juliensimon/nasa-apod huggingface dataset:
Launch of the Sun Pillar (2003-01-23)

On January 16, NASA's space shuttle Columbia roared into blue morning skies above Kennedy Space Center on STS-107, the first shuttle mission of 2003. But this is not a picture of that launch! It was taken on the morning of January 16 though, at sunrise, looking eastward toward Lake Ontario from just outside of Caledon, Ontario, Canada. In the picture a sun pillar, sunlight reflecting from ice crystals gently falling through the cold air, seems to shoot above the fiery Sun still low on the horizon. By chance, fog and clouds forming over the relatively warm lake look like billowing smoke from a rocket's exhaust plume and complete the launch illusion. Amateur photographer Lauri Kangas stopped on his way to work to record the eye-catching sun pillar launch.

Image credit: Lauri A. Kangas
Seyfert's Sextet (2003-01-24)

Known as Seyfert's Sextet, this intriguing group of galaxies lies in the head portion of the split constellation Serpens. The sextet actually contains only four interacting galaxies, though. Near the center of this Hubble Space Telescope picture, the small face-on spiral galaxy lies in the distant background and appears only by chance aligned with the main group. Also, the prominent condensation on the far right is likely not a separate galaxy at all, but a tidal tail of stars flung out by the galaxies' gravitational interactions. About 190 million light-years away, the interacting galaxies are tightly packed into a region around 100,000 light-years across, comparable to the size of our own Milky Way galaxy, making this one of the densest known galaxy groups. Bound by gravity, the close-knit group may coalesce into a single large galaxy over the next few billion years.
Palomar 13's Last Stand (2003-01-25)

Globular star cluster Palomar 13 has roamed the halo of our Milky Way Galaxy for the last 12 billion years. The apparently sparse cluster of stars just left of center in this composite color digital image, it is one of the smallest, faintest globular clusters known. (The bright foreground star near bottom is unrelated and creates the spiky imaging artifacts.) Observations spanning forty years indicate that Palomar 13's galactic halo orbit is a highly eccentric one which, every one or two billion years, brings it relatively close to the galactic center. With each close approach to the Milky Way's central regions, gravitational tidal forces strip away the delicately bound cluster stars. In fact, detailed present day studies offer evidence for a dramatic end to this dwindling cluster's tidal tug of war. Palomar 13's latest close approach was only about 70 million years ago. But, when Palomar 13 again approaches the galaxy, it could well turn out to be the cluster's last stand.
The Lyman Alpha Forest (2003-01-26)

We live in a forest.  Strewn throughout the universe are "trees" of hydrogen gas that absorb light from distant objects.  These gas clouds leave numerous absorption lines in a distant quasar's spectra, together called the Lyman-alpha forest.  Distant quasars appear to be absorbed by many more Lyman-alpha clouds than nearby quasars, indicating a Lyman-alpha thicket early in our universe.  The above image depicts one possible computer realization of how Lyman-alpha clouds were distributed at a redshift of 3.  Each side of the box measures 30 million light-years across.  Much remains unknown about the Lyman-alpha forest, including the real geometry and extent of the clouds, and why there are so many fewer clouds today.

Image credit: J. Shalf, Y. Zhang 
(UIUC) et al., 
GCCC
BHR 71: Stars, Clouds, and Jets (2003-01-27)

What is happening to molecular cloud BHR 71?  Quite possible, a binary star system is forming inside.  Most stars in our Galaxy are part of binary star systems, but few have ever been seen in formation.  Recent observations of dust-darkened Bok Globule BHR 71, however, show evidence for two young stars forming deep in the cloud, likely close enough to form a binary.  Isolated BHR 71 spans about one light year and lies only about 600 light years away in the southern sky.  The brighter embedded star -- not visible here -- is about 10 times as bright as the Sun and drives the jet that swept out the empty lane. The above four-color image was taken with a Very Large Telescope in Chile.

Image credit: J. Alves 
(ESO), 
E. Tolstoy (Groningen), 
R. Fosbury (ST-ECF), & 
R. Hook (ST-ECF), 
VLT
The Lost World of Lake Vida (2003-01-28)

A lake hidden beneath 19 meters of ice and gravel has been found near the bottom of the world that might contain an ecosystem completely separate from our own.  In a modern version of Sir Arthur Conan Doyle's classic book Lost World, scientists are now plotting a mission to drill down into the lake and take out a small part to see what's there.  Lake Vida, buried under Antarctic ice for over 2,500 years, is liquid only because of its high salt content.  Previously, scientists drilled to within a few meters of the lake and indeed found frozen microbes.  Their existence bolsters speculation that similar microorganisms could be found in frozen brine beneath the surface of Mars.  If living organisms are found in Lake Vida, they may give an indication that life might even still exist under similar frozen ice-sheets, such as under the larger Lake Vostok, parts of Mars, and even moons of Jupiter such as Europa.  Pictured above, a robot meteorological station continues to monitor surface conditions over the ice-sealed lake.

Image credit: Thomas Nylen & 
Andrew Fountain 
(PSU), 
NASA, 
NSF
Orion's Horsehead Nebula (2003-01-29)

The Horsehead Nebula is one of the most famous nebulae on the sky.  It is visible as the dark indentation to the red emission nebula seen above and to the right of center in the above photograph.  The bright star on the left is located in the belt of the familiar constellation of Orion. The horse-head feature is dark because it is really an opaque dust cloud which lies in front of the bright red emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After many thousands of years, the internal motions of the cloud will alter its appearance.  The emission nebula's red color is caused by electrons recombining with protons to form hydrogen atoms.  Also visible in the picture are blue reflection nebulae, which preferentially reflect the blue light from nearby stars.

Image credit: StarryScapes
Comet Kudo-Fujikawa: Days in the Sun (2003-01-30)

Cruising through the inner Solar System, new Comet Kudo-Fujikawa reached perihelion, its closest approach to the Sun, yesterday, January 29. Passing within 28.4 million kilometers of the Sun, this comet came much closer than innermost planet Mercury basking only 57.9 million kilometers from our parent star. So close to the Sun, comet Kudo-Fujikawa was extremely bright but impossible for earthbound observers to see against the solar glare. Still, the space-based SOHO observatory captured these views of the comet as it neared perihelion by using a coronograph's occulting disk to block the overwhelming sunlight. In the series of images, the size and location of the blocked-out Sun is indicated by white circles, while arrows point to the traveling comet's bright coma and developing tail. Though fading on its outbound journey, Kudo-Fujikawa should soon be visible to southern hemisphere comet-watchers in February's evening skies.
Auroral Rocket Launch (2003-01-31)

In this striking image, a rocket climbs skyward toward an expansive green auroral display in the first launch of 2003 from the University of Alaska's Poker Flat Research Range. Recorded on January 27th, the view from Cleary Summit near Fairbanks, Alaska shows the fiery tracks of both solid fuel stages of the Black Brant IX sounding rocket that lofted its payload to an altitude of 385 kilometers. Compared to rockets which launch payloads to Earth orbit and beyond, sounding rockets are small and relatively inexpensive. They get their generic name from the nautical term "to sound" which means to take measurements. Known as HIBAR (HIgh Bandwidth Auroral Rocket), this experiment was designed to measure aurora related high-frequency plasma waves which may originate thousands of kilometers above the aurora's visible glow.

Image credit: Chuck Johnson (Cleary Summit)
The Nebula And The Neutron Star (2003-02-01)

The lonely RX J1856.5-3754 was formed from the collapsed core of an exploding star. At a distance of 180 light-years it is the closest known neutron star. More massive than the Sun but only 20 kilometers across, this tiny stellar juggernaut plows through the hydrogen gas and dust clouds of interstellar space at about 200 kilometers per second. The surface of the neutron star is fantastically hot, around 700,000 degrees Celsius, making it detectable with orbiting x-ray telescopes. But optical astronomers were surprised to discover that RX J1856.5-3754 is also surrounded by a cone-shaped nebula. Indicated in this deep image from the European Southern Observatory's Kueyen telescope, the nebula glows in the red light of ionized hydrogen atoms recombining with electrons. Its cone shape is analogous to the bow wave of a ship plowing through water. A faint blue dot near the tip of the cone is the neutron star itself. The nebula appears to have formed very near the surface of the neutron star and astronomers are trying to determine if the observed densities and temperatures can explain the nebula's appearance.
Molecular Cloud Barnard 68 (2003-02-02)

Where did all the stars go?  What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud.  Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars.  The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe.  One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above.  That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across.  It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. It is possible to look right through the cloud in infrared light.
Space Shuttle and Crew Lost During Re-Entry (2003-02-03)

Saturday morning, the Space Shuttle Columbia broke up during re-entry.  Pictured above is the seven-member crew that was lost.  True space pioneers, they were, left to right, David M. Brown, Rick D. Husband, Laurel B. Clark, Kalpana Chawla, Michael P. Anderson, William C. McCool, and Ilan Ramon.  As debris from the shuttle may be toxic, NASA asks that anything found be reported immediately to local authorities and not touched.  For the safety of future missions, investigations into the cause of the tragedy are underway.  If you have any video or photographs that may aid in these investigations, NASA asks that you please see  this web page, call (US) 281-483-3388, or send e-mail to columbiaimages@nasa.gov.
Wisps of the Veil Nebula (2003-02-04)

These wisps of gas are all that remain visible of a Milky Way star.  Many thousands of years ago that star exploded in a supernova leaving the Veil Nebula, pictured above. At the time, the expanding cloud was likely as bright as a crescent Moon toward the constellation of Cygnus, visible for weeks to people living at the dawn of recorded history.  The remaining supernova remnant lies about 1400 light-years away and covers over five times the size of the full Moon.  The bright wisp on the right is known as the Witch's Broom Nebula and can be seen with a small telescope.  The Veil Nebula is also known as the Cygnus Loop.

Image credit: Astropix.com
Unusual Gullies and Channels on Mars (2003-02-05)

What could have formed these unusual channels?  Inside Newton Basin on Mars, numerous narrow channels run from the top down to the floor.  The above picture covers a region spanning about 1500 meters across.  These and other gullies have been found on Mars in recent high-resolution pictures taken by the orbiting Mars Global Surveyor robot spacecraft.  Similar channels on Earth are formed by flowing water, but on Mars the temperature is normally too cold and the atmosphere too thin to sustain liquid water.  Nevertheless, many scientists hypothesize that liquid groundwater can sometimes surface on  Mars, erode gullies and channels, and pool at the bottom before freezing and evaporating.  If so, life-sustaining ice and water might exist even today below the Martian surface -- water that could potentially support a human mission to Mars.  Research into this exciting possibility is sure to continue!
X-Rays from M83 (2003-02-06)

Bright and beautiful spiral galaxy M83 lies a mere twelve million light-years from Earth, toward the headstrong constellation Hydra. Sweeping spiral arms, prominent in visible light images, lend this galaxy its popular moniker -- the Southern Pinwheel. In fact, the spiral arms are still apparent in this Chandra Observatory false-color x-ray image of M83, traced by diffuse, hot, x-ray emitting gas. But more striking in the x-ray image is the galaxy's bright central region. The central emission likely represents even hotter gas created by a sudden burst of massive star formation. Point-like neutron star and black hole x-ray sources, final stages in the life cycles of massive stars, also show a concentration near the center of M83 and offer further evidence for a burst of star formation at this galaxy's core. Light from this burst of star formation would have first reached Earth some 20 million years ago.
Orion on Film (2003-02-07)

Orion, the Hunter, is one of the most easily recognizable constellations in planet Earth's night sky. But Orion's stars and nebulae don't look quite as colorful to the eye as they do in this lovely photograph, taken last month from Vekol Ranch south of Phoenix, Arizona, USA. The celestial scene was recorded in a five minute time exposure using high-speed color print film and a 35mm camera mounted on a small telescope. In the picture, cool red giant Betelgeuse takes on a yellowish tint as the brightest star at the upper left. Otherwise Orion's hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse at the lower right, Bellatrix at the upper right, and Saiph at the lower left. Lined up in Orion's belt (left to right) are Alnitak, Alnilam, and Mintaka all about 1,500 light-years away, born of the constellation's well studied interstellar clouds. And if the middle "star" of Orion's sword looks reddish and fuzzy to you, it should. It's the stellar nursery known as the Great Nebula of Orion.

Image credit: Matthew Spinelli
AB Aurigae: How To Make Planets (2003-02-08)

This enhanced Hubble Space Telescope image shows in remarkable detail the inner portion of the disk of dust and gas surrounding the star AB Aurigae. Knots of material, visible here for the first time, may well represent an early stage of a process which could result in the formation of planets over the next few million years. AB Aurigae is a young star (2-4 million years old), about 469 light-years distant. Its swirling circumstellar disk is large, about 30 times the size of our solar system. Astronomers believe planet-making is just beginning in AB Aurigae's disk because known disks surrounding younger stars (less than 1 million years old) do not show such clumpy structure, while disks of slightly older stars (aged 8-10 million years) have gaps and features suggesting that planets have already been formed. Why the window pane appearance? Wide black stripes in the picture are caused by occulting bars used to block out the overwhelming starlight. The diagonal streaks are due to diffraction spikes.
COBE Dipole: Speeding Through the Universe (2003-02-09)

Our Earth is not at rest.  The Earth moves around the Sun.  The Sun orbits the center of the Milky Way Galaxy.  The Milky Way Galaxy orbits in the  Local Group of Galaxies.  The Local Group falls toward the Virgo Cluster of Galaxies.  But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background (CMB).  In the above all-sky map, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder.  The map indicates that the  Local Group moves at about 600 kilometers per second relative to this primordial radiation.  This high speed was initially unexpected and its magnitude is still unexplained.  Why are we moving so fast? What is out there?
Comet NEAT Approaches the Sun (2003-02-10)

A comet may likely become visible to the unaided eye over the next few days above the horizon where the Sun has just set.  Comet NEAT (C/ 2002 V1), discovered last November, has brightened dramatically as it approached the Sun.  Over the next few days, the quickly setting comet could appear as bright as second magnitude.  On February 18 it will round the Sun well within the orbit of Mercury.  During surrounding days, the Sun's glare will effectively hide the comet to human observers.  It is quite probable, though, that Comet NEAT will standout prominently in images taken by the Sun-looking SOHO satellite.  Pictured above, Comet NEAT's complex and developing tail was photographed on January 29 (top) and February 2.  Sky enthusiasts should remember to never look directly at the Sun.   APOD Update: APOD mirror now on-line from Australia.

Image credit: Anton Spenko 
(Rezmon Observatory)
Dumbbell Nebula Close-Up from Hubble (2003-02-11)

What causes unusual knots of gas and dust in planetary nebulas?  Seen previously in the Ring Nebula, the Helix Nebula, and NGC 2392, the knots' existence was not predicted previously and still not well understood.  Pictured above is a newly released image of the Dumbbell Nebula by the Hubble Space Telescope showing details of its gaseous knots.  Also visible are many bright young stars and dark sheets of interstellar dust.  The Dumbbell Nebula, also known as M27, is a planetary nebula thought similar to what our Sun will become when it runs out of core fuel for nuclear fusion.  Recent study of similar cometary knots indicates that they include concentrations of relatively cold molecular gas and that they change significantly as the planetary nebula ages.   APOD Update: APOD now also available from Japan in Japanese.
WMAP Resolves the Universe (2003-02-12)

Analyses of a new high-resolution map of microwave light emitted only 380,000 years after the Big Bang appear to define our universe more precisely than ever before.  The eagerly awaited results from the orbiting Wilkinson Microwave Anisotropy Probe resolve several long-standing disagreements in cosmology rooted in less precise data.  Specifically, present analyses of above WMAP all-sky image indicate that the universe is 13.7 billion years old (accurate to 1 percent), composed of 73 percent dark energy, 23 percent cold dark matter, and only 4 percent atoms, is currently expanding at the rate of 71 km/sec/Mpc (accurate to 5 percent), underwent episodes of rapid expansion called inflation, and will expand forever.  Astronomers will likely research the foundations and implications of these results for years to come.   APOD Update: APOD now available in Portuguese from Brazil.
The Eagle Nebula from CFHT (2003-02-13)

Bright blue stars are still forming in the dark pillars of the Eagle Nebula.  Made famous by a picture from the Hubble Space Telescope in 1995, the Eagle Nebula shows the dramatic process of star formation.  To the upper right of the nebula in the above picture lies the heart of the open cluster M16.  The bright blue stars of M16 have been continually forming over the past 5 million years, most recently in the famous central gas and dust pillars known as elephant trunks.  Light takes about 7000 years to reach us from M16, which spans about 20 light years and can be seen with binoculars toward the constellation of Serpens.

Image credit: Jean-Charles Cuillandre
The Heart in NGC 346 (2003-02-14)

Yes, it's Valentine's Day (!) and looking toward star cluster NGC 346 in our neighboring galaxy the Small Magellanic Cloud, astronomers have noted this heart-shaped cloud of hot, x-ray emitting gas in the cluster's central region. The false-color Chandra Observatory x-ray image also shows a strong x-ray source just above the heart-shaped cloud which corresponds to HD 5980, a remarkable, massive binary star system that lies within the cluster. HD 5980 has been known to undergo dramatic brightness variations, in 1994 briefly outshining all other stars in the Small Magellanic Cloud, and has been likened to the luminous, eruptive variable star Eta Carinae in our own Milky Way galaxy. At about 100 light-years across, NGC 346's heart-shaped cloud is probably the result of an ancient supernova explosion. Alternatively it may have been produced during past eruptions from the HD 5980 system, analogous to the nebula associated with Eta Carinae.
Happy Birthday Jules Verne (2003-02-15)

One hundred seventy-five years ago (on February 8th), Jules Verne was born in Nantes, France. Inspired by a lifelong fascination with machines, Verne wrote visionary works about "Extraordinary Voyages" including such terrestrial travels as Around the World in 80 Days, Journey to the Centre of the Earth, and Twenty Thousand Leagues Under the Sea. In 1865 he published the story of three adventurers who undertook a journey From the Earth to the Moon. Verne's characters rode a "projectile-vehicle" fired from a huge cannon constructed in Florida, USA. Does that sound vaguely familiar? A century later, the Saturn V rocket and NASA's Apollo program finally turned this work of fiction into fact, propelling adventuresome trios on what was perhaps Verne's most extraordinary voyage. This dramatic view shows the moonbound Apollo 11 space-vehicle riding top a Saturn V rocket as it blasts skyward. Launched from a spaceport in Florida, the Apollo 11 crew traveled to the moon and back again in 1969, making humanity's first landing on the lunar surface.
Southwest Mercury (2003-02-16)

The planet Mercury resembles a moon. Mercury's old surface is heavily cratered like many moons.  Mercury is larger than most moons but smaller than  Jupiter's moon Ganymede and Saturn's moon Titan.  Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth is the only planet more dense.  A visitor to Mercury's surface would see some strange sights.  Because Mercury rotates exactly three times every two orbits around the  Sun, and because Mercury's orbit is so elliptical, a visitor to Mercury might see the Sun rise, stop in the sky, go back toward the rising horizon, stop again, and then set quickly over the other horizon.  From Earth, Mercury's proximity to the Sun causes it to be visible only for a short time just after sunset or just before sunrise.
Universe Age from Microwave Background (2003-02-17)

The above sky map tells us the universe is 13.7 billion years old -- but how? At first look, one only sees the microwave glow of gas from our Milky Way Galaxy, coded red, and a spotty pattern of microwaves emitted from the early universe, coded in gray.  The gray cosmic microwave background is light that used to bounce around randomly but came directly to us when the expanding universe became cool enough for nearly transparent atoms to form.  A close inspection of the spots reveals a slightly preferred angular distance between them.  One expects such a pattern to be generated by sound emanating from slightly over-dense regions of the early universe.  Sound waves will take time to generate such a pattern, and the present age of the universe can then be directly extrapolated.  The above universe age is estimated to be accurate to better than 0.2 billion years.  The above map was taken by the WMAP satellite orbiting the Sun at the L2 point, just outside the orbit of the Earth.