juliensimon/nasa-apod huggingface dataset:
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.

Image credit: Anglo-Australian Telescope
Board
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.

Image credit: Anglo-Australian Telescope
Board
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.
The Shuttle Launches an Inflatable Antenna (1996-05-25)

High above the Earth the Space Shuttle Endeavor launches a new type of instrument - an inflatable antenna. The officially designated Inflatable Antenna Experiment was released Monday, May 20th, as part of a Spartan satellite - which contains many scientific experiments. The antenna is roughly the size of a tennis court and is even visible from Earth. At the end of the mission, the antenna will be jettisoned while the rest of the Spartan is recovered by the Shuttle. The function of an antenna is to broadcast radio messages, and the large dish at the end helps focus radio waves into a narrow beam which can be detected over long distances.
Alpha Centauri: The Closest Star System (1996-05-26)

The closest star system to the Sun is the Alpha Centauri system. Of the three stars in the system, the dimmest -- called Proxima Centauri -- is actually the  nearest star. The bright stars Alpha Centauri A and B form a close binary as they are separated by only 23 times the Earth- Sun distance - slightly greater than the distance between Uranus and the Sun. In the above picture, the brightness of the stars overwhelm the photograph causing an illusion of great size, even though the stars are really just small points of light. The Alpha Centauri system is not visible in much of the northern hemisphere. Alpha Centauri A, also known as Rigil Kentaurus, is the brightest star in the constellation of Centaurus and is the fourth brightest star in the night sky.  Sirius is the brightest even thought it is more than twice as far away. By an exciting coincidence, Alpha Centauri A is the same type of star as our Sun, causing many to speculate that it might contain planets that harbor life.

Image credit: STSci Digitized Sky Survey, Anglo-Australian Observatory
Aurora Crown the Earth (1996-05-27)

What do aurora look like from space? The POLAR spacecraft answered this by photographing an auroral oval surrounding the north pole of the Earth, causing displays on both the night and day side. The auroral sub-storm, pictured in false-color above, developed within 15 minutes and may have lasted as long as on hour.  Aurora are caused by charged particles streaming away from the Sun and towards the Earth. As the particles fall to Earth, they spiral along magnetic field lines and cause colorful radiation. The UVI experiment onboard the POLAR spacecraft is equipped with special filters that allow it to see aurora in a band of ultraviolet light where sunlight is relatively dim.  The more red the emission depicted in the above photo, the more intense the radiation. Earth's continents have been drawn in for clarity
The Pipe Dark Nebula (1996-05-28)

The dark nebula predominant at the lower left of the above photograph is known as the Pipe Nebula.  The dark clouds, suggestively shaped like smoke rising from a pipe, are caused by absorption of background starlight by dust. These dust clouds can be traced all the way to the Rho Ophiuchi nebular clouds on the right. The brightest star in the field is Antares. Many types of nebula are highlighted here: the red are emission nebula, the blue are reflection nebula, and the dark are absorption nebula. This picture has been digitally enhanced.

Image credit: Jerry Lodriguss
The COMPTEL Gamma-Ray Sky (1996-05-29)

This premier gamma-ray view of the sky was produced by the COMPTEL instrument onboard NASA's orbiting Compton Gamma Ray Observatory. The entire sky is seen projected on a coordinate system centered on our Milky Way Galaxy with the plane of the Galaxy running across the middle of the picture. Gamma-ray intensity is represented by a false color map - low (blue) to high (white). COMPTEL's sensitivity to gamma-rays which have over 1 million times the energy of visible light photons reveals the locations of some of the Galaxy's most exotic objects. The brightest source, the Crab pulsar, is located near the plane of the Galaxy on the far right. Moving along the plane from the Crab, more than halfway toward the galactic center, another bright gamma-ray source, the Vela pulsar, appears. The galactic center itself, along with the famous black hole candidate Cygnus X-1 (near the plane, halfway from the center to the left edge) are also seen as bright sources. Both above and below the plane, spots of gamma-ray emission due to distant active galaxies are also visible.
Sunshine, Earthshine at the Lunar Limb (1996-05-30)

This dramatic image of the Moon's edge against a background of distant stars is from a perspective impossible for groundbased telescopes. It was taken by a star tracker camera onboard the Clementine spacecraft. The Solar Corona, the Sun's outer atmosphere, is visible shining brightly behind the lunar limb while the Moon's surface is illuminated by Earthshine, sunlight reflected from the Earth to the Moon. As pictured, the part of the Moon in shadow is the lunar farside, the side not visible from Earth. The highly successful unmanned Clementine probe explored the Moon from lunar orbit during March and April of 1994. Its star tracker cameras were normally used for celestial navigation, producing wide angle images showing relative positions of stars.
The Pulsar Powered Crab (1996-05-31)

In the Summer of 1054 A.D. Chinese astronomers reported that a star in the constellation of Taurus suddenly became as bright as the full Moon. Fading slowly, it remained visible for over a year. It is now understood that a spectacular supernova explosion - the detonation of a massive star whose remains are now visible as the Crab Nebula- was responsible for the apparition. The core of the star collapsed to form a rotating neutron star or pulsar, one of the most exotic objects known to 20th century astronomy. Like a cosmic lighthouse, the rotating Crab pulsar generates beams of radio, visible, x-ray and gamma-ray energy which, as the name suggests, produce pulses as they sweep across our view. Using a stunning series of visible light images taken with the Hubble Space Telescope (HST), astronomers have recently discovered spectacular pulsar powered motions within the Crab nebula. Highlights of this HST Crab "movie" show wisps of material moving away from the pulsar at half the speed of light, a scintillating halo, and an intense knot of emission dancing, sprite-like, above the pulsar's pole. Only 6 miles wide but more massive than the sun, the pulsar's energy drives the dynamics and emission of the nebula itself which is more than 10 lightyears across. In the HST image above, the pulsar is the left most of the two bright central stars.
The Iron Moon (1996-06-01)

In March and April of 1994 the unmanned Clementine spacecraft demonstrated the technique of prospecting on the Moon from lunar orbit. To accomplish this, Clementine turned an array of cameras sensitive to ultraviolet-visible and near-infrared light toward the lunar surface, producing the first broad-spectrum global imaging of the moon. Using this data, scientists were able to create the above map showing the concentration of iron in the lunar soils. The striking difference between the near (left) and farside (right) hemisphere's offers clues about the Moon's early history.
6 Up 5 Down (1996-06-02)

This fish-eye view of a dramatic night launch of the Shuttle Atlantis on mission STS-76 was recorded on March 22, 1996. The mission carried 6 astronauts aloft, and returned with 5 -- delivering one crew member, Shannon Lucid, to the Mir Space Station. Lucid is currently onboard the Mir as a cosmonaut guest researcher. NASA Shuttle flights to Mir are part of the Phase 1 program for construction of the International Space Station.
Mir Dreams (1996-06-03)

This dream-like image of Mir was recorded by astronauts as the Space Shuttle Atlantis approached the Russian Space Station prior to docking during the STS-76 mission. Sporting spindly appendages and solar pannels, Mir resembles a whimsical flying insect as it orbits above New Zealand's South Island near the Cook Strait. Atlantis shuttled astronaut Shannon W. Lucid to Mir for a 140 day visit, increasing the Mir's occupancy from 2 to 3. It will return to pick Lucid up and drop off astronaut John Blaha during the STS-79 mission presently scheduled for launch on July 31, 1996.
Impact! 65 Million Years Ago (1996-06-04)

What killed the dinosaurs? Their sudden disappearance 65 million years ago, along with about 70 percent of all species then living on Earth, is known as the K-T event (Cretaceous-Tertiary Mass Extinction event). Geologists and paleontologists often entertain the idea of a large asteroid or comet impacting the Earth as the culprit. Besides the firestorms, tidal waves, earthquakes, and hurricane winds such an impact would generate, the debris thrown into the atmosphere would have a serious global environmental impact -- creating extended periods of darkness, low temperatures, and acid rains. In 1990, dramatic support for this theory came from cosmochemist Alan Hildebrand's revelation of a 65 million year old, 112 mile wide ring structure still detectable under layers of sediment in the Yucatan Peninsula region of Mexico. The outlines of the structure, called the Chicxulub crater (named for a local village), are visible in the above representation of gravity and magnetic field data from the region. In addition to having the right age, the crater is consistent with the impact of an asteroid of sufficient size (6 to 12 miles wide) to cause the global disruptions. Regardless of the true cause of the K-T event, it is fortunate that such impacts are presently believed to happen only about once every 100 million years!
Sagittarius and the Central Milky Way (1996-06-05)

What does the center of our Milky Way Galaxy look like? No one knows! It is not possible to see the Galactic center in light our eyes are sensitive to because the thick dust in the plane of our Galaxy obscures it. If one looks in the direction of our Galaxy's center - which is toward the constellation of Sagittarius - many beautiful wonders become apparent, though. The center of the Milky Way is behind the center of the photo. Large dust lanes and star clouds dominate the picture.  As many as 30 Messier Objects are visible, including all types of nebula and star clusters. Two notable nebula include the Lagoon Nebula (M8), a small red patch just above center, and slightly above this is the red and blue Trifid Nebula (M20). The lines through picture were caused by airplanes, and the dark objects in the foreground are trees.

Image credit: Dave 
Palmer
The North America Nebula (1996-06-06)

Here's a familiar shape in an unfamiliar location! This emission nebula is famous partly because it resembles Earth's North American Continent. To the right of the North America Nebula is a less luminous Pelican Nebula. Let's be grateful that pelicans aren't really that large! The two emission nebula are located about 1500 light years away and are separated by a dark absorption cloud. The nebulae can be seen without a telescope from a dark location. Look for a small nebular patch north-east of Deneb in the constellation of Cygnus. It is still unknown which star or stars ionize the red-glowing hydrogen gas.

Image credit: Dominique
Dierick and Dirk De la Marche
Apollo 16: Exploring Plum Crater (1996-06-07)

Apollo 16 spent three days on Earth's Moon in April 1972. The fifth lunar landing mission out of six, Apollo 16 was famous for deploying and using an ultraviolet telescope as the first lunar observatory, and for collecting rocks and data on the mysterious lunar highlands.  In the above picture, astronaut John W. Young photographs Charles M. Duke, Jr. collecting rock samples at the Descartes landing site. Duke stands by Plum Crater while the Lunar Roving Vehicle waits parked in the background. The Lunar Roving Vehicle allowed the astronauts to travel great distances to investigate surface features and collect rocks. High above, Thomas K. Mattingly orbits in the Command Module.
The First Lunar Observatory (1996-06-08)

The first and only lunar astronomical observatory was deployed by the Apollo 16 crew in 1972. The Far Ultraviolet Camera / Spectrograph used a 3-inch diameter telescope to photograph the Earth, various nebulae, star clusters, and the Large Magellanic Cloud.  The camera is seen above placed in the shadow of the Lunar Module so it would not overheat. A leg of the Lunar Module enters the picture from the left. The camera took pictures in ultraviolet light which would normally be blocked by the Earth's atmosphere.  The Far Ultraviolet Camera was created by George Carruthers (NRL), had a field of view of 20 degrees, and could detect stars having visual magnitude brighter than 11. 178 images were recorded in a film cartridge which was returned to Earth. The observatory stands on the Moon even today.
Blasting Off From the Moon (1996-06-09)

How did the astronauts get back from the Moon? The Lunar Module that landed two astronauts on the Moon actually came apart. The top part containing the astronauts carried additional rocket fuel which allowed it to blast away, leaving the bottom part on the Moon forever. The top part would later meet up with the Command Module and its astronaut pilot, which were continually orbiting the Moon. All would then return to Earth together. The above picture was taken by a robot TV camera left on the Moon by the crew of Apollo 16.  The frame above captures the top part of the Lunar Module just at it was blasting off.
Ultraviolet Earth (1996-06-10)

Here's a switch: the above picture is of the Earth taken from a lunar observatory! This false color picture shows how the Earth glows in ultraviolet (UV) light. UV light is so blue humans can't see it. Very little UV light is transmitted through the Earth's atmosphere but what sunlight does make it through can cause a sunburn. The Far UV Camera / Spectrograph deployed and left on the Moon by the crew of Apollo 16 took the above picture. The part of the Earth facing the Sun reflects much UV light, but perhaps more interesting is the side facing away from the Sun. Here bands of UV emission are also apparent. These bands are the result of aurora and are caused by charged particles expelled by the Sun spiraling to Earth along magnetic field lines.
Doomed Star Eta Carinae (1996-06-11)

Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - make it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky.  Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This just-released image taken last September resulted from sophisticated image-processing procedures designed to bring out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained. Will these clues tell us how the nebula was formed?  Will they better indicate when Eta Carinae will explode?
Vela Supernova Remnant in X-ray (1996-06-12)

What happens when a star explodes? A huge fireball of hot gas shoots out in all directions. When this gas slams into the existing interstellar medium, it heats up so much it glows in X-rays. The above picture by the ROSAT satellite has captured some of these X-rays and shown -- for the first time -- the Vela supernova explosion was roughly spherical. Non-uniformity of the interstellar medium causes Vela's appearance to be irregular.  The size of this X-ray emitting spherical shell is immense - 230 light years across, covering over 100 times the sky-area of the full Moon. The supernova that created this nebula occurred about 1500 light years away and about 11,000 years ago. Coincidently, a completely different supernova shell can also be seen in X-rays in this picture! It is visible as the bright patch near the upper right. This Puppis supernova remnant nebula is actually about four times farther than the Vela nebula.
Vela Supernova Remnant in Optical (1996-06-13)

About 11,000 years ago a star in the constellation of Vela exploded.  This bright supernova may have been visible to the first human farmers. Today the Vela supernova remnant marks the position of a relatively close and recent explosion in our Galaxy. A roughly spherical, expanding shock wave is visible in X-rays. In the above optical photograph, the upper left corner of the spherical blast wave is shown in detail. As gas flies away from the detonated star, it reacts with the interstellar medium, knocking away closely held electrons from even heavy elements. When the electrons recombine with these atoms, light in many different colors and energy bands is produced.

Image credit: Royal Observatory, Edinburgh,
Anglo-Australian 
Observatory
Floating Free in Space (1996-06-14)

NASA astronauts can float free in space without any connection to a spaceship. Here astronaut Bruce McCandless maneuvers outside the Space Shuttle Challenger by firing nitrogen gas thrusters on his manned maneuvering unit (MMU).  This picture was taken in 1984 and records this first untethered spacewalk. The MMU was developed because astronauts found tethers restrictive.