omnianasa/nasa-apod-metadata huggingface dataset:
Io's Surface: Under Construction (2002-10-19)
Like the downtown area of your favorite city, the roads you drive to work on, and any self-respecting web site ... Io's surface is constantly under construction. This moon of Jupiter holds the distinction of being the Solar System's most volcanically active body -- its bizarre looking surface continuously formed and reformed by lava flows. Generated using 1996 data from NASA's Galileo spacecraft, this high resolution composite image of Io is centered on the side of Io that always faces away from Jupiter. It has been enhanced to emphasize Io's surface brightness and color variations, revealing features as small as 1.5 miles across. The notable absence of impact craters suggests that the entire surface is covered with new volcanic deposits much more rapidly than craters are created. What drives this volcanic powerhouse? A likely energy source is the changing gravitational tides caused by Jupiter and the other Galilean moons as Io orbits the massive gas giant planet. Heating Io's interior, the pumping tides would generate the sulfurous volcanic activity.
The Space Shuttle Docked with Mir (2002-10-20)
Before there was the International Space Station, the reigning orbiting spaceport was Russia's Mir.  Pictured above in 1995, the United States Space Shuttle Atlantis docked with the segmented Mir. During shuttle mission STS-71, astronauts answered questions from school students over amateur radio and performed science experiments aboard Spacelab.  The Spacelab experiments helped to increase understanding of the effects of long-duration space flights on the human body. Last year, after 15 years of successful service, the decaying Mir space station broke up as it entered the Earth's atmosphere.
M31: The Andromeda Galaxy (2002-10-21)
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.
A Small Double Ozone Hole in 2002 (2002-10-22)
As expected, the ozone hole near Earth's South Pole is back again this year. This time, however, it's smaller than the past two years, and has an unusual double lobe structure.  Ozone is important because it shields us from damaging ultraviolet sunlight.  Ozone is vulnerable, though, to CFCs and halons being released into the atmosphere.  International efforts to reduce the use of these damaging chemicals appear to be having a positive effect on their atmospheric abundance.  The smaller size of the ozone hole this year, however, is attributed mostly to warmer than normal air in the surrounding stratosphere.  The above picture of the ozone hole was taken on September 24 by  TOMS on board the orbiting Earth Probe satellite.
Liftoff With the Space Shuttle (2002-10-23)
What would it look like to see a Space Shuttle liftoff from just above the shuttle?  Because the answer has value in assessing spacecraft performance, NASA attached a small RocketCam to the side of the External Tank on the launch of the Space Shuttle Atlantis earlier this month.  The above five-frame movie, excerpted from a longer video sequence, shows in dramatic fashion what it looks like to ride into space while looking back at the Earth.  In the final frame, taken about 15 minutes after liftoff, the shuttle can be seen separating from the External Tank and proceeding to orbit.
Gullies on Mars (2002-10-24)
The Gullies of Mars would probably not have been sensational enough for the title of a vintage Edgar Rice Burroughs story about the Red Planet. But it would get the attention of planetary scientists today. First identified in high resolution images of Mars recorded by the orbiting Mars Global Surveyor spacecraft, the gullies are interpreted as startling evidence that liquid water flowed across the martian surface in geologically recent times. Similar channels on Earth are formed by flowing water, but on Mars the temperature is normally too cold and the atmosphere too thin to sustain liquid water. Still, it is thought possible that water did burst out from underground layers and remain liquid long enough to erode the gullies, while alternative explanations suggest the erosion was produced by a flowing jumble of solid and gaseous carbon dioxide. Spanning a few kilometers along the wall of an impact crater this high resolution image from Mars Global Surveyor shows typical martian gullies near the top of the crater wall giving way to sand dunes toward the crater floor. Whitish frost is visible near the top and on the dark sand dunes below. The muted colors were synthesized from wide angle image data.
Journey to the Center of the Galaxy (2002-10-25)
In Jules Verne's science fiction classic A Journey to the Center of the Earth, Professor Hardwigg and his fellow explorers encounter many strange and exciting wonders. What wonders lie at the center of our Galaxy? Astronomers know of some of the bizarre objects which exist there, like vast cosmic dust clouds, bright star clusters, swirling rings of gas, and even a supermassive black hole. Much of the Galactic Center is shielded from our view in visible light by the intervening dust and gas, but it can be explored using other forms of electromagnetic radiation. This haunting wide angle image of the Galactic Center region in infrared light was constructed using data from the Midcourse Space Experiment (MSX) satellite. The image maps three mid-infrared bands, otherwise invisible to human eyes, into visible blue, green, and red colors revealing the thermal emission from dust clouds near the galactic center that have been heated by starlight. The galactic plane runs along the middle of this image while the galactic center itself is the bright spot at picture center. The field of view of this cropped picture is about 1.5 by 2.5 degrees.
Dark Matter, X-rays, and NGC 720 (2002-10-26)
cal galaxy NGC 720 is enveloped in a cosmic cloud of x-ray emitting gas. Seen in this false color image from the Chandra X-ray Observatory, the extreme temperature of the gas - about 7 million degrees Celsius - makes it impossible to confine the cloud to the vicinity of NGC 720 based on the gravity of this galaxy's visible stars alone. In fact, the x-ray cloud is taken as solid evidence for the presence of dark matter surrounding NGC 720 -- unseen material which has gravitational influence that can keep the x-ray hot gas cloud from escaping. Chandra's remarkable vision clearly distinguishes the bright point-like x-ray sources from the diffuse cloud. Astronomers can then use the detailed shape of the cloud to infer the distribution of dark matter in NGC 720 and even test theories about the fundamental nature of dark matter. According to modern understanding, the mysterious dark matter, whatever it is, is by far the most common form of matter in the Universe. Galaxy NGC 720 lies about 80 million light-years distant toward the constellation Cetus.
Asteroid Gaspra's Best Face (2002-10-27)
Asteroid 951 Gaspra is a huge rock tumbling in space.  Gaspra became one of the best-studied asteroids in 1991 when the spacecraft Galileo flew by. In the above photograph, subtle color variations have been exaggerated to highlight changes in reflectivity, surface structure and composition.  Gaspra is about 20 kilometers long and orbits the Sun in the main asteroid belt between Mars and Jupiter.
Earth's Richat Structure (2002-10-28)
What on Earth is that? The Richat Structure in the Sahara Desert of Mauritania is easily visible from space because it is nearly 50 kilometers across.  Once thought to be an impact crater, the Richat Structure's flat middle and lack of shock-altered rock indicates otherwise.  The possibility that the Richat Structure was formed by a volcanic eruption also seems improbable because of the lack of a dome of igneous or volcanic rock.  Rather, the layered sedimentary rock of the Richat structure is now thought by many to have been caused by uplifted rock sculpted by erosion.  The above image was captured last year by the orbiting Landsat 7 satellite.  Why the Richat Structure is nearly circular remains a mystery.
A Lunar Rille (2002-10-29)
What could cause a long indentation on the Moon?  First discovered over 200 years ago with a small telescope, rilles (rhymes with pills) appear all over the Moon.  Three types of rilles are now recognized: sinuous rilles, which have many meandering curves, arcuate rilles which form sweeping arcs, and straight rilles, like Ariadaeus Rille pictured above.  Long rilles such as Ariadaeus Rille extend for hundreds of kilometers.  Sinuous rilles are now thought to be remnants of ancient lava flows, but the origins of arcuate and linear rilles are still a topic of research.  The above linear rille was photographed by the Apollo 10 crew in 1969 during their historic approach to only 14-kilometers above the lunar surface.  Two months later, Apollo 11, incorporating much knowledge gained from Apollo 10, landed on the Moon.
Leonids Over Uluru (2002-10-30)
Will this year's Leonid meteor shower be as good as last year's?  No one knows for sure.  Possibly, however, in the waning nighttime hours of November 18 and lasting throughout much of November 19, sky gazers across the globe may get their last chance ever to see a meteor storm.  Although the glare of a nearly full Moon will likely hide the presence of many faint meteors, plenty of bright meteors may well streak across the other side of the sky.  The above image was taken during 2001 as Leonids stormed over Uluru (Ayers Rock), Australia.  The image is actually a digital composite of 22 separate frames, including one at sunset.  The Gum Nebula is visible on the upper left.
Aurora in the Night (2002-10-31)
Tomorrow's picture: Europa's Freckles  < | Archive | Index | Search | Calendar | Glossary | Education | About APOD | >  Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA / GSFC & NASA SEU Edu. Forum & Michigan Tech. U.
Europa's Freckles (2002-11-01)
uropa, one of Jupiter's large Galilean moons, may well possess an ocean of liquid water hidden beneath its icy surface -- and so holds the tantalizing possibility of life. In this image, constructed with data recorded in 1996 and 1997 by the Galileo spacecraft, Europa's characteristic surface ridges and cracks are seen along with domes and dark reddish spots called lenticulae from the Latin word for freckles. The freckles are about 10 kilometers across and are believed to be blobs of warmer ice from below that have gradually risen through the colder surface layers, analogous to the motions in a lava lamp. If the freckles do represent material from deeper ice layers closer to the hidden ocean, future space missions to investigate Europa's interior could sample the relatively accessible freckles rather than drill through Europa's potentially thick ice shell.
NGC 604: Giant Stellar Nursery (2002-11-02)
Scattered within this cavernous nebula, cataloged as NGC 604, are over 200 newly formed hot, massive, stars. At 1,500 light-years across, this expansive cloud of interstellar gas and dust is effectively a giant stellar nursery located some three million light-years distant in the spiral galaxy, M33. The newborn stars irradiate the gas with energetic ultraviolet light stripping electrons from atoms and producing a characteristic nebular glow. The details of the nebula's structure hold clues to the mysteries of star formation and galaxy evolution.
The International Space Station Expands Again (2002-11-03)
The developing International Space Station (ISS) has changed its appearance yet again.  Last month the Space Shuttle Atlantis visited the ISS and installed the third of eleven pieces that will compose the Integrated Truss Structure.  The new S-1 Truss is visible on the right, below the extended solar panels across the top.  The world's foremost space outpost can be seen developing over the past few years by comparing the above image to past images.  Also visible above are many different types of modules, a robotic arm, several wing-like solar panels, and a supply ship.  Construction began on the ISS in 1998 and the core structure should be in place before 2005. Yesterday, the ISS celebrated its second anniversary of continuous human habitation.
Cassini Approaches Saturn (2002-11-04)
Cassini, a robot spacecraft launched in 1997 by NASA, is close enough now to resolve many rings and moons of its destination planet: Saturn.  The spacecraft has closed to about two Earth-Sun separations from the ringed giant. Last month, Cassini snapped several images during an engineering test.  These images have been combined into the contrast-enhanced color composite pictured above.  Saturn's rings and cloud-tops are visible on the far right, while Titan, its largest moon, is visible as the speck on the lower left.  When arriving at Saturn in July 2004, the Cassini orbiter will begin to circle and study the Saturnian system.  Several months later, a probe named Huygens will separate and attempt to land on the surface of Titan.
Leonids Over Joshua Tree National Park (2002-11-05)
This year's Leonid Meteor Shower is predicted to have two peaks, like last year's.  The first peak should come at about 04:00 hours Universal Time (UT) on November 19 and be primarily visible from Western Europe before sunrise.  The second peak is predicted to occur at about 10:30 UT and be primarily visible from North America before local sunrise.  During these times, the Leonid Meteor Shower might well develop into a true meteor storm, with rates possibly exceeding those measured during last year's storm.  The meteors in these two peaks come from sand-sized particles ejected from Comet Tempel-Tuttle during trips to the inner Solar System in 1767 and 1866, respectively.  If you're stuck without a view you can still catch the shower by looking for streaks caught by the web cameras of the Night Sky Live Project.  Pictured above are several meteors from the 2001 Leonids streaking over Joshua Tree National Park in California, USA.
The Winter Hexagon (2002-11-06)
Some of the brightest stars form a large and easily found pattern in the winter sky of Earth's northern hemisphere.  Dubbed the  Winter Hexagon, the stars involved can usually be identified even in the bright night skies of a big city.  The six stars that compose the Winter Hexagon are Aldebaren, Capella, Castor, Procyon, Rigel, and Sirius.  Rolling your cursor over the above image will identify them.  The Winter Hexagon asterism engulfs several constellations including Orion and Canis Major.
2001 Leonids: Meteors in Perspective (2002-11-07)
The 2001 Leonid storm was so intense that the meteor shower's radiant, the point on the sky from which the fleeting trails seemed to diverge, was easy to spot. But the bits of debris that created the meteors really moved along parallel paths, following the orbit of  their parent comet Tempel-Tuttle. Their apparent divergence from the shower's radiant point was simply due to perspective as skygazers looked toward the stream of cosmic debris. During the 2001 Leonid storm, while the radiant was above the horizon from SoBaekSan Observatory in South Korea, astronomer Christophe Marlot made this single time exposure recording star trail arcs and a number of meteors. Since Marlot was looking away from the cosmic debris stream, this perspective actually shows red tinged meteor trails converging toward a point below the horizon and opposite the radiant -- the Leonid shower's antiradiant.
NGC 6369: The Little Ghost Nebula (2002-11-08)
This pretty planetary nebula, cataloged as NGC 6369, was discovered by 18th century astronomer William Herschel as he used a telescope to explore the constellation Ophiucus. Round and planet-shaped, the nebula is also relatively faint and has acquired the popular moniker of Little Ghost Nebula. Planetary nebulae in general are not at all related to planets, but instead are created at the end of a sun-like star's life as its outer layers expand into space while the star's core shrinks to become a white dwarf. The transformed white dwarf star, seen near the center, radiates strongly at ultraviolet wavelengths and powers the expanding nebula's glow. Surprisingly complex details and structures of NGC 6369 are revealed in this delightful color image composed from Hubble Space Telescope data. The nebula's main ring structure is about a light-year across and the glow from ionized oxygen, hydrogen, and nitrogen atoms are colored blue, green, and red respectively. Over 2,000 light-years away, the Little Ghost Nebula offers a glimpse of the fate of our Sun, which should produce its own pretty planetary nebula only about 5 billion years from now.
A Cerro Tololo Sky (2002-11-09)
High atop a Chilean mountain lies one of the premier observatories of the southern sky: the Cerro Tololo Inter-American Observatory (CTIO). Pictured above is the dome surrounding one of the site's best known instruments, the 4-meter Blanco Telescope. Far behind the dome are thousands of individual stars and diffuse light from three galaxies: the Small Magellanic Cloud (upper left), the Large Magellanic Cloud (lower left), and our Milky Way Galaxy (right).  Visible just to Blanco's right is the famous superposition of four bright stars known as the Southern Cross. A single 20 second exposure, this digital image was recorded with a sensitive detector intended for astronomical imaging. The observatory structures are lit solely by starlight.
A Green Flash from the Sun (2002-11-10)
Many think it is just a myth.  Others think it is true but its cause isn't known.  Adventurers pride themselves on having seen it.  It's a green flash from the Sun.  The truth is the green flash does exist and its cause is well understood.  Just as the setting Sun disappears completely from view, a last glimmer appears startlingly green.  The effect is typically visible only from locations with a low, distant horizon, and lasts just a few seconds. A green flash is also visible for a rising Sun, but takes better timing to spot.  A dramatic green flash was caught in the above photograph in 1992 from Finland. The Sun itself does not turn partly green, the effect is caused by layers of the Earth's atmosphere acting like a prism.
The Outer Shells of Centaurus A (2002-11-11)
What causes the surrounding shells in peculiar galaxy Cen A? Last month a fascinating image of peculiar galaxy Centaurus A was released, processed to highlight a faint blue arc indicating an ongoing collision with a smaller galaxy.  Another interesting feature of Cen A, however, is the surrounding system of shells, better visible here in this recently released wider pan from the four meter Blanco telescope at Cerro Tololo Inter-American Observatory.  Faint shells around galaxies are not unusual and considered by themselves as evidence of a previous galaxy merger, analogous to water ripples on a pond.  An unexpected attribute of these shells is the abundance of gas, which should become separated from existing stars during the collision.
Terkezi Oasis in the Sahara Desert (2002-11-12)
Dominating the top third of Africa is the largest band of dry land on Earth: the Sahara Desert.  Stretching across the Sahara are vast plains of sand and gravel, seas of sand dunes, and barren rocky mountains.  Only 10,000 years ago, however, grasses covered the region, then rich in mammals such as lions and elephants.  Now only two percent of the Sahara are oases, patches of land where crops will grow and where nearly two million people live.   Oases are usually centered on natural water springs.  Pictured above is colorful and rocky land spanning about 50 kilometers near the Terkezi Oasis in Chad.
Asteroid Annefrank (2002-11-13)
NASA's interplanetary probe STARDUST, on its way to Comet Wild 2 in January 2004, passed asteroid 5535 Annefrank earlier this month.  Annefrank, named for a holocaust victim who kept a famous diary, is a member of the main asteroid belt between Mars and Jupiter.  Just prior to closest approach at about 3300 km distant, the robot spacecraft took the above picture.  Although images obtained were not detailed enough to resolve much of the asteroid's surface, the size, reflectivity, and general shape of the asteroid were recorded.  At 6 kilometers across, asteroid Annefrank turned out to be larger -- and darker -- than expected.   Deadline Approaching: Send your name to Mars!
The Sharpest View of the Sun (2002-11-14)
This stunning image shows remarkable and mysterious details near the dark central region of a planet-sized sunspot in one of the sharpest views ever of the surface of the Sun. Just released, the picture was made using the Swedish Solar Telescope now in its first year of operation on the Canary Island of La Palma. Along with features described as hairs and canals are dark cores visible within the bright filaments that extend into the sunspot, representing previously unknown and unexplored solar phenomena. The filaments' newly revealed dark cores are seen to be thousands of kilometers long but only about 100 kilometers wide. Resolving features 100 kilometers wide or less is a milestone in solar astronomy and has been achieved here using sophisticated adaptive optics, digital image stacking, and processing techniques to counter the blurring effect of Earth's atmosphere. At optical wavelengths, these images are sharper than even current space-based solar observatories can produce. Recorded on 15 July 2002, the sunspot shown is the largest of the group of sunspots cataloged as solar active region AR 10030.
Night Trails of Africa (2002-11-15)
Spanning southern to northern skies, stars trail across this panoramic view of the African night from equatorial Kenya. The three hour long exposure was made on a clear, dark, mid November evening facing due west and covers just over 180 degrees along the horizon. So, the South Celestial Pole is at the center of the concentric arcs on the left and the North Celestial Pole is at the far right (scroll right). And, you guessed it(!), the stars setting along the Celestial Equator leave the straight trails near the middle of the picture. Well illustrated in this thoughtfully composed panorama, the star trails in the African night are, of course, not due to motions of the individual stars but simply reflect the daily rotation of planet Earth itself.
Tempel-Tuttle: The Leonid Comet (2002-11-16)
Star trails streak this composite time exposure of comet Tempel-Tuttle recorded by Tim Puckett on January 26, 1998. Then passing through the inner solar system on its 33 year orbit around the Sun, Tempel-Tuttle brightened unexpectedly, but binoculars or small telescopes were still required to visually observe it. Tempel-Tuttle is also called "the Leonid Comet" as the yearly Leonid meteor shower results when the Earth crosses this comet's orbital plane and encounters a trail of cometary dust. So, while not rivaling spectacular naked-eye comets like Hyakutake or Hale-Bopp, Tempel-Tuttle still puts on a show. The Earth is now approaching relatively dense regions of Tempel-Tuttle's orbiting debris trail, so in the next few days, skywatchers will be searching for leonid meteors. An extremely active meteor shower is expected to be visible over Europe and North America in the early morning hours of Tuesday, November 19, despite interference from a glaring full moon.