visible there are vast clouds of bright stars and long filaments of dark dust.  Jutting out diagonally from the Milky Way in the image center are dark dust bands known as the Dark River.  This river connects to several bright stars on the right that are part of Scorpius' head and claws, and include the bright star Antares.  Above and right of Antares is an even brighter planet: Jupiter. Numerous red emission nebulas and blue reflection nebulas are visible throughout the image. Scorpius appears prominently in southern skies after sunset during the middle of the year.

Image credit: St�phane Guisard, 
TWAN
AZURE Vapor Tracers over Norway (2019-04-08)

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 And�ya 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.

Image credit: Yang Sutie
Moon Occults Saturn (2019-04-09)

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.   Follow APOD on Instagram: English or Persian

Image credit: Cory Schmitz
Martian Moon Phobos Crosses the Sun (2019-04-10)

What's that passing in front of the Sun? It looks like a moon, but it can't be Earth's Moon, because it isn't round. It's the Martian moon Phobos.  The featured video was taken from the surface of Mars late last month by the Curiosity rover. Phobos, at 11.5 kilometers across, is 150 times smaller than Luna (our moon) in diameter, but also 50 times closer to its parent planet.  In fact, Phobos is so close to Mars that it is expected to break up and crash into Mars within the next 50 million years.  In the near term, the low orbit of Phobos results in more rapid solar eclipses than seen from Earth. The featured video has been sped up -- the actual transit took about 35 seconds. A similar video was taken of Mars' smaller and most distant moon Diemos transiting the Sun.  The videographer -- the robotic rover Curiosity -- continues to explore Gale crater, most recently an area with stunning vistas and unusual rocks dubbed Glen Torridon.    Retrospective: Previous APODs that appeared on April 10.
First Horizon-Scale Image of a Black Hole (2019-04-11)

What does a black hole look like? To find out, radio telescopes from around the Earth coordinated observations of black holes with the largest known event horizons on the sky.  Alone, black holes are just black, but these monster attractors are known to be surrounded by glowing gas.  The first image was released yesterday and resolved the area around the black hole at the center of galaxy M87 on a scale below that expected for its event horizon.  Pictured, the dark central region is not the event horizon, but rather the black hole's shadow -- the central region of emitting gas darkened by the central black hole's gravity. The size and shape of the shadow is determined by bright gas near the event horizon, by strong gravitational lensing deflections, and by the black hole's spin.  In resolving this black hole's shadow, the Event Horizon Telescope (EHT) bolstered evidence that Einstein's gravity works even in extreme regions, and gave clear evidence that M87 has a central spinning black hole of about 6 billion solar masses.  The EHT is not done -- future observations will be geared toward even higher resolution, better tracking of variability, and exploring the immediate vicinity of the black hole in the center of our Milky Way Galaxy.
A Cosmic Rose: The Rosette Nebula in Monoceros (2019-04-12)

The Rosette Nebula, NGC 2237, is not the only cosmic cloud of gas and dust to evoke the imagery of flowers, but it is the most famous.  At the edge of a large molecular cloud in Monoceros some 5,000 light years away, the petals of this cosmic rose are actually a stellar nursery. The lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young, O-type stars. Stars in the energetic cluster, cataloged as NGC 2244, are only a few million years young, while the central cavity in the Rosette Nebula, is about 50 light-years in diameter. The nebula can be seen with a small telescope toward the constellation of Monoceros, the Unicorn. This natural appearing telescopic portrait of the Rosette Nebula was made using broadband and narrowband filters, because sometimes roses aren't red.

Image credit: Jean Dean
Rigil Kentaurus and Sandqvist 169 (2019-04-13)

Rigil Kentaurus is the bright star near the top of this broad southern skyscape. Of course it's probably better known as Alpha Centauri, nearest star system to the Sun. Below it sprawls a dark nebula complex. The obscuring interstellar dust clouds include Sandqvist catalog clouds 169 and 172 in silhouette against the rich starfields along the southern Milky Way. Rigil Kent is a mere 4.37 light-years away, but the dusty dark nebulae lie at the edge of the starforming Circinus-West molecular cloud about 2,500 light-years distant. The wide-field of view spans over 12 degrees (24 full moons) across southern skies.

Image credit: Roberto
Colombari
Simulation: Two Black Holes Merge (2019-04-14)

Sit back and watch two black holes merge. Inspired by the first direct detection of gravitational waves in 2015, this simulation video plays in slow motion but would take about one third of a second if run in real time. Set on a cosmic stage the black holes are posed in front of stars, gas, and dust. Their extreme gravity lenses the light from behind them into Einstein rings as they spiral closer and finally merge into one. The otherwise invisible gravitational waves generated as the massive objects rapidly coalesce cause the visible image to ripple and slosh both inside and outside the Einstein rings even after the black holes have merged. Dubbed GW150914, the gravitational waves detected by LIGO are consistent with the merger of 36 and 31 solar mass black holes at a distance of 1.3 billion light-years. The final, single black hole has 63 times the mass of the Sun, with the remaining 3 solar masses converted into energy in gravitational waves. Since then the LIGO and VIRGO gravitational wave observatories have reported several more detections of merging massive systems, while last week the Event Horizon Telescope reported the first horizon-scale image of a black hole.
Enhanced: The Dolphin Cloud on Jupiter (2019-04-15)

Do you see the dolphin-shaped cloud on Jupiter? The cloud was visible last year during perijove 16, the sixteenth time that NASA's robotic spacecraft Juno passed near Jupiter since it arrived in mid-2016.  During each perijove, Juno passes near a slightly different part of Jupiter's cloud tops.  The dolphin shape may be surprising but is not scientifically significant -- clouds on Jupiter and Earth are constantly shifting and can temporarily mimic many familiar shapes. The cloud appears in Jupiter's South Temperate Belt (STB), a band of dark and dropping clouds that rings the planet and also contains Oval BA, dubbed Red Spot Jr.  The featured image was digitally processed to enhance color and contrast.  Juno's next swoop near Jupiter -- perijove 20 -- will occur on late May.
In the Vicinity of the Cone Nebula (2019-04-16)

Strange shapes and textures can be found in neighborhood of the Cone Nebula. The unusual shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars.  The brightest star on the right of the featured picture is S Mon, while the region just below it has been nicknamed the Fox Fur Nebula for its color and structure. The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star. The red glow that encompasses the whole region results not only from dust reflection but also emission from hydrogen gas ionized by starlight. S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of the Unicorn (Monoceros).   Even though it points right at S Mon, details of the origin of the mysterious geometric Cone Nebula, visible on the far left, remain a mystery.

Image credit: Utkarsh Mishra
Messier 81 (2019-04-17)

One of the brightest galaxies in planet Earth's sky is similar in size to our Milky Way Galaxy: big, beautiful Messier 81. Also known as NGC 3031 or Bode's galaxy for its 18th century discoverer, this grand spiral can be found toward the northern constellation of Ursa Major, the Great Bear. The detailed telescopic view reveals M81's bright yellow nucleus, blue spiral arms, pink starforming regions, and sweeping cosmic dust lanes. Some dust lanes actually run through the galactic disk (left of center), contrary to other prominent spiral features though. The errant dust lanes may be the lingering result of a close encounter between M81 and its smaller companion galaxy, M82. Scrutiny of variable stars in M81 has yielded one of the best determined distances for an external galaxy -- 11.8 million light-years.

Image credit: Paolo De
Salvatore
The Leo Trio (2019-04-18)

This group is popular in the northern spring. Famous as the Leo Triplet, the three magnificent galaxies gather in one field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top). All three are large spiral galaxies but they tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628, also known as the Hamburger Galaxy, is temptingly seen edge-on, with obscuring dust lanes cutting across its puffy galactic plane. The disks of M66 and M65 are both inclined enough to show off their spiral structure.  Gravitational interactions between galaxies in the group have left telltale signs, including the tidal tails and warped, inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous view of the region spans almost two degrees (four full moons) on the sky. The field covers about a million light-years at the trio's estimated distance of 30 million light-years. Of course the spiky foreground stars lie within our own Milky Way.

Image credit: Markus Bauer
Milky Way in Northern Spring (2019-04-19)

A postcard from planet Earth, this springtime night skyscape looks over Alandan lake in the Alborz mountains. Taken after local midnight on 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 also gave frogs their voices, heard like a melody across the calm water.

Image credit: Taha Ghouchkanlu
Falcon Heavy Launch Close Up (2019-04-20)

Twenty seven Merlin rocket engines are firing in this close-up of the launch of a Falcon Heavy rocket. Derived from three Falcon 9 first 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 a Falcon Heavy rocket carried the Arabsat 6A communications satellite to space. In February of 2018, the first Falcon Heavy launch carried Starman 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 ship Of Course I Still Love You.
Spiral Aurora over Icelandic Divide (2019-04-21)

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.   APOD in other languages: Arabic, Catalan, Chinese (Beijing), Chinese (Taiwan), Croatian, Czech, Dutch, German, French, French, Indonesian, Japanese, Korean, Montenegrin, Polish, Russian, Serbian, Slovenian,  Spanish and Ukrainian

Image credit: Juan Carlos Casado
(TWAN,
StarryEarth)