juliensimon/nasa-apod huggingface dataset:
Mars at the Moon's Edge (2020-08-15)

Does the Moon ever block out Mars? Yes, the Moon occasionally moves in front of all of the Solar System's planets.  Just this past Sunday, as visible from some locations in South America, a waning gibbous Moon eclipsed Mars.  The featured image from Córdoba, Argentina captured this occultation well, showing a familiar cratered Moon in the foreground with the bright planet Mars unusually adjacent.  Within a few seconds, Mars then disappeared behind the Moon, only to reappear a few minutes later across the Moon.  Today the Moon moves close to, but not in front of, Venus.  Because alignments will not have changed by much, the next two times the Moon passes through this part of the sky – in early September and early October – it will also occult Mars, as seen from parts of South America.    Perseid Meteor Shower: Notable images submitted to APOD

Image credit: Sergio Scauso
NGC 6814: Grand Design Spiral Galaxy from Hubble (2020-08-16)

In the center of this serene stellar swirl is likely a harrowing black-hole beast.  The surrounding swirl sweeps around billions of stars which are highlighted by the brightest and bluest. The breadth and beauty of the display give the swirl the designation of a grand design spiral galaxy. The central beast shows evidence that it is a supermassive black hole about 10 million times the mass of  our Sun.  This ferocious creature devours stars and gas and is surrounded by a spinning moat of hot plasma that emits blasts of X-rays. The central violent activity gives it the designation of a Seyfert galaxy. Together, this beauty and beast are cataloged as NGC 6814 and have been appearing together toward the constellation of the Eagle (Aquila) for roughly the past billion years.   Perseid Meteor Shower: Notable images submitted to APOD
Perseids Around the Milky Way (2020-08-17)

Why would meteor trails appear curved? The arcing effect arises only because the image artificially compresses (nearly) the whole sky into a rectangle. The meteors are from the Perseid Meteor Shower that peaked last week. The featured multi-frame image combines not only different directions from the 360 projection, but different times when bright Perseid meteors momentarily streaked across the sky. All Perseid meteors can be traced back to the constellation Perseus toward the lower left, even the seemingly curved (but really straight) meteor trails.  Although Perseids always point back to their Perseus radiant, they can appear almost anywhere on the sky. The image was taken from Inner Mongolia, China, where grasslands meet sand dunes. Many treasures also visible in the busy night sky including the central arch of our Milky Way Galaxy, the planets Saturn and Jupiter toward the right, colorful airglow on the central left, and some relatively nearby Earthly clouds.  The Perseid Meteor Shower peaks every August.    Perseid Meteor Shower: Notable images submitted to APOD

Image credit: Jingyi Zhang
TYC 8998-760-1: Multiple Planets around a Sun Like Star (2020-08-18)

Do other stars have planets like our Sun? Previous evidence shows that they do, coming mostly from slight shifts in the star's light created by the orbiting planets.  Recently, however, and for the first time, a pair of planets has been directly imaged around a Sun-like star.  These exoplanets orbit the star designated TYC 8998-760-1 and are identified by arrows in the featured infrared image.  At 17 million years old, the parent star is much younger than the 5-billion-year age of our Sun.  Also, the exoplanets are both more massive and orbit further out than their Solar System analogues: Jupiter and Saturn. The exoplanets were found by the ESO's Very Large Telescope in Chile by their infrared glow – after the light from their parent star was artificially blocked.  As telescope and technology improve over the next decade, it is hoped that planets more closely resembling our Earth will be directly imaged.    Experts Debate: How will humanity first discover extraterrestrial life?
The Sun Rotating (2020-08-19)

Does the Sun change as it rotates? Yes, and the changes can vary from subtle to dramatic. In the featured time-lapse sequences, our Sun -- as imaged by NASA's Solar Dynamics Observatory -- is shown rotating though an entire month in 2014.  In the large image on the left, the solar chromosphere is depicted in ultraviolet light, while the smaller and lighter image to its upper right simultaneously shows the more familiar solar photosphere in visible light. The rest of the inset six Sun images highlight X-ray emission by relatively rare iron atoms located at different heights of the corona, all false-colored to accentuate differences. The Sun takes just under a month to rotate completely -- rotating fastest at the equator. A large and active sunspot region rotates into view soon after the video starts.  Subtle effects include changes in surface texture and the shapes of active regions. Dramatic effects include numerous flashes in active regions, and fluttering and erupting prominences visible all around the Sun's edge.  Presently, our Sun is passing an unusually low  Solar minimum in activity of its 11-year magnetic cycle. As the video ends, the same large and active sunspot region previously mentioned rotates back into view, this time looking different.
Seeing Titan (2020-08-20)

Shrouded in a thick atmosphere, Saturn's largest moon Titan really is hard to see. Small particles suspended in the upper atmosphere cause an almost impenetrable haze, strongly scattering light at visible wavelengths and hiding Titan's surface features from prying eyes. But Titan's surface is better imaged at infrared wavelengths where scattering is weaker and atmospheric absorption is reduced. Arrayed around this visible light image (center) of Titan are some of the clearest global infrared views of the tantalizing moon so far. In false color, the six panels present a consistent processing of 13 years of infrared image data from the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini spacecraft. They offer a stunning comparison with Cassini's visible light view.   Experts Debate: How will humanity first discover extraterrestrial life?
Unwinding M51 (2020-08-21)

The arms of a grand design spiral galaxy 60,000 light-years across are unwound in this digital transformation of the magnificent 2005 Hubble Space Telescope portrait of M51. In fact, M51 is one of the original spiral nebulae, its winding arms described by a mathematical curve known as a logarithmic spiral, a spiral whose separation grows in a geometric way with increasing distance from the center. Applying logarithms to shift the pixel coordinates in the Hubble image relative to the center of M51 maps the galaxy's spiral arms into diagonal straight lines. The transformed image dramatically shows the arms themselves are traced by star formation, lined with pinkish starforming regions and young blue star clusters. Companion galaxy NGC 5195 (top) seems to alter the track of the arm in front of it though, and itself remains relatively unaffected by this unwinding of M51. Also known as the spira mirabilis, logarthimic spirals can be found in nature on all scales. For example, logarithmic spirals can also describe hurricanes, the tracks of subatomic particles in a bubble chamber and, of course, cauliflower.

Image credit: Hubble Heritage Project
Yogi And Friends In 3D (2020-08-22)

From July of 1997, a ramp from the Pathfinder lander, the Sojourner robot rover, airbags, a couch, Barnacle Bill and Yogi Rock appear together in this 3D stereo view of the surface of Mars. Barnacle Bill is the rock just left of the solar-paneled Sojourner. Yogi is the big friendly-looking boulder at top right. The "couch" is the angular rock shape visible near center on the horizon. Look at the image with red/blue glasses (or just hold a piece of clear red plastic over your left eye and blue or green over your right) to get the dramatic 3D perspective. The stereo view was recorded by the remarkable Imager for Mars Pathfinder (IMP) camera. The IMP had two optical paths for stereo imaging and ranging and was equipped with an array of color filters for spectral analysis.  Operating as the first astronomical observatory on Mars, the IMP also recorded images of the Sun and Deimos, the smallest of Mars' two tiny moons. This July saw the launch of NASA's Mars Perseverance Rover on a mission to the Red Planet.

Image credit: IMP Team
The Helix Nebula from Blanco and Hubble (2020-08-23)

How did a star create the Helix nebula?  The shapes of planetary nebula like the Helix are important because they likely hold clues to how stars like the Sun end their lives.  Observations by the orbiting Hubble Space Telescope and the 4-meter Blanco Telescope in Chile, however, have shown the Helix is not really a simple helix.  Rather, it incorporates two nearly perpendicular disks as well as arcs, shocks, and even features not well understood.  Even so, many strikingly geometric symmetries remain.  How a single Sun-like star created such beautiful yet geometric complexity is a topic of research.  The Helix Nebula is the nearest planetary nebula to Earth, lies only about 700 light years away toward the constellation of Aquarius, and spans about 3 light-years.
Crescent Moon HDR (2020-08-24)

How come the crescent Moon doesn't look like this?  For one reason, because your eyes can't simultaneously discern bright and dark regions like this. Called earthshine or the da Vinci glow, the unlit part of a crescent Moon is visible but usually hard to see because it is much dimmer than the sunlit arc. In our digital age, however, the differences in brightness can be artificially reduced. The featured image is actually a digital composite of 15 short exposures of the bright crescent, and 14 longer exposures of the dim remainder.  The origin of the da Vinci glow, as explained by Leonardo da Vinci about 510 years ago, is sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth.

Image credit: Miguel Claro
Visualization: A Black Hole Accretion Disk (2020-08-25)

What would it look like to circle a black hole? If the black hole was surrounded by a swirling disk of glowing and accreting gas, then the great gravity of the black hole would deflect light emitted by the disk to make it look very unusual. The featured animated video gives a visualization. The video starts with you, the observer, looking toward the black hole from just above the plane of the accretion disk.  Surrounding the central black hole is a thin circular image of the orbiting disk that marks the position of the photon sphere -- inside of which lies the black hole's event horizon.  Toward the left, parts of the large main image of the disk appear brighter as they move toward you. As the video continues, you loop over the black hole, soon looking down from the top, then passing through the disk plane on the far side, then returning to your original vantage point. The accretion disk does some interesting image inversions -- but never appears flat. Visualizations such as this are particularly relevant today as black holes are being imaged in unprecedented detail by the Event Horizon Telescope.
Cygnus Skyscape (2020-08-26)

In brush strokes of interstellar dust and glowing hydrogen gas, this beautiful skyscape is painted across the plane of our Milky Way Galaxy near the northern end of the Great Rift and the constellation Cygnus the Swan. Composed using 22 different images and over 180 hours of image data, the widefield mosaic spans an impressive 24 degrees across the sky. Alpha star of Cygnus, bright, hot, supergiant Deneb lies 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 and IC 5070, the North America Nebula and Pelican Nebulas, 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 are identifiable throughout the cosmic scene. Of course, Deneb itself is also known to northern hemisphere skygazers for its place in two asterisms -- marking the top of the Northern Cross and a vertex of the Summer Triangle.   Follow APOD on: Instagram, Facebook,  Reddit, or Twitter

Image credit: Alistair Symon
Shell Galaxies in Pisces (2020-08-27)

This intergalactic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent right of center, the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470. The faint, wide arcs or shells of NGC 474 could have been formed by a gravitational encounter with neighbor NGC 470. Alternately the shells could be caused by a merger with a smaller galaxy producing an effect analogous to ripples across the surface of a pond. The large galaxy on the top lefthand side of the deep image, NGC 467, appears to be surrounded by faint shells too, evidence of another interacting galaxy system. Intriguing background galaxies are scattered around the field that also includes spiky foreground stars. Of course, those stars lie well within our own Milky Way Galaxy. The field of view spans 25 arc minutes or about 1/2 degree on the sky.

Image credit: Martin Pugh
The Valley of Orion (2020-08-28)

This exciting and unfamiliar view of the Orion Nebula is a visualization based on astronomical data and movie rendering techniques. Up close and personal with a famous stellar nursery normally seen from 1,500 light-years away, the digitally modeled frame transitions from a visible light representation based on Hubble data on the left to infrared data from the Spitzer Space Telescope on the right. The perspective at the center looks along a valley over a light-year wide, in the wall of the region's giant molecular cloud. Orion's valley ends in a cavity carved by the energetic winds and radiation of the massive central stars of the Trapezium star cluster. The single frame is part of a multiwavelength, three-dimensional video that lets the viewer experience an immersive, three minute flight through the Great Nebula of Orion.
Martian Chiaroscuro (2020-08-29)

Deep shadows create dramatic contrasts between light and dark in this high-resolution close-up of the martian surface. Recorded on January 24, 2014 by the HiRISE camera on board the Mars Reconnaissance Orbiter, the scene spans about 1.5 kilometers. From 250 kilometers above the Red Planet the camera is looking down at a sand dune field in a southern highlands crater. Captured when the Sun was about 5 degrees above the local horizon, only the dune crests were caught in full sunlight. A long, cold winter was coming to the southern hemisphere and bright ridges of seasonal frost line the martian dunes.  The Mars Reconnaissance Orbiter, one of the oldest operating spacecraft at the Red Planet, celebrated the 15th anniversary of its launch from planet Earth on August 12.
NGC 6357: Cathedral to Massive Stars (2020-08-30)

How massive can a normal star be?  Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it one of the most massive stars known.  This star is the brightest object located just above the gas front in the featured image.  Close inspection of images taken with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least.  Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record.  Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon.   Teachers & Students: Ideas for Utilizing APOD in the Classroom
SS 433: Binary Star Micro-Quasar (2020-08-31)

SS 433 is one of the most exotic star systems known.  Its unremarkable name stems from its inclusion in a catalog of Milky Way stars which emit radiation characteristic of atomic hydrogen.  Its remarkable behavior stems from a compact object, a black hole or neutron star, which has produced an accretion disk with jets.  Because the disk and jets from SS 433 resemble those surrounding supermassive black holes in the centers of distant galaxies, SS 433 is considered a micro-quasar.  As illustrated in the animated featured video based on observational data, a massive, hot, normal star is locked in orbit with the compact object.  As the video starts, material is shown being gravitationally ripped from the normal star and falling onto an accretion disk. The central star also blasts out jets of ionized gas in opposite directions – each at about 1/4 the speed of light.  The video then pans out to show a top view of the precessing jets producing an expanding spiral. From even greater distances, the dissipating jets are then visualized near the heart of supernova remnant W50. Two years ago, SS 433 was unexpectedly found by the HAWC detector array in Mexico to emit unusually high energy (TeV-range) gamma-rays. Surprises continue, as a recent analysis of archival data taken by NASA's Fermi satellite find a gamma-ray source -- separated from the central stars as shown -- that pulses in gamma-rays with a period of 162 days – the same as SS 433's jet precession period – for reasons yet unknown.    Teachers & Students: Ideas for utilizing APOD in the classroom.
Salt Water Remnants on Ceres (2020-09-01)

Does Ceres have underground pockets of water? Ceres, the largest asteroid in the asteroid belt, was thought to be composed of rock and ice. At the same time, Ceres was known to have unusual bright spots on its surface. These bright spots were clearly imaged during Dawn's exciting approach in 2015. Analyses of Dawn images and spectra indicated that the bright spots arise from the residue of highly-reflective salt water that used to exist on Ceres' surface but evaporated. Recent analysis indicates that some of this water may have originated from deep inside the dwarf planet, indicating Ceres to be a kindred spirit with several  Solar System moons, also thought to harbor deep water pockets.  The featured video shows in false-color pink the bright evaporated brine named Cerealia Facula in Occator Crater.  In 2018, the mission-successful but fuel-depleted Dawn  spacecraft was placed in a distant parking orbit, keeping it away from the Ceres' surface for at least 20 years to avoid interfering with any life that might there exist.   Experts Debate: How will humanity first discover extraterrestrial life?
Jupiter and the Moons (2020-09-02)

How many moons do you see? Many people would say one, referring to the Earth's Moon, prominent on the lower left. But take a closer look at the object on the upper right. That seeming-star is actually the planet Jupiter, and your closer look might reveal that it is not alone – it is surrounded by some of its largest moons. From left to right these Galilean Moons are Io, Ganymende, Europa and Callisto. These moons orbit the Jovian world just like the planets of our Solar System orbit the Sun, in a line when seen from the side.  The featured single shot was captured from Cancun, Mexico last week as Luna, in its orbit around the Earth, glided past the distant planet.  Even better views of Jupiter are currently being captured by NASA's Juno spacecraft, now in a looping orbit around the Solar System's largest planet.  Earth's Moon will continue to pass nearly in front of both Jupiter and Saturn once a month (moon-th) as the two giant planets approach their own great conjunction in December.   Almost Hyperspace: Random APOD Generator

Image credit: Robert Fedez
A Halo for Andromeda (2020-09-03)

M31, the Andromeda Galaxy, is the closest large spiral galaxy to our Milky Way. Some 2.5 million light-years distant it shines in Earth's night sky as a small, faint, elongated cloud just visible to the unaided eye. Invisible to the eye though, its enormous halo of hot ionized gas is represented in purplish hues for this digital illustration of our neighboring galaxy above rocky terrain. Mapped by Hubble Space Telescope observations of the absorption of ultraviolet light against distant quasars, the extent and make-up of Andromeda's gaseous halo has been recently determined by the AMIGA project. A reservoir of material for future star formation, Andromeda's halo of diffuse plasma was measured to extend around 1.3 million light-years or more from the galaxy. That's about half way to the Milky Way, likely putting it in contact with the diffuse gaseous halo of our own galaxy.
The Wizard Nebula (2020-09-04)

Open star cluster NGC 7380 is still embedded in its natal cloud of interstellar gas and dust popularly known as the Wizard Nebula. Seen on the left, with foreground and background stars along the plane of our Milky Way galaxy it lies some 8,000 light-years distant, toward the constellation Cepheus. In apparent size on the sky, a full moon would cover the 4 million year young cluster and associated nebula, normally much too faint to be seen by eye. Made with telescope and camera firmly planted on Earth, the image reveals multi light-year sized shapes and structures of cosmic gas and dust within the Wizard though, in a color palette made popular in Hubble Space Telescope images. Recorded with narrowband filters, the visible wavelength light from the nebula's hydrogen, oxygen, and sulfur atoms is transformed into green, blue, and red colors in the final digital composite.

Image credit: Andrew Klinger
A Falcon 9 Moon (2020-09-05)

Illuminating planet Earth's night, full moons can have many names. This year the last full moon of northern hemisphere summer was on September 2, known to some as the Full Corn Moon. A few days earlier on August 30 this almost full moon rose just before sunset though, shining through cloudy skies over Cape Canaveral Air Force Station on Florida's Space Coast. A well-timed snapshot caught the glare of rocket engines firing below the lunar disk, a Falcon 9 rocket's first stage successfully returning to Cape Canaveral's landing zone 1. About 9 minutes earlier, the same SpaceX Falcon 9 rocket had launched the SAOCOM 1B satellite toward polar orbit. The fourth launch for this reusable Falcon 9 first stage, it was the first launch to a polar orbit from Cape Canaveral since 1969.

Image credit: Katie Darby
M1: The Crab Nebula from Hubble (2020-09-06)

This is the mess that is left when a star explodes.  The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments.  The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion.  The featured image, taken by the Hubble Space Telescope, is presentedi in three colors chosen for scientific interest.  The Crab Nebula spans about 10 light-years.  In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town.  The Crab Pulsar rotates about 30 times each second.