juliensimon/nasa-apod huggingface dataset:
Arp 220: Spirals in Collision (1997-06-17)

Arp 220 is the brightest object in the local universe. But why does it shine so brightly?  Arp 220 was cataloged as a peculiar galaxy in the 1960s. In the late 1980s, it was discovered to be an ultraluminous infrared galaxy and headed a list compiled from observations with the now-defunct IRAS satellite.  New observations with the Hubble Space Telescope are quite revealing.  Photos by NICMOS in the infrared taken in April and released just last week now better resolve the two colliding spiral galaxies at the center of Arp 220.  A result of this spiral collision are fantastic knots of new star formation visible as the bright spots on the above photograph. Below the "half-moon" shaped knot on the right is a massive disk of dust possibly hiding a dying spiral's central black hole. The bright knot to the left is the center of the other broken spiral galaxy. The galaxy cores are about 1200 light years apart and are orbiting each other.
Asteroid 3753: Earth's Curious Companion (1997-06-18)

rth is not alone. It orbits the Sun with a small companion: Asteroid 3753.  First discovered in 1986 and designated 1986 OT, this five kilometer rock was recently found to orbit the Sun while executing a strange dance with the Earth. A portion of the asteroid's complex orbit is shown above. As the Earth orbits once, Asteroid 3753 follows the yellow line - while also orbiting the Sun.  Each time around, however, the yellow kidney-bean traced by Asteroid 3753 shifts slightly - eventually going from trailing the Earth to leading the Earth.  Every 385 years the cycle repeats.  Because the plane of 3753's orbit is tilted when compared to the Earth's orbit, the two will never collide. In autumn 1997, Asteroid 3753 will pass below the Earth's South Pole at about 100 times the distance to the Moon. It will, however, be very faint - about 15th magnitude - 10,000 times fainter than the dimmest star without a telescope. Suggestions are being taken for a good name for this asteroid.

Image credit: P. Weigert 
(York U.) et al.
HH1/HH2: Star Jets (1997-06-19)

A cloud of interstellar gas and dust collapses and a star is born. At its core temperatures rise, a nuclear furnace ignites, and a rotating dusty disk forms surrounding the newborn star. According to current understanding, as material continues to fall onto the disk it is heated and blasted back out along the disk's axis of rotation, forming a pair of high speed jets. This Hubble Space Telescope image shows two nebulosities at the ends of opposing jets from a young star. The bright blobs at either end are where the jet material has slammed into interstellar gas. Tip to tip, the distance is about one light-year. Located near the Orion Nebula, these nebulosities have catalog designations HH1 and HH2 for their discoverers astronomers George Herbig and Guillermo Haro. The nascent star which produced the jets is in the middle, hidden by a cloud of obscuring dust. Yet the structures and details visible in the star jets offer clues to events which also occured in our own Solar System - when the Sun was formed from a collapsing interstellar cloud 4.5 billion years ago.
NGC1850: Star Cluster in the LMC (1997-06-20)

NGC1850 is a large cluster of stars located a mere 166,000 light-years from Earth in our neighboring galaxy the Large Magellanic Cloud (LMC). The colors in this beautiful Hubble Space Telescope composite image of the cluster reveal different populations of stars. Yellowish stars are the main cluster stars, sun-like main sequence hydrogen burners about 50 million years old. The white stars are massive, hotter, and younger, about 4 million years old. Radiating strongly in ultraviolet light, they represent a loose cluster themselves, perhaps within 200 light-years of the main cluster. Massive stars which formed in the older main cluster have long since disappeared, ending their lives in spectacular supernova explosions. Did expanding debris from these supernovae trigger the formation of the nearby younger cluster? Probably so. In any event, a few million years from now a similar fate awaits the massive stars of the younger cluster - burning brightly but briefly before they explode sending new clouds of stellar debris into space.
The Pipe Dark Nebula (1997-06-21)

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
Distant Galaxies (1997-06-22)

This Hubble Space Telescope image of a group of faint galaxies "far, far away" is a snap shot of the Universe when it was young. The bluish, irregularly shaped galaxies revealed in the image are up to eight billion light years away and seem to have commonly undergone galaxy collisions and bursts of star formation. Studying these objects is difficult because they are so faint, however they may provide clues to how our own Milky Way Galaxy formed.
Eruption on Io (1997-06-23)

There it goes again.  Gas and rock were catapulted hundreds of kilometers into space as Jupiter's most volatile moon, Io, showed yet another impressive volcanic display in this just-released photograph by the Hubble Space Telescope. This time the culprit was Pele, a volcano thought previously inactive since photographed by the passing Voyager 1 spacecraft in 1979. The explosion is visible on Io's lower left in this false-color photograph, taken in July 1996. Io's thin atmosphere and low gravity allow volcanic plumes to rise higher than they would on Earth.
Antares (1997-06-24)

Antares is a huge star. In a class called red supergiant, Antares is about 700 times the size of our own Sun, 15 times more massive, and 10,000 times brighter.  Antares is the brightest star in the constellation of Scorpius and one of the brighter stars in all the night sky.  Antares is surrounded by a nebula of gas which it has itself expelled. Radiation from Antares' blue stellar companion helps cause the nebular gas to glow, as photographed above.  Antares is located about 500 light years away.

Image credit: D. Malin 
(AAO),
AATB, 
UKS Telescope
A GRB Host? (1997-06-25)

Where do gamma-ray bursts (GRBs) originate? The most powerful explosions in the universe have recently been located with record accuracy.  But do GRBs occur in galaxies or out alone in deep space?  This picture taken with the Hubble Space Telescope of the field surrounding GRB 970228 might provide a clue.  It appears to show an extended structure to the lower right of the GRB, which is identified with an arrow. Many astronomers speculate that this extended structure is a distant galaxy, as its colors and subsequent steady emission indicate. Other astronomers worry that the extended emission is variable and so cannot be a galaxy. Astronomers hoping for more cases to study were rewarded just last Monday with a new, well-located event: GRB 970616. The location of this burst was determined by an unprecedented collaboration involving the tandem use of NASA satellites Compton, Ulysses and Rossi.
A Close Encounter of the Stellar Kind (1997-06-26)

The unassuming star centered in this sky view will one day be our next door stellar neighbor. The faint 9th magnitude red dwarf currently 63 light-years away in the constellation Ophiucus was recently discovered to be on a course toward our Solar System. Known in catalogs of nearby stars as Gliese 710 it is predicted to come within 1 light-year of the Sun ... a million years from now. At that distance this star, presently much too faint to be seen by the naked eye, will blaze at 0.6 magnitude - rivaling the apparent brightness of the mighty red giant Antares. Gliese 710 poses no direct collision danger itself although its gravitational influence will likely scatter comets out of the Solar System's reservoir, the Oort cloud, sending some inbound. This future stellar encounter was discovered by researchers Joan Garcia-Sanchez and Robert Preston (JPL), and collaborators while studying stars in the solar neighborhood using data from the Hipparcos Astrometry Satellite. The star field shown is based on the Palomar Digitized Sky Survey and is 1/4 degree wide (about half the diameter of the full moon).
Mars: Just The Facts (1997-06-27)

Mars, the freeze-dried planet, orbits 137 million miles from the Sun or at about 1.5 times the Earth-Sun distance. It has two diminutive moons, towering extinct volcanos, an immense canyon system, a thin atmosphere chiefly composed of carbon dioxide (CO2), a frigid average surface temperature of -63 degrees Celsius, and permanent frozen CO2 polar caps which contain some water ice. Mars' surface presently lacks liquid water and has a reddish color because of an abundance of oxidized iron compounds (rust). A small terrestrial planet, fourth from the Sun, Mars has only about 3/8 the surface gravity of Earth. So for example, if you tip the scale at a hefty 200 pounds on Earth you'd be a 75 pound featherweight on Mars. The low martian gravity will be good for NASA's Mars Pathfinder spacecraft scheduled to land on Mars next Friday, July 4th. Using rockets, parachutes, and airbags, Mars Pathfinder will be the first spacecraft to touchdown on the planet since the Viking landers in 1976. Pathfinder is also scheduled to begin the first ever mobile surface exploration by releasing the robot rover, "Mars Sojourner".
Barsoom (1997-06-28)

"Yes, I have been to Barsoom again ..." begins John Carter in Edgar Rice Burroughs' 1913 science fiction classic "The Gods of Mars". In Burroughs' novels describing Carter's adventures on Mars, "Barsoom" is the local name for the red planet. Mars continues to inspire Earthdwellers' interests and imagination. Soon it will again be invaded by spacecraft from Earth. This dramatic picture of a crescent Mars was taken by NASA's Viking 2 spacecraft in 1976.
Ida and Dactyl: Asteroid and Moon (1997-06-29)

This asteroid has a moon! The robot spacecraft Galileo currently exploring the Jovian system, encountered and photographed two asteroids during its long journey to Jupiter. The second asteroid it photographed, Ida, was discovered to have a moon which appears as a small dot to the right of Ida in this picture. The tiny moon, named Dactyl, is about one mile across, while the potato shaped Ida measures about 36 miles long and 14 miles wide. Dactyl is the first moon of an asteroid ever discovered. The names Ida and Dactyl are based on characters in Greek mythology. Do other asteroids have moons?
NEAR Mathilde (1997-06-30)

Hey Earth, look what I found! On the way to visiting the  asteroid 433 Eros in February 1999, the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew right by another asteroid: 253 Mathilde last Friday.  Shown above is one picture from the encounter.  Mathilde is a large chunk of rock roughly 60 kilometers across that orbits the Sun between Mars and Jupiter in the main asteroid belt.  Mathilde's surface is very dark and heavily cratered. The NEAR pictures of Mathilde received so far indicate that the asteroid has undergone spectacular collisions, one of which created the huge impact basin in the center, which is estimated to be about 10 kilometers deep.
Asteroid 253 Mathilde:'s Large Craters (1997-07-01)

You're zipping through the Solar System when you pass ... asteroid 253 Mathilde. This actually happened to NASA's NEAR spacecraft just last Friday.  The above picture of the previously unresolved asteroid was released just yesterday.  Mathilde's large craters and irregular shape indicates that it has undergone huge collisions with other large space rocks in the past.  Mathilde has more large craters than asteroids 243 Ida and 951 Gaspra, which were photographed by the Galileo spacecraft now orbiting Jupiter. In the image center is a crater over 20 kilometers across.  Asteroids are rare enough so that spacecraft traveling through even the main asteroid belt need not fear colliding with any - let alone one as large as Mathilde.
Gamma-Ray Burst: A Milestone Explosion (1997-07-02)

Gamma-Ray Bursts (GRBs) were discovered by accident. In fact, GRBs always seem to be where scientists least expect them.  Thirty years ago today, satellites first recorded a GRB. The burst data plotted in this histogram show that the count rate of the gamma-ray instrument abruptly jumped indicating a sudden flash of gamma-rays. The Vela satellites that detected this and other GRBs were developed to test technology to monitor nuclear test ban treaties. With on board sensors they watched for brief X-ray and gamma-ray flashes, the telltale signs of nuclear explosions from the vicinity of the Earth. As intended, the Velas found flashes of gamma-rays - but not from nuclear detonations near Earth. Instead, the flashes came from deep space! Dubbed "cosmic gamma-ray bursts" their origin was then unknown and is still controversial. However, the gamma-ray surprises were not over. Exploring the high-energy sky nearly 25 years later, the orbiting Compton Observatory's Burst and Transient Source Experiment (BATSE), intentionally designed to detect cosmic gamma-ray bursts, was searching for clues to the GRB mystery. But the second burst BATSE recorded did not come from deep space. It came from near the Earth! Don't worry, these terrestrial GRBs are not nuclear bombs exploding. They are a new phenomenon now thought to be related to a recently discovered type of high altitude lightning.  Exploring new horizons continues to yield unexpected results.
Mars: A Journey's End (1997-07-03)

Mars Pathfinder is nearing the end of its 7 month journey. The robot spacecraft is scheduled to use parachutes, rockets, and airbags to "bouncedown" on the red planet tomorrow - July 4th. This Hubble Space Telescope image of Mars was taken a few days ago to check on the weather. The pathfinder landing site, on the ancient floodplain Ares Vallis, is just right of center - 500 miles southeast of where Viking 1 landed in 1976. Along with the martian north polar cap, some water ice clouds are visible in both the northern and southern hemisphere. About 600 miles south of the landing site a dust storm can be seen as a brownish ribbon stretching through the the Valles Marineris, a continent sized canyon system. Fortunately, the dust storm is not expected to seriously affect operations at the landing site.
A Landing On Mars (1997-07-04)

Today, July 4th, at about 10:00 AM Pacific Daylight Time (PDT), the Mars Pathfinder spacecraft will land on Mars. Ninety minutes before reaching the surface Pathfinder will begin a flurry of activity. The robot spacecraft is scheduled to vent cooling fluid, jettison its cruise stage, decelerate at 20 gees on atmospheric entry, deploy a 24 foot parachute, jettison its heat shield, slide down a 60 foot bridle, fire solid fuel braking rockets, deploy a cocoon of airbags, separate from the bridle, impact the martian surface, bounce a few times (traveling about 300 - 600 feet between bounces), settle on the surface, deflate the airbags, right itself, deploy its landing petals, and resume communication with planet Earth, all under the autonomous control of the onboard computer. If all goes well, at about 4:30 PM PDT the Pathfinder's camera "IMP" will spring into action recording frame by frame a panoramic view of the surface. Dubbed "Mission Success" the mosaic above is a laboratory simulation of the planned first image sequence to be downlinked from the surface of Mars.
Pathfinder on Mars (1997-07-05)

Yesterday, July 4th, using its own array of fireworks, a parachute, and a cocoon of airbags, the Mars Pathfinder spacecraft successfully bounced and came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. And the news is wonderful - the spacecraft appears to be in good health after having performed its complicated landing sequence superbly. Above is a mosaic of images from the martian surface transmitted shortly after Pathfinder reestablished communication with its mission operators on Earth. The solar powered, two foot long, 25 pound Mars Sojourner robot rover is visible crouched on the unfolded spacecraft. Surrounding Pathfinder are deflated airbags and a rock-strewn terrain. In the distance martian hills appear against a dusty brownish sky. The IMP camera which produced this view is also capable of stereo images and promises further spectacular pictures from Mars.
A Martian Day's End (1997-07-06)

A Day or "Sol" on Mars is only 40 minutes longer than an Earth day - and Pathfinder's first day on Mars, Sol 1 according to its local calendar, was an eventful one. Still, late in the martian afternoon of Sol 1, the camera on board the Mars Pathfinder spacecraft recorded this panorama of the ancient floodplain Ares Vallis. Two of the three landing petals lie in the foreground at the edges of this scene surrounded by deflated and partially gathered airbags. The martian soil near the spacecraft has been disturbed by the airbag retraction. The petal holding the undeployed robot rover Sojourner is at the left. One of Sojourner's planned routes to the surface will be down the ramp seen rolled up at the petal's edge. Mission teams have overcome some rover communications problems and are proceding carefully with plans to roll the Sojourner out onto the martian surface. NASA has announced that the Pathfinder station on Mars will be renamed in honor of astronomer Carl Sagan.
Sojourner On Mars (1997-07-07)

The six wheeled robot rover Mars Sojourner rolled onto the martian surface on July 5th (Sol 2) at about 10:40 PM Pacific Daylight Time. This image confirms that its descent down the lander's rear deployment ramp was successful. Click on the image to download a "movie gif" constructed from 9 images taken by the Sagan Memorial Station's IMP camera which shows the rover rolling down the ramp! The rover moved only a short distance from the ramp and spent the night analyzing the martian soil with its Alpha Proton X-Ray Spectrometer. Its next destination will be a tantalizing rock about 1 foot away that scientists have named "Barnacle Bill". A slow but steady off-road vehicle powered by a 1.9 square foot solar array, the rover can negotiate obstacles tilted at a 45 degree angle and travels at less than half an inch per second or nearly 0.03 miles per hour.
Barnacle Bill And Sojourner (1997-07-08)

Deployed on a pop-up mast to its full height, the Sagan Memorial Station's IMP camera now stands about 5 feet above the surface of Ares Vallis - on Mars. This is one of the first images from its new vantage point, showing the rover Sojourner near a rock named Barnacle Bill. This particularly interesting rock, with a variety of surface textures, appears to be about 8 to 10 inches high. Sojourner performed an analysis of Barnacle Bill by successfuly maneuvering to place its Alpha Proton X-Ray Spectrometer (APXS) instrument against the rock. The APXS, located at the rear of the rover, is not visible in this picture. Sojourner's next destination is ... a rock named Yogi. Results describing the composition of Barnacle Bill, the martian soil and a color panorama of the landing site will be presented at a Pathfinder press briefing today scheduled for 11:00 AM Pacific Daylight Time.
Sol 4: Mars Color Panorama (1997-07-09)

These mosaicked images form a color panorama of the region immediately surrounding the Sagan Memorial Station on Mars. The most recent images were recorded on Sol 4 - the 4th day of operations on the martian surface. The composite view reveals the reddish soil and rock-strewn terrain of an ancient martian flood channel. At top panel left the unused forward rover deployment ramp is seen extending from the bottom of the frame while farther to the right the Sojourner rover is visible. The large dark looking rock at the top of the panel near the right-hand side is called "Yogi". The now famous martian rock, Barnacle Bill, is seen just to the left of the rover itself. Sojourner's analysis shows that Barnacle Bill is unexpectedly similar to common quartz containing volcanic rocks on Earth! In the bottom panel yellowish material from some of the airbags that were used during landing can be seen along with regions of the martian soil that have been disturbed by the retraction of the deflated airbags.
Sojourner's View: The Sagan Memorial Station (1997-07-10)

The robot rover Sojourner sees Mars from the perspective of a house cat. During the 7 month cruise to Mars aboard the Pathfinder spacecraft, Sojourner measured only seven inches tall in a stowed position but prowling the martian landscape it has stretched to its full height of 1 foot (30 centimeters). In this mosaic of images Sojourner's cameras look back on its mother ship, now the Sagan Memorial Station, which seems to loom above it. The deployment ramp is visible along with deflated airbags, instrumentation masts and tracks left in the martian soil by the robot's six cleated 5-inch aluminum wheels. So far the rover has been directed to analyze soil and the composition of two rocks, Barnacle Bill (seen just to the right of the ramp) and Yogi. Human operators select Sojourner's targets but the robot rover is relied on to navigate to its destination autonomously. Click here to download a movie gif of Sojourner creeping toward Yogi.
Yogi Rock (1997-07-11)

This portrait of Yogi Rock, a now famous boulder on Mars, was recorded on Sol 3 by the Imager for Mars Pathfinder (IMP). Big and friendly looking like its Earth cartoon namesake Yogi Bear, Yogi Rock is a prominent visible feature at the Pathfinder landing site. Yogi and surrounding soil are being examined close up by the Sojourner robot rover. Initial attempts to approach the rock and to place Sojourner's Alpha Proton X-ray Spectrometer against it have met with some minor, but not unusual, difficulties. It is speculated that the light colored "moat-like" terrain around Yogi is the result of the evaporation of surface water deposited by ancient floods.
Doomed Star Eta Carinae (1997-07-12)

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 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 Optical (1997-07-13)

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: Anglo-Australian Telescope Board