juliensimon/nasa-apod huggingface dataset:
Mars Methane Mystery Deepens (2019-04-22)

The methane mystery on Mars just got stranger. New results from ESA and Roscosmos' ExoMars Trace Gas Orbiter, has unexpectedly not detected methane in the atmosphere of Mars. This result follows the 2013 detection of methane by NASA's Curiosity rover, a result seemingly confirmed by ESA's orbiting Mars Express the next day.  The issue is so interesting because life is a major producer of methane on Earth, leading to intriguing speculation that some sort of life -- possibly microbial life -- is creating methane beneath the surface of Mars.  Non-biological sources of methane are also possible.  Pictured is a visualization of the first claimed methane plume over Mars as detected from Earth in 2003.  The new non-detection of methane by the ExoMars Orbiter could mean that Mars has some unexpected way of destroying methane, or that only some parts of Mars release methane -- and possibly only at certain times. As the mystery has now deepened, humanity's scrutiny of our neighboring planet's atmosphere will deepen as well.
Meteors, Comet, and Big Dipper over La Palma (2019-04-23)

Meteor showers are caused by streams of solid particles, dust size and larger, moving as a group through space.  In most cases, the orbits of these meteor streams can be identified with dust expelled from a comet.  When the Earth passes through a stream, the particles leave brilliant trails through the night sky as they disintegrate in Earth's atmosphere.  The meteor paths are all parallel to each other, but, like train tracks, the effect of perspective causes them to appear to originate from a radiant point in the distance.  The featured image composite was taken during January's Quadrantid meteor shower from La Palma, one of Spain's Canary Islands, off the northwest coast of Africa. The Quadrantids radiant is visible just below the handle of the Big Dipper. A careful eye will also discern the faint green coma of Comet Wirtanen.  Tonight is the peak of the modest Lyrid meteor shower, with several meteors per hour visible from dark locations with clear skies.

Image credit: Vincent Duparc
The Shape of the Southern Crab (2019-04-24)

The symmetric, multi-legged appearance of the Southern Crab Nebula is certainly distinctive. About 7,000 light-years distant toward the southern sky constellation Centaurus, its glowing nested hourglass shapes are produced by the remarkable symbiotic binary star system at its center. The nebula's dramatic stellar duo consists of a hot white dwarf star and cool, pulsating red giant star shedding outer layers that fall onto the smaller, much hotter companion. Embedded in a disk of material, outbursts from the white dwarf cause an outflow of gas driven away both above and below the disk resulting in the bipolar hourglass shapes. The bright central shape is about half a light-year across. This new Hubble Space Telescope image celebrates the 29th anniversary of Hubble's launch on April 24, 1990 on board the Space Shuttle Discovery.
Pan-STARRS Across the Lagoon (2019-04-25)

Ridges of glowing interstellar gas and dark dust clouds inhabit the turbulent, cosmic depths of the Lagoon Nebula. Also known as M8, the bright star forming region is about 5,000 light-years distant. But it still makes for a popular stop on telescopic tours of the constellation Sagittarius, toward the center of our Milky Way Galaxy. Dominated by the telltale red emission of ionized hydrogen atoms recombining with stripped electrons, this stunning view of the Lagoon is over 100 light-years across.  At its center, the bright, compact, hourglass shape is gas ionized and sculpted by energetic radiation and extreme stellar winds from a massive young star. In fact, the many bright stars of open cluster NGC 6530 drift within the nebula, just formed in the Lagoon several million years ago. Broadband image data from Pan-STARRS (Panoramic Survey Telescope & Rapid Response System) was combined with narrowband data from amateur telescopes to create this wide and deep portrait of the Lagoon Nebula.
Southern Cross to Eta Carinae (2019-04-26)

Tracking along the southern Milky Way this beautiful celestial mosaic was recorded under dark Brazilian skies. Spanning some 20 degrees it actually starts with the dark expanse of the Coalsack nebula at the lower left, tucked under an arm of the Southern Cross. That compact constellation is topped by bright yellowish Gamma Crucis, a cool giant star a mere 88 light-years distant. A line from Gamma Crucis through the blue star at the bottom of the cross, Alpha Crucis, points toward the South Celestial Pole. Follow the Milky Way to the right and your gaze will sweep across IC 2948, popularly known as the Running Chicken nebula, before it reaches Eta Carinae and the Carina Nebula near the right edge of the frame. About 200 light-years across, the Carina Nebula is a star forming region much larger than the more northerly stellar nursery the Orion Nebula. The Carina Nebula lies around 7,500 light-years from Earth along the plane of the Milky Way.

Image credit: Carlos Fairbairn
The Galaxy, the Jet, and the Black Hole (2019-04-27)

Bright elliptical galaxy Messier 87 (M87) is home to the supermassive black hole captured by planet Earth's Event Horizon Telescope in the first ever image of a black hole. Giant of the Virgo galaxy cluster about 55 million light-years away, M87 is the large galaxy rendered in blue hues in this infrared image from the Spitzer Space telescope.  Though M87 appears mostly featureless and cloud-like, the Spitzer image does record details of relativistic jets blasting from the galaxy's central region. Shown in the inset at top right, the jets themselves span thousands of light-years. The brighter jet seen on the right is approaching and close to our line of sight. Opposite, the shock created by the otherwise unseen receding jet lights up a fainter arc of material. Inset at bottom right, the historic black hole image is shown in context, at the center of giant galaxy and relativistic jets. Completely unresolved in the Spitzer image, the supermassive black hole surrounded by infalling material is the source of the enormous energy driving the relativistic jets from the center of active galaxy M87.
All of Mercury (2019-04-28)

Only six years ago, the entire surface of planet Mercury was finally mapped. Detailed observations of the innermost planet's surprising crust began when the robotic MESSENGER spacecraft first passed Mercury in 2008 and continued until its controlled crash landing in 2015.  Previously, much of the Mercury's surface was unknown as it is too far for Earth-bound telescopes to see clearly, while the Mariner 10 flybys in the 1970s observed only about half. The featured video is a compilation of thousands of images of Mercury rendered in exaggerated colors to better contrast different surface features. Visible on the rotating world are rays emanating from a northern impact that stretch across much of the planet, while about half-way through the video the light colored Caloris Basin rotates into view, a northern ancient impact feature that filled with lava. Recent analysis of MESSENGER data indicates that Mercury has a solid inner core.   Surf the Universe: Click here to see a randomly selected APOD!
N11: Star Clouds of the LMC (2019-04-29)

Massive stars, abrasive winds, mountains of dust, and energetic light sculpt one of the largest and most picturesque regions of star formation in the Local Group of Galaxies.  Known as N11, the region is visible on the upper right of many images of its home galaxy, the Milky Way neighbor known as the Large Magellanic Clouds (LMC).  The featured image was taken for scientific purposes by the Hubble Space Telescope and reprocessed for artistry by an amateur to win a Hubble's Hidden Treasures competition.  Although the section imaged above is known as NGC 1763, the entire N11 emission nebula is second in LMC size only to the Tarantula Nebula.  Compact globules of dark dust housing emerging young stars are also visible around the image.  A new study of variable stars in the LMC with Hubble has helped to recalibrate the distance scale of the  observable universe, but resulted in a slightly different scale than found using the pervasive cosmic microwave background.   Astrophysicists: Browse 1,900+ codes in the Astrophysics Source Code Library
Meteor Misses Galaxy (2019-04-30)

The galaxy was never in danger. For one thing, the Triangulum galaxy (M33), pictured, is much bigger than the tiny grain of rock at the head of the meteor. For another, the galaxy is much farther away -- in this instance 3 million light years as opposed to only about 0.0003 light seconds.  Even so, the meteor's path took it angularly below the galaxy. Also the wind high in Earth's atmosphere blew the meteor's glowing evaporative molecule train away from the galaxy, in angular projection.  Still, the astrophotographer was quite lucky to capture both a meteor and a galaxy in a single exposure -- which was subsequently added to two other images of M33 to bring up the spiral galaxy's colors.  At the end, the meteor was gone in a second, but the galaxy will last billions of years.    Follow APOD on: Instagram, Facebook,  Reddit, or Twitter
The Cat's Eye Nebula in Optical and X-ray (2019-05-01)

To some it looks like a cat's eye. To others, perhaps like a giant cosmic conch shell.  It is actually one of brightest and most highly detailed planetary nebula known, composed of gas expelled in the brief yet glorious phase near the end of life of a Sun-like star. This nebula's dying central star may have produced the outer circular concentric shells by shrugging off outer layers in a series of regular convulsions. The formation of the beautiful, complex-yet-symmetric inner structures, however, is not well understood. The featured image is a composite of a digitally sharpened Hubble Space Telescope image with X-ray light captured by the orbiting Chandra Observatory.  The exquisite floating space statue spans over half a light-year across. Of course, gazing into this Cat's Eye, humanity may well be seeing the fate of our sun, destined to enter its own planetary nebula phase of evolution ... in about 5 billion years.
Manicouagan Impact Crater from Space (2019-05-02)

Orbiting 400 kilometers above Quebec, Canada, planet Earth, the International Space Station Expedition 59 crew captured this snapshot of the broad St. Lawrence River and curiously circular Lake Manicouagan on April 11. Right of center, the ring-shaped lake is a modern reservoir within the eroded remnant of an ancient 100 kilometer diameter impact crater. The ancient crater is very conspicuous from orbit, a visible reminder that Earth is vulnerable to rocks from space. Over 200 million years old, the Manicouagan crater was likely caused by the impact of a rocky body about 5 kilometers in diameter.  Currently, there is no known asteroid with a significant probability of impacting Earth in the next century.  But a fictional scenario to help practice for an asteroid impact is on going at the 2019 IAA Planetary Defense Conference.
Clouds of the Large Magellanic Cloud (2019-05-03)

The Large Magellanic Cloud (LMC) is an alluring sight in southern skies. But this deep and detailed telescopic view, over 10 months in the making, goes beyond what is visible to most circumnavigators of planet Earth. Spanning over 5 degrees or 10 full moons, the 4x4 panel mosaic was constructed from 3900 frames with a total of 1,060 hours of exposure time in both broadband and narrowband filters. The narrowband filters are designed to transmit only light emitted by sulfur, hydrogen, and oxygen atoms. Ionized by energetic starlight, the atoms emit their characteristic light as electrons are recaptured and the atoms transition to a lower energy state. As a result, in this image the LMC seems covered with its own clouds of ionized gas surrounding its massive, young stars. Sculpted by the strong stellar winds and ultraviolet radiation, the glowing clouds, dominated by emission from hydrogen, are known as H II (ionized hydrogen) regions. Itself composed of many overlapping H II regions, the Tarantula Nebula is the large star forming region at the left. The largest satellite of our Milky Way Galaxy, the LMC is about 15,000 light-years across and lies a mere 160,000 light-years away toward the constellation Dorado.

Image credit: Team Ciel Austral
Saturn and the Da Vinci Glow (2019-05-04)

On February 2nd early morning risers saw Saturn near an old Moon low on the eastern horizon. On that date bright planet, sunlit crescent, and faint lunar night side were captured in this predawn skyscape from Bursa, Turkey. Of course the Moon's ashen glow is earthshine, earthlight reflected from the Moon's night side. A description of earthshine, in terms of sunlight reflected by Earth's oceans illuminating the Moon's dark surface, was written over 500 years ago by Leonardo da Vinci. On May 2nd an old Moon also rose in the predawn twilight. On that date its ashen glow shared the sky with Venus, the brilliant morning star. May 2nd also marked the 500th anniversary of Leonardo's death in 1519.

Image credit: Tunc Tezel
Saturn, Titan, Rings, and Haze (2019-05-05)

This is not a solar eclipse. Pictured here is a busy vista of moons and rings taken at Saturn. The large circular object in the center of the image is Titan, the largest moon of Saturn and one of the most intriguing objects in the entire Solar System. The dark spot in the center is the main solid part of the moon.  The bright surrounding ring is atmospheric haze above Titan, gas that is scattering sunlight to a camera operating onboard the robotic Cassini spacecraft. Cutting horizontally across the image are the rings of Saturn, seen nearly edge on.  At the lower right of Titan is Enceladus, a small moon of Saturn. Since the image was taken pointing nearly at the Sun, the surfaces of Titan and Enceladus appear in silhouette, and the rings of Saturn appear similar to a photographic negative. Now if you look really really closely at Enceladus, you can see a hint of icy jets shooting out toward the bottom of the image. It is these jets that inspired future proposals to land on Enceladus, burrow into the ice, and search for signs of extraterrestrial life.
Virtual Flyby of the Whirlpool Galaxy (2019-05-06)

What would it look like to fly over a spiral galaxy? To help visualize this, astronomers and animators at the Space Telescope Science Institute computed a virtual flyby of the Whirlpool Galaxy (M51) using data and images from the Hubble Space Telescope.  At only 25 million light years distant and fully 50 thousand light years across, the Whirlpool is one of the brightest and most picturesque galaxies on the sky. Visible during the virtual flyby are spiral arms dominated by young blue stars, older lighter-colored stars, dark lanes of dust, and bright red emission nebulae. Many galaxies far in the distance can be seen right through M51.  The visualization should be considered a time-lapse, because otherwise the speed of the virtual camera would need to be very near the speed of light.
The Great Nebula in Carina (2019-05-07)

What's happening in the center of the Carina Nebula?  Stars are forming, dying, and leaving an impressive tapestry of dark dusty filaments.  The entire Carina Nebula, cataloged as NGC 3372, spans over 300 light years and lies about 8,500 light-years away in the constellation of Carina. The nebula is composed predominantly of hydrogen gas, which emits the pervasive red glow seen in this highly detailed featured image.  The blue glow in the center is created by a trace amount of glowing oxygen. Young and massive stars located in the nebula's center expel dust when they explode in supernovae.  Eta Carinae, the most energetic star in the nebula's center, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.

Image credit: Dieter Willasch
(Astro-Cabinet)
Jupiter Marble from Juno (2019-05-08)

What does Jupiter look like up close? Most images of Jupiter are taken from far away, either from Earth or from a great enough distance that nearly half the planet is visible. This shot, though, was composed from images taken relatively close in, where less than half of the planet was visible.  From here, Jupiter still appears spherical but perspective distortion now makes it look more like a marble. Visible on Jupiter's cloud tops are a prominent dark horizontal belt containing a white oval cloud, and a white zone cloud, both of which circle the planet. The Great Red Spot looms on the upper right. The featured image was taken by the robotic Juno spacecraft in February during its 17th close pass of our Solar System's largest planet.  Juno's mission, now extended into 2021, is to study Jupiter in new ways. Juno's data has already enabled discoveries that include Jupiter's magnetic field being surprisingly lumpy, and that some of Jupiter's cloud systems run about 3,000 kilometers into the planet.
Messier 5 (2019-05-09)

"Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..." begins the description of the 5th entry in 18th century astronomer Charles Messier's famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one of the oldest globulars, its stars estimated to be nearly 13 billion years old. The beautiful star cluster is a popular target for earthbound telescopes. Even close to its dense core, the cluster's red and blue giant stars, and rejuvenated blue stragglers stand out with yellowish and blue hues in this sharp color image.

Image credit: Adam Block
Halley Dust and Milky Way (2019-05-10)

Grains of cosmic dust streaked through the mostly moonless night skies of May 7. Swept up as planet Earth plowed through the debris streams left behind by periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. Though it was made about a day after the shower's predicted maximum, this composite image still captures 20 meteors in exposures taken over a 2 hour period, registered on a background exposure of the sky. The meteor trails point back to the shower radiant near eponymous faint star Eta Aquarii close to the horizon, seen from 100 kilometers south of Sydney Australia. Known for speed, Eta Aquarid meteors move fast, entering the atmosphere at about 66 kilometers per second. Brilliant Jupiter shines near the central bulge of the Milky Way high above the horizon. The Southern Cross is just tucked in to the upper right corner of the frame.

Image credit: Gang Li
Milky Way, Launch, and Landing (2019-05-11)

The Milky Way doesn't look quite this colorful and bright to the eye, but a rocket launch does. So a separate deep exposure with a sensitive digital camera was used in this composite skyscape to bring out our galaxy's central crowded starfields and cosmic dust clouds. In the scene from Merritt Island National Wildlife Refuge, a nine minute long exposure begun about 20 minutes after the Miky Way image recorded a rocket launch and landing. The Falcon 9 rocket, named for the Millennium Falcon of Star Wars fame, appropriately launched a Dragon resupply ship to the International Space Station in the early morning hours of May the 4th. The plume and flare at the peak of the launch arc mark the rocket's first stage boost back burn. Two shorter diagonal streaks are the rocket engines bringing the Falcon 9 stage back to an offshore landing on autonomous drone ship Of course I Still Love You.

Image credit: Devin Boggs
Ash and Lightning above an Icelandic Volcano (2019-05-12)

Why did a picturesque volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well-populated areas. The Eyjafjallaj�kull volcano in southern Iceland began erupting on 2010 March 20, with a second eruption starting under the center of a small glacier on 2010 April 14. Neither eruption was unusually powerful.  The second eruption, however, melted a large amount of glacial ice which then cooled and fragmented lava into gritty glass particles that were carried up with the rising volcanic plume.  Pictured here during the second eruption, lightning bolts illuminate ash pouring out of the Eyjafjallaj�kull volcano.    Follow APOD on: Instagram, Facebook,  Reddit, or Twitter

Image credit: Sigur�ur Stefnisson
Rho Ophiuchi Wide Field (2019-05-13)

The colorful clouds surrounding the star system Rho Ophiuchi compose one of the closest star forming regions.  Rho Ophiuchi itself is a binary star system visible in the blue reflection nebula just to the left of the image center.  The star system, located only 400 light years away, is distinguished by its multi-colored surroundings, which include a red emission nebula and numerous light and dark brown dust lanes. Near the lower left of the Rho Ophiuchi molecular cloud system is the yellow star Antares, while a distant but coincidently-superposed globular cluster of stars, M4, is visible just to the right of Antares. Near the image top lies IC 4592, the Blue Horsehead nebula.  The blue glow that surrounds the Blue Horsehead's eye -- and other stars around the image -- is a reflection nebula composed of fine dust. On the featured image right is a geometrically angled reflection nebula cataloged as Sharpless 1.  Here, the bright star near the dust vortex creates the light of surrounding reflection nebula. Although most of these features are visible through a small telescope pointed toward the constellations of Ophiuchus, Scorpius, and Sagittarius, the only way to see the intricate details of the dust swirls, as featured above, is to use a long exposure camera.

Image credit: Mario Cogo 
(Galax Lux)
Young Star Cluster Trumpler 14 from Hubble (2019-05-14)

Why does star cluster Trumpler 14 have so many bright stars? Because it is so young. Many cluster stars have formed only in the past 5 million years and are so hot they emit detectable X-rays.  In older star clusters, most stars this young have already died -- typically exploding in a supernova -- leaving behind stars that are fainter and redder. Trumpler 14 spans about 40 light years and lies about 9,000 light years away on the edge of the famous Carina Nebula. A discerning eye can spot two unusual objects in this detailed 2006 image of Trumpler 14 by the Hubble Space Telescope. First, a dark cloud just left of center may be a planetary system trying to form before being destroyed by the energetic winds of Trumpler 14's massive stars. Second is the arc at the bottom left, which one hypothesis holds is the supersonic shock wave of a fast star ejected 100,000 years ago from a completely different star cluster.