juliensimon/nasa-apod huggingface dataset:
Human as Spaceship (2019-08-18)

You are a spaceship soaring through the universe. So is your dog. We all carry with us trillions of microorganisms as we go through life. These multitudes of bacteria, fungi, and archaea have different DNA than you. Collectively called your microbiome, your shipmates outnumber your own cells. Your crew members form communities, help digest food, engage in battles against intruders, and sometimes commute on a liquid superhighway from one end of your body to the other.  Much of what your microbiome does, however, remains unknown. You are the captain, but being nice to your crew may allow you to explore more of your local cosmos.

Image credit: Charis Tsevis; 
 Composition:  R. J. Nemiroff
Lenticular Clouds over Mount Etna (2019-08-19)

What's happening above that volcano? Although Mount Etna is seen erupting, the clouds are not related to the eruption. They are lenticular clouds formed when moist air is forced upwards near a mountain or volcano.  The surreal scene was captured by chance late last month when the astrophotographer went to Mount Etna, a UNESCO World Heritage Site in Sicily, Italy, to photograph the conjunction between the Moon and the star Aldebaran. The Moon appears in a bright crescent phase, illuminating an edge of the lower lenticular cloud.  Red hot lava flows on the right.  Besides some breathtaking stills, a companion time-lapse video of the scene shows the lenticular clouds forming and wavering as stars trail far in the distance.    Follow APOD in English on: Instagram, Facebook,  Reddit, or Twitter

Image credit: Dario Giannobile
Animation: Spiral Disk around a Black Hole (2019-08-20)

What would it look like to orbit a black hole? Many black holes are surrounded by swirling pools of gas known as accretion disks. These disks can be extremely hot, and much of the orbiting gas will eventually fall through the black hole's event horizon -- where it will never be seen again. The featured animation is an artist's rendering of the curious disk spiraling around the supermassive black hole at the center of spiral galaxy NGC 3147.  Gas at the inner edge of this disk is so close to the black hole that it moves unusually fast -- at 10 percent of the speed of light. Gas this fast shows relativistic beaming, making the side of the disk heading toward us appear significantly brighter than the side moving away.  The animation is based on images of NGC 3147 made recently with the Hubble Space Telescope.    Astrophysicists: Browse 2,000+ codes in the Astrophysics Source Code Library
The Orion You Can Almost See (2019-08-21)

Do you recognize this constellation?  Although it is one of the most recognizable star groupings on the sky, this is a more full Orion than you can see -- an Orion only revealed with long exposure digital camera imaging and post-processing.  Here the cool red giant Betelgeuse takes on a strong orange tint as the brightest star at the lower left.  Orion's hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse on the upper right, and Bellatrix at the upper left. Lined up in Orion's belt are three stars all about 1,500 light-years away, born from the constellation's well-studied interstellar clouds. To the right of Orion's belt is a bright but fuzzy patch that might also look familiar -- the stellar nursery known as Orion's Nebula.  Finally, just barely visible to the unaided eye but quite striking here is Barnard's Loop -- a huge gaseous emission nebula surrounding Orion's Belt and Nebula discovered over 100 years ago by the pioneering Orion photographer E. E. Barnard.   APOD Podcasts: Available on iTunes and YouTube.

Image credit: John Gleason
&
Rogelio
Bernal Andreo
Nearby Spiral Galaxy NGC 4945 (2019-08-22)

Large spiral galaxy NGC 4945 is seen edge-on near the center of this cosmic galaxy portrait. In fact, it's almost the size of our Milky Way Galaxy. NGC 4945's own dusty disk, young blue star clusters, and pink star forming regions standout in the sharp, colorful telescopic image. About 13 million light-years distant toward the expansive southern constellation Centaurus, NGC 4945 is only about six times farther away than Andromeda, the nearest large spiral galaxy to the Milky Way. Though this galaxy's central region is largely hidden from view for optical telescopes, X-ray and infrared observations indicate significant high energy emission and star formation in the core of NGC 4945. Its obscured but active nucleus qualifies the gorgeous island universe as a Seyfert galaxy and home to a central supermassive black hole.

Image credit: Martin Pugh
NGC 1499: The California Nebula (2019-08-23)

Drifting through the Orion Arm of the spiral Milky Way Galaxy, this cosmic cloud by chance echoes the outline of California on the west coast of the United States. Our own Sun also lies within the Milky Way's Orion Arm, only about 1,500 light-years from the California Nebula. Also known as NGC 1499, the classic emission nebula is around 100 light-years long. The California Nebula shines with the telltale reddish glow characteristic of hydrogen atoms recombining with long lost electrons. The electrons have been stripped away, ionized by energetic starlight. Most likely providing the energetic starlight that ionizes much of the nebular gas is the bright, hot, bluish star Xi Persei just to the right of the nebula.  A popular target for astrophotographers, this deep California Nebula image is a 6 panel telecopic mosaic and covers a wide field of view. The nebula lies toward the constellation Perseus, not far from the Pleiades.

Image credit: Sara Wager
Millions of Stars in Omega Centauri (2019-08-24)

Globular star cluster Omega Centauri, also known as NGC 5139, is some 15,000 light-years away. The cluster is packed with about 10 million stars much older than the Sun within a volume about 150 light-years in diameter. It's the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way.

Image credit: Michael Miller
Leaving Earth (2019-08-25)

What it would look like to leave planet Earth? Such an event was recorded visually in great detail by the MESSENGER spacecraft as it swung back past the Earth in 2005 on its way in toward the planet Mercury. Earth can be seen rotating in this time-lapse video, as it recedes into the distance. The sunlit half of Earth is so bright that background stars are not visible. The robotic MESSENGER spacecraft is now in orbit around Mercury and has recently concluded the first complete map of the surface. On occasion, MESSENGER has continued to peer back at its home world. MESSENGER is one of the few things created on the Earth that has left and will never return -- at the end of its mission MESSENGER crashed into Mercury's surface.
NGC 2170: Angel Nebula Still Life (2019-08-26)

Is this a painting or a photograph? In this classic celestial still life composed with a cosmic brush, dusty nebula NGC 2170, also known as the Angel Nebula, shines near the image center. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection nebulae, a red emission region, many dark absorption nebulae, and a backdrop of colorful stars. Like the common household items that still life painters often choose for their subjects, the clouds of gas, dust, and hot stars featured here are also commonly found in this setting --  a massive, star-forming molecular cloud in the constellation of the Unicorn (Monoceros). The giant molecular cloud, Mon R2, is impressively close, estimated to be only 2,400 light-years or so away. At that distance, this canvas would be over 60 light-years across.

Image credit: Juan Lozano de Haro
Dark Dust and Colorful Clouds near Antares (2019-08-27)

Why is the sky near Antares and Rho Ophiuchi so dusty yet colorful?  The colors result from a mixture of objects and processes.  Fine dust illuminated from the front by starlight produces blue reflection nebulae. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. Backlit dust clouds block starlight and so appear dark.   Antares, a red supergiant and one of the brighter stars in the night sky, lights up the yellow-red clouds on the lower left of the featured image. Rho Ophiuchi lies at the center of the blue nebula near the top.   The distant globular cluster M4 is visible to the right of Antares. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum.
Messier 61 Close Up (2019-08-28)

Image data from the Hubble Space Telescope, the European Southern Observatory, and small telescopes on planet Earth are combined in this magnificent portrait of face-on spiral galaxy Messier 61 (M61). A mere 55 million light-years away in the Virgo Cluster of Galaxies, M61 is also known as NGC 4303. It's considered to be an example of a barred spiral galaxy similar to our own Milky Way. Like other spiral galaxies, M61 also features sweeping spiral arms, cosmic dust lanes, pinkish star forming regions, and young blue star clusters. The bright galactic core is offset to the left in this 50 thousand light-year wide close-up.
M27: Not a Comet (2019-08-29)

While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it's not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This impressive color composite highlights details within the well-studied central region and fainter, seldom imaged features in the nebula's outer halo. It incorporates broad and narrowband images recorded using filters sensitive to emission from hydrogen and oxygen atoms.

Image credit: Bob Franke
NGC 7129 and NGC 7142 (2019-08-30)

This wide-field telescopic image looks toward the constellation Cepheus and an intriguing visual pairing of dusty reflection nebula NGC 7129 (right) and open star cluster NGC 7142. The two appear separated by only half a degree on the sky, but they actually lie at quite different distances. In the foreground, dusty nebula NGC 7129 is about 3,000 light-years distant, while open cluster NGC 7142 is likely over 6,000 light-years away. In fact, pervasive and clumpy foreground dust clouds in this region redden the light from NGC 7142, complicating astronomical explorations of the cluster. Still, NGC 7142 is thought to be an older open star cluster, while the bright stars embedded in NGC 7129 are perhaps a few million years young. The telltale reddish crescent shapes around NGC 7129 are associated with energetic jets streaming away from newborn stars.

Image credit: Steve
Cannistra
Spitzer's Orion (2019-08-31)

Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Spanning about 40 light-years across the region, this infrared image from the Spitzer Space Telescope was constructed from data intended to monitor the brightness of the nebula's young stars, many still surrounded by dusty, planet-forming disks. Orion's young stars are only about 1 million years old, compared to the Sun's age of 4.6 billion years. The region's hottest stars are found in the Trapezium Cluster, the brightest cluster near picture center. Launched into orbit around the Sun on August 25, 2003 Spitzer's liquid helium coolant ran out in May 2009. The infrared space telescope continues to operate though, its mission scheduled to end on January 30, 2020. Recorded in 2010, this false color view is from two channels that still remain sensitive to infrared light at Spitzer's warmer operating temperatures.
M45: The Pleiades Star Cluster (2019-09-01)

Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city.  With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured exposure took over 12 hours and covers a sky area several times the size of the full moon.  Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus).  A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.

Image credit: Marco Lorenzi 
(Glittering Lights)
The Moon and Jupiter over the Alps (2019-09-02)

What are those bright lights in the sky ahead?  When hiking a high mountain pass in northern Italy three weeks ago, a conjunction between our Moon and the distant planet Jupiter was visible toward the south just after sunset. The picturesque mountains in the distance are Tre Cime di Lavaredo (Three Peaks of Lavaredo), a UNESCO World Heritage Site and three of the best known mountain peaks in Italy, the Dolomites, and the entire Alps. In the foreground on the left is Locatelli Hut, a refuge for tired hikers as it is located over an hour from nearest parking lot. The bright sky object on the upper left is Saturn.  The entire scene was captured on a single 8-second exposure.  Jupiter and Saturn will remain prominent in the southwestern sky after sunset this month, while the Moon, in its monthly orbit around the Earth, will pass near Jupiter again in about four days.

Image credit: Giorgia Hofer
(Cortina Astronomical Association)
Unusual Signal Suggests Neutron Star Destroyed by Black Hole (2019-09-03)

What created this unusual explosion? Three weeks ago, gravitational wave detectors in the USA and Europe -- the LIGO and Virgo detectors -- detected a burst of gravitational radiation that had the oscillating pattern expected when a black hole destroys a neutron star.  One object in event S190814bv was best fit with a mass greater than five times the mass of the Sun -- making it a good candidate for a black hole, while the other object appeared to have a mass less than three times the mass of the Sun -- making it a good candidate for a neutron star. No similar event had been detected with gravitational waves before.  Unfortunately, no light was seen from this explosion, light that might have been triggered by the disrupting neutron star. It is theoretically possible that the lower mass object was also a black hole, even though no clear example of a black hole with such a low mass is known. The featured video was created to illustrate a previously suspected black hole - neutron star collision detected in light in 2005, specifically gamma-rays from the burst GRB 050724. The animated video starts with a foreground neutron star orbiting a black hole surrounded by an accretion disk. The black hole's gravity then shreds the neutron star, creating a jet as debris falls into the black hole. S190814bv will continue to be researched, with clues about the nature of the objects involved possibly coming from future detections of similar systems.   Follow APOD in English on: Instagram, Facebook,  Reddit, or Twitter
The Spider Nebula in Infrared (2019-09-04)

Will the spider ever catch the fly? Not if both are large emission nebulas toward the constellation of the Charioteer (Auriga).  The spider-shaped gas cloud on the left is actually an emission nebula labelled IC 417, while a smaller fly-shaped cloud off the image to the left is dubbed  NGC 1931 and is both an emission nebula and a reflection nebula.  About 10,000 light-years distant, both nebulas harbor young, open star clusters. For scale, the more compact NGC 1931 (Fly) is about 10 light-years across. The featured picture in scientifically-assigned, infrared colors combines images from the Spitzer Space Telescope and the Two Micron All Sky Survey (2MASS).  Spitzer is celebrating its 16th year orbiting the Sun near the Earth.    APOD in other languages: Arabic, Catalan, Chinese (Beijing), Chinese (Taiwan), Croatian, Czech, Dutch, Farsi, French, French, German, Hebrew, Indonesian, Japanese, Korean, Montenegrin, Polish, Russian, Serbian, Slovenian,  Spanish and Ukrainian
The Large Cloud of Magellan (2019-09-05)

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

Image credit: Alessandro
Cipolat Bares
Recycling Cassiopeia A (2019-09-06)

Massive stars in our Milky Way Galaxy live spectacular lives.  Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant would have been first seen in planet Earth's sky about 350 years ago, although it took that light about 11,000 years to reach us. This false-color image, composed of X-ray and optical image data from the Chandra X-ray Observatory and Hubble Space Telescope, shows the still hot filaments and knots in the remnant. It spans about 30 light-years at the estimated distance of Cassiopeia A. High-energy X-ray emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help astronomers explore the recycling of our galaxy's star stuff. Still expanding, the outer blast wave is seen in blue hues. The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core.
In Wolf's Cave (2019-09-07)

The mysterious blue reflection nebula found in catalogs as VdB 152 or Ced 201 really is very faint. It lies at the tip of the long dark nebula Barnard 175 in a dusty complex that has also been called Wolf's Cave. At the center of this deep and widefield telescopic view, the cosmic apparitions are nearly 1,400 light-years away along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving the the nebula its characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. Another dense, obscuring dark nebula, LDN 1221, is easy to spot at the upper right in the frame, while the more colorful planetary nebula Dengel-Hartl 5 is just below center. Faint reddish emission from an ancient supernova remnant can also be traced (lower right to upper left) against the dust-rich complex in Cepheus.

Image credit: Charlie Bracken
Perijove 11: Passing Jupiter (2019-09-08)

Here comes Jupiter! NASA's robotic spacecraft Juno is continuing on its 53-day, highly-elongated orbits around our Solar System's largest planet.  The featured video is from perijove 11 in early 2018, the eleventh time Juno has passed near Jupiter since it arrived in mid-2016.  This time-lapse, color-enhanced movie covers about four hours and morphs between 36 JunoCam images. The video begins with Jupiter rising as Juno approaches from the north. As Juno reaches its closest view -- from about 3,500 kilometers over Jupiter's cloud tops -- the spacecraft captures the great planet in tremendous detail. Juno passes light zones and dark belt of clouds that circle the planet, as well as numerous swirling circular storms, many of which are larger than hurricanes on Earth.  After the perijove, Jupiter recedes into the distance, now displaying the unusual clouds that appear over Jupiter's south.  To get desired science data, Juno swoops so close to Jupiter that its instruments are exposed to very high levels of radiation.
M31: The Andromeda Galaxy (2019-09-09)

How far can you see? The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy, over two million light-years away.  Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda.  But a bright yellow nucleus, dark winding dust lanes, luminous blue spiral arms, and bright red emission nebulas are recorded in this stunning six-hour telescopic digital mosaic of our closest major galactic neighbor.  While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers seriously debated this fundamental concept only 100 years ago.  Were these "spiral nebulae" simply outlying gas clouds in our own Milky Way Galaxy or were they "island universes" -- distant galaxies of stars comparable to the Milky Way itself?  This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations favoring Andromeda being just like our Milky Way Galaxy -- a conclusion making the rest of the universe much more vast than many had ever imagined.

Image credit: Amir H. Abolfath 
(TWAN)
Pluto in True Color (2019-09-10)

What color is Pluto, really? It took some effort to figure out.  Even given all of the images sent back to Earth when the robotic New Horizons spacecraft sped past Pluto in 2015, processing these multi-spectral frames to approximate what the human eye would see was challenging. The result featured here, released three years after the raw data was acquired by New Horizons, is the highest resolution true color image of Pluto ever taken. Visible in the image is the light-colored, heart-shaped, Tombaugh Regio, with the unexpectedly smooth Sputnik Planitia, made of frozen nitrogen, filling its western lobe. New Horizons found the dwarf-planet to have a surprisingly complex surface composed of many regions having perceptibly different hues.  In total, though, Pluto is mostly brown, with much of its muted color originating from small amounts of surface methane energized by ultraviolet light from the Sun.