juliensimon/nasa-apod huggingface dataset:
M86 in the Virgo Cluster (2008-04-25)

Bright lenticular galaxy M86 is near center of this cosmic view, at the heart of the Virgo Galaxy Cluster. Other bright galaxies in the neighborhood include M84 at the upper right, edge-on spiral NGC4388 near the right edge, a striking pair of interacting galaxies, Markarian's Eyes, in the lower left corner, and edge-on spiral NGC 4402 at about 11 o'clock. With well over a thousand members, the Virgo Cluster is the closest large cluster of galaxies. On average the cluster galaxies are measured to be about 50 million light-years away. The entire Virgo Cluster is difficult to appreciate because it covers such a large area, spanning over 10 degrees on the sky. This cluster close-up covers a region just under 1 degree wide or about 1.5 times the size of the full moon.

Image credit: Sierra
Remote Observatories
The Tarantula Zone (2008-04-26)

The Tarantula Nebula is more than 1,000 light-years in diameter -- a giant star forming region within our neighboring galaxy the Large Magellanic Cloud (LMC). That cosmic arachnid lies at the upper left of this expansive mosiac covering a part of the LMC over 6,000 light-years across. Within the Tarantula (NGC 2070), intense radiation, stellar winds and supernova shocks from the central young cluster of massive stars, cataloged as R136, energize the nebular glow and shape the spidery filaments. Around the Tarantula are other violent star-forming regions with young star clusters, filaments and bubble-shaped clouds. The small but expanding remnant of supernova 1987a, the closest supernova in modern history, is located near the center of the view. The rich field is about as wide as four full moons on the sky, located in the southern constellation Dorado.

Image credit: Robert Gendler
The Galactic Center Radio Arc (2008-04-27)

What causes this unusual structure near the center of our Galaxy? The long parallel rays slanting across the top of the above radio image are known collectively as the Galactic Center Radio Arc and jut straight out from the Galactic plane.  The Radio Arc is connected to the Galactic center by strange curving filaments known as the Arches.  The bright radio structure at the bottom right likely surrounds a black hole at the Galactic center and is known as Sagittarius A*.  One origin hypothesis holds that the Radio Arc and the Arches have their geometry because they contain hot plasma flowing along lines of constant magnetic field.  Images from the Chandra X-ray Observatory appear to show this plasma colliding with a nearby cloud of cold gas.
Star Forming Region NGC 3582 (2008-04-28)

What's happening in the NGC 3582 nebula?  Bright stars and interesting molecules are forming. The complex nebula resides in the star forming region called RCW 57.  Visible in this image are dense knots of dark interstellar dust, bright stars that have formed in the past few million years, fields of glowing hydrogen gas ionized by these stars, and great loops of gas expelled by dying stars. A recent detailed study of NGC 3582 uncovered at least 33 massive stars in the end stages of formation, and the clear presence of the complex carbon molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs are thought to be created in the cooling gas of star forming regions, and their development in the Sun's formation nebula five billion years ago may have been an important step in the development of life on Earth. This picture was taken last year with the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO), in Chile.

Image credit: T. A. Rector
Airplane Flight Patterns over the USA (2008-04-29)

What are these Earthlings going?  Millions of people move about planet Earth by airplane every day.  Hundreds of thousands of airplane flights take place over the US every day.  A dramatic graphical depiction of these flights was created by Aaron Koblin and is shown above.  Clicking on the above image will bring up a movie in many web browsers, a movie that might better be visible here. The movie depicts flight patterns that occurred over a few days in 2005 March.  The count on the lower left shows the number of USA-related flights at the time listed on the lower right.  The trails shown are not contrails but rather generated artificially by a computer algorithm. Major cities in North America and the USA are discernable. Inspection of the movie shows that some times of the day are busier than others, indicating that flights leave some destinations at times that are convenient for travelers. In terms of distance, flying to a distant location is much safer than driving to that location.  Flying in an airplane, however, remains slightly more dangerous than driving to a nearby airport.

Image credit: Aaron Koblin,
FAA
Arp 272 (2008-04-30)

Linking spiral arms, two large colliding galaxies are featured in this Hubble Space Telescope view, part of a series of cosmic snapshots released to celebrate the Hubble's 18th anniversary. Recorded in astronomer Halton Arp's Atlas of Peculiar Galaxies as Arp 272, the pair is otherwise known as NGC 6050 and IC 1179. They lie some 450 million light-years away in the Hercules Galaxy Cluster. At that estimated distance, the picture spans over 150 thousand light-years. Although this scenario does look peculiar, galaxy collisions and their eventual mergers are now understood to be common, with Arp 272 representing a stage in this inevitable process. In fact, the nearby large spiral Andromeda Galaxy is known to be approaching our own galaxy and Arp 272 may offer a glimpse of the far future collision between Andromeda and the Milky Way.
The Giants of Omega Centauri (2008-05-01)

Globular star cluster Omega Centauri is some 15,000 light-years away and 150 light-years in diameter. Packed with about 10 million stars, Omega Cen is the largest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. This intriguing color picture combines a visible light image of the cluster in blue hues with infrared image data from the Spitzer Space Telescope. The Spitzer data includes images in two infrared bands, one shown in green and one in red. Both infrared bands are sensitive to light from the cool, giant stars in the cluster. Adding the red and green colors together creates yellow, showing off the cluster's giant stars as yellow spots. Of course, red spots also indicate cool, giant stars in the image, but some of the red spots are even more distant background galaxies. Also known simply as Red Giant Stars, they represent a stage in the life-cycle of stars more evolved than our own Sun, a stage the Sun will reach in about 5 billion years. Dust grains formed in the atmospheres of cool, giant stars are ultimately involved in the formation of other stars and planets.
Shaping NGC 6188 (2008-05-02)

Dark shapes with bright edges winging their way through dusty NGC 6188 are tens of light-years long. The emission nebula is found near the edge of an otherwise dark large molecular cloud in the southern constellation Ara, about 4,000 light-years away. Formed in that region only a few million years ago, the massive young stars of the embedded Ara OB1 association sculpt the fantastic shapes and power the nebular glow with stellar winds and intense ultraviolet radiation. The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas. A false-color Hubble palette was used to create the this gorgeous wide-field image and shows emission from sulfur, hydrogen, and oxygen atoms in red, green, and blue hues. At the estimated distance of NGC 6188, the picture spans about 300 light-years.

Image credit: John Ebersole
Alborz Mountain Milky Way (2008-05-03)

Snow-capped stratovolcano Mt. Damavand climbs to 5,670 meters (18,598 feet) near the left edge in this panoramic view of the world at night. In the sky to the left of Damavand's peak are the stars of the Big Dipper in Ursa Major. Pan to the right and your gaze will sweep across the arch of our Milky Way Galaxy above the Alborz Mountain Range bordering the Caspian Sea. Near the center of the panorama, recorded in the predawn hours of April 4th, bright stars Deneb and Altair lie close to the curve of the Milky Way, above the glow of the Haraz valley. Farther right, brilliant Jupiter dominates the sky near the stars, nebulae, and dark dust clouds toward the bulging galactic center. Finally, the horizon glow at the right edge, below bright yellowish giant star Antares, is from the city of Damavand, named for the legendary mountain peak.

Image credit: Babak Tafreshi
An Antarctic Total Solar Eclipse (2008-05-04)

The Sun, the Moon, Antarctica, and two photographers all lined up in 2003  Antarctica during an unusual total eclipse of the Sun.  Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon.  One of the treasures collected was the above picture -- a composite of four separate images digitally combined to realistically simulate how the adaptive human eye saw the eclipse.  As the image was taken, both the Moon and the Sun peaked together over an Antarctic ridge.  In the sudden darkness, the magnificent corona of the Sun became visible around the Moon.  Quite by accident, another photographer was caught in one of the images checking his video camera.   Visible to his left are an equipment bag and a collapsible chair.

Image credit: Fred Bruenjes 
(moonglow.net)
A Persistent Electrical Storm on Saturn (2008-05-05)

How do large storms evolve on Saturn? On Earth, a hurricane can persist for weeks, while the Great Red Spot on Jupiter has been in existence for over 150 years. On Saturn, a storm system has now set a new endurance record, now being discernable for greater than three months.  Electrical signals were detected from the storm in late November of 2007, while the above image was taken in early March 2008.  The storm has roughly the width of planet Earth.  Planetary scientists hypothesize that the storm runs deep into Saturn's cloud tops.  The above image is shown in exaggerated colors combining violet and green light with light normally too red for humans to see. Visible on the upper right are shadows of Saturn's expansive ring system.  Careful inspection will reveal Saturn's small moon Janus just below a ring shadow.  Understanding weather on other planets helps atmospheric scientists better understand our Earth's weather.  Observers of our Solar System's huge ringed world will be tracking the storm to see how it evolves and how long it will ultimately last.
Galaxies Collide in NGC 3256 (2008-05-06)

Galaxies don't normally look like this.  NGC 3256 actually shows a current picture of two galaxies that are slowly colliding.   Quite possibly, in hundreds of millions of years, only one galaxy will remain.  Today, however, NGC 3256 shows intricate filaments of dark dust, unusual tidal tails of stars, and a peculiar center that contains two distinct nuclei.  Although it is likely that no stars in the two galaxies will directly collide, the gas, dust, and ambient magnetic fields do interact directly.  NGC 3256, part of the vast Hydra-Centaurus supercluster of galaxies, spans over 100 thousand light-years across and is located about 100 million light-years away.
The Gegenschein Over Chile (2008-05-07)

Is the night sky darkest in the direction opposite the Sun? No. In fact, a rarely discernable faint glow known as the gegenschein (German for "counter glow") can be seen 180 degrees around from the Sun in an extremely dark sky. The gegenschein is sunlight back-scattered off small interplanetary dust particles.  These dust particles are millimeter sized splinters from asteroids and orbit in the ecliptic plane of the planets.  Pictured above from last October is one of the most spectacular pictures of the gegenschein yet taken. Here a deep exposure of an extremely dark sky over Paranal Observatory in Chile shows the gegenschein so clearly that even a surrounding glow is visible.   In the foreground are several of the European Southern Observatory's Very Large Telescopes, while notable background objects include the Andromeda galaxy toward the lower left and the Pleiades star cluster just above the horizon.  The gegenschein is distinguished from zodiacal light near the Sun by the high angle of reflection.  During the day, a phenomenon similar to the gegenschein called the glory can be seen in reflecting air or clouds opposite the Sun from an airplane.

Image credit: Yuri Beletsky
(ESO)
The Dark Tower in Scorpius (2008-05-08)

In silhouette against a crowded star field toward the constellation Scorpius, this dusty cosmic cloud evokes for some the image of an ominous dark tower. In fact, clumps of dust and molecular gas collapsing to form stars may well lurk within the dark nebula, a structure that spans almost 40 light-years across the gorgeous telescopic view. Known as a cometary globule, the swept-back cloud, extending from the upper right to the head (top of the tower) left and below center, is shaped by intense ultraviolet radiation from the OB association of very hot stars in NGC 6231, off the left edge of the scene. That energetic ultraviolet light also powers the globule's bordering reddish glow of hydrogen gas. Hot stars embedded in the dust can be seen as small bluish reflection nebulae. This dark tower, NGC 6231, and associated nebulae are about 5,000 light-years away.

Image credit: Robert Gendler
Moon Meets Mercury (2008-05-09)

On Tuesday, May 6, while standing on planet Earth and sweeping your binoculars along the western horizon just after sunset, you might have encountered this arresting skyscape. The view features a slender crescent Moon and bright planet Mercury separated on the sky by only about 2 degrees. Cradled in the sunlit lunar crescent, the night side of the Moon is faintly illuminated by earthshine -- sunlight reflected from planet Earth. Of course, the clouds in silhouette and fading twilight colors are common elements in pictures of the sky after sunset, but much less often seen is inner planet Mercury, usually hiding close to the Sun in Earth's sky. Still, the coming week will be a good time to spot Mercury near the western horizon about 30 minutes after sunset. As for the Moon, tonight and tomorrow night the crescent Moon will wander close to Mars in the early evening sky.

Image credit: Clear Skies
Stars and Mars (2008-05-10)

Wandering through the evening sky, on May 4th planet Mars stood in line with Castor and Pollux, the two bright stars of the constellation Gemini.  In this time exposure of the celestial alignment, Mars actually takes on a distinct yellowish hue, contrasting in color with Pollux; a giant star known to have a Jupiter-class planet, and Castor; itself a multiple star system. Though in mythology Pollux and Castor are twin brothers, the two stars are physically unrelated and are about 34 and 50 light-years distant respectively. Included in the skyview are Procyon, alpha star of Canis Minor, and famous star cluster M44 also known as the Beehive Cluster. Dust in our own solar system reflecting sunlight creates the faint band of Zodiacal light emerging from the lower right corner of the frame. Just put your cursor over the picture for help with identifications. Of course, bright Mars can still be found in the western evening skies and tonight wanders near the crescent Moon.

Image credit: Doug Zubenel
Retrograde Mars (2008-05-11)

Why would Mars appear to move backwards?  Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars.  About every two years, however, the Earth passes Mars as they orbit around the Sun.  During the most recent such pass over the last year, the proximity of Mars made the red planet appear larger and brighter than usual.  Also during this time, Mars appeared to move backwards in the sky, a phenomenon called retrograde motion.  Pictured above is a series of images digitally stacked so that all of the stars images coincide.  Here, Mars appears to trace out a loop in the sky.  Near the top of the loop, Earth passed Mars and the retrograde motion was the highest.  Retrograde motion can also be seen for other Solar System planets.

Image credit: Tunç Tezel
The M81 Galaxy Group Through the Integrated Flux Nebula (2008-05-12)

Large galaxies and faint nebulae highlight this deep image of the M81 Group of galaxies.  First and foremost in the wide-angle 12-hour exposure is the grand design spiral galaxy M81, the largest galaxy visible in the image.  M81 is gravitationally interacting with M82 just below it, a big galaxy with an unusual halo of filamentary red-glowing gas.  Around the image many other galaxies from the M81 Group of galaxies can be seen.  Together with other galaxy congregates including our Local Group of galaxies and the Virgo Cluster of galaxies, the M81 Group is part of the expansive Virgo Supercluster of Galaxies.  This whole galaxy menagerie is seen through the faint glow of an Integrated Flux Nebula, a little studied complex of diffuse gas and dust clouds in our Milky Way Galaxy.

Image credit: Jordi Gallego
Ancient Craters of Southern Rhea (2008-05-13)

Saturn's ragged moon Rhea has one of the oldest surfaces known.  Estimated as changing little in the past billion years, Rhea shows craters so old they no longer appear round � their edges have become compromised by more recent cratering.   Like Earth's Moon, Rhea's rotation is locked on Saturn, and the above image shows part of Rhea's surface that always faces Saturn.  Rhea's leading surface is more highly cratered than its trailing surface.   Rhea is composed mostly of water-ice but is thought to include about 25 percent rock and metal.  The above image was taken by the robot Cassini spacecraft now orbiting Saturn.   Cassini swooped past Rhea last month and captured the above image from about 350,000 kilometers away.  Rhea spans 1,500 kilometers making it Saturn's second largest moon after Titan.  Several surface features on Rhea remain unexplained including large light patches like those seen near the image top.
A Supply Ship Docks with the International Space Station (2008-05-14)

Looking out a window of the International Space Station brings breathtaking views.  Visible vistas include a vast and colorful Earth, a deep dark sky, and an occasional spaceship sent to visit the station.  Visible early last month was a Soyuz TMA-12 spacecraft carrying not only supplies but also three newcomers.   The three new astronauts were Expedition 17 commander Sergei Volkov, flight engineer Oleg Kononenko, and spaceflight participant So-yeon Yi.  Yi returned to Earth a few days later, while Volkov and Konenenko are scheduled to return in a few months.   The docking module pictured above involved the Pirs Docking Compartment.   The Expedition 17 crew, including NASA flight engineer  Gregory Chamitoff, will carry out repairs on the ISS, explore new methods of living in space, and conduct research in space including the effects of space radiation on vitamin molecules.
Sideways Galaxy NGC 3628 (2008-05-15)

Dark dust lanes cut across the middle of this gorgeous island universe, a strong hint that NGC 3628 is a spiral galaxy seen sideways. About 35 million light-years away in the northern springtime constellation Leo, NGC 3628 also bears the distinction of being the only member of the well known Leo triplet of galaxies not in Charles Messier's famous catalog. Otherwise similar in size to our Milky Way Galaxy, the disk of NGC 3628 is clearly seen to fan out near the edges. A faint arm of material also extends to the left in this sharp and deep view of the region. The distorted shape and faint tidal tail suggest that NGC 3628 is interacting gravitationally with the other spiral galaxies in the Leo triplet, M66 and M65.

Image credit: Keith Quattrocchi
Circles in the Sky (2008-05-16)

Gazing skyward on a sunny day in May, photographer Jean-Marc Lecleire captured this engaging display of ice halos forming complete circles in the sky. Recorded with a fish-eye lens from a spot near the grand Château de Chambord in France, the picture looks straight up, spanning almost 180 degrees from horizon to horizon. Surrounding the Sun is a halo formed by sunlight refracting through hexagonal-shaped ice crystals in high, thin clouds. The halo is circular and exactly 22 degrees in radius, but it looks squashed because of the distortion of the extremely wide-angle lens. Surrounding the zenith (the point directly above the observer) and always at the same altitude as the Sun is a lovely parhelic circle, caused by sunlight reflecting from ice crystals with nearly vertical faces. On average more common than rainbows, beautiful ice halos can often be seen in planet Earth's sky by those who know how to look for them.

Image credit: Jean-Marc Lecleire
Logarithmic Spirals (2008-05-17)

Uncomfortably close Typhoon Rammasun (right) and 25 million light-year distant galaxy M101 don't seem to have much in common. For starters, Rammasun was only a thousand kilometers or so across while M101 (aka the Pinwheel Galaxy) spans about 170,000 light-years, making them vastly dissimilar in scale, not to mention the different physical environments that control their formation and development. But they do look amazingly alike: each with arms exhibiting the shape of a simple and beautiful mathematical curve known as a logarithmic spiral, a spiral whose separation grows in a geometric way with increasing distance from the center. Also known as the equiangular spiral, growth spiral, and Bernoulli's spiral or spira mirabilis, this curve's rich properties have fascinated mathematicians since its discovery by 17th century philosopher Descartes. Intriguingly, this abstract shape is much more abundant in nature than suggested by the striking visual comparison above. For example, logarithmic spirals can also describe the tracks of subatomic particles in a bubble chamber, the arrangement of sunflower seeds and, of course, cauliflower.
On the Origin of Gold (2008-05-18)

Where did the gold in your jewelry originate?  No one is completely sure.  The relative average abundance in our Solar System appears higher than can be made in the early universe, in stars, and even in typical supernova explosions.  Some astronomers have recently suggested that neutron-rich heavy elements such as gold might be most easily made in rare  neutron-rich explosions such as the collision of neutron stars.  Pictured above is an artist's illustration depicting two neutron stars spiraling in toward each other, just before they collide.  Since neutron star collisions are also suggested as the origin of short duration gamma-ray bursts, it is possible that you already own a souvenir from one of the most powerful explosions in the universe.
Flying Over the Columbia Hills of Mars (2008-05-19)

What it would be like to fly over Mars? Combining terrain data from the orbiting Mars Reconnaissance Orbiter spacecraft with information about the robotic Spirit rover currently rolling across Mars has resulted in a digital movie that shows what a flight over the Columbia Hills might look like.  Dark rippled sand dunes are highlighted against the Columbia Hills in the above opening image.  Clicking on the above image, though, will launch you across Mars, approaching the Columbia Hills.  On the far side of the hills, the dark sand dunes come into view.   Soon you pass an unusual white-rimmed structure, slightly raised, known as Home Plate, the origin of which is currently unknown and being researched.  Turning, you re-approach the hills from a different angle, this time zooming in on Spirit, a curious alien rover sent from planet Earth.  A final zoom pans out over the region.  This coming Sunday, NASA's Phoenix Lander will attempt to set down near the icy North Pole of Mars and search for signs of ancient life.