juliensimon/nasa-apod huggingface dataset:
Eclipsed Moonlight from Connelly's Springs (2003-11-11)

Happily, skies over Connelly's Springs, North Carolina, USA were not mostly cloudy, as forecast, on the evening of November 8. In fact they were mostly clear early on, allowing photographer David Cortner to record the evening's scheduled celestial entertainment, a total lunar eclipse. Cortner took telescopic pictures of the Moon every eight minutes as it entered partial eclipse around 6:30pm EST and progressed through the reddish total eclipse phase while rising higher in the sky. Near the end of the eclipse he also recorded a wide-angle view in a long exposure, bringing out the thickening clouds and a landscape silhouetted by still partially eclipsed moonlight. Later, the telescopic views were carefully combined along the Moon's trail through the wide-angle image to create this dramatic composite eclipse sequence.

Image credit: David Cortner
Mars Then and Now (2003-11-12)

Does Mars have canals?  A hot debate topic of the late 1800s, several prominent astronomers including Percival Lowell not only claimed to see an extensive system of long straight canals on Mars, but used them to indicate that intelligent life exists there.  The relatively close opposition of 1894 was used to make drawings like the one digitally re-scaled on the above left.  The above map was originally prepared by Eugene Antoniadi and redrawn by Lowell Hess for the book Exploring Mars, by Roy A. Gallant. In more modern times, the latest Mars opposition has allowed the Hubble Space Telescope to capture a picture of similar orientation.  Comparison of the two images shows that large features were impressively recorded, but that an extensive system of long and straight canals just does not exist.  Satellites orbiting Mars have now shown conclusively that the red planet does indeed have surface features similar to canals, but that these are usually smaller, curved, and less extensive than that previously claimed.  Real canyon systems like Noctis Labyrinthus are most likely cracks caused by surface stress.

Image credit: Tom Ruen, 
Eugene Antoniadi, Lowell Hess, 
Roy A. Gallant, 
HST, 
NASA
Aurora Oklahoma (2003-11-13)

Nestled in the central US, the state of Oklahoma is noted for its gorgeous prairie skies and wide-open spaces, but not for frequent visitations of the northern lights. Still, following the intense solar activity late last month, aurora did come sweeping down the Oklahoma plains and skywatcher Dave Ewoldt managed to catch up with this photogenic apparition 40 miles northwest of Oklahoma City at about 3am CST on October 29. Anticipating aurora sightings, Ewoldt had spent the evening photographing nighttime views of small towns in the area while keeping an eye toward the north. He reports, "I was just about ready to call it a night when the show started. When it did, it was like someone turned on a lightswitch. I wish it would have lasted longer... [it] seemed like it was completely done in about 25 minutes." Watery reflections of the colorful show highlight the foreground in the stunning image while stars of the Big Dipper and the northern sky shine behind the dazzling Oklahoma auroral display.  Skywatchers' note: First of two Leonid meteor shower peaks tonight.

Image credit: Dave Ewoldt
(Okarche, Oklahoma)
Jupiter Portrait (2003-11-14)

very day is a cloudy day on Jupiter, the Solar System's reigning gas giant. And swirling cloud tops are all you see in this stunningly detailed true color image, a portion of a large digital mosaic portrait of Jupiter recorded from the Cassini spacecraft during its Jovian flyby in December 2000. The smallest features visible are about 60 kilometers across. Jupiter's composition is dominated by hydrogen and the clouds contain hydrogen compounds like ammonia, hydrogen sulfide, and even water. A truly giant planet, Jupiter's diameter is over 11 times the diameter of Earth and the smallest storms visible in the Cassini Jupiter portrait are similar in size to large terrestrial hurricanes. Now traveling beyond Jupiter, the Cassini spacecraft is scheduled to reach the Saturnian system in July of 2004.
LL Orionis: When Cosmic Winds Collide (2003-11-15)

This arcing, graceful structure is actually a bow shock about half a light-year across, created as the wind from young star LL Orionis collides with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the lower right hand edge of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The complex stellar nursery in Orion shows a myriad of similar fluid shapes associated with star formation, including the bow shock surrounding a faint star at the upper right. Part of a mosaic covering the Great Nebula in Orion, this composite color image was recorded in 1995 by the Hubble Space Telescope.
Leonids from Leo (2003-11-16)

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 Leonids Meteor Shower of 2003 is expected to have two peaks, the first three days ago and the second a long-duration peak covering much of November 19.  Although visible meteor rates might approach one per minute, they are predicted to be much less than in the previous few years.

Image credit: Juraj Toth 
(Comenius U. Bratislava), 
Modra Observatory
Canis Major Dwarf: A New Closest Galaxy (2003-11-17)

What is the closest galaxy to the Milky Way?  The new answer to this old question is the Canis Major dwarf galaxy.  For many years astronomers thought the Large Magellan Cloud (LMC) was closest, but its title was supplanted in 1994 by the Sagittarius dwarf galaxy.  Recent measurements indicate that the Canis Major dwarf is only 42,000 light years from the Galactic center, about three quarters of the distance to the Sagittarius dwarf and a quarter of the distance to the LMC.  The discovery was made in data from the 2MASS-sky survey, where infrared light allows a better view through our optically opaque Galactic plane.  The labeled illustration above shows the location of the newly discovered Canis Major dwarf and its associated tidal stream of material in relation to our Milky Way Galaxy.  The Canis Major dwarf and other satellite galaxies are slowly being gravitationally ripped apart as they travel around and through our Galaxy.

Image credit: R. Ibata 
(Strasbourg Observatory, 
ULP) et al., 
2MASS,
NASA
Leonids Over Indian Cove (2003-11-18)

One year ago today an impressive meteor shower graced the skies of Earth.  Pictured above from last year, at least six bright meteors are visible in only part of the sky above Indian Cove campground in California, USA, during a four-minute exposure.  The 2002 Leonids packed a double punch with planet Earth plunging through two dense clouds of meteroids, dusty debris left by the passage of Comet Tempel-Tuttle.  This year, unfortunately, the main peak of the Leonids Meteor Shower is not expected to be so impressive, with the Earth passing though parts of meteoroid clouds predicted to be much less dense.  The main peak of the 2003 Leonids is predicted for tomorrow where some locations might see a bright meteor every minute.

Image credit: Wally Pacholka (Astropics)
Light Can Twist as Well as Spin (2003-11-19)

Light is more complicated than we thought.  When astronomers measure light, they are usually concerned with its direction, energy, and spin polarization (sometimes).  Recently, however, it has been more broadly realized that photons can also have orbital angular momentum (OAM), an attribute classically analogous to the Earth orbiting the Sun as well as spinning on its axis.  Pictured above, the wave-front of a photon with OAM is shown to be twisted, in contrast to the flat plane of zero OAM light. Light with OAM might be used to increase the information content of communication or to discern specific types of astronomical sources. Passing through a common lens, light without OAM focuses to a point, whereas light with OAM focuses to a ring.  Most light bouncing around the cosmos, however, is expected to have so little (or zero) OAM that the created ring is too small to measure.  Even given other promising methods for measurement, exploiting OAM for astronomical discovery might be as much an issue of observational practicality as theoretical possibility.   APOD Update: APOD mirror now on-line from Poland with archive in Polish.

Image credit: M. J. Padgett, J. Leach 
(U. Glasgow) et al., 
Royal Society
Voyager at 90 AU (2003-11-20)

Launched in 1977, Voyager 1 is now about 12 light-hours or 90 astronomical units (AU) from the Sun, making this spacecraft humanity's most distant ambassador to the cosmos. Well beyond the orbits of the outer planets, Voyager 1 is believed to be entering the realm of deep space near the edge of the heliosphere, the region dominated by the solar wind and magnetic field. Causing some debate, new results from instruments still operating have given indications that the spacecraft could finally be encountering a fluctuating boundary known as the solar wind's termination shock. Illustrated above, the bubble-shaped termination shock is produced when the wind from the Sun slows dramatically and piles up as it runs in to the tenuous interstellar gas. Still farther out, beyond the heliopause, solar wind and interstellar gas begin to mix, while the heliosphere's motion through interstellar space creates a bow shock, analogous to a boat moving through water. Estimates are that both Voyager 1 and 2 have enough power and fuel to operate until about the year 2020. The spacecraft continue to coast toward interstellar space at over 3 AU per year.
Sunset Moonlight (2003-11-21)

November's lunar eclipse was one of the shortest in recent years and also one of the brightest -- demonstrating that the Earth's shadow is not completely dark. The eclipsed Moon remained easily visible during totality, reflecting reddened light filtering on to its surface from all the sunsets and sunrises, as seen from the lunar perspective, around the edges of a silhouetted Earth. Hoping to view the celestial shadow play from the Earth's night side near Cologne, Germany, about 400,000 kilometers from the lunar surface, amateur astronomer Markus Strassfeld packed a digital camera and telescope and drove about 10 kilometers outside the city to escape the bright city lights. Fortunately, the sky cleared about an hour before the eclipse began and he was able to record this sharp image of sunsets illuminating the totally eclipsed Moon. Young ray crater Tycho, about 85 kilometers across, stands out near the Moon's brighter southern edge.

Image credit: Markus Strassfeld
Moon AND Sun (2003-11-22)

This composite image was made from 22 separate pictures of the Moon and Sun all taken from Chisamba, Zambia during the total phase of the 2001 June 21 solar eclipse. The multiple exposures were digitally processed and combined to simultaneously show a wealth of detail which no single camera exposure or naked-eye observation could easily reveal. Most striking are the incredible flowing streamers of the Sun's outer atmosphere or solar corona, notoriously difficult to see except when the new Moon blocks the bright solar disk. Features on the darkened near side of the Moon can also be made out, illuminated by sunlight reflected from a full Earth. A giant solar prominence seems to hang just beyond the Moon's eastern (left) edge while about one diameter farther east of the eclipsed Sun is the relatively faint (4th magnitude) star 1 Geminorum. The still active Sun will be totally eclipsed by the Moon tomorrow, but the path of the total eclipse will mostly cross the relatively inaccessible continent of Antarctica.

Image credit: Fred Espenak (courtesy of
www.MrEclipse.com)
A Superwind from the Cigar Galaxy (2003-11-23)

What's lighting up the Cigar Galaxy?  M82, as this irregular galaxy is also known, was stirred up by a recent pass near large  spiral galaxy M81.  This doesn't fully explain the source of the red-glowing outwardly expanding gas, however.  Recent evidence indicates that this gas is being driven out by the combined emerging particle winds of many stars, together creating a galactic "superwind."  The above recently released photograph from the new Subaru Telescope highlights the specific color of red light strongly emitted by ionized hydrogen gas, showing detailed filaments of this gas.  The filaments extend for over 10,000 light years.  The 12-million light-year distant Cigar Galaxy is the brightest galaxy in the sky in infrared light, and can be seen in visible light with a small telescope towards the constellation of Ursa Major.

Image credit: FOCAS, 
Subaru 8.2-m Telescope, 
NAOJ
IC 405: The Flaming Star Nebula (2003-11-24)

Rippling dust and gas lanes give the Flaming Star Nebula its name.  The red and purple colors of the nebula are present in different regions and are created by different processes.  The bright star AE Aurigae, visible toward the image right, is so hot it is blue, emitting light so energetic it knocks electrons away from surrounding gas.  When a proton recaptures an electron, red light is frequently emitted. The purple region's color is a mix of this red light and blue light emitted by AE Aurigae but reflected to us by surrounding dust. The two regions are referred to as emission nebula and reflection nebula, respectively.  Pictured above, the Flaming Star Nebula, officially known as IC 405, lies about 1500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of Auriga.

Image credit: Robert Gendler
A Late Leonid from a Sparse Shower (2003-11-25)

The 2003 Leonids Meteor Shower contained relatively few meteors.  As expected and unlike the last few years, the Earth just did not pass through any dense particle streams left over by the Sun-orbiting Comet Tempel-Tuttle.  Preliminary reports had the peak meteor rates only as high as about one relatively faint meteor a minute even from good locations at good times.  Pictured above is one of the brighter Leonids of 2003, caught by one of the continuously operating night sky web cameras (CONCAMs) of the global Night Sky Live project.  The fisheye image shows the night sky from horizon to horizon above Mauna Kea, Hawaii, USA.  The image is annotated with several bright stars and planets.  Note that this meteor, as do all Leonids, appears to emanate from the constellation Leo, labeled on the upper left.  Although the peak of the Leonids this year was on November 19, this meteor flashed through the sky the next night.
The Turbulent Neighborhood of Eta Carina (2003-11-26)

How do violent stars affect their surroundings?  To help find out, astronomers pointed the Hubble Space Telescope to the regions surrounding Eta Carina, a star showing signs that it may explode sometime in the next million years.  The nearby nebulosity, shown above, is home to streams of hot gas, pools of cool gas, knots of dark globules, and pillars of dense dusty interstellar matter likely forming young stars.  The above image explores about three light-years, a region size intermediate to the Eta Carina cocoon, which spans only about one-half of a light year, and the Great Nebula in Carina, which spans over 300 light years.  In April of 1843 Eta Car briefly became second only to Sirius as the brightest star in planet Earth's night sky, even though at a distance of about 7,500 light-years, it is about 800 times farther away.
The Long Shadow of the Moon (2003-11-27)

The long shadow of the Moon fell across the continent of Antarctica on November 23rd, during the second solar eclipse of 2003. In this view from orbit, based on data from the MODIS instrument on board the Earth observing Aqua satellite, the Moon's shadow stretches for almost 500 kilometers. Recorded between 23:15 and 23:20 Universal Time, the shadow was cast by a lunar disk silhouetted by the Sun hanging only about 15 degrees above the antarctic horizon. Observers within the central dark portion of the oval-shaped shadow could view the totally eclipsed sun. Shadows of mountains and clouds are also visible over the Norwegian named Queen Maud Land, Antarctica with the South Pole just beyond the lower right corner of the image.
The Most Distant X-Ray Jet (2003-11-28)

A false-color x-ray image inset at upper left reveals emission from a cosmic jet of high-energy particles, 100,000 light-years in length, emerging from quasar GB1508+5714. An estimated 12 billion (12,000,000,000) light-years away, this appears to be the most distant energetic jet in the known Universe. Astrophysical jets of many sizes seem to be produced in a range of environments where significant accretion, or infalling matter is thought to arrange itself in a disk, from contracting star-forming clouds to supermassive black holes in active galactic nuclei. Here, as depicted in the illustration, the accretion disk is thought to surround a supermassive black hole, accelerating particles to near the speed of light in two jets at right angles to the disk itself. In the case of this quasar, the jet tilted towards us is visible in x-rays as the particles collide with low energy photons from the cosmic background radiation. The collisions boost the photons to higher x-ray energies and scatter some of them in our direction.
Phobos Over Mars (2003-11-29)

Hurtling through space a mere 3,000 miles above the Martian surface, the diminutive moon Phobos (below and left of center) was imaged against the backdrop of a large shield volcano by the Viking 2 Orbiter in 1977. This dramatic picture looks down from the Orbiter's viewpoint about 8,000 miles above the volcano, Ascraeus Mons. Phobos itself is 5,000 miles below the Orbiter. North is toward the top with the Sun illuminating the scene from the South (black dots are reference marks). For scale, Ascraeus Mons is about 200 miles across at its base while asteroid sized Phobos is about 15 miles in diameter. In this spectacular moon-planet image, volcanic calderas (craters) are visible at the summit of Ascraeus Mons -- while impact craters on the sunlit side of Phobos' surface can also be seen!
A Venus Landing (2003-11-30)

This image is part of the first color panoramic view from Venus.  A TV camera on the Soviet Venera 13 lander that parachuted to the surface on 1982 March 1 transmitted it.  Venus' clouds are composed of sulfuric acid droplets while its surface temperature is about 482 degrees Celsius at an atmospheric pressure of 92 times that of sea-level on Earth.  Despite these harsh conditions, the Venera 13 lander survived long enough to send back a series of images and perform an analysis of the Venusian soil.  Part of the lander itself is visible in the lower right portion of the image.  An earlier Soviet Venus lander, Venera 7 (1970), was the first spacecraft to return data from the surface of another planet.
A Lenticular Cloud Over Hawai'i (2003-12-01)

Can a cloud do that?  Actually, pictured above are several clouds all stacked up into one striking lenticular cloud.  Normally, air moves much more horizontally than it does vertically.  Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes.  The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms  clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance. The above picture was taken last week near Mauna Kea, Hawaii, USA.

Image credit: Peter Michaud 
(Gemini Obs.)
NGC 869 & NGC 884: A Double Open Cluster (2003-12-02)

Most star clusters are singularly impressive.  Open clusters NGC 869 and NGC 884, however, are doubly impressive.  Also known as "h and chi Persei", this unusual double cluster, shown above, is bright enough to be seen from a dark location without even binoculars.  Although their discovery surely predates written history, the Greek astronomer Hipparchus notably cataloged the "double cluster".  The clusters are over 7000 light years distant toward the constellation of Perseus, but are separated by only hundreds of light years.

Image credit: Michael Fulbright
(MSFAstro.net)
Moonrise Through Mauna Kea's Shadow (2003-12-03)

How can the Moon rise through a mountain?  It cannot -- what was photographed here is a moonrise through the shadow of a large volcano.  The volcano is Mauna Kea, Hawai'i, USA, a frequent spot for spectacular photographs since it is arguably the premier observing location on planet Earth. The Sun has just set in the opposite direction, behind the camera. Additionally, the Moon has just passed full phase -- were it precisely at full phase it would rise, possibly eclipsed, at the very peak of the shadow. Refraction of moonlight through the Earth's atmosphere makes the Moon appear slightly oval.  Cinder cones from old volcanic eruptions are visible in the foreground. Cloud tops below Mauna Kea's summit have unusually flat tops, indicating a decrease in air moisture that frequently keeps the air unusually dry, another attribute of this stellar observing site.

Image credit: Michael Connelley 
(U. Hawaii)
New Horizons at Jupiter (2003-12-04)

Headed for the first close-up exploration of the Pluto-Charon system and the icy denizens of the Kuiper belt, NASA's New Horizons spacecraft is pictured here in an artist's vision of the robot probe outward bound. The dramatic scene depicts the 465 kilogram spacecraft about one year after a planned 2006 launch, following a flyby of gas giant Jupiter. While the Jupiter flyby will be used as a gravity assist maneuver to save fuel and cut travel time to the outer reaches of the Solar System, it will also provide an opportunity to test instruments and study the giant planet, its moons, and magnetic fields. The Sun is seen from eight hundred million kilometers away, with inner planets Earth, Venus, and Mercury aligned on the left. A dim crescent of outermost Galilean moon Callisto, orbiting Jupiter just inside of the spacecraft's trajectory, appears to the upper right of the fading Sun. Left of Jupiter itself is Europa and in the distant background are the faint, unresolved stars and dust clouds of the Milky Way. New Horizons' planned arrival at Pluto-Charon is in the summer of 2015.

Image credit: Dan Durda
(SwRI)