omnianasa/nasa-apod-metadata huggingface dataset:
Earth at Twilight (2005-06-11)
No sudden, sharp boundary marks the passage of day into night in this gorgeous view of ocean and clouds over our fair planet Earth. Instead, the shadow line or terminator is diffuse and shows the gradual transition to darkness we experience as twilight. With the Sun illuminating the scene from the right, the cloud tops reflect gently reddened sunlight filtered through the dusty troposphere, the lowest layer of the planet's nurturing atmosphere. A clear high altitude layer, visible along the dayside's upper edge, scatters blue sunlight and fades into the blackness of space. This picture actually is a single digital photograph taken in June of 2001 from the International Space Station orbiting at an altitude of 211 nautical miles.
M2-9: Wings of a Butterfly Nebula (2005-06-12)
Are stars better appreciated for their art after they die?  Actually, stars usually create their most artistic displays as they die.  In the case of low-mass stars like our Sun and  M2-9 pictured above, the stars transform themselves from normal stars to white dwarfs by casting off their outer gaseous envelopes.  The expended gas frequently forms an impressive display called a planetary nebula that fades gradually over thousand of years.  M2-9, a butterfly planetary nebula 2100 light-years away shown in representative colors, has wings that tell a strange but incomplete tale.  In the center, two stars orbit inside a gaseous disk 10 times the orbit of Pluto.  The expelled envelope of the dying star breaks out from the disk creating the bipolar appearance.  Much remains unknown about the physical processes that cause planetary nebulae.
Tornado and Rainbow Over Kansas (2005-06-13)
The scene might have been considered serene if it weren't for the tornado. Last June in Kansas, storm chaser Eric Nguyen photographed this budding twister in a different light -- the light of a rainbow.  Pictured above, a white tornado cloud descends from a dark storm cloud.  The Sun, peeking through a clear patch of sky to the left, illuminates some buildings in the foreground. Sunlight reflects off raindrops to form a rainbow.  By coincidence, the tornado appears to end right over the rainbow.  Streaks in the image are hail being swept about by the high swirling winds. Over 1,000 tornadoes, the most violent type of storm known, occur on Earth every year, many in tornado alley.  If you see a tornado while driving, do not try to outrun it -- park your car safely, go to a storm cellar, or crouch under steps in a basement.
Gliese 876 System Includes Large Terrestrial Planet (2005-06-14)
Is our Earth unique?  In continuing efforts to answer this question, astronomers have now discovered an Earth-like planet orbiting a distant normal star.  Previously over 150 gas-giant planets like Jupiter had been so discovered. Slight, fast, but regular wobbles of nearby small M-dwarf star Gliese 876 showed evidence for a planet with a likely mass slightly higher than a minimum six times the mass of Earth.  The planet's small mass indicates that it is likely terrestrial in nature, similar in composition to the inner planets of our Solar System.   If indeed made predominantly of rock, the planet's surface gravity would not even be able to contain the gasses of a Jupiter-like planet. The newly discovered planet would not make a good vacation spot for humans, however, as it orbits so close that the surface temperature probably tops a searing 200 degrees Celsius.  The system is illustrated in the above drawing as seen from a hypothetical moon orbiting one of the two Jupiter-like planets already known.  The newly discovered terrestrial-like planet is depicted in the insert. Gliese 876 lies only 15 light-years away and is visible with binoculars toward the constellation of Aquarius.
Cassiopeia A Light Echoes in Infrared (2005-06-15)
Why is the image of Cassiopeia A changing?  Two images of the nearby supernova remnant taken a year apart in infrared light appear to show outward motions at tremendous speeds.  This was unexpected since the supernova that created the picturesque nebula was seen 325 years ago.  The reason is likely light echoes.  Light from the supernova heated up distant ambient dust that is just beginning to show its glow.  As time goes by, more distant dust lights up, giving the appearance of outward motion.  The above image is a composite of X-ray, optical, and infrared light exposures that have been digitally combined.  The infrared light image was taken by the orbiting Spitzer Space Telescope and was used in the discovery of the light echo.  The portion of Cassiopeia A shown spans about 15 light years and lies 10,000 light years away toward the constellation of Cassiopeia.
APOD Is Ten Years Old Today (2005-06-16)
Welcome to the eleventh year of Astronomy Picture of the Day! In a decade of editing the APOD web pages, the industrious Robert Nemiroff (left) and persistent Jerry Bonnell (right) have enjoyed exploring compelling images of the cosmos that are not limited to those taken from earth orbit, much less to those taken by professional astronomers. In fact, seen in this recently released Vermeer, the editors are extremely grateful for the continued large volume of gracious e-mail and APOD submissions. Today, they would like to offer a sincere thank you to all. And while these APOD editors are definitely not getting any younger, tomorrow's picture may actually be ...
The Small Cloud of Magellan (2005-06-17)
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 celestial wonders easily visible for southern hemisphere skygazers are known as the Clouds of Magellan. These cosmic clouds are now understood to be dwarf irregular galaxies, satellites of our larger spiral Milky Way Galaxy. The Small Magellanic Cloud pictured above actually spans 15,000 light-years or so and contains several hundred million stars. About 210,000 light-years distant in the constellation Tucana, it is the fourth closest of the Milky Way's known satellite galaxies, after the Canis Major and Sagittarius Dwarf galaxies and the Large Magellanic Cloud. This gorgeous view also includes two foreground globular star clusters NGC 362 (top left) and 47 Tucanae. Spectacular 47 Tucanae is a mere 13,000 light-years away and seen here to the right of the Small Magellanic Cloud.
Visitors' Galaxy Gallery (2005-06-18)
A tantalizing assortment of island universes is assembled here. From top left to bottom right are the lovely but distant galaxies M61, NGC 4449, NGC 4725, NGC 5068, NGC 5247, and NGC 5775/5774. Most are spiral galaxies more or less like our own Milky Way. The color images reveal distinct pink patches marking the glowing hydrogen gas clouds in star forming regions along the graceful spiral arms. While Virgo cluster galaxy M61 is perhaps the most striking of these spirals, the interesting galaxy pair NGC 5775/5774 neatly contrasts the characteristic spiral edge-on and face-on appearance. The one exception to this parade of photogenic spiral galaxies is the small and relatively close irregular galaxy NGC 4449 (top middle). Similar to the Large Magellanic Cloud, companion galaxy to the Milky Way, NGC 4449 also sports young blue star clusters and pink star forming regions. All the galaxies in this gallery were imaged with a small (16 inch diameter) reflecting telescope and digital camera by public participants in the Kitt Peak National Observatory Visitor Center's Advanced Observing Program.
Noctilucent Clouds (2005-06-19)
Sometimes it's night on the ground but day in the air.  As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above.  Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark.  Pictured above, a network of noctilucent clouds casts a colorful but eerie glow visible above the dark.  Although noctilucent clouds are thought to be composed of small ice-coated particles, much remains unknown about them. Recent evidence indicates that at least some noctilucent clouds result from freezing water exhaust from Space Shuttles.
Sunset Over Gusev Crater (2005-06-20)
What would it be like to see a sunset on Mars?  To help find out, the robotic rover Spirit was deployed last month to park and serenely watch the Sun dip below the distant lip of Gusev crater.  It was a tough job, but some robot had to do it.  Now on Earth a red sunset is caused by two effects -- by blue light being preferentially scattered out of sunlight by oxygen and nitrogen molecules in the atmosphere, and by scattering off a small amount of impurities like volcanic dust.  (The magnitude of the first effect was computed in one of Albert Einstein's most cited papers.) Although Mars lacks oxygen and nitrogen, it is covered in red dust frequently hoisted into the atmosphere by fast but thin winds.  Analyses of images like the above photograph show that at least some Martian days are capped by a sunset significantly longer and redder than typical on Earth.  For up to two hours after twilight, sunlight continued to reflect off Martian dust high in the atmosphere, casting a diffuse glow.  The result helps atmospheric scientists understand not only the atmosphere of Mars, but atmospheres across the Solar System, including our home Earth.
The Cygnus Wall of Star Formation (2005-06-21)
The North America Nebula in the sky can do what North Americans on Earth cannot -- form stars.  Specifically, in analogy to the Earth-confined continent, the bright part that appears as Central America and Mexico is actually a hot bed of gas, dust, and newly formed stars known as the Cygnus Wall.  The above image in representative colors shows the star forming wall lit and eroded by bright young stars, and partly hidden by the dark dust they have created.  The part of the North America nebula (NGC 7000) shown spans about 15 light years and lies about 1,500 light years away toward the constellation of Cygnus.   News: Solar Sail Spacecraft Launch
Saturn's Rings from the Other Side (2005-06-22)
What do Saturn's rings look like from the other side?  From Earth, we usually see Saturn's rings from the same side of the ring plane that the Sun illuminates them. Geometrically, in the above picture taken in April by the robot Cassini spacecraft now orbiting Saturn, the Sun is behind the camera but on the other side of the ring plane.  Such a vantage point gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the rings have similarities to a photographic negative of a front view. For example, the dark band in the middle is actually the normally bright B-ring. The ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles.  Images like these are also interesting for what they do not show: spokes.  The unexpected shadowy regions once recorded by the Voyager missions when they passed Saturn in the early 1980s are not, so far, being seen by Cassini.  Extra credit: Can you spot the small moon (Prometheus) among the rings?
Moonrise, Cape Sounion, Greece (2005-06-23)
The Moon was full this month on June 22nd, only a day after the northern hemisphere's summer solstice. Since this solstice marked the northernmost point of the Sun's annual motion through planet Earth's sky, the full Moon rising near the ecliptic plane opposite the Sun was at its farthest south for the year. Only a month earlier, on May 23rd, astronomer Anthony Ayiomamitis recorded this picture of another southerly full Moon rising above Cape Sounion, Greece. The twenty-four hundred year old Temple of Poseidon lies in the foreground, also visible to sailors on the Aegean Sea. In this well-planned, single exposure, a long telephoto lens makes the Moon loom large, but even without optical aid casual skygazers often find the full Moon looking astonishingly large when seen near the horizon. That powerful visual effect is known as the Moon Illusion.
Planets in the West (2005-06-24)
This weekend three planets will grace the western sky, forming a lovely trio easily visible shortly after sunset. Saturday evening in particular will find Saturn, Venus, and Mercury all within a 2 degree circle (about the size of your thumb held at arm's length) above the western horizon. Recorded last Sunday, June 19, this image shows the same three planets arrayed along the ecliptic plane above a Colorado Rocky Mountain skyline. Venus is easiest to pick out of the twilight, the brightest celestial beacon below picture center, with Saturn above and to the left of Venus, and Mercury closest to the horizon, right of prominent Pinnacle Peak. By Saturday, the wandering planets will draw even closer together. For help spotting the planets here, put your cursor over the picture.
Venus: Just Passing By (2005-06-25)
Venus, the second closest planet to the Sun, is by far the brightest of the three planets gathered in this weekend's western sky at sunset. It has also proven to be a popular way-point for spacecraft headed for the gas giant planets in the outer reaches of the solar system. Why visit Venus first? Using a gravity assist maneuver, spacecraft can swing by planets and gain energy during their brief encounter, saving fuel for use at the end of their long interplanetary voyage. This colorized image of Venus was recorded by the Jupiter-bound Galileo spacecraft shortly after its gravity assist flyby of Venus in February of 1990. Galileo's glimpse of the veiled planet shows structure in swirling sulfuric acid clouds. The bright area is sunlight glinting off the upper cloud deck.
The 2MASS Galaxy Sky (2005-06-26)
Are the nearest galaxies distributed randomly? A plot of over one million of the brightest "extended sources" detected by the Two Micron All Sky Survey (2MASS) shows that they are not.  The vast majority of these infrared extended sources are galaxies.  Visible above is an incredible tapestry of structure that provides limits  on how the universe formed and evolved.  Many galaxies are gravitationally bound together to form clusters, which themselves are loosely bound into superclusters, which in turn are sometimes seen to align over even larger scale structures.  In contrast, very bright stars inside our own Milky Way Galaxy cause the vertical blue sash.
Globular Cluster M22 from CFHT (2005-06-27)
The globular cluster M22, pictured above, contains over 100,000 stars.  These stars formed together and are gravitationally bound.  Stars orbit the center of the cluster, and the cluster orbits the center of our Galaxy.  So far, about 140 globular clusters are known to exist in a roughly spherical halo around the Galactic center.  Globular clusters do not appear spherically distributed as viewed from the Earth, and this fact was a key point in the determination that our Sun is not at the center of our Galaxy.  Globular clusters are very old.  There is a straightforward method of determining their age, and this nearly matches the 13.7 billion-year age of our entire universe.
The Giant Radio Lobes of Fornax A (2005-06-28)
Together, the radio lobes span over one million light years -- what caused them? In the center is a large but peculiar elliptical galaxy dubbed NGC 1316.  Detailed inspection of the NGC 1316 system indicates that it began absorbing a small neighboring galaxy about 100 million years ago. Gas from the galactic collision has fallen inward toward the massive central black hole, with friction heating the gas to 10 million degrees.  For reasons not yet well understood, two oppositely pointed fast moving jets of particles then developed, eventually smashing into the ambient material on either side of the giant elliptical galaxy. The result is a huge reservoir of hot gas that emits radio waves, observed as the orange (false-color) radio lobes in the above image.  The radio image is superposed on an optical survey image of the same part of the sky. Strange patterns in the radio lobes likely indicate slight changes in the directions of the jets.   First Annual Radio Astronomy Image Contest
Thirteen Million Kilometers from Comet Tempel 1 (2005-06-29)
The Deep Impact spacecraft continues to close on Comet Tempel 1, a comet roughly the size of Manhattan.  Early on July 3 (EDT), the Deep Impact spacecraft will separate in to two individual robotic spaceships, one called Flyby and the other called Impactor.  During the next 24 hours, both Flyby and Impactor will fire rockets and undergo complex maneuvers in preparation for Impactor's planned collision with Comet Tempel 1.  On July 4 (1:52 am EDT) if everything goes as scheduled, the 370-kilogram Impactor will strike Tempel 1's surface at over 14,000 kilometers per hour.  Impactor will attempt to photograph the oncoming comet right up to the time of collision, while Flyby photographs the result from nearby.  The above image was taken on 19 June from about 13 million kilometers out and used to help identify the central nucleus of the comet inside the diffuse coma.  Telescopes around the Earth, including the Hubble Space Telescope, will also be closely watching the distant silent space ballet.  The result may give crucial information about the structure of comets and the early history of our Solar System.
Three Planets from Mt. Hamilton (2005-06-30)
Venus, Mercury, and Saturn wandered close together in western evening skies last week. On Saturnday, June 25, astronomer R. Jay GaBany recorded this snapshot of their eye-catching planetary conjunction, from historic Lick Observatory on Mt. Hamilton, California, USA. The view looks toward the Pacific shortly after sunset with the lights of San Jose and the southern San Francisco Bay area in the foreground. Of course, Venus is the brightest of the trio. Mercury is nearby on the right and Saturn is below and left, closest to the horizon. Farther to the right of the planetary triangle are Pollux and Castor, twin stars of Gemini, with Regulus, bright star of the constellation Leo, at the very upper left corner of the picture. In the coming days, Venus and Mercury remain close, while Saturn continues to drop below them, toward the horizon.
Ring Around Fomalhaut (2005-07-01)
Fomalhaut (sounds like "foam-a-lot") is a bright, young, star, a mere 25 light-year trip from planet Earth in the direction of the constellation Piscis Austrinus. Earlier infrared observations identified a torus of cold material surrounding the nearby star but the panels above detail the sharpest ever visible light-image of Fomalhaut's dusty debris ring, recorded by the Hubble Space Telescope's ACS camera. Overwhelming glare from the star is masked by an occulting disk in the camera's coronagraph. The off-center ring with a sharp inner boundary is taken to be strong evidence of a massive planet orbiting far from Fomalhaut, shaping and maintaining the ring's inner edge. Starting 133 astronomical units (Earth-Sun distances) from Fomalhaut, the dusty ring itself is likely a larger, younger analog of our own Kuiper Belt - the solar system's outer reservoir of icy bodies.
Three Planets by the Sea (2005-07-02)
On Tuesday, June 28th, the setting Sun flooded the horizon with a beautiful warm light in this view from the beach beside the pier at Brighton in Adelaide, South Australia. The Sun also illuminated three planets gathered in the western sky, Mercury, Venus, and Saturn. From this perspective Mercury is at the highest point in the celestial triangle, brilliant Venus is just below, and Saturn stands farther to the left and below the close pair. Of course, the planets only appear close together on the sky but are actually quite far apart in space. The orbits of Mercury and Venus are both interior to Earth's orbit, while gas giant Saturn lies in the outer solar system, over nine astronomical units from the Sun. Late next week, Venus and Mercury will share western skies with the young crescent Moon.
A Swift Look at Tempel 1 (2005-07-03)
Comet Tempel 1 is targeted for a collision with the impactor probe from NASA's Deep Impact Spacecraft at about 1:52am EDT on July 4th (other time zones). Cameras on the impactor probe and the flyby spacecraft will capture close-up images of the event - expected to produce a crater on the surface of the comet's nucleus. Of course, Earth-orbiting and ground-based telescopes will be watching too, including instruments on the Swift satellite normally used to spot gamma-ray bursts in the distant universe. Swift's ultraviolet telescope recorded this picture of Tempel 1 on June 29th. Because the image is registered on the comet, the background stars appear as short trails. Want to follow the encounter? Media coverage chronicling the event, and the possibilities for viewing the comet with small telescopes can be found through the Deep Impact website. Updated images will also be available from the Kitt Peak National Observatory.
A Panorama from Mauna Kea (2005-07-04)
Typically, views from Mauna Kea are up and dark.  That's because the famous dormant volcano in Hawaii is arguably Earth's premier observing platform of the complex and ever changing night sky.  However, this daytime view is across and bright.  White snow and white clouds seem to blend together to make an alien landscape.  Cinder cones from extinct volcanic outbursts dominate the foreground.  Scrolling right will reveal structures visually incongruous even here: an armada of the largest optical telescopes on Earth.  The observatories seen include Subaru and Keck.  In the distance on the far left is Mauna Loa, Earth's largest volcano.
Thirteen Seconds After Impact (2005-07-05)
Fireworks came early on July 4th when, at 1:52am EDT, the Deep Impact spacecraft's probe smashed into the surface of Comet Tempel 1's nucleus at ten kilometers per second. The well-targeted impactor probe was vaporized as it blasted out an expanding cloud of material, seen here 13 seconds after the collision. The image is part of a stunning series of frames documenting the event from the high resolution camera onboard the flyby spacecraft. Tempel 1's potato-shaped nucleus is approximately 5 kilometers across as seen from this perspective. Cameras onboard the impactor probe were also able to image the nucleus and impact site up-close ... until about 3 seconds before the impact. Of course, telescopes nearer to planet Earth followed the event, detecting a significant brightening of comet Tempel 1.
The Landscape on Comet Tempel 1 (2005-07-06)
This diverse landscape is the surface of comet Temple 1's nucleus as seen by the Deep Impact probe's Impactor Targeting Sensor. Within minutes of recording the rugged view, the landscape had changed dramatically though, as the impactor smashed into the surface near the two large, half kilometer-sized craters at picture center. Indications are that the probe penetrated well below the surface before vaporizing, sending a relatively narrow plume of debris blasting back into space. Researchers are still speculating on the final size of the crater produced by the July 4th comet crash, but material continues to spew from the impact site and has caused the faint comet to brighten significantly. Determining the crater dimensions and analyzing the debris ejected from the comet's interior will provide premier insights into the formation of comet Tempel 1, a primordial chunk of our own solar system.
Fire Glow and Star Trails at Sunset Crater (2005-07-07)
Stars gracefully arc over the glow from a not too distant forest fire in this dramatic time exposure. A recent camping trip with family and friends to Sunset Crater Volcano National Monument, near Flagstaff, Arizona, USA produced the opportunity to record the subtle lighting from Earth and sky.  Pointed south with the shutter held open for five minutes, camera and tripod were fixed to planet Earth, producing the gently curving, concentric star trails - a reflection of the planet's daily rotation about its axis. Rising beyond the forest fire's glow is the slope of Sunset Crater, a cinder cone produced by volcanic eruptions some 900 years ago.