juliensimon/nasa-apod huggingface dataset:
The Dark Tower in Scorpius (2010-06-24)

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 lower left to the head (top of the tower) right and above center, is shaped by intense ultraviolet radiation from the OB association of very hot stars in NGC 6231, off the right 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 bluish reflection nebulae. This dark tower, NGC 6231, and associated nebulae are about 5,000 light-years away.

Image credit: tvdavisastropix.com
The Starry Night of Alamut (2010-06-25)

A meteor's streak and the arc of the Milky Way hang over the imposing mountain fortress of Alamut in this starry scene. Found in the central Alborz Mountains of Iran, Alamut Castle was built into the rock in the 9th century. The name means Eagle's Nest. Home of the legendary Assassins featured in the adventure movie Prince of Persia, Alamut was also historically a center for libraries and education. For a time, it was the residence of important 13th century Persian scholar and astronomer Nasir al-Din al-Tusi. To identify the stars in a night sky Tusi certainly pondered, just slide your cursor over the image. Highlights include bright white stars Deneb (in Cygnus), Vega, and Altair, nebulae near the Galactic Center, and the dark obscuring dust clouds of the Milky Way also known as the Great Rift. Lights at the lower right are from small villages and the capital Tehran, over 100 kilometers away to the southwest.

Image credit: Babak Tafreshi
Young Star Cluster Westerlund 2 (2010-06-26)

Dusty stellar nursery RCW 49 surrounds young star cluster Westerlund 2 in this remarkable composite skyscape from beyond the visible spectrum of light. Infrared data from the Spitzer Space Telescope is shown in black and white, complementing the Chandra X-ray image data (in false color) of the hot energetic stars within the cluster's central region. Looking toward the grand southern constellation Centaurus, both views reveal stars and structures hidden from optical telescopes by obscuring dust. Westerlund 2 itself is a mere 2 million years old or less, and contains some of our galaxy's most luminous, massive and therefore short-lived stars. The infrared signatures of proto-planetary disks have also been identified in the intense star forming region. At the cluster's estimated distance of 20,000 light-years, the square marking the Chandra field of view would be about 50 light-years on a side.   Curious about the Universe?: Download a free online astronomy lecture.
All the Colors of the Sun (2010-06-27)

It is still not known why the Sun's light is missing some colors. Shown above are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device.  The above spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our white-appearing Sun emits light of nearly every color, it does indeed appear brightest in yellow-green light.  The dark patches in the above spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below.  Since different types of gas absorb different colors of light, it is possible to determine what gasses compose the Sun.  Helium, for example, was first discovered in 1870 on a solar spectrum and only later found here on Earth.  Today, the majority of spectral absorption lines have been identified - but not all.

Image credit: Nigel Sharp
A Partial Lunar Eclipse (2010-06-28)

What's happened to the Moon? This past weekend, once again, part of the Moon moved through the Earth's shadow. This happens about once or twice a year, on the average, but not each month since the Moon's orbit around the Earth is slightly tilted. Pictured above, the face of a full moon is partly blocked by Earth's clouds, and partly darkened on the upper right by Earth's umbral shadow. Clouds permitting, the partial lunar eclipse was visible from the half of the Earth facing the Moon at the time of the eclipse, which included much of Earth's Pacific Rim.  On July 11, a total eclipse of the Sun will be visible in a thin swath of Earth crossing the southern Pacific Ocean.

Image credit: Brad Riza
Trees, Sky, Galactic Eye (2010-06-29)

Is beauty in the eye of this beholder? Earlier this month, over R�union Island in the Indian Ocean, a playful photographer with an eye for the sky took eight images and composed the above intriguing picture. The full fisheye frame shows everything above the horizon, including a lamp-illuminated landscape around the edges, and the zenith of the sky directly overhead. The image, however, may be more than beautiful -- it may also be a scavenger hunt. Can you find the photographer's tent, the slope of a volcano (active Piton de la Fournaise), a picturesque shoreline, and the lights of the nearby town (Saint Philippe)? One remarkable feature of the above image is that its center contains the very center of our Milky Way Galaxy.

Image credit: Luc Perrot
Fast Gas Bullet from Cosmic Blast N49 (2010-06-30)

What is that strange blue blob on the far right? No one is sure, but it might be a speeding remnant of a powerful supernova that was unexpectedly lopsided. Scattered debris from supernova explosion N49 lights up the sky in this gorgeous composited image based on data from the Chandra and Hubble Space Telescopes. Glowing visible filaments, shown in yellow, and X-ray hot gas, shown in blue, span about 30 light-years in our neighboring galaxy, the Large Magellanic Cloud. Light from the original exploding star reached Earth thousands of years ago, but N49 also marks the location of another energetic outburst -- an extremely intense blast of gamma-rays detected by satellites about 30 years ago on 1979 March 5. The source of the March 5th Event is now attributed to a magnetar - a highly magnetized, spinning neutron star also born in the ancient stellar explosion which created supernova remnant N49. The magnetar, visible near the top of the image, hurtles through the supernova debris cloud at over 70 thousand kilometers per hour. The blue blob on the far right, however, might have been expelled asymmetrically just as a massive star was exploding. If so, it now appears to be moving over 7 million kilometers per hour.
Above Aurora Australis (2010-07-01)

On May 29, looking southward from a vantage point about 350 kilometers above the southern Indian Ocean, astronauts onboard the International Space Station watched this enormous, green ribbon shimmering below. Known as aurora australis or southern lights, the shifting, luminous bands are commonly seen at high northern latitudes as well, there known as the aurora borealis or northern lights. North or south their cause is the same though, as energetic charged particles from the magnetosphere pile into the atmosphere near the Earth's poles. To produce the characteristic greenish glow, the energetic particles excite oxygen atoms at altitudes of 100 kilometers or more. Aurora on May 29 were likely triggered by the interaction of the magnetosphere with a coronal mass ejection erupting from the Sun on May 24.   Join Starship Asterisk: Discuss APODs, see the lastest space images, and browse the latest astronomy stories.
Galaxies on a String (2010-07-02)

Galaxies NGC 5216 (top) and NGC 5218 really do look like they are connected by a string. Of course, that string is a cosmic trail of gas, dust, and stars about 22,000 light-years long. Also known as Keenan's system (for its discoverer) and Arp 104, the interacting galaxy pair is some 17 million light-years away in the constellation Ursa Major. The debris trail that joins them, along with NGC 5218's comma-shaped extension and the distorted arms of NGC 5216, are a consequence of mutual gravitational tides. The tides disrupt the galaxies as they repeatedly swing close to one another. Drawn out over billions of years, the encounters will likely result in their merger into a single galaxy of stars. Such spectacular galactic mergers are now understood to be a normal part of the evolution of galaxies, including our own Milky Way.

Image credit: Adam Block
A Giant Planet for Beta Pic (2010-07-03)

A mere 50 light-years away, young star Beta Pictoris became one of the most important stars in the sky in the early 1980s. Satellite and ground-based telescopic observations revealed the presence of a surrounding outer, dusty, debris disk and an inner clear zone about the size of our solar system -- strong evidence for the formation of planets. Infrared observations from European Southern Observatory telescopes subsequently detected a source in the clear zone, now confirmed as a giant planet orbiting Beta Pic. The confirmation comes as the planet is detected at two different positions in its orbit. Designated Beta Pictoris b, the giant planet must have formed rapidly as Beta Pic itself is only 8 to 20 million years old. With an orbital period estimated between 17 and 44 years, Beta Pictoris b could lie near the orbit of Saturn if found in our solar system, making it the closest planet to its parent star directly imaged ... so far.
Companion of a Young, Sun-like Star Confirmed (2010-07-04)

The first direct image of an extrasolar planet orbiting a star similar to our Sun has been confirmed. Located just 500 light-years away toward the constellation Scorpius, the parent star, cataloged as 1RXS J160929.1-210524, is only slightly less massive and a little cooler than the Sun. The star is, however, much younger, a few million years old compared to the middle-aged Sun's 5 billion years. This sharp infrared image shows the young star's planetary companion positioned above and left of center. The planet is estimated to have a mass about 8 times the mass of Jupiter, and orbit a whopping 330 times the Earth-Sun distance from its parent star. The young planetary companion is still hot and relatively bright in infrared light, likely due to the heat generated during its formation by gravitational contraction. In fact, such newborn planets are easier to detect before they age and cool and become much more faint. The discovery image, shown above, was taken in 2008 but confirmed only recently by noting that the planet stayed with its parent star as background stars slightly shifted over time.
The Milky Way Over Pulpit Rock (2010-07-05)

Can a picture of the sky be relaxing? A candidate for such a picture might be this image taken only last month from Cape Schank, Victoria, Australia. The frame is highlighted by a dreamlike lagoon, two galaxies, and tens of thousands of stars. The rock cropping on the left may appear from this angle like a human head, but the more famous rock structure is on the far right and known as Pulpit Rock.  Across the top of the image runs a distant stream of bright stars and dark dust that is part of the disk of our spiral Milky Way Galaxy.     On the right, just above Pulpit Rock, is the Milky Way's small neighboring galaxy the Small Magellanic Cloud (SMC). The bright white object just to the left of the SMC is a globular cluster of stars in the Milky Way known as 47 Tucana.    Best Space Images: APOD Editor to Speak at AstroFest Penn State this Friday Night

Image credit: Alex Cherney
(Terrastro)
HCG 87: A Small Group of Galaxies (2010-07-06)

Sometimes galaxies form groups. For example, our own Milky Way Galaxy is part of the Local Group of Galaxies.  Small, compact groups, like Hickson Compact Group 87 (HCG 87) shown above, are interesting partly because they slowly self-destruct.  Indeed, the galaxies of HCG 87 are gravitationally stretching each other during their 100-million year orbits around a common center.  The pulling creates colliding gas that causes bright bursts of star formation and feeds matter into their active galaxy centers.  HCG 87 is composed of a large edge-on spiral galaxy visible on the lower left, an elliptical galaxy visible on the lower right, and a spiral galaxy visible near the top.  The small spiral near the center might be far in the distance.  Several stars from our Galaxy are also visible in the foreground.  The above picture was taken in 1999 July by the Hubble Space Telescope's Wide Field Planetary Camera 2.  Studying groups like HCG 87 allows insight into how all galaxies form and evolve.
Concept Plane: Supersonic Green Machine (2010-07-07)

What will passenger airplanes be like in the future? To help brain storm desirable and workable attributes, NASA sponsors design competitions. Shown here is an artist's depiction of a concept plane that has been recently suggested. This futuristic plane would be expected to achieve supersonic speeds, possibly surpassing the speeds of the supersonic transport planes that ran commercially in the late twentieth century. In terms of noise reduction, the future aircraft has been drawn featuring an inverted V wing stretched over its engines. The structure is intended to reduce the sound from annoying sonic booms. Additionally, future airplanes would aim to have relatively little impact on our environment, including green limits on pollution and fuel consumption. Aircraft utilizing similar design concepts might well become operational by the 2030s.
Dim World, Dark Nebula (2010-07-08)

Dim, distant, dwarf planet Pluto can be hard to spot, especially in recent months as it wanders through the crowded starfields of Sagittarius and the central Milky Way. But fortunately for backyard Pluto hunters, it crossed in front of a dark nebula in early July. The diminutive world is marked with two short lines near the center of this skyscape recorded from New Mexico Skies on July 5. Pluto stands out only because obscuring dark nebula Barnard 92 (B92) blocks the background of the Milky Way's congeries of faint, innumerable stars. Another of astronomer E. E. Barnard's cataloged dark markings on the sky, B93, is easy to pick out just left of B92. Prominent at the lower left is open star cluster NGC 6603. In fact, Pluto, dark nebulae, and star cluster all lie within a portion of M24, also known as the Sagittarius Star Cloud, filling most of the frame.

Image credit: Ray Gralak
Microwave Milky Way (2010-07-09)

Seen from our edge-on perspective, the Milky Way Galaxy sprawls across the middle of this false-color, all sky view. The expansive microwave map is based on 1 year's worth of data from instruments onboard the sky-surveying Planck spacecraft. Remarkably, the bright stripe of gas and dust clouds along the galactic plane and the galaxy's enormous arcing structures seen at microwave energies are hundreds or thousands of light-years away, while the mottled regions at the top and bottom represent the Cosmic Microwave Background (CMB) radiation, some 13.7 billion light-years distant. Left over from the Big Bang, fluctuations in the CMB reflect the origins of structure in the evolving universe. Analyzing the microwave data, Planck scientists plan to separate the contributions of the Milky Way and CMB radiation. The work will ferret out the characteristics of the CMB across the entire sky and glean information about the make up of our Milky Way Galaxy.
Ecliptic New Zealand (2010-07-10)

Four bright celestial beacons and a faint triangle of light follow the plane of the ecliptic as it arcs high through this southern hemisphere night skyscape. Seen on a July winter night from Lake Taupo on New Zealand's North Island, the line-up features Venus, Regulus (alpha star of Leo), Mars, and Saturn from lower left to upper right. Just put your cursor over the picture to identify the planets and constellations. The delicate luminous glow of Zodiacal Light, sunlight scattered by dust along the ecliptic, also rises above the horizon from the lower left. Of course, defined by the path of the Sun through planet Earth's sky, the ecliptic plane rides low during July nights in the northern hemisphere's summer skies. Tomorrow, the Moon and Sun will meet on the ecliptic. Along a track across the southern Pacific Ocean, the daytime sky will feature a total solar eclipse.  Total Solar Eclipse: Times and Visibility | Webcast

Image credit: Tunç Tezel
Warped Sky: Star Trails Panorama (2010-07-11)

What's happened to the sky?  A time warp, of sorts, and a digital space warp too.  The time warp occurs because this image captured in a single frame a four hour exposure of the night sky.  As a result, prominent star trails are visible.  The space warp occurs because the picture is actually a full 360 degree panorama, horizontally compressed to fit your browser.  As the Earth rotated, stars appeared to circle both the South Celestial Pole, on the left, and the North Celestial Pole, just below the horizon on the right.  The image captured the sky over Mudgee, New South Wales, Australia, including the domes of two large telescopes illuminated by red lighting. A horizontally unwarped image is visible by clicking on the image.   Total Solar Eclipse Today: Times and Visibility | Webcast

Image credit: Peter Ward
Moons Beyond the Rings of Saturn (2010-07-12)

What's happened to that moon of Saturn? Nothing -- Saturn's moon Rhea is just partly hidden behind Saturn's rings. In April, the robotic Cassini spacecraft now orbiting Saturn took this narrow-angle view looking across the Solar System's most famous rings. Rings visible in the foreground include the thin F ring on the outside and the much wider A and B rings just interior to it. Although it seems to be hovering over the rings, Saturn's moon Janus is actually far behind them.  Janus is one of Saturn's smaller moons and measures only about 180 kilometers across. Farther out from the camera is the heavily cratered Rhea, a much larger moon measuring 1,500 kilometers across. The top of Rhea is visible only through gaps in the rings. The Cassini mission around Saturn has been extended to 2017 to better study the complex planetary system as its season changes from equinox to solstice.
Mosaic: Welcome to Planet Earth (2010-07-13)

Welcome to Planet Earth, the third planet from a star named the Sun. The Earth is shaped like a sphere and composed mostly of rock. Over 70 percent of the Earth's surface is water. The planet has a relatively thin atmosphere composed mostly of nitrogen and oxygen. This picture of Earth, dubbed Blue Marble, was taken from Apollo 17 in 1972 and features Africa and Antarctica.  It is thought to be one of the most widely distributed photographs of any kind. Here, the world famous image has been recast as a spectacular photomosaic using over 5,000 archived images of Earth and space. With its abundance of liquid water, Earth supports a large variety of life forms, including potentially intelligent species such as dolphins and humans. Please enjoy your stay on Planet Earth.
Easter Island Eclipse (2010-07-14)

Makemake, a god in Easter Island mythology, may have smiled for a moment as clouds parted long enough to reveal this glimpse of July 11's total solar eclipse to skygazers. In the foreground of the dramatic scene, the island's famous large, monolithic statues (Moai) share a beachside view of the shimmering solar corona and the darkened daytime sky. Other opportunities to see the total phase of this eclipse of the Sun were also hard to come by. Defined by the dark part of the Moon's shadow, the path of totality tracked eastward across the southern Pacific Ocean, only making significant landfall at Mangaia (Cook Islands) and Easter Island (Isla de Pascua), ending shortly after reaching southern Chile and Argentina.  But a partial eclipse phase could be enjoyed over a broader region, including many southern Pacific islands and wide swath of South America.

Image credit: Stéphane Guisard
Andes Sunset Eclipse (2010-07-15)

On July 11, after a long trek eastward across the southern Pacific Ocean, the Moon's shadow reached landfall in South America. In a total solar eclipse close to sunset, silhouetted Moon and Sun hugged the western horizon, seen here above the Andes mountains near the continent's southern tip. To enjoy a good vantage point, the photographer hiked to a windy spot about 400 meters above a lake, Lago Argentino, climbing into the picture after setting up his camera on a tripod. At left, the sky outside the shadow cone is still bright. Below, the lights of El Calafate, Patagonia, Argentina, shine by the lake shore.

Image credit: Janne Pyykkö
Shaping NGC 6188 (2010-07-16)

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 this sharp close-up 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 200 light-years.

Image credit: Piotrek Sadowski
Galaxies in the River (2010-07-17)

Large galaxies grow by eating small ones. Even our own galaxy practices galactic cannibalism, absorbing small galaxies that get too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus (The River). Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531, a struggle the smaller galaxy will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. Nicely detailed in this sharp image, the NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.

Image credit: Martin Pugh
The Antennae Galaxies in Collision (2010-07-18)

Two galaxies are squaring off in Corvus and here are the latest pictures. But when two galaxies collide, the stars that compose them usually do not. That's because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space.  During the slow, hundred million year collision, one galaxy can still rip the other apart gravitationally, and dust and gas common to both galaxies does collide.  In this clash of the titans, dark dust pillars mark massive molecular clouds are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.
Dark River, Wide Field (2010-07-19)

A Dark River of dust seems to run from our Galactic Center, then pool into a starfield containing photogenic sky wonders. Scrolling right will reveal many of these objects including (can you find?) the bright orange star Antares, a blue(-eyed) horsehead nebula, the white globular star cluster M4, the bright blue star system Rho Ophiuchi, the dark brown Pipe nebula, the red Lagoon nebula, the red and blue Trifid nebula, the red Cat's Paw Nebula, and the multicolored but still important center of our Galaxy. This wide view captures in exquisite detail about 50 degrees of the nighttime sky, 100 times the size of the full Moon, covering constellations from the Archer (Sagittarius) through the Snake Holder (Ophiuchus), to the Scorpion (Scorpius). The Dark River itself can be identified as the brown dust lane connected to Antares, and spans about 100 light years. Since the Dark River dust lane lies only about 500 light years away, it only appears as a bridge to the much more distant Galactic Center, that actually lies about 25,000 light years farther away.

Image credit: Rogelio Bernal Andreo