omnianasa/nasa-apod-metadata huggingface dataset:
Analemma over Ancient Nemea (2004-06-21)
An analemma is that figure-8 curve that you get when you mark the position of the Sun at the same time each day throughout planet Earth's year. Above, 44 separate exposures (plus one foreground exposure) were recorded on a single piece of film to illustrate the regular solar motion -- a Herculean task performed during the calendar year 2003. Appropriately, in the foreground are the ruins at Ancient Nemea where the hero of Greek Mythology pursued the first of his twelve labours. Solstices, like the one that occurred at 0057 UT on June 21, correspond to the top and bottom of the figure-8 or the northern and southernmost excursions of the Sun in the sky. The tilt of planet Earth's axis and the variation in speed as it moves around its orbit combine to produce the graceful analemma curve.
Unusual Spires Found on Comet Wild 2 (2004-06-22)
How did unusual spires form on comet Wild 2?  Close inspection of images taken of Comet Wild 2 by the passing Stardust spacecraft in January show numerous strange pinnacles as long as 100 meters long jutting off the surface.  The pinnacles were unexpected - close-ups of other comets and asteroids show no such features.  In fact, no other Solar System object besides Earth is known to show such unusual structures.  Other unusual Wild 2 surface features including long cliffs, deep pits and craters, and numerous active jets.  Together with the spires, these features are hypothesized to be indicative of a very rigid surface sculpted by impacts and explosive sublimation. Initially, Wild 2 was expected by many to be held together only quite loosely.  Stardust is scheduled to fly by the Earth in 2006 and drop off a sample of Wild 2 for detailed scrutiny.
A Picturesque Venus Transit (2004-06-23)
The rare transit of Venus across the face of the Sun earlier this month was one of the better-photographed events in sky history.  Both scientific and artistic images have been flooding in from the areas that could see the transit: Europe and much of Asia, Africa, and North America.  Scientifically, solar photographers confirmed that the black drop effect is really better related to the viewing clarity of the camera or telescope than the atmosphere of Venus.  Artistically, images might be divided into several categories.  One type captures the transit in front of a highly detailed Sun.  Another category captures a double coincidence such as both Venus and an airplane simultaneously silhouetted, or Venus and the International Space Station in low Earth orbit. A third image type involves a fortuitous arrangement of interesting looking clouds, as shown by example in the above image taken from North Carolina, USA. There the distant orb of giant Venus might have been mistaken, at first glance, for a small but unusually circular cloud.
The Galaxy Within Centaurus A (2004-06-24)
Peering deep inside Centaurus A, the closest active galaxy to Earth, the Spitzer Space Telescope's penetrating infrared cameras recorded this startling vista. About 1,000 light-years across, the twisted cosmic dust cloud apparently shaped like a parallelogram is likely the result of a smaller spiral galaxy falling into the giant Centaurus A. The parallelogram lies along the active galaxy's central band of dust and stars visible in more familiar optical images. Astronomers believe that the striking geometric shape represents an approximately edge-on view of the infalling spiral galaxy's disk in the process of being twisted and warped by the interaction. Ultimately, debris from the ill-fated spiral galaxy should provide fuel for the supermassive black hole lurking at the center of Centaurus A.
Planet Earth from SpaceShipOne (2004-06-25)
On June 21st, pilot Mike Melvill made a historic flight in the winged craft dubbed SpaceShipOne -- the first private manned mission to space. The spaceship reached an altitude of just over 62 miles (100 kilometers) on a suborbital trajectory, similar to the early space flights in NASA's Mercury Program. So, how was the view? A video camera on an earlier test flight that climbed 40 miles recorded this picture looking west over the southern California coast and the Earth's limb. In the foreground, the nozzle of SpaceShipOne's hybrid rocket is visible along with the edge of the wing in a "feathered" configuration for reentry. SpaceShipOne was designed and built by Burt Rutan and his company Scaled Composites to compete for the 10 million dollar X Prize.
Neptune: Still Springtime After All These Years (2004-06-26)
In the 1960s spring came to the southern hemisphere of Neptune, the Solar System's outermost gas giant planet. Of course, since Neptune orbits the Sun once every 165 earth-years, it's still springtime for southern Neptune, where each season lasts over four decades. Astronomers have found that in recent years Neptune has been getting brighter as illustrated in this Hubble Space Telescope image made in 2002. Compared to Hubble pictures taken as early as 1996, the 2002 image shows a dramatic increase in reflective white cloud bands in Neptune's southern hemisphere. Neptune's equator is tilted 29 degrees from the plane of its orbit, about the same as Earth's 23.5 degree tilt, and Neptune's weather seems to be dramatically responding to the similar relative seasonal increase in sunlight -- even though sunlight is 900 times less intense for the distant gas giant than for planet Earth. Meanwhile, summer is really just around the corner, coming to Neptune's southern hemisphere in 2005.
Galaxy Cluster Abell 1689 Warps Space (2004-06-27)
Two billion light-years away, galaxy cluster Abell 1689 is one of the most massive objects in the Universe. In this view from the Hubble Space Telescope's Advanced Camera for Surveys, Abell 1689 is seen to warp space as predicted by Einstein's theory of gravity -- bending light from individual galaxies which lie behind the cluster to produce multiple, curved images. The power of this enormous gravitational lens depends on its mass, but the visible matter, in the form of the cluster's yellowish galaxies, only accounts for about one percent of the mass needed to make the observed bluish arcing images of background galaxies. In fact, most of the gravitational mass required to warp space enough to explain this cosmic scale lensing is in the form of still mysterious dark matter. As the dominant source of the cluster's gravity, the dark matter's unseen presence is mapped out by the lensed arcs and distorted background galaxy images.
Spirit Rover Reaches the Columbia Hills on Mars (2004-06-28)
The Spirit robotic rover on Mars has now reached the Columbia Hills on Mars. Two of the hills are shown on approach near the beginning of June.  The above true-color picture shows very nearly what a human would see from Spirit's vantage point.  The red color of the rocks, hills, and even the sky is caused by pervasive rusting sand.  Spirit has now traveled over 3 kilometers since it bounced down onto the red planet in January.  The robotic explorer, controlled and programmed remotely from Earth, is now investigating a rock called Pot of Gold.  On the other side of Mars, Spirit's twin Opportunity is now inspecting unusual rocks inside a pit dubbed Endurance crater.
In the Center of NGC 6559 (2004-06-29)
Bright gas and dark dust permeate the space between stars in the center of a nebula known as NGC 6559.  The gas, primarily hydrogen, is responsible for the diffuse red glow of the emission nebula.  As energetic light from neighboring stars ionizes interstellar hydrogen, protons and  electrons recombine to emit light of very specific colors, including the red hue observed.  Small dust particles reflect blue starlight efficiently and so creates the blue reflection nebulosity seen near two of the bright stars.  Dust also absorbs visible light, causing the dark clouds and filaments visible.  NGC 6559 lies about 5000 light-years away toward the constellation of Sagittarius.
Phoebe: Comet Moon of Saturn (2004-06-30)
Was Saturn's moon Phoebe once a comet?  Images from the robotic Cassini spacecraft taken two weeks ago when entering the neighborhood of Saturn indicate that Phoebe may have originated in the outer Solar System.  Phoebe's irregular surface, retrograde orbit, unusually dark surface, assortment of large and small craters, and low average density appear consistent with the hypothesis that Phoebe was once part of the Kuiper belt of icy comets beyond Neptune before being captured by Saturn.  Visible in the above image of Phoebe are craters, streaks, and layered deposits of light and dark material.  The image was taken from around 30,000 kilometers out from this 200-kilometer diameter moon. Late today, Cassini will begin to fire its engines to decelerate into orbit around Saturn.
NGC 7331: A Galaxy So Inclined (2004-07-01)
If our own Milky Way galaxy were 50 million light-years away with its disk inclined slightly to our line of sight, it would look a lot like large spiral galaxy NGC 7331. In fact, seen here in a false-color infrared image from the Spitzer Space Telescope, NGC 7331 is interesting in part because it is thought to be so similar to the Milky Way. Light from older, cooler stars, shown in blue, dominates the central bulge of NGC 7331, while Spitzer data also indicates the presence of a black hole within this galaxy's central regions - about the same size as the black hole at our own galactic core. Shown in red and brown, radiation from complex molecules associated with dust traces NGC 7331's star forming spiral arms. The arms span around 100,000 light-years, about the size of the Milky Way. Curiously, a further star forming ring is visible in yellowish hues, 20,000 light-years or so from the center of NGC 7331, but it is not known if such a structure exists within our own galaxy.
The Encke Gap: A Moon Goes Here (2004-07-02)
Yesterday, Cassini became the first spacecraft to enter orbit around gas giant Saturn, rocketing through a 25,000 kilometer wide gap in the distant planet's magnificent system of icy rings at about 15 kilometers per second. Turning to snap pictures, Cassini's narrow angle camera recorded this stunning close-up of a much smaller gap in the rings, the Encke Gap. A mere 300 kilometers wide, the Encke Gap is flanked by amazing structures within the rings -- scalloped edges and patterns of density waves are clear in the sharp image. While the rings of Saturn are likely debris from the breakup of a fair-sized icy moon, the Encke Gap itself is created by the repeated passage of a tiny moon. Only 20 kilometers wide that tiny moon, Pan, was also detected by Cassini's camera as the spacecraft approached the Saturnian system.
Cassini To Venus (2004-07-03)
Saturn Orbiter Cassini with Titan Probe Huygens attached rocketed into early morning skies on October 15, 1997. The mighty Titan 4B Centaur rocket is seen here across the water, arcing away from Launch Complex 40 at Cape Canaveral Air Station. Cassini, a sophisticated robot spacecraft was actually headed toward inner planet Venus, the first way point in its 7 year, 2.2 billion mile interplanetary journey to Saturn. In fact, Cassini swung by Venus during April 1998 and June 1999, Earth in August 1999, and Jupiter in December 2000. During each of these "gravity assist" encounters the six ton spacecraft picked up speed, reaching Saturn only three days ago. Cassini is now orbiting the ringed gas giant, with the Huygens Probe scheduled to separate from the spacecraft in December. The probe's descent to the surface of Saturn's large moon Titan will be the most distant landing ever attempted.
M57: The Ring Nebula (2004-07-04)
cept for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. This planetary nebula's simple, graceful appearance is thought to be due to perspective -- our view from planet Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Astronomers of the Hubble Heritage Project produced this strikingly sharp image from  Hubble Space Telescope observations using natural appearing colors to indicate the temperature of the stellar gas shroud. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. Dark, elongated structures can also be seen near the nebula's edge. The Ring Nebula is about one light-year across and 2,000 light-years away in the northern constellation Lyra.
Cassini Images Density Waves in Saturn's Rings (2004-07-05)
What causes the patterns in Saturn's rings?  The Cassini spacecraft just entering orbit around Saturn has started sending back spectacular images of Saturn's immense ring system in unprecedented detail.  The physical cause for many of newly resolved ring structures is not always understood.   The cause for the beautifully geometric type of ring structure shown above in Saturn's A ring, however, is hypothesized to be a spiral density wave.  A small moon systematically perturbing the orbits of ring particles orbiting at slightly different distances causes such a density wave bunching.  Also visible on the image right is a bending wave, a vertical wave in ring particles also caused by the gravity of a nearby moon.  This close-up spans about 220 kilometers. Cassini is scheduled to take and send back images of the distant ringed Saturn and its unusual moons for the next four years.
Titan from Cassini in Infrared (2004-07-06)
Could the building blocks of life exist under the smog of Titan?  What is creating all of the methane?  To help answer these questions, the largest and most mysterious moon of Saturn got a quick first look from the Cassini robot spacecraft soon after entering orbit around the giant planet last week.  Although thick atmospheric smog prevented detailed surface images in visible light, infrared light was able to provide interesting clues to the nature of Titan's surface.  The above images show Titan in three different colors of infrared light, with the most energetic on the left.  The leftmost image is the most detailed but shows surface features that are not yet well understood.  The smoothness of the middle image is consistent with a large frozen ocean of water ice containing simple hydrocarbons.  The darker regions on the rightmost image might indicate areas relatively rich in hydrocarbons.  The white spot visible near the South Pole is hypothesized to be a persistent cloud of large particles containing methane.  A better understanding of the mysterious surface of Titan will hopefully be forthcoming as scientists study these images and those from a planned 45 flybys over the next four years.  In January, Cassini is scheduled to drop the Huygens probe onto Titan's surface.
N11B: Star Cloud of the LMC (2004-07-07)
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 above image actually highlights N11B, part of the nebula that spans about 100 light years and is particularly active.  The entire emission nebula N11 is second in LMC size only to 30 Doradus.  Studying the stars in N11B has shown that it actually houses three successive generations of star formation.  Compact globules of dark dust housing emerging young stars are also visible on the upper right.
Southern Cross Star Colors (2004-07-08)
Fix your camera to a tripod, lock the shutter open, and you can easily record an image of star trails, the graceful concentric arcs traced by the stars as planet Earth rotates on its axis. Gradually change the focus of the camera lens during the exposure, and you could end up with a dramatic picture like this one where the out-of-focus portion of the trail shows off the star's color. In this case, the subject is one of the most famous constellations in the night sky, Crux, the Southern Cross. Gacrux or gamma Crucis is the bright red giant star only 88 light-years distant that forms the top of the Cross seen here near top center. Acrux, the hot blue star at the bottom of the Cross is about 320 light-years distant. Actually a binary star system, Acrux is the alpha star of the compact Southern Cross and lies along a line pointing from Gacrux to the South Celestial Pole, off the lower right edge of the picture. Adding a separate short exposure to the end of the step-focussed trails to better show the positions of the stars themselves, astronomer Stefan Seip recorded this remarkable image last May in the dark night skies above Namibia.
Ringed Nebulae (2004-07-09)
Have you heard a lot about ringed planets lately? Well, consider this gorgeous celestial vista centered on the Milky Way's own planetary nebula M57, the famous Ring Nebula. The wide view is a composite of three exposures; one to record the details of the inner roughly one light-year span of the familiar nebula, one to record the surprisingly intricate but faint outer rings of glowing hydrogen gas, and one to pick up the rich assortment of distant background galaxies. By chance, one of the background galaxies, IC 1296 at the upper left, is close enough to show its barred, spiral structure making an attractive visual comparison with M57. Interestingly, though IC 1296 is 200 million light-years away compared to only 2 thousand light-years for M57, a faint ring is also apparent around the outer reaches of the distant spiral galaxy.
Phoebe Craters in Stereo (2004-07-10)
Get out your red/blue glasses and gaze across the spectacular, cratered terrain of Saturn's icy moon Phoebe in stereo. The dramatic 3-D perspective spans roughly 50 kilometers and is based on two raw, uncalibrated images (N00004840.jpg and N00004838.jpg) from the Cassini spacecraft's narrow angle camera taken during the flyby on June 11 at a range of just over 13,500 kilometers. Phoebe itself is only about 200 kilometers in diameter. Stereo experimenter Patrick Vantuyne noted the substantial overlap in the raw image data and was able to assemble the dramatic view of the overlapping region as a red/blue stereo anaglyph. Looking for a cool project? Stereo glasses can be easily constructed using red and blue plastic for filters. To view this image, the red filter is used for the left eye.
WMAP Resolves the Universe (2004-07-11)
Analyses of a new high-resolution map of microwave light emitted only 380,000 years after the Big Bang appear to define our universe more precisely than ever before.  The eagerly awaited results announced last year from the orbiting Wilkinson Microwave Anisotropy Probe resolve several long-standing disagreements in cosmology rooted in less precise data.  Specifically, present analyses of above WMAP all-sky image indicate that the universe is 13.7 billion years old (accurate to 1 percent), composed of 73 percent dark energy, 23 percent cold dark matter, and only 4 percent atoms, is currently expanding at the rate of 71 km/sec/Mpc (accurate to 5 percent), underwent episodes of rapid expansion called inflation, and will expand forever.  Astronomers will likely research the foundations and implications of these results for years to come.
Cassini Images Saturn's A Ring (2004-07-12)
What are Saturn's rings made of?  In an effort to find out, the robot spacecraft Cassini that entered orbit around Saturn two weeks ago took several detailed images of the area surrounding Saturn's large A ring in ultraviolet light.  In the above image, the bluer an area appears, the richer it is in water ice. Conversely, the redder an area appears, the richer it is in some sort of dirt. This and other images show that inner rings have more dirt than outer rings.  Specifically, as shown above, the thin rings in the Cassini Division on the left have relatively high dirt content compared to the outer parts of Saturn's A ring, shown on the right.  This dirt/ice trend could be a big clue to the ring's origin.  The thin red band in the otherwise blue A ring is the Encke Gap.  The exact composition of dirt remains unknown.
Orion Nebula in Oxygen, Hydrogen, and Sulfur (2004-07-13)
The Great Nebula in Orion, an immense, nearby starbirth region, is arguably the most famous of all astronomical nebulae.  The Orion Nebula, also known as M42, is shown above through ultraviolet and blue filters augmented with three exact colors specifically emitted by hydrogen, oxygen, and sulfur.  In addition to housing a bright open cluster of stars known as the Trapezium, the Orion Nebula contains many stellar nurseries.  These nurseries contain glowing gas, hot young stars, proplyds, and stellar jets spewing material at high speeds.  Many of the filamentary structures visible in this image are actually shock waves - fronts where fast moving material encounters slow moving gas.  The Orion Nebula spans about 40 light years and is located about 1500 light years away in the same spiral arm of our Galaxy as the Sun.
Polar Polygons on Mars (2004-07-14)
What's the best way to the city center?  What looks like a street map of some city on Earth is actually a series of naturally-formed fragmented polar polygons on Mars.  The existence of polar polygons on Mars is particularly interesting as they may indicate regions where water ice lies within a few meters of the surface.  Similar looking polygons are commonly found in the arctic and Antarctic of Earth, where they typically form from a repetitive cycle of freezing and thawing.  The above image spans a distance of about 3 kilometers and was taken recently by the orbiting Mars Global Surveyor.
Stars and Dust in Corona Australis (2004-07-15)
A cosmic dust cloud sprawls across a rich field of stars in this gorgeous wide field telescopic vista looking toward Corona Australis, the Southern Crown. Probably less than 500 light-years away and effectively blocking light from more distant, background stars in the Milky Way, the densest part of the dust cloud is about 8 light-years long. At its tip (lower left) is a series of lovely blue nebulae cataloged as NGC 6726, 6727, 6729, and IC 4812. Their characteristic blue color is produced as light from hot stars is reflected by the cosmic dust. The tiny but intriguing yellowish arc visible near the blue nebulae marks young variable star R Coronae Australis. Magnificent globular star cluster NGC 6723 is seen here below and left of the nebulae. While NGC 6723 appears to be just outside Corona Australis in the constellation Sagittarius, it actually lies nearly 30,000 light-years away, far beyond the Corona Australis dust cloud.
The Bubble (2004-07-16)
Blown by the wind from a star, this tantalizing, ghostly apparition is cataloged as NGC 7635, but known simply as The Bubble Nebula. Astronomer Ken Crawford's striking view combines a long exposure through a hydrogen alpha filter with color images to reveal the intricate details of this cosmic bubble and its environment. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Seen here above and left of the Bubble's center is a bright hot star embedded in telltale blue hues characteristic of dust reflected starlight. A fierce stellar wind and intense radiation from the star, which likely has a mass 10 to 20 times that of the Sun, has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia.