juliensimon/nasa-apod huggingface dataset:
Elements in the Aftermath (2001-10-26)

Massive stars spend their brief lives furiously burning nuclear fuel. Through fusion at extreme temperatures and densities surrounding the stellar core, nuclei of light elements like Hydrogen and Helium are combined to heavier elements like Carbon, Oxygen, etc. in a progression which ends with Iron. And so a supernova explosion, a massive star's inevitable and spectacular demise, blasts back into space debris enriched in heavier elements to be incorporated into other stars and planets (and people!). This detailed false-color x-ray image from the orbiting Chandra Observatory shows such a hot, expanding stellar debris cloud about 36 light-years across. Cataloged as G292.0+1.8, this young supernova remnant in the southern constellation Centaurus resulted from a massive star which exploded an estimated 1,600 years ago. Bluish colors highlight filaments of the mulitmillion degree gas which are exceptionally rich in Oxygen, Neon, and Magnesium. Just below and left of center, a point like object in the Chandra image suggests that the enriching supernova also produced a pulsar in its aftermath, a rotating neutron star remnant of the collapsed stellar core.
Sher 25: A Pending Supernova? (2001-10-27)

No supernova has ever been predicted. These dramatic stellar explosions that destroy stars and disperse elements that compose people and planets are not so well understood that astronomers can accurately predict when a star will explode - yet. Perhaps Sher 25 will be the first. Sher 25, designated by the arrow, is a blue supergiant star located just outside the star cluster and emission nebula NGC 3603. Sher 25 lies in the center of an hourglass shaped nebula much like the one that surrounds the last bright supernova visible from Earth: SN1987a. Now the hourglass shaped rings around SN1987a were emitted before that blue supergiant exploded.  Maybe Sher 25 has expelled these bipolar rings in a step that closely precedes a supernova.  If so, Sher 25 may be within a few thousand years of its spectacular finale.

Image credit: W. Brandner 
(UIUC), 
et al., 
ESO, 
1.54-m Telescope, 
Chile
NGC 2346: A Butterfly-Shaped Planetary Nebula (2001-10-28)

It may look like a butterfly, but it's bigger than our Solar System.  NGC 2346 is a planetary nebula made of gas and dust that has evolved into a familiar shape.  At the heart of the bipolar planetary nebula is a pair of close stars orbiting each other once every sixteen days.  The tale of how the butterfly blossomed probably began millions of years ago, when the stars were farther apart.  The more massive star expanded to encompass its binary companion, causing the two to spiral closer and expel rings of gas.  Later, bubbles of hot gas emerged as the core of the massive red giant star became uncovered.  In billions of years, our Sun will become a red giant and emit a planetary nebula - but probably not in the shape of a butterfly, because the Sun has no binary star companion.
Spinning Black Holes and MCG-6-30-15 (2001-10-29)

What makes the core of galaxy MCG-6-30-15 so bright?  Some astronomers believe the answer is a massive spinning black hole.  If so, this would be the first observational indication that it is possible to make a black hole act like a battery -- and tap into its rotational energy.  MCG-6-30-15 is a distant galaxy that has recently been observed with the orbiting XMM-Newton satellite in X-ray light.  These observations show the galaxy's nucleus not only to be very bright but also to show evidence that much of the light is climbing out of a deep gravitational well.  A spinning black hole could explain both effects.  A strong magnetic field could be the mediator transferring rotational energy from the black hole to the surrounding gas.  Pictured above is an artist's illustration of a black hole surrounded by an accretion disk.  For clarity, the illustration does not include distorting gravitational lens effects.
Anticrepuscular Rays Over Colorado (2001-10-30)

What's happening over the horizon?  Although the scene may appear somehow supernatural, nothing more unusual is occurring than a setting Sun and some well placed clouds.  Pictured above are anticrepuscular rays.  To understand them, start by picturing common crepuscular rays that are seen any time that sunlight pours though scattered clouds.  Now although sunlight indeed travels along straight lines, the projections of these lines onto the spherical sky are great circles.  Therefore, the crepuscular rays from a setting (or rising) sun will appear to re-converge on the other side of the sky.  At the anti-solar point 180 degrees around from the Sun, they are referred to as anticrepuscular rays.  Pictured above is a particularly striking set of anticrepuscular rays photographed earlier this month from a moving car just outside of Boulder, Colorado, USA.

Image credit: John Britton
Halloween and the Ghost Head Nebula (2001-10-31)

Halloween's origin is ancient and astronomical.  Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere).  With our modern calendar, however, the real cross-quarter day will occur next week.  Another cross-quarter day is Groundhog's Day. Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead.  A perhaps-fitting modern tribute to this ancient holiday is the above-pictured Ghost Head Nebula taken with the Hubble Space Telescope.  Appearing similar to the icon of a fictional ghost, NGC 2080 is actually a star forming region in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way Galaxy.  The Ghost Head Nebula spans about 50 light-years and is shown in representative colors.
M87's Energetic Jet (2001-11-01)

An energetic jet from the core of giant elliptical galaxy M87 stretches outward for 5,000 light-years. This monstrous jet appears in the panels above to be a knotted and irregular structure, dectected across the spectrum, from x-ray to optical to radio wavelengths. In all these bands, the observed emission is likely created as high energy electrons spiral along magnetic field lines, so called synchrotron radiation. But what powers this cosmic blowtorch? Ultimately, the jet is thought to be produced as matter near the center of M87 swirls toward a spinning, supermassive black hole. Strong electromagnetic forces are generated and eject material away from the black hole along the axis of rotation in a narrow jet. Galaxy M87 is about 50 million light-years away and reigns as the large central elliptical galaxy in the Virgo cluster.
THEMIS of Mars (2001-11-02)

Not an ancient Greek goddess, THEMIS is modern acronese for THermal EMission Imaging System. Above is this remarkable instrument's premier infrared image of Mars, from the newly orbiting Mars Odyssey spacecraft. Taken on October 30th, the sharp infrared picture covers the indicated swath of the martian southern hemisphere and shows surface temperatures in false-colors ranging from red, a warm 0 degrees Celsius, to cool purple shades of -120 degrees C. The striking, cold circular feature is Mars' south polar ice cap. Composed of frozen carbon dioxide, the ice cap is about 900 kilometers wide and shrinking during the onslaught of southern hemisphere summer. Temperatures are also seen to drop as the bottom portion of the THEMIS image sweeps beyond the terminator or shadow line, into the martian night. A thin, light blue crescent along the upper edge of the planet is the martian atmosphere.  The THEMIS image data was recorded as a test of the camera system from an altitude of about 22,000 kilometers .
Bright Stars, Dim Galaxy (2001-11-03)

These two clusters of bright, newly formed stars surrounded by a glowing nebula lie 10 million light-years away in the dim, irregular galaxy cataloged as NGC 2366. The Hubble Space Telescope image shows that the youngest cluster, the bottom one at about 2 million years old, is still surrounded by the gas and dust cloud it condensed from, while powerful stellar winds from the stars in the older cluster at the top (4-5 million years old), have begun to clear away its central areas giving the entire nebula an apparent inverted hook shape. Compared to the sun, the stars in these clusters are massive and short lived. The brightest one, near the tip of the hook, is a rare Luminous Blue Variable with 30 to 60 times the mass of the sun - similar to the erruptive Eta Carinae in our own Milky Way. Stars this massive are extremely variable. A comparison with ground based images indicates that in three years this star's brightness increased by about 40 times making it currently the brightest star in this dim galaxy.
Leonids from Leo (2001-11-04)

Is Leo leaking? Leo, the famous sky constellation visible on the left of the above all-sky photograph, appears to be the source of all the meteors seen in 1998's Leonids Meteor Shower.  That Leonids point back to Leo is not a surprise - it is the reason that this November meteor shower is called the Leonids.  Sand-sized debris expelled from Comet Tempel-Tuttle follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation Leo.  Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Leo.  Over 150 meteors can be seen in the above four-hour effort.  The intensity of the Leonid Meteor Shower in 2001 is uncertain but may approach one per second for some locations on November 18.
Aurora Over Winnipeg (2001-11-05)

What's happening above that city?  The city is Winnipeg, Canada, and the phenomenon is aurora.  These past few months have been active ones for our Sun, producing several coronal mass ejections (CMEs) of particles that have swept past our Earth and caused many spectacular auroras.  Specifically in this case, a CME that occurred on October 9 impacted the Earth on October 11 and 12, causing nearly 12 hours of auroras.  The above-pictured aurora had to be very bright to be seen over the lights of Winnipeg, the city well below and in front of the cascading atmospheric airglow.  Lights reflecting off of a slight haze cause an unrelated glow that emanates from some of the buildings.
In the Center of Spiral Galaxy M83 (2001-11-06)

What's happening at the center of spiral galaxy M83?  Just about everything, from the looks of it.  M83, visible in the inset image on the upper left, is one of the closest spiral galaxies to our own Milky Way Galaxy and from a distance of 15 million light-years, appears to be relatively normal.  Zooming in on M83's nucleus with the latest telescopes, however, shows the center to be an energetic and busy place.  Visible in the above image from the Hubble Space Telescope are bright, newly formed stars and giant lanes of dark dust.  An image with similar perspective from the Chandra X-ray Observatory shows the region is also rich in very hot gas and small bright sources.  Observations with the large ground-based VLT telescopes show the very center likely has two separate nuclei.
A Sun Pillar in Red and Violet (2001-11-07)

Sometimes the unknown is beautiful.  In 2000 February near Lake Tahoe, Nevada, two amateur photographers noticed an unusual red column of light rise mysteriously from a setting sun.  During the next few minutes, they were able to capture the pillar and a photogenic sunset on film.  Pictured above, the red column is seen above a serene Lake Tahoe and snow-capped mountains across from Lake Tahoe-Nevada State Park.  The mysterious column, they learned later, is a Sun Pillar, a phenomenon where sunlight reflects off of distant falling ice crystals.

Image credit: Jim Kirkpatrick & Brigitte Heiter-Kirkpatrick
Under A Sunspot (2001-11-08)

At the Sun's surface, sunspots are known to be dark, planet-sized regions of intense magnetic fields. But what lies below? Using observations from the Michelson Doppler Imager (MDI) instrument aboard the space-based SOHO observatory, astronomers have derived this premier picture of the flow of material just beneath a visible sunspot. The MDI data indicate that immediately under the sunspot a strong inflowing current exists, shown above by the dark arrows. This converging undertow pulls near-surface material toward the spot and prevents the concentrated magnetic fields from flying apart, like repelling poles of iron magnets. Such a configuration appears to divert the normal flow of plasma bubbling up from the solar interior, creating a self-sustaining sunspot. The MDI instrument can explore the properties of the solar interior by detecting motions produced by sound waves as they interact at the solar surface.
SOHO Comet 367: Sungrazer (2001-11-09)

The most prolific comet discovering instrument in history rides aboard the sun-staring SOHO spacecraft, 1.5 million kilometers sunward of planet Earth. Of course, most of these SOHO comets have been sungrazers - like the one illustrated in the dramatic montage above. Three frames taken hours apart on October 23rd, show bright SOHO comet number 367 plunging toward the fiery solar surface, its tail streaming away from the Sun located just beyond the left hand border. Each panel spans about one million kilometers at the distance of the Sun. From bottom to top, the comet's tail grows as the intensifying solar radiation heats the frozen comet material and increases the outflow of gas and dust. Because of their orbits, sungrazers are believed to belong to a family of comets produced by the breakup of a single much larger comet. Coincidentally, this sungrazer was discovered shortly after solar active regions blasted out clouds of energetic particles, like those that triggered the recent spectacular auroral storms. And like all SOHO sungrazers so far, comet number 367 was not seen to survive its close solar encounter.
Lunar Dust and Duct Tape (2001-11-10)

Why is the Moon dusty? On Earth, rocks are weathered by wind and water, creating soil and sand. On the Moon, the long history of micrometeorite bombardment has blasted away at the rocky surface creating a layer of powdery lunar soil or regolith. This lunar regolith could be a scientific and industrial bonanza. But for the Apollo astronauts and their equipment, the pervasive, fine, gritty dust was definitely a problem. On the lunar surface in December 1972, Apollo 17 astronauts Harrison Schmitt and Eugene Cernan needed to repair one of their lunar rover's fenders in an effort to keep the "rooster tails" of dust away from themselves and their gear. This picture reveals the wheel and fender of their dust covered rover along with the ingenious application of spare maps, clamps, and a grey strip of "duct tape".
An Annotated Leonid (2001-11-11)

The 1998 Leonids Meteor Shower was one of the most photographed meteor events in history.  Patient observers saw bright meteors streak across dark skies every few minutes, frequently leaving fading trails stretching across the sky.  High above the Anza-Borrego Desert, a meteor was photographed streaking up from the radiant constellation of the Leonids: Leo.  This meteor train covered over 40 degrees, and changed colors from green to red.  The intensity of the Leonid Meteor Shower in 2001 is uncertain but may approach one per second for some locations on November 18.
Is Mystery Object an Orphan Afterglow? (2001-11-12)

What is that unusual object?  Astronomers can identify most objects that are imaged on the sky, but not all.  Pictured above is one that currently defies classification.  Attributes of the object include that it has unusual colors, appears to be fading as months go by, and appears to be associated with a distant galaxy.  Its discoverers hold hope that they have uncovered the first known orphan afterglow, an explosion that would have been classified as a gamma-ray burst if the gamma-rays were beamed in our direction.  Orphan afterglows, if they exist, could have unparalleled brightness, and hence be visible so far away that they yield key information about the early years of our universe. A bit of caution might be merited, however, as the last well-publicized mystery object turned out not to be a new member of the astronomical zoo, but rather an unusual type of quasar.  Follow-up observations and analysis over the next year may find more objects like this and/or solve this mystery.
A Gravity Map of Earth (2001-11-13)

Is gravity the same over the surface of the Earth?  No -- it turns out that in some places you will feel slightly heavier than others.  The above relief map shows in exaggerated highs and lows where the gravitational field of Earth is relatively strong and weak.  A low spot can be seen just off the coast of India, while a relative high occurs in the South Pacific Ocean.  The cause of these irregularities is unknown since present surface features do not appear dominant.  Scientists hypothesize that factors that are more important lay in deep underground structures and may be related to the Earth's appearance in the distant past.  To better map Earth's gravity and hence better understand its interior and past, NASA plans to launch the Gravity Recovery and Climate (GRACE) satellite in February.
Auroras Over Both Earth Poles (2001-11-14)

Auroras in the north and south can be nearly mirror images of each other.  Such mirroring had been suspected for centuries but dramatically confirmed only last month by detailed images from NASA's orbiting Polar spacecraft.  Pictured above, a time-lapse movie shows simultaneous changes in aurora borealis, at the top, and aurora australis, at the bottom.  A cloud of electrons and ions moving out from the Sun on October 22 created the auroras.   The solar explosion that released the particles occurred about three days earlier.
Recycling Columbia (2001-11-15)

Twenty years ago this week, the Space Shuttle Columbia became the first reusable spaceship. Its second trip to low Earth orbit and back again began on November 12, 1981, following its maiden voyage by only seven months. Seen above Columbia, 56 meters (184 feet) long with a 24 meter (78 foot) wingspan, is launched mated to an external fuel tank and two solid rocket boosters producing dramatic exhaust plumes. The solid rocket boosters, one on each side of the external tank, provide most of the thrust in the first 2 minutes after launch and are then jettisoned for later recovery. Supplying the main shuttle engines during liftoff, the external fuel tank separates after about 8 minutes. The largest shuttle element not recycled for a future flight, the external tank falls back toward Earth breaking up and descending into a remote ocean area. Still the oldest operating shuttle, Columbia is pictured here in June of 1992 rocketing toward a cloud bank on its twelfth flight. Officially designated OV-102, Columbia is fittingly named after the 18th century sailing vessel which became the first American ship to circumnavigate planet Earth.
Leonid Watching (2001-11-16)

Will the Leonids storm this year? The annual Leonid meteor shower should peak this weekend and some predictions suggest that "storm" rates of a thousand or more meteors per hour are possible for observers located in eastern North and Central America during the early morning hours of Sunday, November 18. Similar high rates are also anticipated for the western Pacific region on the morning of November 19th. In any event, the 2001 Leonid shower should be dramatic and easy to watch, as were the Leonids of recent years. From top left to bottom right above are spectacular examples of bright fireball meteors from the 1998 Leonid shower as recorded by V. Winter and J. Dudley, Lorenzo Lovato, and Wally Pacholka. A 1998 image from the Puckett Observatory at lower left features the source of the debris stream which supplies the Leonid meteors, comet Tempel-Tuttle.
Catching Falling Stardust (2001-11-17)

This carrot-shaped track is actually little more than 5 hundredths of an inch long. It is the trail of a meteroid through the high-tech substance aerogel exposed to space by the shuttle launched EURECA (European Recoverable Carrier) spacecraft. Like those in the ongoing Leonid meteor shower, this meteoroid is about a thousandth of an inch in diameter. It is visible where it came to rest, just beyond the tip of the carrot at the far right. Chemical analyses of interplanetary dust particles similar to this one suggest that some of them may be bits of comets and thus represent samples of material from the early stages of the formation of the Solar System.
A Leonid Meteor Explodes (2001-11-18)

Last night and tonight, a lucky few may see a meteor explode.  As our Earth passes unusually close to debris expelled from Comet Tempel-Tuttle, many sand-sized particles from this comet are entering and burning up in the Earth's atmosphere.  This yearly phenomenon is known as the Leonids Meteor Shower, but the location the Earth passes through this year holds promise to provide relatively high activity.  In particular, the 1998 Leonids was noteworthy for its many bright meteors.  In the above slow-loading sequence, a 1998 Leonid was caught exploding over Los Alamos, New Mexico.  In the last one-minute exposure, another Leonid streaks past.
A 2001 Leonids Meteor Shower Fireball (2001-11-19)

The 2001 Leonids Meteor Shower gave quite a show to many parts of the world yesterday during the early morning hours.  Many sleepy observers venturing into their own backyards were treated to several bright meteors per minute streaking across the sky.  This rate made the 2001 Leonids the most active meteor shower in over three decades.  Pictured above is a bright Leonid fireball that briefly lit up Hawaii yesterday morning.  A CONCAM nighttime all-sky monitor on Mauna Kea, a dormant volcano, caught the bright meteor, seen as the very bright streak across the lower part of the fisheye image.  The meteor track crossed the Galactic plane (the faint glow that runs from the lower left to upper right), passed below the planet Jupiter, and through the constellation Orion.  CONCAMs in Hawaii, Arizona, and California all recorded numerous bright meteors during this year's Leonids.
A Leonids Star Field (2001-11-20)

As meteor after meteor streaked across a moonless sky, photographers across the world snapped pictures of the 2001 Leonids Meteor Shower.  Many recognized this as the best meteor shower they had ever seen.  In fact, the 2001 Leonids was the most active meteor shower since the mid-1960s.  The above photo captures three Leonid meteors crossing a photogenic star-field.  On the far right is the Pleiades star cluster.  The brightest meteor crosses right in front of the Hyades star cluster, situated below the image center.  Just left of center is the bright planet Saturn, and the bright star below Saturn is Aldebaran.  The ten-minute exposure was taken near Victoria, British Columbia, Canada at 2:45 am PST on 2001 November 18.

Image credit: Sherry Buttnor
The Galactic Ring of NGC 6782 (2001-11-21)

Do spiral galaxies look the same in every color?  NGC 6782 demonstrates colorfully that they do not.  In visible light, NGC 6782 appears to be a normal spiral galaxy with a bright bar across its center.  In ultraviolet light, however, the central region blossoms into a spectacular and complex structure highlighted by a circumnuclear ring, as shown in the above representative color Hubble Space Telescope image.  Many of the young stars that formed in a recent burst of star formation emit the ultraviolet light.  Astronomers are studying possible relationships between the central bar and the ring.  Light we see today from NGC 6782 left about 180 million years ago, while dinosaurs roamed the Earth.  The galaxy spans about 80,000 light-years and can be seen with a telescope toward the constellation of Pavo.