juliensimon/nasa-apod huggingface dataset:
Moon Setting Behind Teide Volcano (2020-03-22)

These people are not in danger. What is coming down from the left is just the Moon, far in the distance. Luna appears so large here because she is being photographed through a telescopic lens.  What is moving is mostly the Earth, whose spin causes the Moon to slowly disappear behind Mount Teide, a volcano in the Canary Islands off the northwest coast of Africa. The people pictured are 16 kilometers away and  many are facing the camera because they are watching the Sun rise behind the photographer. It is not a coincidence that a full moon rises just when the Sun sets because the Sun is always on the opposite side of the sky from a full moon. The featured video was made two years ago during the full Milk Moon.  The video is not time-lapse -- this was really how fast the Moon was setting.   Free Video Lectures: Introductory Astronomy

Image credit: El Cielo de Canarias
From the Pleiades to the Eridanus Loop (2020-03-23)

If you stare at an interesting patch of sky long enough, will it look different? In the case of Pleiades and Hyades star clusters -- and surrounding regions -- the answer is: yes, pretty different. Long duration camera exposures reveal an intricate network of interwoven interstellar dust and gas that was previously invisible not only to the eye but to lower exposure images. In the featured wide and deep mosaic, the dust stands out spectacularly, with the familiar Pleaides star cluster visible as the blue patch near the top of the image.  Blue is the color of the Pleiades' most massive stars, whose distinctive light reflects from nearby fine dust. On the upper left is the Hyades star cluster surrounding the bright, orange, foreground-star Aldebaran.  Red glowing emission nebula highlight the bottom of the image, including the curving vertical red ribbon known as the Eridanus Loop.  The pervasive dust clouds appear typically in light brown and are dotted with unrelated stars.   Almost Hyperspace: Random APOD Generator

Image credit: Hirofumi Okubo
A Black Hole Disrupts a Passing Star (2020-03-24)

What happens to a star that goes near a black hole? If the star directly impacts a massive black hole, then the star falls in completely -- and everything vanishes. More likely, though, the star goes close enough to have the black hole's gravity pull away the outer layers of the star, or disrupt the star. Then most of the star's gas does not fall into the black hole.  These stellar tidal disruption events can be as bright as a supernova, and an increasing amount of them are being discovered by automated sky surveys. In the featured artist's illustration, a star has just passed a massive black hole and sheds gas that continues to orbit.  The inner edge of a disk of gas and dust surrounding the black hole is heated by the disruption event and may glow long after the star  is gone.
Star Forming Region S106 (2020-03-25)

Massive star IRS 4 is beginning to spread its wings.  Born only about 100,000 years ago, material streaming out from this newborn star has formed the nebula dubbed Sharpless 2-106 Nebula (S106), featured here.  A large disk of dust and gas orbiting Infrared Source 4 (IRS 4), visible in brown near the image center, gives the nebula an hourglass or butterfly shape.  S106 gas near IRS 4 acts as an emission nebula as it emits light after being ionized, while dust far from IRS 4 reflects light from the central star and so acts as a reflection nebula.  Detailed inspection of a relevant  infrared image of S106  reveal hundreds of low-mass brown dwarf stars lurking in the nebula's gas.  S106 spans about 2 light-years and lies about 2000 light-years away toward the  constellation of the Swan (Cygnus).

Image credit: Utkarsh Mishra
Andromeda Station (2020-03-26)

This surreal picture isn't from a special effects sci-fi movie. It is a digital composite of frames of the real Andromeda Galaxy, also known as M31, rising over a real mountain. Exposures tracking the galaxy and background stars have been digitally combined with separate exposures of the foreground terrain. All background and foreground exposures were made back to back with the same camera and telephoto lens on the same night from the same location. In the "Deepscape" combination they produce a stunning image that reveals a range of brightness and color that your eye can't quite see on its own. Still, it does look like you could ride a cable car up this mountain and get off at the station right next to Andromeda. But at 2.5 million light-years from Earth the big beautiful spiral galaxy really is a little out of reach as a destination. Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you. This Andromeda Station is better known as Weisshorn, the highest peak of the ski area in Arosa, Switzerland.

Image credit: Ralf Rohner
A Little Drop of Galaxy (2020-03-27)

A drop of water seems to hold an entire galaxy in this creative macro-astrophotograph. In the imaginative work of cosmic nature photography a close-up lens was used to image a previously made picture of a galaxy, viewed through a water drop suspended from a stem. A favorite of many telescope-wielding astroimagers, the galaxy is the Andromeda Galaxy, also known as M31. About 100,000 light-years across that majestic galaxy's spiral arms and dust lanes are curved and distorted in the image contained in the centimeter-sized droplet. Andromeda is some 2.5 million light-years distant, but this project was still carried out while spending time indoors.

Image credit: Massimo Tamajo
Stars Trail over Ragusa (2020-03-28)

In trying times, stars still trail in the night. Taken on March 14, this night skyscape was made by combining 230 exposures each 15 seconds long to follow the stars' circular paths. The camera was fixed to a tripod on an isolated terrace near the center of Ragusa, Italy, on the island of Sicily. But the night sky was shared around the rotating planet. A friend to celestial navigators and astrophotographers alike Polaris, the north star, makes the short bright trail near the center of the concentric celestial arcs.

Image credit: Gianni Tumino
A 212-Hour Exposure of Orion (2020-03-29)

The constellation of Orion is much more than three stars in a row. It is a direction in space that is rich with impressive nebulas. To better appreciate this well-known swath of sky, an extremely long exposure was taken over many clear nights in 2013 and 2014. After 212 hours of camera time and an additional year of processing, the featured 1400-exposure collage spanning over 40 times the angular diameter of the Moon emerged.  Of the many interesting details that have become visible, one that particularly draws the eye is Barnard's Loop, the bright red circular filament arcing down from the middle. The Rosette Nebula is not the giant red nebula near the top of the image -- that is a larger but lesser known nebula known as Lambda Orionis.  The Rosette Nebula is visible, though: it is the red and white nebula on the upper left.  The bright orange star just above the frame center is Betelgeuse, while the bright blue star on the lower right is Rigel. Other famous nebulas visible include the Witch Head Nebula, the Flame Nebula, the Fox Fur Nebula, and, if you know just where to look, the comparatively small Horsehead Nebula. About those famous three stars that cross the belt of Orion the Hunter -- in this busy frame they can be hard to locate, but a discerning eye will find them just below and to the right of the image center.

Image credit: Stanislav Volskiy,
 Rollover Annotation:  Judy Schmidt
The Colors of Saturn from Cassini (2020-03-30)

What creates Saturn's colors?  The featured picture of Saturn only slightly exaggerates what a human would see if hovering close to the giant ringed world.   The image was taken in 2005 by the robot Cassini spacecraft that orbited Saturn from 2004 to 2017.  Here Saturn's majestic rings appear directly only as a curved line, appearing brown, in part, from its infrared glow.  The rings best show their complex structure in the dark shadows they create across the upper part of the planet.   The northern hemisphere of Saturn can appear partly blue for the same reason that Earth's skies can appear blue -- molecules in the cloudless portions of both planet's atmospheres are better at scattering blue light than red.  When looking deep into Saturn's clouds, however, the natural gold hue of Saturn's clouds becomes dominant.   It is not known why southern Saturn does not show the same blue hue -- one hypothesis holds that clouds are higher there.   It is also not known why some of Saturn's clouds are colored gold.   Activities: NASA Science at Home
The Galactic Center from Radio to X-ray (2020-03-31)

In how many ways does the center of our Galaxy glow?  This enigmatic region, about 26,000 light years away toward the constellation of the Archer (Sagittarius), glows in every type of light that we can see.  In the featured image, high-energy X-ray emission captured by NASA's orbiting Chandra X-Ray Observatory appears in green and blue, while low-energy radio emission captured by SARAO's ground-based MeerKAT telescope array is colored red. Just on the right of the colorful central region lies Sagittarius A (Sag A), a strong radio source that coincides with Sag A*, our Galaxy's central supermassive black hole. Hot gas surrounds Sag A, as well as a series of parallel radio filaments known as the Arc, seen just left of the image center.  Numerous unusual single radio filaments are visible around the image. Many stars orbit in and around Sag A, as well as numerous small black holes and dense stellar cores known as neutron stars and white dwarfs.  The Milky Way's central supermassive black hole is currently being imaged by the Event Horizon Telescope.   Activities: NASA Science at Home
Asteroid or Potato? (2020-04-01)

Is this asteroid Arrokoth or a potato? Perhaps, after all the data was beamed back to Earth from NASA's  robotic New Horizons spacecraft, the featured high resolution image of asteroid Arrokoth was constructed.  Perhaps, alternatively, the featured image is of a potato. Let's consider some facts.  Arrokoth is the most distant asteroid ever visited and a surviving remnant of the early years of our Solar System. A potato is a root vegetable that you can eat.  Happy April Fool's Day from the folks at APOD!  Although asteroid Arrokoth may look like a potato, in fact very much like the featured potato, Arrokoth (formerly known as Ultima Thule) is about 200,000 times wider and much harder to eat.    Activities: NASA Science at Home
Venus and the Pleiades in April (2020-04-02)

Venus is currently the brilliant evening star. Shared around world, in tonight's sky Venus will begin to wander across the face of the lovely Pleiades star cluster. This digital sky map illustrates the path of the inner planet as the beautiful conjunction evolves, showing its position on the sky over the next few days. The field of view shown is appropriate for binocular equipped skygazers but the star cluster and planet are easily seen with the naked-eye. As viewed from our fair planet, Venus passed in front of the stars of the Seven Sisters 8 years ago, and will again 8 years hence. In fact, orbiting the Sun 13 Venus years are almost equal to 8 years on planet Earth. So we can expect our sister planet to visit nearly the same place in our sky every 8 years.

Image credit: Fred Espenak
The Traffic in Taurus (2020-04-03)

There's a traffic jam in Taurus lately. On April 1, this celestial frame from slightly hazy skies over Tapiobicske, Hungary recorded an impressive pile up toward the zodiacal constellation of the Bull and the Solar System's ecliptic plane. Streaking right to left the International Space Station speeds across the bottom of the telescopic field of view. Wandering about as far from the Sun in planet Earth's skies as it can get, inner planet Venus is bright and approaching much slower, overexposed at the right. Bystanding at the upper left are the sister stars of the Pleiades. No one has been injured in the close encounter though, because it really isn't very close. Continuously occupied since November 2000, the space station orbits some 400 kilometers above the planet's surface. Venus, currently the brilliant evening star, is almost 2/3 of an astronomical unit away. A more permanent resident of Taurus, the Pleiades star cluster is 400 light-years distant.

Image credit: Lionel Majzik
Venus and the Sisters (2020-04-04)

After wandering about as far from the Sun on the sky as Venus can get, the brilliant evening star is crossing paths with the sister stars of the Pleiades cluster. Look west after sunset and you can share the ongoing conjunction with skygazers around the world. Taken on April 2, this celestial group photo captures the view from Portal, Arizona, USA. Even bright naked-eye Pleiades stars prove to be much fainter than Venus though. Apparent in deeper telescopic images, the cluster's dusty surroundings and familiar bluish reflection nebulae aren't quite visible, while brighter Venus itself is almost overwhelming in the single exposure. And while Venus and the Sisters do look a little star-crossed, their spiky appearance is the diffraction pattern caused by multiple leaves in the aperture of the telephoto lens. The last similar conjunction of Venus and Pleiades occurred nearly 8 years ago.

Image credit: Fred Espenak
Color the Universe (2020-04-05)

Wouldn't it be fun to color in the universe? If you think so, please accept this famous astronomical illustration as a preliminary substitute.  You, your friends, your parents or children, can print it out or even color it digitally.  While coloring, you might be interested to know that even though this illustration has appeared in numerous places over the past 100 years, the actual artist remains unknown.  Furthermore, the work has no accepted name -- can you think of a good one?  The illustration, first appearing in a book by Camille Flammarion in 1888, is used frequently to show that humanity's present concepts are susceptible to being supplanted by greater truths.   Notable APOD Submissions: Gallery of Venus passing in front of the Pleiades
NGC 1672: Barred Spiral Galaxy from Hubble (2020-04-06)

Many spiral galaxies have bars across their centers.  Even our own Milky Way Galaxy is thought to have a modest central bar. Prominently barred spiral galaxy NGC 1672, featured here, was captured in spectacular detail in an image taken by the orbiting Hubble Space Telescope. Visible are dark filamentary dust lanes, young clusters of bright blue stars, red emission nebulas of glowing hydrogen gas, a long bright bar of stars across the center, and a bright active nucleus that likely houses a supermassive black hole.  Light takes about 60 million years to reach us from NGC 1672, which spans about 75,000 light years across. NGC 1672, which appears toward the constellation of the Dolphinfish (Dorado), has been studied to find out how a spiral bar contributes to star formation in a galaxy's central regions.    Notable APOD Submissions: Gallery of Venus passing in front of the Pleiades
A Path North (2020-04-07)

What happens if you keep going north? The direction north on the Earth, the place on your horizon below the northern spin pole of the Earth -- around which other stars appear to slowly swirl, will remain the same. This spin-pole-of-the-north will never move from its fixed location on the sky -- night or day -- and its height will always match your latitude.  The further north you go, the higher the north spin pole will appear.  Eventually, if you can reach the Earth's North Pole, the stars will circle a point directly over your head.  Pictured, a four-hour long stack of images shows stars trailing in circles around this north celestial pole.  The bright star near the north celestial pole is Polaris, known as the North Star.  The bright path was created by the astrophotographer's headlamp as he zigzagged up a hill just over a week ago in Lower Saxony, Germany. The astrophotographer can be seen, at times, in shadow. Actually, the Earth has two spin poles -- and much the same would happen if you started below the Earth's equator and went south.

Image credit: Mario Konang
Country Sky versus City Sky (2020-04-08)

Dark skies are disappearing from the world.  With modernization comes artificial lighting that brightens the night.  While these lights allow modern humans to see, much light is wasted up into the sky.  This light pollution not only wastes energy, but, when reflected by the Earth's atmosphere back down, creates a nighttime brightness that  disrupts wildlife and harms human health, while doing very little to prevent crime.  Light pollution is also making a dark night sky a scarcity for new generations.  While there is little that can be done in large cities, rural country areas could benefit from lighting that is fully shielded from exposing the night sky where it is not needed.  The featured panorama contains 6 adjacent vertical segments taken from different locations across Slovakia -- but with the same equipment and at the same time of night, and then subjected to the same digital post-processing.  Although no stars are visible on the left-most city sky, the right-most country sky is magnificently dark.  You can help protect the wonders of your night sky by favoring, when possible, dark sky friendly lighting.

Image credit: Tomas Slovinsky;
 Text: 
Matipon Tangmatitham 
(NARIT)
A Flow of Time (2020-04-09)

This surreal timelapse, landscape, panorama spans predawn, blue hour, and sunrise skies. Close to the start of planet Earth's northern hemisphere spring, the flow of time was captured between 4:30 and 7:00 am from a location overlooking northern New Mexico's Rio Grande Valley. In tracked images of the night sky just before twilight begins, the Milky Way is cast across the southern (right) edge of the panoramic frame. Toward the east, a range of short and long exposures resolves the changing brightness as the Sun rises over the distant peaks of the Sangre de Cristo Mountains. In between, exposures made during the spring morning's tantalizing blue hour are used to blend the night sky and sunrise over the high desert landscape.

Image credit: Paul Schmit
Full Moon of Spring (2020-04-10)

From home this Full Moon looked bright. Around our fair planet it rose as the Sun set on April 7/8, the first Full Moon after the vernal equinox and the start of northern hemisphere spring. April's full lunar phase was also near perigee, the closest point in the Moon's elliptical orbit. In fact, it was nearer perigee than any other Full Moon of 2020 making it the brightest Full Moon of the year. To create the visual experience a range of exposures was blended to capture the emerging foreground foliage and bright lunar disk. The hopefull image of spring was recorded from a home garden in skies over Chongqing, China.   April Full Moon Gallery: Notable images submitted to APOD

Image credit: Jeff Dai
Venus and the Pleiades in April (2020-04-11)

Shared around world in early April skies Venus, our brilliant evening star, wandered across the face of the lovely Pleiades star cluster. This timelapse image follows the path of the inner planet during the beautiful conjunction showing its daily approach to the stars of the Seven Sisters. From a composite of tracked exposures made with a telephoto lens, the field of view is also appropriate for binocular equipped skygazers. While the star cluster and planet were easily seen with the naked-eye, the spiky appearance of our sister planet in the picture is the result of a diffraction pattern produced by the camera's lens. All images were taken from a home garden in Chiuduno, Bergamo, Lombardy, Italy, fortunate in good weather and clear spring nights.   Notable APOD Submissions: Gallery of Venus passing in front of the Pleiades

Image credit: Antonio
Finazzi
The Horsehead Nebula in Infrared from Hubble (2020-04-12)

While drifting through the cosmos, a magnificent interstellar dust cloud became sculpted by stellar winds and radiation to assume a recognizable shape.  Fittingly named the Horsehead Nebula, it is embedded in the vast and complex Orion Nebula (M42).  A potentially rewarding but difficult object to view personally with a small telescope, the above gorgeously detailed image was taken in 2013 in infrared light by the orbiting Hubble Space Telescope in honor of the 23rd anniversary of Hubble's launch. The dark molecular cloud, roughly 1,500 light years distant, is cataloged as Barnard 33 and is seen above primarily because it is backlit by the nearby massive star Sigma Orionis. The Horsehead Nebula will slowly shift its apparent shape over the next few million years and will eventually be destroyed by the high energy starlight.   April:  (AWB's) Global Astronomy Month
A Sailing Stone across Death Valley (2020-04-13)

How did this big rock end up on this strange terrain? One of the more unusual places here on Earth occurs inside Death Valley, California, USA.  There a dried lakebed named Racetrack Playa exists that is almost perfectly flat, with the odd exception of some very large stones, one of which is pictured here in April of 2019 beneath a dark, Milky-Way filled sky.  Now the flatness and texture of large playa like Racetrack are fascinating but not scientifically puzzling -- they are caused by mud flowing, drying, and cracking after a heavy rain.  Only recently, however, has a viable scientific hypothesis been given to explain how heavy  sailing stones end up near the middle of such a large flat surface.  Unfortunately, as frequently happens in science, a seemingly surreal problem ends up having a relatively mundane solution.  It turns out that in winter thin floating ice sheets form in a rare ephemeral lake, and light winds push ice sections that then push even heavy rocks across the temporarily flooded playa when sunlight begins to melt the ice.
NGC 253: The Silver Coin Galaxy (2020-04-14)

NGC 253 is one of the brightest spiral galaxies visible, but also one of the dustiest.  Dubbed the Silver Coin for its appearance in smalltelescopes, it is more formally known as the Sculptor Galaxy for its location within the boundaries of the southern constellation Sculptor.  Discovered in 1783 by mathematician and astronomer Caroline Herschel, the dusty island universe lies a mere 10 million light-years away. About 70 thousand light-years across, NGC 253, pictured, is the largest member of the Sculptor Group of Galaxies, the nearest to our own Local Group of galaxies.  In addition to its spiral dust lanes, tendrils of dust seem to be rising from a galactic disk laced with young star clusters and star forming regions in this sharp color image. The high dust content accompanies frantic star formation, earning NGC 253 the designation of a starburst galaxy. NGC 253 is also known to be a strong source of high-energy x-rays and gamma rays, likely due to massive black holes near the galaxy's center. Take a trip through extragalactic space in this short video flyby of NGC 253.   Astrophysicists: Browse 2,100+ codes in the Astrophysics Source Code Library
A Cosmic Triangle (2020-04-15)

It was an astronomical triple play. Setting on the left, just after sunset near the end of last month, was our Moon -- showing a bright crescent phase.  Setting on the right was Venus, the brightest planet in the evening sky last month -- and this month, too.  With a small telescope, you could tell that Venus' phase was half, meaning that only half of the planet, as visible from Earth, was exposed to direct sunlight and brightly lit. High above and much further in the distance was the Pleiades star cluster.  Although the Moon and Venus move with respect to the background stars, the Pleiades do not -- because they are background stars. In the beginning of this month, Venus appeared to move right in front of the Pleiades, a rare event that happens only once every eight years.  The featured image captured this cosmic triangle with a series of exposures taken from the same camera over 70 minutes near Avonlea, Saskatchewan, Canada. The positions of the celestial objects was predicted. The only thing unpredicted was the existence of the foreground tree -- and the astrophotographer is still unsure what type of tree that is.

Image credit: Scott
Aspinall