omnianasa/nasa-apod-metadata huggingface dataset:
Venus on the Horizon (1999-06-19)
Venus can appear as a brilliant evening star. Besides the sun and moon, Venus is the brightest object visible in Earth's sky. Because it is closer to the sun than Earth, Venus never strays far from the sun in its apparent position and is seen during the year as either a bright morning or evening star. This beautiful sunset imaged from low earth orbit by the Atlantis space shuttle crew in May 1989 also reveals the planet Venus blazing above Earth's horizon. It is a fitting image for this mission and crew. It was recorded following the successful release of the robot Venus-explorer Magellan, the first planetary probe to be deployed from a space shuttle.
A Very Large Array of Radio Telescopes (1999-06-20)
Pictured above is one of the world's premiere radio astronomical observatories: The Very Large Array (VLA). Each antenna dish is as big as a house (25 meters across) and mounted on railroad tracks.  The VLA consists of 27 dishes - together capable of spanning the size of a city (35 kilometers).  The VLA is the most sensitive  radio telescope ever, and, through interferometry, can resolve a golf ball-sized radio source 150 kilometers away (0.04 arcsec).  The VLA is continually making new discoveries, including determining the composition of galaxies, passing comets, quasars, HII regions, and clusters of galaxies.  The VLA is also used to receive the weak radio signals broadcast from interplanetary spacecraft. The VLA is located in New Mexico, USA. A significant upgrade of VLA's capabilities is planned.
The Galactic Center in Infrared (1999-06-21)
The center of our Galaxy is a busy place. In visible light, much of the Galactic Center is obscured by opaque dust.  In infrared light, however, dust glows more and obscures less, allowing nearly one million stars to be recorded in the above photograph.  The Galactic Center itself appears on the right and is located about 30,000 light years away towards the constellation of Sagittarius.  The Galactic Plane of our Milky Way Galaxy, the plane in which the Sun orbits, is identifiable by the dark diagonal dust lane.  The absorbing dust grains are created in the atmospheres of cool red-giant stars and grow in molecular clouds.  The region directly surrounding the Galactic Center glows brightly in radio and high-energy radiation, and is thought to house a large black hole.
PKS285-02: A Young Planetary Nebula (1999-06-22)
How do planetary nebulae acquire their exquisite geometrical shapes?  To investigate this, astronomers used the Hubble Space Telescope to image several young planetary nebulae.  These nebulae are the outer envelopes of stars like our Sun that have recently been cast away to space, leaving behind a core fading to become a white dwarf.  In this photograph in red H-alphacarbon that composes humans is thought to be created by red giant stars and ejected into the cosmos in planetary nebulae like PKS285-02. The complexity of this nebula leads some astronomers to hypothesize that these shells were created by high-speed, collimated outflows during a late phase of this star's evolution.
The Sudbury Neutrino Detector (1999-06-23)
Tomorrow's picture: A Barred Galaxy  < 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 & Michigan Tech. U.
NGC 1365: A Nearby Barred Spiral Galaxy (1999-06-24)
Many spiral galaxies have bars across their centers.  Even our own Milky Way Galaxy is thought to have a bar, but perhaps not so prominent as the one in NGC 1365, shown above.   The persistence and motion of the bar imply relatively massive spiral arms.  The placements of bright young blue stars and dark dust lanes also indicate a strong rotating density wave of star formation.  NGC 1365 is a member of the Fornax Cluster of Galaxies. Because NGC 1365 is relatively nearby, simultaneous measurements of its speed and distance are possible, which help astronomers estimate how fast our universe is expanding.
The Gegenschein (1999-06-25)
If you look carefully enough, you can even see the glow of the Sun in the opposite direction.  At night this glow is known as the gegenschein (German for "counter glow"), and can be seen as a faint glow in an extremely dark sky, as pictured above.  The gegenschein is sunlight back-scattered off small dust particles. These dust particles are millimeter sized splinters from asteroids and orbit in the ecliptic plane of the planets.  The gegenschein is distinguished from zodiacal light by the high angle of reflection. At day, a phenomenon similar to the gegenschien called the glory can be seen in clouds opposite the Sun from an airplane.
Shells in the Egg Nebula (1999-06-26)
The Egg Nebula is taking a beating. Like a baby chick pecking its way out of an egg, the star in the center of the Egg Nebula is casting away shells of gas and dust as it slowly transforms itself into a white dwarf star.  The above picture was taken by the newly installed Near Infrared Camera and Multi-Object Spectrometer (NICMOS) now on board the Hubble Space Telescope.  A thick torus of dust now surrounds the star through which the shell gas is escaping.  Newly expelled gas shells escape in beams as can be seen in the original HST image and in the image shown above.  This infrared image is coded in false color to highlight two different types of emission. The red light represents hot hydrogen gas heated by the collisions of expanding shells.  The blue light represents light from the central star scattered by the dust in the nebula.  It takes light about 3000 years to reach us from the Egg Nebula, which is hundreds of times the size of our Solar System.
COBE Dipole: Speeding Through the Universe (1999-06-27)
Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group. The Local Group falls toward the Virgo Cluster of Galaxies. But these speeds are less than the speed that all of these objects together move relative to the microwave background. In the above all-sky map, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder.  The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation. This high speed was initially unexpected and its magnitude is still unexplained. Why are we moving so fast? What is out there?
From Mars with Love (1999-06-28)
Are Martians trying to tell us something?  An indentation has been recently photographed on Mars that resembles a heart, a common human symbol for love.  Because intelligent Martians have never been known to exist, and because formations with similarities have been found that clearly result from natural phenomena, the pit shown above is thought not to be a form of interplanetary communication.  Many scientists believe instead that the right-most wall of the two-kilometer wide heart-shaped pit was created by a naturally occurring graben, a surface drop caused by expansion along a fault-line.  Perhaps love is easier to find here on Earth.
Gemini North Telescope Inaugurated (1999-06-29)
A new mammoth telescope has begun to inspect the northern sky.  The 8-meter Gemini North telescope, pictured above, was dedicated last week in Hawaii, with images documenting its unprecedented abilities being released.  Within two years, sister telescope Gemini South will begin similar observations of the southern sky from Chile.  The Gemini telescopes will collect an enormous amount of visible and infrared light. In the infrared, a Gemini can resolve objects that even appear blurred to the Hubble Space Telescope.  To achieve such high resolution, the Gemini's use adaptive optics, a technique that continually flexes Gemini's main mirrors to counteract the defocusing effects of Earth's turbulent atmosphere.  A seven-nation collaboration is completing the Geminis under the direction of the US National Science Foundation.
NGC 6934 from Gemini North (1999-06-30)
What's going on near the center of globular cluster NGC 6934?  The blur caused by the Earth's atmosphere has prevented astronomers from discerning individual stars in this unusual environment.  Telescopes in space can help, but the new Gemini North telescope took the above picture from the ground. In infrared light, Gemini was able to use its adaptive optic mirrors to resolve stars even near the globular cluster's center.  NGC 6934 is a 15 billion-year-old ball of hundreds of thousands of stars. Dating stars in ancient globular clusters like NGC 6934 provide valuable constraints on the minimum age of the universe.
Apollo 17's Lunar Rover (1999-07-01)
In December of 1972, Apollo 17 astronauts Eugene Cernan and Harrison Schmitt spent about 75 hours exploring the Moon's Taurus-Littrow valley while colleague Ronald Evans orbited overhead. Cernan and Schmitt were the last humans to walk or ride on the Moon - aided in their explorations by a Lunar Roving Vehicle. The skeletal-looking lunar rover was just over 10 feet long, 6 feet wide and easily carried astronauts, equipment, and rock samples in the Moon's low gravity (about 1/6 Earth's). In this picture, Cernan stands at the back of the rover which carried the two astronauts in lawn-chair style seats. An umbrella-shaped high gain antenna and TV camera are mounted in the front. Powered by four 1/4 horsepower electric motors, one for each wheel, this rover was driven a total of about 18 miles across the lunar surface. Its estimated top speed was nearly 8 miles per hour.
Shadow Of A Comet (1999-07-02)
Hale-Bopp, the Great Comet of 1997, may have been the most viewed comet in history - visible even from bright metropolitan skies. Astronomers are now reporting that this magnificent comet also cast a shadow against the glare of the solar system's ultraviolet haze. This false-color image represents a slice of the sky viewed by the SWAN (Solar Wind ANisotropy) instrument aboard the space-based SOHO observatory. Recorded on March 8, 1997 it shows a general haze of solar ultraviolet light scattered by interstellar hydrogen. The sun itself is positioned below the bottom center of the cropped image and the large bright spot is ultraviolet sunlight scattered by the cloud of hydrogen gas surrounding Hale-Bopp's nucleus. Just above and to the left is a broad, diffuse, dark streak - the 150 million kilometer long shadow produced by the denser regions of this hydrogen envelope. Why are comets surrounded by hydrogen? The hydrogen comes from the breakup of water (H20) vapor released as the comet nucleus approaches the sun. These observations indicate that Hale-Bopp's nucleus was producing about 300 tons of water per second.
NGC 2440: Cocoon of a New White Dwarf (1999-07-03)
Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self.  In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! The above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf can be seen as the bright dot near the photo's center. Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years. The above false color image and was post-processed by Forrest Hamilton.
A Landing On Mars (1999-07-04)
On July 4th, 1997 - using its own array of fireworks, a parachute, and airbags - the Mars Pathfinder spacecraft successfully came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. Ninety minutes before reaching the surface Pathfinder began a flurry of activity. The robot spacecraft vented cooling fluid, jettisoned its cruise stage, decelerated at 20 gees on atmospheric entry, deployed a 24 foot parachute, jettisoned its heat shield, slid down a 60 foot bridle, fired solid fuel braking rockets, deployed a cocoon of airbags, separated from the bridle, impacted the martian surface, bounced a few times (traveling about 300 - 600 feet between bounces), settled on the surface, deflated the airbags, and righted itself, all under the autonomous control of the onboard computer. Above is a mosaic of images transmitted shortly after Pathfinder reestablished communication with its operators on Earth. The solar powered, two foot long, 25 pound Mars Sojourner robot rover is visible crouched on the unfolded spacecraft. Beyond lie deflated airbags, rock-strewn terrain, distant hills, and a dusty brown martian sky.
Four Faces of Mars (1999-07-05)
As Mars rotates, most of its surface becomes visible. During Earth's recent pass between Mars and the Sun, the Hubble Space Telescope was able to capture the most detailed time-lapse pictures ever from the Earth.  Dark and light sand and gravel create an unusual blotted appearance for the red planet.  Winds cause sand-tinted features on the Martian surface to shift over time.  Visible in the above pictures are the north polar cap, made of water ice and  dry ice, clouds including an unusual cyclone, and huge volcanoes leftover from ancient times.  The Mars Global Surveyor satellite orbiting Mars continues to scan the surface for good places to land future robot explorers.
A Sun Pillar (1999-07-06)
Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light.  Ice sometimes forms flat, stop-sign shaped crystals as it falls from high-level clouds.  Air resistance causes these crystals to lie nearly flat much of the time as they flutter to the ground.  Sunlight reflects off crystals that are properly aligned, creating the sun-pillar effect.  In the above picture, the sun-pillar can be traced up to the cloud that is raining the reflecting ice-crystals.
M80: A Dense Globular Cluster (1999-07-07)
If our Sun were part of M80, the night sky would glow like a jewel box of bright stars.  M80, also known as NGC 6093, is one of about 250 globular clusters that survive in our Galaxy.  Most of the stars in M80 are older and redder than our Sun, but some enigmatic stars appear to be bluer and younger.  Young stars would contradict the hypothesis that all the stars in M80 formed at nearly the same time.  These unusual stars are known as blue stragglers, and by analyzing pictures like the Hubble Space Telescope image above, astronomers have been able to find the largest population of blue stragglers yet.  As blue stragglers are now thought to be due to stars coalescing, the collision and capture rate at the dense center of M80 must be very high.
Eruptive Prominence (1999-07-08)
Activity on our parent star continues to increase as the sun approaches a maximum in its 11-year solar cycle, expected in the year 2000. On June 14 - only a week before the solstice - the space-based SOHO observatory recorded this stunning view of an immense prominence erupting from the sun's southern latitudes (south is up). The false-color image was made in the extreme Ultraviolet light produced by ionized Helium atoms in the solar plasma. Earth dwellers fortunate enough to be well located in Europe, the Middle East, Asia may be able to view for themselves activity above the solar limb during the upcoming August solar eclipse - the last total eclipse of the second millennium.
NGC 7789: Galactic Star Cluster (1999-07-09)
At 1.6 billion years old, this cluster of stars is beginning to show its age. NGC 7789 is an open or galactic star cluster about 8,000 light-years distant toward the constellation Cassiopeia and lies near the plane of our Milky Way galaxy. All the stars in the cluster were likely born at the same time but the brighter and more massive ones have more rapidly exhausted the hydrogen fuel in their cores. These have evolved from main sequence stars like the sun into the gaggle of red giant stars apparent (with a reddish-yellow cast) in this lovely composite color image. Comparing computer models to observations of the red giants and main sequence stars astronomers can determine the mass and hence the age of the cluster stars just starting to "turn off" the main sequence to become red giants.
Southern Neptune (1999-07-10)
Neptune, the Solar System's outermost gas giant planet, is 30 times farther from the Sun than Earth. Twelve years after a 1977 launch, Voyager 2 flew by Neptune and found surprising activity on a planet that receives only 3 percent as much sunlight as Jupiter. In its brief but tantalizing close-up glimpse of this dim and distant world, the robot spacecraft recorded pulses of radio emission, zonal cloud bands, and large scale storm systems with up to 1500 mile per hour winds - the strongest measured on any planet. This mosaic of 5 Voyager images shows Neptune's Southern Hemisphere. Cloud bands and the Earth-sized, late "Great Dark Spot" with trailing white clouds located at about 22 degrees southern latitude are clearly visible.  The distance from the Great Dark Spot feature to Neptune's South Pole (image center) is about 17,000 miles.
Barringer Crater on Earth (1999-07-11)
What happens when a meteor hits the ground?  Usually nothing much, as most meteors are small, and indentations they make are soon eroded away.  49,000 years ago, however, a large meteor created Barringer Meteor Crater in Arizona, pictured above.  Barringer is over a kilometer across.  In 1920, it was the first feature on Earth to be recognized as an impact crater. Today, over 100 terrestrial impact craters have been identified.  Recent computer modeling now indicates how some of the Canyon Diablo impactor melted during the impact that created Barringer.
A Delta Rocket Launches (1999-07-12)
Tomorrow's picture: The Flame Nebula  < 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 & Michigan Tech. U.
The Flame Nebula in Infrared (1999-07-13)
What lights up the Flame Nebula? Fifteen hundred light years away towards the constellation of Orion lies a nebula which, from its glow and dark dust lanes, appears like a billowing fire.  But fire, the rapid acquisition of oxygen, is not what makes this Flame glow.  Rather the bright star Alnitak, the easternmost star in the Belt of Orion visible to the nebula's right, shines energetic light into the Flame that knocks electrons away from the great clouds of hydrogen gas that reside there.  Much of the glow results when the electrons and ionized hydrogen recombine. The above false-color picture of the Flame Nebula (NGC 2024) was taken in infrared light, where a young star cluster becomes visible.  The Flame Nebula is part of the Orion Molecular Cloud Complex, a star-forming region that includes the famous Horsehead Nebula.
Moon, Planets, and Rocket Trails (1999-07-14)
Tomorrow's picture: Charles Conrad 1930-1999  < 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 & Michigan Tech. U.
Charles P. Conrad, Jr. 1930-1999 (1999-07-15)
Known for his sense of humor and infectious grin, Charles P. "Pete" Conrad, as commander of the Apollo 12 mission, was the third person to walk on the moon. Not a tall man, Conrad stepped down onto the lunar surface in November of 1969 and gleefully commented, "Whoopie! Man, that may have been a small one for Neil, but that's a long one for me." Born June 2nd, 1930 in Philadelphia, Pennsylvania, he graduated from Princeton University in 1953 and went on to become a Navy test pilot. Selected as a NASA astronaut in 1962, Conrad is seen here in 1965 during a suiting up activity in preparation for his first space flight - the endurance record setting Gemini 5 mission. His final space flight was to Skylab in 1973. Tragically, Conrad died from injuries in a motorcycle accident on Thursday, July 8.
Solar Surfin' (1999-07-16)
The sun's corona is a tenuous outer atmosphere composed of streams of energetic charged particles, but it is only easily seen from Earth during a total solar eclipse. For example, this 1991 image of totality from atop Mauna Kea, Hawaii forms a fleeting snapshot of the mysterious corona's beautiful, intricate structures and streams. However in space, instruments can use occulting disks to simulate eclipses and more readily monitor the corona beyond the sun's edge. Combined observations from the space-based SOHO UCVS and shuttle-borne Spartan 201 experiments have recently contributed to a major advance in understanding the high-speed component of the wind of particles in the corona. They reveal evidence for magnetic waves within the corona itself that push solar wind particles along, like an ocean wave gives a surfer a ride. Surprisingly, heavier charged particles can surf the magnetic waves faster - oxygen ions were found to achieve speeds of up to 500 miles per second, faster than the lighter hydrogen ions which make up most of the solar wind.
Rockets and Robert Goddard (1999-07-17)
Robert H. Goddard, one of the founding fathers of modern rocketry, was born in Worcester Massachusetts in 1882. As a 16 year old, Goddard read H.G. Wells' science fiction classic "War Of The Worlds" and dreamed of space flight. By 1926 he had designed, built, and launched the world's first liquid fuel rocket. During his career he was ridiculed by the press for suggesting that rockets could be flown to the Moon, but he kept up his experiments in rocketry supported in part by the Smithsonian Institution and championed by Charles Lindbergh. Pictured above in 1937 in the desert near Roswell, New Mexico, Goddard examines a nose cone and parachute from one of his test rockets. Widely recognized as a gifted experimenter and engineering genius, his rockets were many years ahead of their time. He died in 1945 holding over 200 patents in rocket technology. A liquid fuel rocket constructed on principles developed by Goddard landed humans on the Moon in 1969.
Jupiter from Voyager (1999-07-18)
This picture of the planet Jupiter was taken by the Voyager 1 spacecraft as it passed the planet in 1979.  Jupiter, a gas giant planet with no solid surface, is the largest planet in the Solar System and is made mostly of the hydrogen and helium.  Clearly visible in the above photo is the Great Red Spot, a giant, hurricane-like storm system that rotates with the clouds of Jupiter.  It is so large three complete Earths could fit inside it. Astronomers have recorded this giant storm on Jupiter for over 300 years.
NGC 3372: The Great Nebula in Carina (1999-07-19)
In one of the brightest parts of the Milky Way lies a nebula where some of the oddest things occur.  NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula.  Eta Carina, the most energetic star in the nebula was one of the brightest stars in the sky in the 1830s, but then faded dramatically.  The Keyhole Nebula, visible near the center, houses several of the most massive stars known and has also changed its appearance.  The Carina Nebula is about 7000 light-years away in the constellation of Carina.  The CTIO Curtis-Schmidt Telescope in Chile, South America took the above photograph.  Eta Carina might explode in a dramatic supernova within the next thousand years, and has even flared in brightness over just the past two years.
Moon Rocket (1999-07-20)
On July 20, 1969, only four days after leaving planet Earth 250,000 miles behind them, Apollo 11 astronauts landed on the moon - the first humans to reach another celestial body. But the Saturn V rocket which took them there actually "began" the journey two months before traveling at a blinding speed of one mile per hour. Seen here in a dramatic aerial view, the giant moon rocket rides on top of a slow moving crawler-transporter vehicle toward Kennedy Space Center's launch complex 39 pad A. The NASA History Office's new Apollo web site celebrates the 30th anniversary of the first moon landing with this and other images, documents, and collections of links commemorating this profound achievement and the people who made it possible.