juliensimon/nasa-apod huggingface dataset:
Resolving Mira (1997-08-13)

Most stars appear only as points of light. Recently, Betelgeuse became the second star, after our Sun, to have it surface resolved.  Now add Mira to the list.  Mira A is a red giant star undergoing dramatic pulsations, causing it to become more than 100 times brighter over the course of a year.  Mira was discovered to be the first variable star 401 years ago today by David Fabricus.  Mira can extend to over 700 times the size of our Sun, and is only 400 light-years away. The above photograph released last week from the Hubble Space Telescope shows the true face of Mira. But what are we seeing?  The unusual extended feature off the lower left of the star remains somewhat mysterious.  Possible explanations include gravitational perturbation and/or heating from Mira's white dwarf star companion
Mars Rocks, Sojourner Rolls (1997-08-14)

This sharp color image featuring Mars rock Yogi and the rolling Sojourner robot shows off Yogi's startling two-toned surface. Yogi appears to be leaning into the prevailing winds causing some to suggest that its color contrast may be caused by the accumulation of rust colored dust on its windward face. The Pathfinder spacecraft, now the Sagan Memorial Station, has ended the primary mission phase after returning a scientific bonanza from the surface of Mars. The Sojourner robot has now traveled 171 feet on the martian surface, circumnavigated the lander, and also produced a wealth of data and images. Entering the extended mission phase of operations, controllers will concentrate on conserving battery power while continuing to explore the red planet.
Impact On Europa (1997-08-15)

This bull's-eye pattern marks the impact of a mountain-sized comet or asteroid on the icy surface of Jupiter's moon Europa. Recorded by the Galileo spacecraft in April of this year, the composite false color image clearly reveals the telltale concentric fractures which cover about 86 miles - roughly equivalent to the Island of Hawaii. The fat reddish and finer blue-green lines overlay the impact fractures and must therefore be younger surface features formed after the impact. The dark red color may be the result of a a relatively dirty water-ice mixture. The possibility of liquid water below the ice has fueled speculation that life may exist on this large and distant moon.
Pictured: An Ancient Martian? (1997-08-16)

Alien! Alien? Is this what an ancient Martian looked like? The tube-like form on the above highly magnified image is now believed by many to be a fossil of a simple Martian organism that lived over 3.6 billion years ago. If this extraordinary claim is true, this alien could hardly have been less intimidating as its fossil measures less than 1/100th the width of a human hair. A reconstruction of events indicates that the meteorite that housed this potential fossil was catapulted from Mars during a huge impact 16 million years ago and fell to Earth's Antarctica only 13,000 years ago.  Evidence supporting this claim of early Martian life includes organic molecules and mineral features characteristic of biological activity found in the meteorite.  NASA's current missions to Mars are Mars Global Surveyor and Mars Pathfinder. Though not designed to look for martian fossils, these missions may reveal information about conditions on early Mars which might have been more favorable for life.
Astro 1 In Orbit (1997-08-17)

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.
Io: The Prometheus Plume (1997-08-18)

Two sulfurous eruptions are visible on Jupiter's volcanic moon Io in this color composite Galileo image. On the left, over Io's limb, a new bluish plume rises about 86 miles above the surface of a volcanic caldera known as Pillan Patera. In the middle of the image, near the night/day shadow line, the ring shaped Prometheus plume is seen rising 45 miles above Io while casting a shadow to the right of the volcanic vent. Named for the Greek god who gave mortals fire, the Prometheus plume is visible in every image ever made of the region dating back to the Voyager flybys of 1979 - presenting the possibility that this plume has been continuously active for at least 18 years. This image was recorded on June 28 at a distance of 372,000 miles.
Super Typhoon Winnie (1997-08-19)

Super Typhoon Winnie raged through parts of the Eastern Hemisphere last week. Swirling in the Pacific Ocean with winds in excess of 160 miler per hour, Winnie became one of the stronger storm systems in modern times: a Category 5 Hurricane. The above picture, taken August 13th by crew member of Space Shuttle Discovery, showed the extent of this huge storm: the central eye measured fully 8 miles in diameter. Last week, Winnie hit the Northern Mariana Islands at full strength, but then weakened before heading toward China. Studying large storms systems on other planets give insight into the workings of Earth bound storms like Winnie.
Bright Meteor, Dark Sky (1997-08-20)

Has Orion the Hunter acquired a new weapon?  If you turn your head sideways (counterclockwise) you might notice the familiar constellation of Orion, particularly the three consecutive bright stars that make up Orion's belt.  But in addition to the stars that compose his sword, Orion appears to have added some sort of futuristic light-saber, possibly in an attempt to finally track down Taurus the Bull.  Actually, the bright streak is a meteor from the Perseid Meteor Shower, a shower that put on an impressive display last Tuesday morning, when this photograph was taken. This meteor was likely a small icy pebble shed years ago from Comet Swift-Tuttle that evaporated as it entered Earth's atmosphere.

Image credit: W. Pacholka
A Universe in a Box (1997-08-21)

Is this our universe? Possibly. It is one computerized guess of how gas in the universe was distributed billions of years ago, at redshift 3, when the universe was only a quarter of its present age.  Using supercomputers at the National Center for Supercomputing Applications and assumptions about the composition and beginning of the universe, the GC3 team was able to reconstruct a hypothetical universe. A cube of this universe was cut out and displayed, with each side being about 8 million light years across. Color represents temperature of the hot gas.  At the bottom a single slice through this cube is displayed, with helium abundance superposed with a wire mesh.  The small structures appearing here give insight into the past and present structure of the intergalactic medium, the matter inhabiting the regions between galaxies and clusters of galaxies.
IP Pegasi: Spiral Star (1997-08-22)

Spiral arms aren't just for galaxies. A hot disk of gas surrounding a compact white dwarf star in the constellation of Pegasus has recently been revealed to be imprinted with this dramatic pattern. The white dwarf is part of the interacting binary star system IP Pegasi and the disk of gas is an accretion disk formed of material lost from a companion star and falling toward the white dwarf. The disk itself is smaller than the Sun's diameter, so the spiral pattern can not be imaged directly by telescopes. Instead, the spiraling disk of gas is mapped over a series of observations using a spectroscopic technique known as doppler tomography. The left panel above shows a tomogram, the directly measured gas velocity map for the system. The relative brightness corresponds to the intensity of light emitted by Hydrogen gas moving at the indicated velocity. The position at the center of this panel represents the velocity of the binary system's center of mass. In the middle panel, a simple model velocity field consistent with the measurements is shown. At the right, the calculated position map of the IP Pegasi accretion disk reveals a striking two armed trailing spiral pattern.
A Star Forming Region in the LMC (1997-08-23)

Stars sometimes form in colorful ways.  Pictured above is a small region in the nearby LMC galaxy where stars are forming. After a star is born, it may do several things to energize its immediate neighborhood. It may develop a strong wind which pushes away nearby gas; it may be so hot and intense that emitted light boils away nearby dust and gas, and it may be so massive that it soon goes supernova and catapults its elements back to the interstellar medium. Astronomers study regions like this - named DEM192 - to better understand how these and other processes proceed. This picture is a composite of three separate photographs, each sensitive to only one specific color of light - a color that distinguishes a specific chemical element.
The Snake Nebula in Ophiuchus (1997-08-24)

What slithers there? The dark winding lanes visible in part of the constellation Ophiuchus belong to the Snake Nebula. The Snake Nebula is a series of dark absorption clouds made up of Interstellar dust. Interstellar dust grains - composed predominantly of carbon - absorb visible starlight and reradiate much of it in the infrared. This absorption causes stars behind the clouds to be obscured from view, hence the appearance of starless voids on the sky.

Image credit: B. Wallis and R. Provin
A Fisheye View of Comet Hale-Bopp (1997-08-25)

Thousands of stars, several constellations, a planet and a comet all graced the western horizon over Ujue, Spain just after sunset on April 4th, 1997. Because the picture was taken with a fisheye lens, much of the whole night sky is visible. Comet Hale-Bopp, with both tails blazing, appears right of center. The brightest star is Sirius near the edge, well to the left of the constellation Orion.  The red star above the belt of Orion is Betelgeuse, while the red star near the center is Aldebaran, just to the left of the bright Pleaides star cluster.  Many other interesting astronomical objects are visible, including zodiacal light, which is the diffuse triangular glow in the center.  Even the planet Mercury appears just over the horizon.

Image credit: J. C. Casado
Zodiacal Light (1997-08-26)

Sometimes the sky itself seems to glow.  Usually, this means you are seeing a cloud reflecting sunlight or moonlight.  If the glow appears as a faint band of light running across the whole sky, you are probably seeing the combined light from the billions of stars that compose our Milky Way Galaxy.  But if the glow appears triangular and near the horizon, you might be seeing something called zodiacal light. Pictured above, zodiacal light is just sunlight reflected by tiny dust particles orbiting in our Solar System.  Many of these particles were ejected by comets. Zodiacal light is easiest to see in September and October just before sunrise from a very dark location.

Image credit: D. Malin (AAO),
AATB
A Fleeting Eclipse (1997-08-27)

A lunar eclipse can be viewed in a leisurely fashion. Visible to anyone on the night side of planet Earth (weather permitting), totality often lasts an hour or so as the moon glides through the Earth's shadow. But a solar eclipse is more fleeting. Totality can last a few minutes only for those fortunate enough to stand in the path of the Moon's shadow as it races across the Earth's surface. For the April 29, 1995 annular solar eclipse, photographer Olivier Staiger was standing in Macara, Ecuador under partially cloudy skies. Just before the maximum annular eclipse phase he recorded this dramatic moment as a bird flew near the sun. Very accurate predictions of eclipses have long been possible. The next solar eclipse will occur on September 2 and be visible from Australia, New Zealand, and Antarctica. The next lunar eclipse on September 16 will be visible from the Eastern Hemisphere.

Image credit: Olivier Staiger
Infrared Trifid (1997-08-28)

The Trifid nebula (M20) is a bright star forming region in Sagittarius, 5000 light years from Earth. In visible light, the interstellar gas cloud is crossed by dark, obscuring dust lanes which roughly divide the glowing emission nebula into three major parts. But the Trifid nebula's well known appearance is dramatically reversed in this infrared view. At longer infrared wavelengths the dust lanes are brighter, radiating more energy than the gas. This image was recorded by the liquid helium cooled Infrared Space Observatory (ISO).
Cassini To Saturn (1997-08-29)

Scheduled for launch in October, the Cassini spacecraft will spend seven years traveling through the Solar System -- its destination, Saturn. On arrival Cassini will begin an ambitious mission of exploration which will include parachuting a probe to the surface of Titan, Saturn's largest moon. This artist's vision offers a dramatic view of Cassini's engine firing during the SOI (Saturn Orbit Insertion) maneuver as it passes above the ring plane. Before the development of the telescope, the gas giant Saturn was the most distant planet known to astronomers. Ten times farther from the Sun it receives only 1 percent of the sunlight that Earth does. Operating in this faint sunlight, the Cassini spacecraft can't use solar arrays so, like other missions to the outer Solar System, it will be powered by radioisotope thermoelectric generators (RTGs).
The United States at Night (1997-08-30)

This is what the United States of America looks like at night! Can you find your favorite US city on this image? Surprisingly, city lights make this task quite possible. The above picture is actually a composite of over 200 images made by satellites orbiting the Earth. Scans were made by the USAF Defense Meteorological Satellite Program (DMSP) Operational Linescan System. The DMSP satellites continue to help in the understanding and prediction of weather phenomena as well as provide key information about population patterns, city light levels, and even rural forest fires.

Image credit: NOAA/
NGDC, 
DMSP 
Digital Archive
Arp 230: Two Spirals in One? (1997-08-31)

Is this one galaxy or two? Analysis of Arp 230 has shown evidence that this seemingly single spiral galaxy is actually the result of the recent collision of two spiral galaxies. The slow motion collision took place over about 100 million years and induced a burst of star formation that has begun to subside. The collision apparently had many similarities to the colliding galaxy sequence in the IMAX movie "Cosmic Voyage."
Infrared Helix (1997-09-01)

Five hundred light years from Earth, in the constellation Aquarius, a sun-like star is dying. Its last few thousand years have produced the Helix, a well studied and nearby example of a Planetary Nebula - typical of this final phase of stellar evolution. The emission in this Infrared Space Observatory image of the Helix nebula comes mostly from the expanding shells of molecular hydrogen gas. Dust, normally expected in such nebulae, should also radiate strongly at infrared wavelengths but mysteriously seems to be absent here. The culprit may may well be the Helix's central star, a contracting white dwarf. This small but extremely hot star radiates most of its energy at short Ultraviolet wavelengths and is invisible in this infrared mage.  Astronomers suspect that over time, this intense Ultraviolet radiation may have destroyed the dust. The Sun is expected to go through its own Planetary Nebula phase ... in another 5 billion years.
Dark Sky, Bright Sun (1997-09-02)

In low Earth orbit there is not enough atmosphere to diffuse and scatter sunlight, so shadows are black and the sky is dark - even when the Sun shines.  The harsh lighting produced this dramatic effect as mission specialist Gregory Harbaugh photographed colleague Joseph Tanner during their second spacewalk to service the Hubble Space Telescope in February 1997. The aft section of the Space Shuttle Discovery is visible in the background with the Sun hanging over a delicate crescent of the Earth's limb. A checklist is attached to Tanner's left arm, and Harbaugh's reflection is just visible in Tanner's visor.
A Partial Eclipse in Southern Skies (1997-09-03)

Location is everything, especially if you want to see a Solar Eclipse. These fleeting events are only visible to those in the path of the Moon's shadow as it races across the Earth. This path is usually less than 200 miles wide while covering only a fraction of a percent of the Earth's surface. And chances are, much of it will be over water. This view of the September 2nd eclipse was recorded by Olivier Staiger from Kingscote, Kangaroo Island, South Australia. He used a video camera equipped with a teleconverter and solar filter. This Solar Eclipse was a partial one, seen here near maximum for Staiger's location. The deepest eclipse - almost 90 percent of the Sun's surface was eclipsed by the Moon - was visible only from Antarctica. Want to see a total eclipse of the Sun? Locate yourself near the northern tip of South America on February 26, 1998.

Image credit: Olivier Staiger
Rivers in the Sun (1997-09-04)

The surface of the Sun is shifting. By watching sunspots, it has long been known that our Sun rotates. It was also known that the center of the Sun rotates faster than the poles. Now, recent measurements by the Solar Oscillations Investigations group of the SOHO Observatory have found that the surface of the sun moves in other ways, too.  Hot, electrically charged gas flows along and beneath the Sun's surface as depicted in the above computer generated diagram. The speed of these solar rivers is false-color coded with red hydrogen moving faster than blue. Over the course of a year plasma moves from the equator to the poles, while internal eddies circulate gas from deep inside the Sun.  One surprise is the similarity to the motion of air in the Earth's atmosphere - indicating that scientists might learn more about Earth's global weather by studying the Sun.
Apollo 17: Boulder on the Moon (1997-09-05)

Twenty five years ago humans roamed the Moon.  Pictured here during the last moon landing, scientist-astronaut Harrison Schmitt was photographed standing next to a huge, split boulder. Apollo 17 was one of six missions that landed humans on the moon and returned them safely.  Apollo 17 explored the unusually dark terrain at the Taurus-Littrow landing site, deployed explosives to test the internal geology of the Moon, and returned the most rocks of any lunar mission.
Isaac Newton Explains the Solar System (1997-09-06)

Sir Isaac Newton changed the world. Born in 1643, Newton was only an above-average student. But he went home from Cambridge one summer in 1665, thought a lot about the physical nature of the world, and came back two years later with a revolutionary understanding of mathematics, gravitation, and optics. A Professor of his, upon understanding what Newton had done, resigned his own position at Cambridge so Newton could have it. Newton's calculus provided a new mathematical framework for the rapid solution of whole classes of physical problems.  Newton's law of gravitation explained in one simple formula how apples fall and planets move.  Newton's insights proved to be so overwhelmingly powerful he was the first scientist ever knighted.
Luna 9: First Soft Lander (1997-09-07)

The Luna 9 spacecraft above performed the first soft landing on another planetary body. Following a series of failures, the Soviet probe touched down in the Moon's Oceanus Procellarum region February 3, 1966. It accomplished this milestone in lunar exploration only shortly after the death of Sergei Korolev, the father of the Soviet Space Program. Reportedly, Korolev's colleagues wished to dedicate the Luna 9 mission to him but were unable to as his role as the Chief Designer was still a state secret. A pole, just visible extending at the lower left, sensed the impact with the lunar surface, triggering the spacecraft to eject the weighted, egg-shaped capsule (upper right). The 250 pound capsule then struck the surface, rolled upright, unfolded four spring actuated petals to steady itself, and transmitted the first views from the lunar surface back to Earth.
A Map of Asteroid Vesta (1997-09-08)

Vesta is a huge rock 500 kilometers across that orbits out past Mars. Last week, the above map of Vesta created using the Hubble Space Telescope was released showing a rugged surface highlighted by a single crater spanning nearly the entire length of the asteroid.  The large crater dominates the lower part of the false-color conglomerate image: blue indicates low terrain, while red indicates raised terrain. Evidence indicates that Vesta underwent a tremendous splintering collision about a billion years ago.  In October 1960, a small chunk of this rock believed to have originated on Vesta fell to Earth and was recovered in Australia.
A Green Flash from the Sun (1997-09-09)

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 slight variant of this was caught in the above photograph, where much of the Sun was still visible, but the very top appeared momentarily green. The Sun itself does not turn partly green, the effect is caused by layers of the Earth's atmosphere acting like a prism.

Image credit: J. C. Casado
Comet Hale-Bopp Outbound (1997-09-10)

Hale-Bopp, the Comet of the Century, is leaving the inner Solar System. Outbound at about 12 miles per second it is presently nearing the main asteroid belt between Mars and Jupiter. This false-color image represents a recent view from low Earth orbit showing the comet surrounded by its shrinking coma against a background of stars. It was constructed from a fraction of the data taken aboard the Space Shuttle Discovery in August by a small innovative telescopic camera known as the Southwest Ultraviolet Imaging System or SWUIS. SWUIS (sounds like "swiss") images will be particularly interesting to astronomers who wish to continue to follow the Great Comet's interaction with the Solar Wind. The once bright Hale-Bopp has faded below 4th magnitude but is still visible to Earthbound observers south of 35 degrees north latitude.
Mars Global Surveyor: Aerobraking (1997-09-11)

Completing a 10 month journey, another spacecraft from Earth arrives at Mars today.  The Mars Global Surveyor (MGS) is scheduled to fire its main rocket engine for 22 minutes at 6:17 p.m. PDT and enter a highly elliptical orbit, with a low point 186 miles and a high point 34,800 miles above the surface of Mars. This robot spacecraft is aptly named. Its mission is to undertake a detailed planetwide survey of Mars. But first MGS must circularize its orbit, lowering the high point to about 250 miles. Instead of relying solely on its rocket engine, MGS mission controllers will use a fuel-saving technique known as aerobraking - dipping the spacecraft into the Martian atmosphere where it will encounter increased atmospheric drag. This early artist's conception emphasizes the drag created by the wing-like solar panels. The cumulative effect should find MGS in a more circular mapping orbit by March 1998. To successfully use aerobraking, mission controllers must achieve an exact orbit and will be handicapped by a limited knowledge of the thickness of the Martian atmosphere. They may even need to alter the spacecraft's course to compensate for changes in Martian weather.