omnianasa/nasa-apod-metadata huggingface dataset:
A Giant Globular Cluster in M31 (1996-04-26)
G1, pictured above, is the brightest known globular cluster in the whole Local Group of galaxies. Also called Mayall II, it orbits the center of the largest nearby galaxy: M31.  G1 contains over 300,000 stars and is almost as old as the entire universe.  In fact, observations of this globular cluster show stars as old as the oldest of the roughly 250 known globular clusters in our own Milky Way Galaxy.  This image was taken with the Hubble Space Telescope in July of 1994.  It shows, for the first time, the same fine detail in a distant globular cluster as can be discerned from a ground-based telescope of a globular cluster in our own Galaxy.
Apollo 14: Rickshaw Tracks Across the Moon (1996-04-27)
Brilliant sunlight glints off tracks gently winding across the the Moon's Frau Maro highlands. The tracks were made by the Apollo 14 crew's two-wheeled Modularized Equipment Transporter (MET), fondly known as the "rickshaw". The MET was designed as an aid to surface exploration. Serving as a workbench with a place for the lunar handtools, it also carried cameras, sample containers, spare film and a Lunar Surface Penetrometer. The path outlined in the lunar soil leads away from Alan Shepard and Edgar Mitchell's Lunar landing Module, tracing the path of their first venture across the lunar landscape.
The Sun Sets on Comet Hyakutake (1996-04-28)
Comet Hyakutake is seen here just as the Sun sets on April 22. As April draws to a close, Comet Hyakutake will be visible only just after sunset and will be hard to discern against the brightly lit sky. Unfortunately, Comet Hyakutake did not brighten as much as hoped during its journey to the inner Solar System, and is now not supposed to get as bright as it did when it passed the Earth in late March. Nevertheless, Comet Hyakutake is still a bright comet and spectacular sight.  Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs.,
Saturn's Rings Seen Sideways (1996-04-29)
Saturn's rings are actually very thin.  This picture from the Hubble Space Telescope was taken on August 6, 1995 when the rings lined up sideways as seen from Earth.  Saturn's largest moon Titan is seen on the left, and Titan's shadow can be seen on Saturn's cloud tops!  Titan itself looks a brownish color because of its thick atmosphere. Four other moon's of Saturn can be seen just above the ring plane, which are, from left to right: Mimas, Tethys, Janus, and Enceladus. If you look carefully, you will note that the dark band across the planet is actually the shadow of the rings, and is slightly displaced from the real rings - which are best seen away from the planet.  Saturn's rings are not solid - they are composed of ice chunks which range in size from a grain of sand to a house.
Uranus' Ring System (1996-04-30)
The rings of Uranus are thin, narrow, and dark compared to other planetary ring systems. Brightened artificially by computer, the ring particles reflect as little light as charcoal, although they are really made of ice chucks darkened by rock. This false-color, infrared picture from the Hubble Space Telescope taken in July 1995 shows the rings in conjunction to the planet. The infrared light allows one to see detail in different layers of Uranus' atmosphere, which has been digitally enhanced with false color. Three other planets in our Solar System are known to have rings: Jupiter, Saturn, and Neptune.  Four of Uranus' moons are visible outside the ring plane. The rings of Uranus were discovered from ground-based observations in 1977.
Comet Hyakutake and a Cactus (1996-05-01)
Comet Hyakutake is shown photographed the night of March 27 in Arizona, USA, with a cactus in the foreground.  Polaris, the north star, is the bright star seen just to the upper right of the comet's head. Today Comet Hyakutake reaches its closest approach to the Sun. Comet Hyakutake is now at its intrinsic brightest, but because of its distance from the Earth, it will appear less bright to us than it did during its closest approach to the Earth in late March. In fact, due to the comet's angular proximity to the Sun, it will difficult to see at all from the Earth! Comet Hyakutake will reach less than one quarter of the Earth-Sun distance - inside the orbit of Mercury. Comet Hyakutake will not venture near the Sun again for another about 15,000 years.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs.,
The Tails of Comet Hyakutake (1996-05-02)
What makes comet tails so colorful?  This photograph of Comet Hyakutake was taken the night of April 18th and highlights different components of the tail. The gold and red tail features are dust, made predominately of little bits of rock and carbon. The dust tail shines by reflecting sunlight. Extending past the dust tail is the comet's ion tail, shown here glowing in blue. The ion tail is composed mostly of ions of water, carbon monoxide, and cyanogen. The ion tail glows by emitting light when elections re-combine with electrically charged ions to make uncharged molecules. The photograph was taken just north of Kansas City, Missouri, USA.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs.,
The Milky Way Near the Southern Cross (1996-05-03)
This breathtaking patch of sky would be above you were you to stand at the south pole of the Earth. Just above and to the right of the photograph's center are the four stars that mark the boundaries of the famous Southern Cross.  At the top of this constellation, also known as "The Crux," is the orange star Gamma Crucis. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy.  In the very center of the photograph is the dark Coal Sack Nebula, and the bright nebula on the far right is the Eta Carina Nebula. The southern cross is so famous a constellation that it is depicted on the Australian National Flag.
Astro 1 In Orbit (1996-05-04)
In December of 1990, the Space Shuttle Columbia carried an array of astronomical telescopes high above the Earth's obscuring atmosphere to observe the Universe at ultraviolet and x-ray wavelengths. The telescopes, known by the acronyms UIT, HUT, WUPPE, and BBXRT, are seen here in Columbia's payload bay against a spectacular view of the constellation Orion. The ultraviolet telescopes were mounted on a common structure - HUT is visible in this view along with a star tracker (the silver cone at the left). The mission studied solar system, galactic, and extra-galactic sources.
Planet Near a Galaxy Core (1996-05-05)
What would the night sky look like if you lived on a planet near the center of a galaxy? Now imagine that this galaxy houses a black hole billions of times more massive than a star. From this spectacular vantage point, the sky might look like the above illustration. This drawing is based on recent observations of the center of NGC 4261, made by the Hubble Space Telescope.  Results indicate that a disk of dust 800-light years wide surrounds the black hole. The hypothetical planet depicted above lies within this disk. The black hole itself heats gas to white-hot temperatures, generating light that is reddened when reflected off the dust. Jets shoot off from the poles of the black hole, perpendicular to the disk. However, friction with the dust and gas would cause planets near the black hole to spiral in and disappear forever.  NASA has recently announced a new initiative to search for Earth-like planets in our Galaxy.
Southern Lights and Shuttle Glow (1996-05-06)
A background of distant stars, sinuous and spiky bands of Southern Lights (Aurora Australis), and the faint glow of charged plasma (ionized atomic gas) surrounding the Space Shuttle Discovery's engines give this photo from the STS-39 mission an eerie, otherworldly look. This image reflects Discovery's April 1991 mission well - its payload bay (PLB) was filled with instruments designed to study celestial objects, aurora and atmospheric phenomena, and the low Earth orbit environment around the PLB itself. The aurora seen here are at a height of about 50-80 miles and caused by charged particles in the solar wind, channeled through the van Allen Radiation Belts which excite atoms of oxygen in the upper atmosphere.
The Clouds of Neptune (1996-05-07)
These Hubble Space Telescope (HST) images reveal glimpses of the dynamic atmosphere of Neptune, the Solar System's most distant gas giant planet. The first close-up of Neptune's clouds was provided by NASA's Voyager 2 spacecraft during its August 1989 flyby, giving a tantalizingly brief look. From its vantage point in Earth orbit, HST can patiently watch in detail as the planet's massive weather systems change over time. These three pictures, taken during October and November 1994 when Neptune was only 2.8 billion miles distant, show the planet's characteristic aqua-blue colored atmosphere highlighted by pink, high altitude clouds and streaked with dark bands. The aqua-blue color is caused by gaseous methane which absorbs red light. Here, the high altitude clouds were intentionally given a pink tint to indicate that they were imaged in near infrared light - in true color images they would appear white.
Neptune's Great Dark Spot: Gone But Not Forgotten (1996-05-08)
When NASA's Voyager 2 spacecraft flew by distant Neptune in August of 1989, astronomers were shocked. Since Neptune receives only 3 percent the sunlight Jupiter does, they expected to find a dormant, dark, frigid planet. Instead, the Voyager images revealed evidence of a dynamic and turbulent world. One of the most spectacular discoveries was of the Great Dark Spot, shown here in close-up.  Surprisingly, it was comparable in size and at the same relative southern latitude as Jupiter's Great Red Spot, appearing to be a similar rotating storm system. Winds near the spot were measured up to 1500 miles per hour, the strongest recorded on any planet. The Voyager data also revealed that the Great Dark Spot varied significantly in size during the brief flyby.  When the Hubble Space Telescope viewed the planet in 1994, the spot had vanished -- only to be replaced by another dark spot in the planet's northern hemisphere!
Supernova Remnant: Cooking Elements In The LMC (1996-05-09)
Massive stars cook elements in their cores through nuclear fusion. Starting with the light elements of hydrogen and helium, their central temperatures and pressures produce progressively heavier elements, carbon, oxygen, nitrogen, etc. up through iron. At the end of their lives they explode in a spectacular supernova, scattering these elements into space, contributing material to the formation of other stars and star systems. In fact, the elements making up life on Earth were baked in such a stellar oven! This Hubble Space Telescope image of a supernova remnant known as N132D in the Large Magellanic Cloud (LMC) allows astronomers to explore the details of this nuclear processing and mixing. It reveals luminous clouds of cooked supernova debris energized by shocks -- singly ionized sulfur appears red, doubly ionized oxygen, green, and singly ionized oxygen, blue. The region shown above is about 50 lightyears across.
Henize 70:  A SuperBubble In The LMC (1996-05-10)
Massive stars (tens of times the mass of the Sun) profoundly affect their galactic environment. Churning and mixing the clouds of gas and dust between the stars, they leave their mark in the compositions and locations of future generations of stars and star systems. Dramatic evidence of this is beautifully illustrated in our neighboring galaxy, the Large Magellanic Cloud (LMC), by the lovely ring shaped nebula, Henize 70 (also known as N70 and DEM301).  It is actually a luminous "superbubble" of interstellar gas about 300 lightyears in diameter, blown by winds from hot, massive stars and supernova explosions, its interior filled with tenuous hot expanding gas. These superbubbles offer astronomers a chance to explore this crucial connection between the lifecycles of stars and the evolution of galaxies.
Sunlight Through Saturn's Rings (1996-05-11)
Normally, Earth based astronomers view Saturn's spectacular ring system fully illuminated by reflected sunlight. However, this November 1995 Hubble Space Telescope composite image was made to take advantage of an unusual perspective, with the Sun actually illuminating the rings from below. The three bright ring features are visible because the rings themselves are not solid. Composed of many separate chunks of rocky, icy material, the rings allow the scattered sunlight to pass through them -- offering a dramatic demonstration that they are not continuous, uninterrupted bands of material.
Tracking Saturn's Moons (1996-05-12)
These five pairs of Hubble Space Telescope images track some of Saturn's moons as they orbit the ringed planet. A pair of images was taken every 97 minutes on November 21, 1995 with the Wide Field Planetary Camera-2, the normally bright ring system appearing nearly edge-on. In the top pair, the large bright moon Dione hangs above center while the smaller moons Pandora, Prometheus, and Mimas (top right image) appear near the planet's disk close to the outer ring. By the second and third pair of images, moons Rhea and Epimetheus have joined the dance. During the Saturn ring plane crossings, the reduction in light from the edge-on rings provided an opportunity for astronomer's to explore Saturn's complex moon system and search for elusive undiscovered satellites.
Hubble's Constant and The Expanding Universe (I) (1996-05-13)
Our Universe is expanding. Distant galaxies appear to recede from us at ever-increasing speeds. What is the rate of expansion? How long has it been expanding? What will be its ultimate fate? Two groups of astronomers are searching vigorously for answers to these fundamental questions using the Hubble Space Telescope (HST). The teams have recently announced conflicting measurements of the Hubble constant, a number which represents the expansion rate of the Universe. Astronomer Wendy Freedman and her collaborators have used pulsating stars called Cepheids to measure the distance to galaxies like the Fornax cluster barred spiral galaxy NGC1365 shown above. The ground based photo (left) shows an inset locating the HST image (right) which Freedman and team have used to identify some 50 Cepheids. Their distance and velocity measurements determine Hubble's constant to be about 80 kilometers per second per megaparsec which means that galaxies one megaparsec (3 million lightyears) distant appear to recede from us at a speed of 80 kilometers per second. Conflicting results indicating a substantially slower expansion rate (smaller Hubble constant) are being reported by astronomer Allan Sandage and collaborators. The value of Hubble's constant was recently the subject of a popular public debate titled "The Scale of the Universe 1996: The Value of Hubble's Constant".
Hubble's Constant and The Expanding Universe (II) (1996-05-14)
In this century, the discovery that the Universe is expanding has produced a revolution in human thought about the Cosmos. American astronomer Edwin Hubble played a major role in this profound discovery, coining the "Hubble constant". This single number describes the rate of the cosmic expansion, relating the apparent recession velocities of external galaxies to their distance. Two groups of astronomers trying to measure this fundamental constant using the Hubble Space Telescope (HST) are continuing to report conflicting results. One group, led by astronomer Allan Sandage, measures distances to galaxies using pulsating Cepheid variable stars and supernovae observed in galaxies like the Virgo Cluster spiral galaxy, NGC4639, shown above. This galaxy is the most distant one to which Cepheid-based determinations have been made and was also the site of a well-studied 1990 supernova. Their results favor a relatively small Hubble constant (slow expansion rate) of about 55 kilometers per second per megaparsec which means that galaxies one megaparsec (3 million lightyears) distant appear to recede from us at a speed of 55 kilometers per second. A substantially faster expansion rate (larger Hubble constant) is being reported by astronomer Wendy Freedman and collaborators, also based on HST data. The value of Hubble's constant was recently the subject of a popular public debate titled "The Scale of the Universe 1996: The Value of Hubble's Constant".
The Milky Way Near the Northern Cross (1996-05-15)
This beautiful image of the sky near the bright star Deneb (just above center) reveals the stars, nebulae, and dark clouds along the plane of our Milky Way Galaxy as seen from the northern hemisphere (near Columbia Missouri, USA). Just below Deneb lies the suggestively shaped North America emission nebula. Deneb is the brightest star in the constellation Cygnus, located in the tail of this celestial swan. Cygnus contains the asterism known as the Northern Cross and marks one side of the "Great Rift" in the Milky Way, a series of dark obscuring dust clouds which stretches on through the constellation Sagittarius. Deneb defines the top of the Northern Cross while the body of the cross extends past the upper right corner of the picture. Cygnus also harbors the most famous candidate for a black hole in our galaxy, Cygnus X-1.
Comet Hyakutake Passes the Sun (1996-05-16)
On May 1, Comet Hyakutake made its closest approach to the Sun. During this time it was not possible to view the comet with most astronomical instruments because of the brightness of the nearby Sun. But the orbiting Solar and Heliospheric Observatory (SOHO) spacecraft contains telescopes meant to look directly at the Sun and so were able to track the comet during this crucial time.  This picture, taken May 2, shows the tails of Comet Hyakutake pointing away from the Sun, as expected. During its closest approach, Comet Hyakutake passed inside the orbit of Mercury. Comet Hyakutake will not return to the inner Solar System for another 14,000 years.
Comet Hyakutake and a Solar Flare (1996-05-17)
A rare coincidence was recently captured by the orbiting SOHO spacecraft. During the closest approach to the Sun of Comet Hyakutake on May 1, SOHO photographed the comet.  By accident -- during the time this photograph was being taken -- a solar flare was being ejected from the Sun. Therefore, at the top of this false-color picture, Comet Hyakutake is visible, while emission to the left of the Sun is a solar flare. The Sun, at the center of the picture, was blocked by an artificial occulter in the LASCO telescope, allowing objects much dimmer than the Sun to be observed. SOHO was launched in December of 1995 and contains many instruments which study the Sun.
The Sun Today (1996-05-18)
Our Sun shows a different face every day. The above picture was taken on May 15, but a similar picture of the Sun actually taken today can be found here. The above picture was taken in red light and so is shown in red. The bright spots to the right of center are active regions known as plages. Currently, the Sun is showing very few active regions or sunspots, and is considered to be in a solar minimum. Solar activity will pick up over the next six years until a "solar maximum" is reached. The Sun goes through this cycle of maxima and minima every 11 years. Sol, our Sun, is hundreds of times more massive than all the planets in the Solar System combined. However, the Sun itself contains only a small amount of the total angular momentum of the Solar System.
Nearby Dwarf Galaxy Leo I (1996-05-19)
Leo I is a dwarf spheroidal galaxy in the Local Group of galaxies dominated by our Milky Way Galaxy and M31. Leo I is thought to be the most distant of the eleven known small satellite galaxies orbiting our Milky Way Galaxy. Besides the LMC and the SMC, all Milky Way satellite galaxies are small, dim, dwarf spheroidals, including the closest galaxy - the Sagittarius Dwarf. Leo I is most distant than most of them, thought to be about 250 kpc away. Analysis of stars in Leo I show it contains many stars only about 3 billion years old - much younger than in most galaxies.
Helios Helium (1996-05-20)
Above is an image of the relatively quiet Sun made on May 18 in light emitted by ionized Helium atoms in the Solar chromosphere. Helium was first discovered in the Sun in 1868, its name fittingly derived from from the Greek word Helios, meaning Sun. Credit for the discovery goes to astronomer Joseph Lockyer. Lockyer relied on a recently developed technique of spectroscopy, dissecting sunlight into a spectrum, and the idea that each element produces a characteristic spectral pattern of bright lines. He noticed a yellow line in a solar spectrum made during an eclipse which could not be accounted for by elements known on Earth. Almost 27 years later Helium was finally discovered on Earth when the spectrum of a Helium bearing mineral of Uranium provided an exact match to the previously detected element of the Sun. Helium is now known to be the second most abundant element (after Hydrogen) in the Universe.
The Iron Sun (1996-05-21)
The ultraviolet light emitted by eleven times ionized iron at temperatures over 2 million degrees Farenheit was used to record the above picture of the Sun on May 16. The image was made by the EIT camera onboard the SOHO spacecraft, a space observatory which can continuously observe the Sun. Eleven times ionized iron is atomic iron with eleven of its electrons stripped away. Here the electrons are stripped by the frantic collisions with other atoms and electrons which occur at the extreme temperatures in the Solar Corona. Since electrons are negatively charged, the resulting ionized iron atom is highly positively charged. Astronomer's "shorthand" for eleven times ionized iron is written "Fe XII", the chemical symbol for iron followed by a Roman numeral 12 (Fe I is neutral iron).
Star Cluster in the Rosette Nebula (1996-05-22)
mbedded in the center of the colorful and photogenic Rosette Nebula is a bright, young open cluster. The bright blue stars in this cluster, labelled NGC 2244, emit ultraviolet light that knocks electrons away from hydrogen atoms.  When the electrons fall back, they emit the red light which distinctively defines the glow of all emission nebulae. The Rosette Nebula is thousands of light years distant, but light would take only about 100 years to cross it. The Rosette Nebula is not difficult to observer and, although faint, actually appears larger than the full moon.
Stellar Violence in 30 Doradus (1996-05-23)
The largest, most violent star forming region known in the whole Local Group of galaxies lies in our neighboring galaxy the LMC. Were 30 Doradus at the distance of the Orion Nebula -- a local star forming region -- it would take up fully half the sky. Also called the Tarantula Nebula, the red gas indicates a massive emission nebula, although supernova remnants and dark nebula also exist in 30 Doradus. The bright knot of stars just below center is called R136 and contains many of the most massive, hottest, and brightest stars known.
In the Center of 30 Doradus (1996-05-24)
In the center of 30 Doradus lies a huge cluster of the largest, hottest, most massive stars known. The center of this cluster, known as R136, is boxed in the upper right portion of the above picture. The gas and dust filling the rest of the picture is predominantly ionized hydrogen from the emission nebula 30 Doradus. R136 is composed of thousands of hot blue stars, some about 50 times more massive than our Sun. 30 Doradus and R136 lie in the LMC - a satellite galaxy to our own Milky Way Galaxy. Although the ages of stars in R136 cause it to be best described as an open cluster, R136's density will likely make it a low mass globular cluster in a few billion years.