omnianasa/nasa-apod-metadata huggingface dataset:
Transit of Venus Stereogram (2004-07-17)
Venus glides in front of an enormous solar disk in these two frames from the TRACE satellite imaging of the inner planet's 2004 transit. Arranged in a "right/left" stereogram, the frames are intended to be viewed at a comfortable distance from the screen with your eyes gently crossed, allowing the images to merge and produce a pleasing stereo effect. Shown during the ingress (beginning) phase of the transit, the silhouetted portion of the planet appears to float dramatically in front of the Sun's granulated surface. Of course, the dense Cytherian (Venusian) atmosphere also scatters and refracts the intense sunlight. The effect is visible across the portion of the planet still beyond the Sun's edge and viewed against the blackness of space.
M31: The Andromeda Galaxy (2004-07-18)
Andromeda is the nearest major galaxy to our own Milky Way Galaxy.  Our Galaxy is thought to look much like Andromeda.  Together these two galaxies dominate the Local Group of galaxies.  The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it.  The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object.  Andromeda is frequently referred to as M31 since it is the 31st object on  Messier's list of diffuse sky objects.  M31 is so distant it takes about two million years for light to reach us from there.  Although visible without aid, the above image of M31 is a digital mosaic of 20 frames taken with a small telescope.  Much about M31 remains unknown, including how the center acquired two nuclei.
Attacking Mars (2004-07-19)
The Spirit rover attacked Mars again late last month.  What might look, above, like a military attack, though, was once again just a scientific one - Spirit was instructed to closely inspect some interesting rocks near Columbia Hills.  Spirits Front Hazard Avoidance Camera captured the rover's Instrument Deployment Device above as it guided the Microscopic Imager to get a closer look at a rock dubbed Breadbox.   Images taken by the Microscopic Imager show a rock surface consistent with basalt corroded by ancient groundwater.  Structures with similar origins can be found, for example, in the Western Desert of Egypt on Earth. The above picture taken on June 30, the 175th Martian day that the Spirit rover has been on the red planet.
Space Station, Venus, Sun (2004-07-20)
On June 8, Venus was not the only celestial object to pass in front of the Sun.  A few well-situated photographers caught the International Space Station also crossing the Sun simultaneously.  Pictured above is a unique time-lapse image of the unprecedented double transit, a rare event that was visible for less than a second from a narrow band on Earth.   The above image is a combination of 12 frames taken 0.033 seconds apart and each themselves lasting only 1/10,000 th of a second.  The image was taken from the small village of Stupava in Slovakia.  The next time Venus will appear to cross the Sun from Earth will be in 2012.   News: Today is the 35th anniversary of the Apollo 11 Moon landing.
A Shadow on the Rings of Saturn (2004-07-21)
This picture of Saturn could not have been taken from Earth.  No Earth based picture could possibly view the night side of Saturn and the corresponding shadow cast across Saturn's rings.  Since Earth is much closer to the Sun than Saturn, only the day side of the planet is visible from the Earth.  Rather, this picture was taken by the robot Cassini spacecraft that began orbiting Saturn earlier this month.  The dark western limb of Saturn looms large on the image right, while complex concentrations of small ring particles reflect sunlight on the image left.  Saturn's enigmatic F ring is visible around the outside, showing mysterious knots.  The small moon Epimetheus, only about 100 kilometers across, can also been seen on the far left.  Cassini is scheduled to drop a probe toward the largest moon Titan in December.
Aura Launch (2004-07-22)
In this alluring time exposure, star trails arc across the night sky above Monterey Bay and the lights of Santa Cruz, California, USA. But since the exposure began around 3:01am PDT on July 15 it also records the long trail of a Delta II rocket lofting NASA's Aura spacecraft into Earth orbit. Watching from a vantage point about 200 miles north of the Vandenberg Air Force Base launch site, photographer Rick Baldridge reports that the trail represents the first five minutes of the rocket's powered flight with the ignition of additional solid fuel strap-on motors visible after liftoff, near the beginning of the track. The rocket trail ends at first stage shutdown. Seen under the rocket's path, the two brightest star trails mark the alpha and beta stars of the high-flying constellation Grus. The Aura spacecraft's goal is a comprehensive study of planet Earth's nurturing atmosphere.
Saturn's Rings in Natural Color (2004-07-23)
What colors are Saturn's rings?  Recent images from the Cassini spacecraft now orbiting Saturn confirm that different rings have slightly different colors.  The above image shows their sometimes-subtle differences in brightness and color.  The rings reflect sunlight and so, even if they were perfectly reflecting, would appear the color of the Sun.  The ring particles are mostly light water-ice, although these particles can be shaded by an unknown type of darker dirt.  Thinner and more isolated rings also naturally appear darker.  The brightest section pictured above is Saturn's B ring.
A String Of Pearls (2004-07-24)
Comet Shoemaker-Levy 9, named after its co-discoverers, was often referred to as the "string of pearls" comet. It is famous for its suggestive appearance as well as its collision with the planet Jupiter! The comet's original single nucleus was torn to pieces by Jupiter's strong gravity during a close encounter with the solar system's largest planet in 1992. The pieces are seen (scroll right) in this composite of Hubble Space Telescope images to be "pearls" strung out along the comet's orbital path. Only ten years ago, in July of 1994, these pieces collided with Jupiter in a rare and spectacular series of events.
A Solar Filament Lifts Off (2004-07-25)
Hot gas frequently erupts from the Sun.  One such eruption produced the glowing filament pictured above, which was captured in 2000 July by the Earth-orbiting TRACE satellite.  The filament, although small compared to the overall size of the Sun, measures over 100,000 kilometers in height, so that the entire Earth could easily fit into its outstretched arms.  Gas in the filament is funneled by the complex and changing magnetic field of the Sun.  After lifting off from the Sun's surface, most of the filamentary gas will eventually fall back.  More powerful solar eruptions emit particles that reach the Earth and can disrupt manmade satellites.  The cause and nature of solar eruptions are the topic of much research.
A Large Active Region Crosses the Sun (2004-07-26)
An unexpectedly large sunspot region is now crossing the Sun.  The active region is home to rivers of hot plasma, explosive flares, strong magnetic fields, a powerful Coronal Mass Ejection (CME), and a sunspot group so large it can be seen by the protected eye without magnification.  In fact, this region appears larger than Venus did when it crossed the Sun last month.  Pictured above is a close-up of this sunspot group, officially tagged AR 10652, taken just four days ago.  The region is now nearing the Sun's eastern limb and will disappear from view in a few days.  Energetic ions from sunspot group 652 continue to impact the Earth and create rare purple auroras.
Razorbacks in Endurance Crater (2004-07-27)
Over one year after its launch, robot geologist Opportunity has been spending recent sols on Mars inching its way down the slopes of Endurance crater. Littered with martian blueberries, some flat rocks within the crater also seem to have surprising razorbacks -- narrow slabs sticking up along their edges. Like the blueberries, it's possible that the sharp, narrow features are related to water. They could be formed by minerals deposited by water in cracks, with the surrounding softer material subsequently eroded away. How narrow are they? The ones pictured here in an enhanced color image from Opportunity's panoramic camera are actually only a few centimeters high and about half a centimeter wide. Impressive 3D views have been constructed by stereo experimenter P. Vantuyne based on the camera's left and right eye images of the region.
A Cygnus Starfield (2004-07-28)
In the constellation of the swan near the nebula of the pelican lies the gas cloud of the butterfly surrounding a star known as the hen.  That star, given the proper name Sadr, is visible to the unaided eye but found here as the brightest object on the upper left.  Sadr, at 1500 light years distant, is near the center of the Butterfly Nebula (IC 1318) in a bright region given the comparatively staid label of IC 1318B.  The fantastic starfield that surrounds Sadr contains stars old and young, an open cluster of stars (NGC 6910 visible on the image left), vast clouds of hydrogen gas that glow red, and picturesque pockets and filaments of dark dust.  The above image is a digital fusion of several different color images of the gamma Cygni (Sadr) region
Melas Chasma (2004-07-29)
Steep cliffs drop into the rugged terrain of Melas Chasma in this stunning view from the Mars Express spacecraft orbiting the Red Planet. At a scale of 16 meters per pixel, the image data from the orbiter's High Resolution Stereo Camera offers evidence that volcanic activity, water, wind erosion and marsquakes may all have shaped the region. Melas Chasma lies along the central southern edge of the large Valles Marineris, the grand canyon of Mars. While the Valles Marineris is itself over 4,000 kilometers long and up to 10 kilometers deep, the region pictured spans about 70 kilometers. The floor of Melas Chasma seen here is several kilometers below the surrounding plateau.
Northern Lights (2004-07-30)
While enjoying the spaceweather on a gorgeous summer evening in mid-July, astronomer Philippe Moussette captured this colorful fish-eye lens view looking north from the Observatoire Mont Cosmos, Quebec, Canada, planet Earth. In the foreground, lights along the northern horizon give an orange cast to the low clouds. But far above the clouds, at altitudes of 100 kilometers or more, are alluring green and purple hues of the aurora borealis or northern lights, a glow powered by energetic particles at the edge of space. In the background are familiar stars of the northern sky. In particular, that famous celestial kitchen utensil, the Big Dipper (left), and the W-shaped constellation Cassiopeia (right) are easy to spot. Then, just follow the pointer stars of the Big Dipper to Polaris, perhaps the most famous northern light of all.
Tonight: A Blue Moon (2004-07-31)
How often does a full moon occur twice in a single month?  Exactly once in a Blue Moon.  In fact, the modern usage of the term "Blue Moon" refers to the second Full Moon in a single month.  Tonight's Blue Moon will be the first since November 2001.  A Blue Moon typically occurs every few years.  The reason for the rarity of the Blue Moon is that the 29.53 days between full moons is just slightly shorter than the number of days in the average month.  Don't, however, expect the moon to look blue tonight!  The term "Blue Moon" has recently been traced to an error in a magazine article in 1946.  It is possible for the Moon to appear tinged by a blue hue, sometimes caused by fine dirt circulating in the Earth's atmosphere, possibly from a volcanic explosion.  The above picture was taken not during a full moon but through a morning sky that appeared dark blue.  The bright crescent is the only part directly exposed to sunlight - the rest of the Moon glows from sunlight reflected from the Earth.  In this dramatic photo, however, the planet Jupiter is also visible along with its four largest moons.
A Force from Empty Space: The Casimir Effect (2004-08-01)
This tiny ball provides evidence that the universe will expand forever.  Measuring slightly over one tenth of a millimeter, the ball moves toward a smooth plate in response to energy fluctuations in the vacuum of empty space.  The attraction is known as the Casimir Effect, named for its discoverer, who, 50 years ago, was trying to understand why fluids like mayonnaise move so slowly.  Today, evidence is accumulating that most of the energy density in the universe is in an unknown form dubbed dark energy.  The form and genesis of dark energy is almost completely unknown, but postulated as related to vacuum fluctuations similar to the Casimir Effect but generated somehow by space itself.  This vast and mysterious dark energy appears to gravitationally repel all matter and hence will likely cause the universe to expand forever.  Understanding vacuum fluctuations is on the forefront of research not only to better understand our universe but also for stopping micro-mechanical machine parts from sticking together.
Spicules: Jets on the Sun (2004-08-02)
Imagine a pipe as wide as a state and as long as half the Earth.  Now imagine that this pipe is filled with hot gas moving 50,000 kilometers per hour.  Further imagine that this pipe is not made of metal but a transparent magnetic field.  You are envisioning just one of thousands of young spicules on the active Sun.  Pictured above is perhaps the highest resolution image yet of these enigmatic solar flux tubes.  Spicules dot the above frame of solar active region 10380 that crossed the Sun in June, but are particularly evident as a carpet of dark tubes on the right.  Time-sequenced images have recently shown that spicules last about five minutes, starting out as tall tubes of rapidly rising gas but eventually fading as the gas peaks and falls back down to the Sun.  These images also indicate, for the first time, that the ultimate cause of spicules is sound-like waves that flow over the Sun's surface but leak into the Sun's atmosphere.
Shadow of a Martian Robot (2004-08-03)
What if you saw your shadow on Mars and it wasn't human?  Then you might be the Opportunity rover currently exploring Mars.  Opportunity and sister robot Spirit have been probing the red planet since January, finding evidence of ancient water, and sending breathtaking images across the inner Solar System.  Pictured above, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow.  Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background.  Opportunity is cautiously edging its way into this enigmatic crater, hoping to find new clues into the wet ancient past of our Solar System's second most habitable planet.
Solar Arcs and Halos (2004-08-04)
Have you ever seen a bright halo around the Sun?  Unusual halos and arcs were so bright one recent afternoon in Trier, Germany that even casual people on the street noticed them.  The fantastic sky display is pictured above and included a 22 degree halo arc, a complete parhelic circle, a circumhorizon arc and even an infralateral arc.  A computer simulation has been run that mimics the above rare display.  A cloud partially blocked the usually more intense direct glare of the Sun. Sunlight refracting through falling and fluttering hexagonal ice crystals creates such displays.  Such atmospheric ice crystals also cause sundogs and Moon halos.
Emission Nebula IC 1396 (2004-08-05)
Sprawling across hundreds of light-years, emission nebula IC 1396 mixes glowing cosmic gas and dark dust clouds. Stars are forming in this area, only about 3,000 light-years from Earth. This particularly colorful view of the region is a composite of digital images recorded through narrow band filters. The filters actually block out most of the light ... but narrowly transmit wavelengths characteristic of specific glowing atoms in the nebula. In fact, the color scheme used here makes it easy to trace some of the elements which contribute to the emission from IC 1396. Emission from sulfur atoms is shown in red, hydrogen atoms green, and oxygen in blue. The beautiful and useful result is still very different from what the eye might see. IC 1396 lies in the high and far off constellation of Cepheus.
The Giant and the Glory (2004-08-06)
On a flight from Vienna to Brussels, astronomer Franz Kerschbaum looked out the window and photographed this beautiful atmospheric phenomenon, the glory, shining in the direction directly opposite the Sun.  Before airplanes, the glory, known to some as the heiligenschein or the Specter of the Brocken, was occasionally seen from mountaintops.  There, when conditions were right, one could look away from the Sun and see what appeared to be the shadow of a giant surrounded by a bright halo.  Of course, the giant turns out to be the observer, and in the modern version a silhouette of a plane frequently occupies the glory's center. The cause of the glory is relatively complex.  Briefly, small droplets of water reflect, refract, and diffract sunlight backwards towards the Sun. The phenomenon has a counterpart in astronomy, where looking out from planet Earth in the direction opposite the Sun yields a bright spot called the gegenschein.
Giant Cluster Bends, Breaks Images (2004-08-07)
What are those strange blue objects?  Many are images of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant  cluster of galaxies.  Cluster galaxies here appear yellow and -- together with the cluster's dark matter -- act as a gravitational lens.  A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light.  The distinctive shape of this background galaxy -- which is probably just forming -- has allowed astronomers to deduce that it has separate images at 4, 8, 9 and 10 o'clock, from the center of the cluster.  Possibly even the blue smudge just left of center is yet another image!  This spectacular photo from the Hubble Space Telescope was taken in October 1994.
Contemplating the Sky (2004-08-08)
Have you contemplated your sky recently?  This week will be a good one for midnight meditators at many northerly locations as meteors from the Perseid meteor shower will frequently streak through.  The Perseid meteor shower has slowly been building to a crescendo and should peak on the nights of August 11 and 12. Pictured above on 2002 August 1, a group of celestial sightseers near Quebec, Canada are treated to a dark and wondrous night sky that contained bright stars, green auroras, the band of our Milky Way galaxy, a majestic Moon rising, the International Space Station slowly gliding by, and the occasional flash of a Perseid meteor.  Although no meteors were caught in this frame, the Big Dipper remained quite prominent.
The Dark River to Antares (2004-08-09)
Connecting the Pipe Nebula to the bright star Antares is a flowing dark cloud nicknamed the Dark River.  The murkiness of the Dark River is caused by absorption of background starlight by dust, although the nebula contains mostly hydrogen and molecular gas.  Antares, the brightest star in the frame, is embedded in the colorful Rho Ophiuchi nebula clouds.  The Dark River, pictured above across the upper left, spans over 20 times the angular diameter of the Moon and lies about 500 light years distant.  Other types of nebula visible here include red emission nebula and the blue reflection nebula.
The Double Haze above Titan (2004-08-10)
Most moons have no haze layer at all - why does Titan have two?  Images from the Cassini spacecraft that  slipped into orbit around Saturn last month confirm that the Solar System's most mysterious moon is surrounded not only by a thick atmosphere but also by two distinct spheres of haze.  These layers are visible as purple in the above false-color ultraviolet image.  Titan's opaque atmosphere is similar to Earth's atmosphere in that it is composed mostly of nitrogen.  As energetic sunlight strikes high level atmospheric nitrogen and methane, trace amounts of organic compounds such as ethane and carbon dioxide appear to form.  These and other complex organic molecules likely populate the detached haze layer.  In December 2004, Cassini will launch the Huygens probe to land on Titan.
A Perseid Meteor (2004-08-11)
The ongoing Perseid Meteor Shower should be at its strongest tonight and tomorrow night. Although meteors should be visible all night long, the best time to watch will be between 2:00 AM and dawn each night. In dark, moonless, predawn skies you may see dozens of meteors per hour. Sky enthusiasts in Europe and Asia might see an unusual burst of meteors near 2100 hours UT. Grains of cosmic sand and gravel shed from Comet Swift-Tuttle will streak across the sky as they vaporize during entry into Earth's atmosphere. Tracing the meteor trails backwards, experienced skygazers will find they converge on the constellation Perseus, thus this annual meteor shower's name. Pictured above is a Perseid meteor from 2002 over a rock formation in the US Southwest desert. Shadowing and blurring are caused by the long 10-minute exposure. The brightest Perseids can be seen from anywhere on Earth by monitoring the continuously returning images from the Night Sky Live cameras.
The Spectrum of a Meteor (2004-08-12)
Chasing the brief flash of a meteor trail across the sky with a very large telescope is a nearly impossible task. But on May 12, 2002, astronomers got lucky, as a bright meteor chanced across the narrow slit of their spectrograph at the Paranal Observatory. At the time, the spectrograph was being used to study the light from a supernova, separating and recording the many near-infrared emission lines produced by atoms in the distant stellar explosion. Below this artistic montage of a meteor streak and Very Large Telescope units at Paranal, panel a shows the near-infrared sky background spectrum and the May 12 meteor combined. Panel b shows the emission spectrum of the meteor alone, after subtracting away the background contributions. The meteor emission is due to colliding oxygen and nitrogen atoms and molecules in the superheated air along the glowing trail at an altitude of about 100 kilometers.
Perseid Fireball Over Japan (2004-08-13)
joying the bright Moon's absence from early morning skies, observers around the world reported lovely displays during this year's Perseid meteor shower. As anticipated, peak rates were about one meteor per minute. Though most Perseids were faint, this bright and colorful fireball meteor flashed through skies over Japan on August 12 at 0317 JST. Ending at the upper right, the meteor's trail points down and to the left, back to the shower's radiant point between the constellations of Perseus and Cassiopeia, seen here just above the tower structure in the foreground. The Pleiades star cluster is also visible well below the meteor's trail. Perseid shower meteors can be traced to particles of dust from the tail of comet Swift-Tuttle. The comet dust impacts the atmosphere at speeds of around 60 kilometers per second. While this annual shower's peak has come and gone, Perseid meteors should still be visible over the next few nights, but at a greatly reduced rate.
Messenger Launch (2004-08-14)
Streaking into the early morning sky on August 3rd, a Delta II rocket launches NASA's Messenger spacecraft on an interplanetary voyage to Mercury. Scheduled to become the first probe to orbit Mercury, Messenger will begin by looping through the inner Solar System in a series of close flybys of planet Earth and Venus. The flybys are designed as trajectory changing gravity assist encounters to ultimately achieve the goal of orbiting Mercury in 2011. Prior to entering orbit, Messenger will also flyby Mercury in 2008 and 2009 as the first spacecraft to visit the Solar System's innermost planet since Mariner 10 in the mid 1970s. This dramatic view of the Messenger launch was recorded from a pier in Jetty Park at the north end of Cocoa Beach about 2.5 miles from the Cape Canaveral launch site. So what's that erratic blue streak on the right? It's the reflection from a camera blurred in the time exposure.