juliensimon/nasa-apod huggingface dataset:
In the Vicinity of the Cone Nebula (2003-05-12)

Strange shapes and textures can be found in neighborhood of the Cone Nebula. The unusual shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars.  The brightest star on the right of the above picture is S Mon, while the region just above it has been nicknamed the Fox Fur Nebula for its color and structure.  The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star.  The orange glow that encompasses the whole region results not only from dust reflection but also emission from hydrogen gas ionized by starlight. S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of Monoceros.   The origin of the mysterious geometric Cone Nebula, visible on the far left, remains a mystery.

Image credit: T. A. Rector
Mercury Transits the Sun (2003-05-13)

How big is the Sun?  The Sun is not only larger than any planet, it is larger than all of the planets put together.  The Sun accounts for about 99.9 percent of all the mass in its Solar System.  Merely stating the Sun's diameter is about 1,400,000 kilometers does not do it justice.  Last week a chance to gain visual size perspective occurred when planet Mercury made a rare crossing in front to Sun.  Mercury, a planet over a third of the diameter of our Earth, is the dark dot on the upper right.  In comparison to the Sun, Mercury is so small it is initially hard to spot.  Also visible on the Sun are dark circular sunspots, bright plages, and dark elongated prominences -- many of which are larger than Mercury.  The above contrast-enhanced picture was captured last week from France.

Image credit: Thierry Legault
The North Pole of Venus (2003-05-14)

If you could look down on the North Pole of Venus what would you see?  The Magellan probe that orbited Venus from 1990 to 1994 was able to peer through the thick Venusian clouds and build up the above image by emitting and re-detecting cloud-penetrating radar.  Visible as the bright patch below central North is Venus' highest mountain Maxwell Montes.  Other notable features include numerous mountains, coronas, impact craters, tessera, ridges, and lava flows.  Although the size and mass of Venus are similar to the Earth, its thick carbon-dioxide atmosphere has trapped heat so efficiently that surface temperature usually exceeds 700 kelvins, hot enough to melt lead.  News: Are you ready for tomorrow's lunar eclipse? Times | Webcast | Photo Tips
Moon Slide Slim (2003-05-15)

No special filters - or even a telescope - are required to enjoy a leisurely lunar eclipse. In fact, watched from all over the night side of planet Earth, these regular celestial performances have entertained many casual skygazers. Still, this eye-catching picture of a lunar eclipse may look unfamiliar. To make it, astrophotographer Doug Murray set his camera on a tripod and locked the shutter open during the total lunar eclipse of January 2000. The resulting image records the trail of the Moon sliding through the night, steadily progressing toward the total eclipse phase as seen from Florida, USA. Haunting red hues of diminished moonlight, common during the total phase of a lunar eclipse, are evident at the far right, along the slimmer portion of the trail. At least part of tonight's lunar eclipse will be visible in clear night skies over the Americas, Europe, and Africa. The eclipse should last over three hours from start to finish, with about 53 minutes of totality.  Lunar eclipse: Times | Webcast | Photo Tips

Image credit: Doug Murray
A Tale of Two Nebulae (2003-05-16)

This colorful telescopic view towards the northern constellation Lyra reveals dim outer regions around M57, popularly known as the Ring Nebula. While modern astronomers still refer to M57 as a planetary nebula, at one light-year across M57 is not a planet but the gaseous shroud of a dying sun-like star. Roughly the same apparent size as M57, the fainter, often overlooked barred spiral galaxy IC1296 is at the lower right and would have been referred to in the early 20th century as a spiral nebula. By chance the pair are in the same field of view, and while they appear to have similar sizes they are actually very far apart. M57 lies at a distance of a mere 2,000 light-years, well within our own Milky Way galaxy. Extragalactic IC1296 is more like 200,000,000 light-years distant or about 100,000 times farther away. Since they appear roughly similar in size, spiral nebula IC1296 must also be about 100,000 times larger than planetary nebula M57.

Image credit: Brian Lula
Dark Sky, Bright Sun (2003-05-17)

In low Earth orbit there is not enough atmosphere to diffuse and scatter sunlight, so shadows are black and the sky is dark - even when the Sun shines.  The harsh lighting produced this dramatic effect as mission specialist Gregory Harbaugh photographed colleague Joseph Tanner during their second spacewalk to service the Hubble Space Telescope in February 1997. The aft section of the Space Shuttle Discovery is visible in the background with the Sun hanging over a delicate crescent of the Earth's limb. A checklist is attached to Tanner's left arm, and Harbaugh's reflection is just visible in Tanner's visor.
The Holographic Principle (2003-05-18)

Is this image worth a thousand words?  According to the Holographic Principle, the most information you can get from this image is about 3 x 1065 bits for a normal sized computer monitor.  The Holographic Principle, yet unproven, states that there is a maximum amount of information content held by regions adjacent to any surface.  Therefore, counter-intuitively, the information content inside a room depends not on the volume of the room but on the area of the bounding walls.  The principle derives from the idea that the  Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information.  The limit was first postulated by physicist Gerard 't Hooft in 1993.  It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon.  The term "holographic" arises from a hologram analogy where three-dimension images are created by projecting light though a flat screen.  Beware, other people looking at the above image may not claim to see 3 x 1065 bits -- they might claim to see a teapot.

Image credit: E. Winfree, 
K. Fleischer, A. Barr 
et al. 
(Caltech)
The Andromeda Deep Field (2003-05-19)

What can you learn from looking into the depths of space?  In an effort to find out true ages of stars in neighboring Andromeda galaxy's halo, astronomers stared into the galaxy giant with the new Advanced Camera for Surveys through the Hubble Space Telescope.  The resulting exposure of over three days, shown above, is the deepest exposure in visible light ever taken, although shorter in duration than the multi-wavelength effort toward the Hubble Deep Field.  The final image illuminated not only Andromeda (M31) but the distant universe.  Andromeda's halo stars turned out to be have a wider range of ages than our Milky Way's halo stars, likely indicating more encounters with small neighboring galaxies.  Visible on the above left is one of Andromeda's globular star clusters, while literally thousands of background galaxies are seen in the distance universe, far beyond M31.
A Primordial Quasar (2003-05-20)

What did the first quasars look like?  The nearest quasars are now known to be supermassive black holes in the centers of galaxies.  Gas and dust that falls toward a quasar glows brightly, sometimes outglowing the entire home galaxy.  The quasars that formed in the first billion years of the universe are more mysterious, though, with even the nature of the surrounding gas still unknown.  Above, an artist's impression shows a primordial quasar as it might have been, surrounded by sheets of gas, dust, stars, and early star clusters.  Exacting observations of three distant quasars now indicate emission of very specific colors of the element iron.  These Hubble Space Telescope observations, which bolster recent results from the WMAP mission, indicate that a whole complete cycle of stars was born, created this iron, and died within the first few hundred million years of the universe.
Copper Moon, Golden Gate (2003-05-21)

When the Moon rose over San Francisco's Golden Gate Bridge on May 15, both bridge and Moon were in already in Earth's shadow. Of course, the bridge is in the Earth's shadow nightly, while the Moon only has that opportunity about twice a year, during a lunar eclipse. And even though in western North America the total phase of the lunar eclipse began before moonrise, many in areas with clear skies came out to enjoy the spectacle. For this eclipse, skygazers reported a darker than normal, copper-colored Moon during totality. The dramatic color is evident in this multiple exposure of the reddened Moon rising, taken by astrophotographer Evad Damast. Damast viewed the eclipse from the Marin Headlands north and west of the famous bridge, looking back toward the bay and the city lights.

Image credit: Evad Damast
Eclipsed Moon Montage (2003-05-22)

After watching this month's lunar eclipse, amateur astronomer Sebastien Gauthier carefully composed this montage of telescopic images of the Moon sliding through planet Earth's shadow. While the deepest part of the total eclipse corresponds to the central exposure, the play of light across the lunar surface nicely demonstrates that the planet's shadow is not uniformly dark as it extends into space. In fact, lunar maria and montes are still visible in the dimmed, reddened sunlight scattered into the cone-shaped shadow region, or umbra, by Earth's atmosphere. For this eclipse, the Moon's trajectory took it North of the umbra's darker core, seen here cast over the Moon's cratered southern highlands. Gauthier's telescope and camera equipment were set up near the Trois-Rivieres College Champlain Observatory in Quebec, Canada.

Image credit: Sebastien Gauthier
Eclipsed Moon and Stars (2003-05-23)

Half-shadowed by the Earth, the Moon takes on a remarkable appearance against a field of stars in this intriguing telephoto picture recorded during a partial phase of last week's lunar eclipse. The picture is not a composite, but it has been digitally enhanced to bring out features covering a large range in brightness. On the Moon itself, surface details are visible in both the bright uneclipsed portion in direct sunlight, and the very much dimmer copper-colored, eclipsed region. Also much fainter than the Moon's sunlit surface, the background star field, along with the unusual lighting, seems to contribute to an eerie "3D" perception of the lunar orb. Canadian astrophotographer Jay Ouellet took the picture from l'Observatoire de la Decouverte in Val Belair, a suburb of Quebec City, where about 200 skygazers gathered to enjoy the celestial exposition.

Image credit: Jay Ouellet
M74: The Perfect Spiral (2003-05-24)

If not perfect, then this spiral galaxy is at least one of the most photogenic. An island universe of about 100 billion stars, 30 million light-years away toward the constellation Pisces, NGC 628 or M74 presents a gorgeous face-on view to earthbound astronomers. Classified as an Sc galaxy, the grand design of M74's graceful spiral arms traced by bright blue star clusters and dark cosmic dust lanes, is similar in many respects to our own home galaxy, the Milky Way. Recorded with a 28 million pixel detector array, this impressive image celebrated first light for the Gemini Multi-Object Spectrograph (GMOS), a state-of-the-art instrument operational at the 8-meter Gemini North telescope. The Gemini North Observatory gazes into the skies above Mauna Kea, Hawaii, USA, while its twin observatory, Gemini South, operates from Cerro Pach�n in central Chile.
Spiral Galaxy NGC 253 Almost Sideways (2003-05-25)

NGC 253 is a normal spiral galaxy seen here almost sideways.  It is the largest member of the Sculptor Group of Galaxies, the nearest group to our own Local Group of Galaxies.  NGC 253, pictured above, appears visually as one of the brightest spirals on the sky, and is easily visible in southern hemisphere with a good pair of binoculars.  The type Sc galaxy is about 10 million light years distant.  NGC 253 is considered a starburst galaxy because of high star formation rates and dense dust clouds in its nucleus.  The energetic nuclear region is seen to glow in X-ray and gamma-ray light.

Image credit: Jean-Charles Cuillandre
The Earth and Moon from Mars (2003-05-26)

What does Earth look like from Mars?  The first image of Earth from the red planet was captured earlier this month by the camera onboard the Mars Global Surveyor spacecraft currently orbiting Mars.  Features visible on Earth include the Pacific Ocean, clouds, much of South America, and part of North America.  Earth's Moon is visible on the upper right, with the crater Tycho brightening the lower part.  Previously, Earth has been imaged from the Moon and spacecraft across the Solar System.
A Mercury Transit Sequence (2003-05-27)

rlier this month, the planet Mercury crossed the face of the Sun, as seen from Earth.  Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun.  The above time-lapse sequence, superimposed on a single frame, was taken from a balcony in Belgium on May 7 and shows the entire transit.  The solar crossing lasted over five hours, so that the above 23 images were taken roughly 15 minutes apart.  The north pole of the Sun, the Earth, Mercury's orbit, although all different, all occur in directions slightly above the left of the image. Near the center and on the far right, sunspots are visible.

Image credit: Dominique Dierick
SNR 0103-72.6: Oxygen Supply (2003-05-28)

A supernova explosion, a massive star's inevitable and spectacular demise, blasts back into space debris enriched in the heavy elements forged in its stellar core. Incorporated into future stars and planets, these are the elements ultimately necessary for life. Seen here in a false-color x-ray image, supernova remnant SNR 0103-72.6 is revealed to be just such an expanding debris cloud in neighboring galaxy, the Small Magellanic Cloud. Judging from the measured size of the expanding outer ring of shock-heated gas, about 150 light-years, light from the original supernova explosion would have first reached Earth about 10,000 years ago. Hundreds of supernova remnants have been identified as much sought after astronomical laboratories for studying the cycle of element synthesis and enrichment, but the x-ray data also show that the hot gas at the center of this particular supernova remnant is exceptionally rich in neon and oxygen.
Frizion Illume (2003-05-29)

Scientific images of cosmic dust clouds or even frozen water can be esthetic too. In fact, this picture of thin layers of forming ice crystals uses a scientific understanding of light's wave properties solely for artistic purposes. Titled "Illume", the picture was created by astrophysicist Peter Wasilewski. To make the picture, the crystals were illuminated by light shining through a polarizing filter -- a filter that restricts the otherwise randomly oriented light waves to vibrate in only one direction.  While passing through the ice, different colors of the polarized light are then refracted and reflected along slightly different paths by the delicate crystalline layers. Viewing the scene with a second polarizing filter brings out the wondrous display of structure and color. Painting with "light, the laws of physics, and an attitude" Wasilewski has created a series of these evocative ice images that he refers to as Frozen Vision or Frizion.

Image credit: Peter Wasilewski
(Goddard Space Flight Center)
Ring of Fire Revisited (2003-05-30)

rly on Saturday, May 31 (UT) the new Moon will once again slide across the Sun's fiery disk, and once again an annular solar eclipse will be the result -- since the Moon's apparent diameter will be a little too small to completely cover the Sun. But this time celestial geometry has conspired to produce a broad D-shaped region for viewing the annular phase that extends into the far northern hemisphere, rather than creating a thin track racing across land and sea. The characteristic ring of fire will be visible from northern Scotland, Iceland, and parts of Greenland. Otherwise a partial eclipse will be more widely visible as across Europe, along with parts of Asia and North America, the Moon will appear to take a "bite" out of the Sun. While the northerly observers might certainly expect a dramatic view, it will probably not look quite like this one, recorded with a foreground of palm trees during a 1992 annular eclipse. Want to watch Saturday's eclipse on the web? Check out the planned webcasts from Astronet.

Image credit: Dennis Mammana
(Skyscapes)
NGC 1818: Pick A Star (2003-05-31)

This is NGC 1818, a youthful, glittering cluster of 20,000 stars residing in the Large Magellanic Cloud, 180,000 light-years away. Pick a star. Any star. Astronomers might pick the unassuming bluish-white one (circled) which appears to be a hot newly formed white dwarf star. What makes it so interesting? The standard astronomical wisdom suggests that stars over 5 times as massive as the sun rapidly exhaust their nuclear fuel and end their lives in a spectacular supernova explosion. With less than this critical mass they evolve into red giants, pass through a relatively peaceful planetary nebula phase, and calmly fade away as white dwarf stars like this one. Except that as a member of the NGC 1818 cluster, this new white dwarf would have evolved from a red giant star over 7.6 times as massive as the sun -- which should have exploded! Its discovery will likely force astronomers to revise the limiting mass estimate for supernovae upward.
GRO J1655-40: Evidence for a Spinning Black Hole (2003-06-01)

In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole.  Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes.  The gas surrounding GRO J1655-40, for example, has been found to display an unusual flickering at a rate of 450 times a second.  Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly.  What physical mechanisms actually cause the flickering -- and a slower quasi-periodic oscillation (QPO) -- in  accretion disks surrounding black holes and neutron stars remains a topic of much research.
The Fogs of Mars (2003-06-02)

Fogs of clouds and dust covered parts of southern Mars during last Martian winter.  Giant volcanoes, such as Ascraeus Mons, the central circular feature near the top of the image, were surrounded by large water clouds.  Slightly southwest, Pavonis Mons and Arisa Mons also peeked above their water clouds.  The rough terrain below center is Labyrinthus Noctis, a maze of deep troughs running over 200 kilometers long.   Directly south, a large white dust storm fogs Syria Planum, a large plateau.  This image mosaic was taken by the Mars Global Surveyor spacecraft currently orbiting Mars.  Soon, five more Earth-launched spacecraft should arrive at the Red Planet, named for the Roman god of war.
The Milky Way Behind an Eclipsed Moon (2003-06-03)

What's behind the Moon? Each month, our Moon passes in front of -- and outshines -- many an interesting star field.  Exceptions occur during a new Moon and during a total eclipse.  In the background of a new Moon is usually the Sun, an even brighter orb that even more easily outshines everything behind it, except during a total solar eclipse.  Even the longest total solar eclipse lasts just a few minutes, while the Sun's corona still remains bright.  During a total lunar eclipse, however, the full Moon dims and a majestic star field may present itself for an hour or more.  Such was the case during the middle of last month, when a rare glimpse of an eclipsed Moon superposed in front of the disk of our home Milky Way Galaxy was captured.  Although fully in the Earth's shadow, the eclipsed Moon is still the brightest object on the right.  The above image was captured during sub-zero weather from the Teide 2003 expedition to Mirador del Pico Viejo, a mountain in the Canary Islands, Spain, off the northwest coast of Africa.

Image credit: Juan Carlos Casado
Eclipse in the Mist (2003-06-04)

The Sun and Moon rose together over much of Europe on the morning of May 31st with the first solar eclipse of 2003 already in progress. And while sightings of the full annular phase of the eclipse were restricted to far northern regions, early morning risers were still treated to inspiring views of two celestial bodies which are most important to life on planet Earth. Following the dawn's spectacle from Charneux, Belgium, astrophotographer Olivier Meeckers recorded this evocative image of the partially eclipsed Sun rising above a primeval apparition of mists and trees. Last month was indeed a rewarding one for eclipse watchers as May's full Moon and (second) new Moon lined up for their respective lunar and solar eclipses. November 2003 will also host both a total lunar and total solar eclipse.

Image credit: Olivier
Meeckers
(Groupe Astronomie
de Spa)
Ring of Fire from Cape Wrath (2003-06-05)

If the Moon's apparent diameter is not quite large enough to cover the Sun during a solar eclipse, an annular eclipse can be the result -- a spectacle of silhouetted Moon surrounded by a solar "ring of fire". Just such a view was possible for observers in the far northern hemisphere as the new Moon slid across the solar disk on May 31st. Still, for astronomical adventurers at Cape Wrath on the northwestern coast of Scotland, the eastern sky was cloudy on eclipse day. But fortunately the Sun became visible a few minutes prior to the annular phase and determined astronomer Hans Coeckelberghs was able to capture this dramatic telescopic image of the eclipsed Sun's ring of fire looming through a reddened, cloud-streaked sky. Not to be outdone by the north, the far southern hemisphere will host the next solar eclipse, with the path of totality racing across Antarctica on November 23rd.

Image credit: Hans Coeckelberghs
Sun, Moon, Hot Air Balloon (2003-06-06)

Anticipating the celestial shadow play of a solar eclipse, sky gazers across Germany watched the Sun rise on May 31. In Bonn, astrophotographer Thilo Kranz had set up his small refractor telescope and camera on the Kennedy Bridge across the Rhein river to get a good view to the northeast. The timing of this eclipse must have seemed ideal for a local balloon flight too, as hot air balloonists also favor early morning hours with usually calm surface winds. Kranz and colleagues had noticed a balloon drifting in the hazy sky near the horizon and speculated about viewing the eclipse from on board. But when the eclipsed Sun finally emerged into view they were delighted to see the lighter-than-air craft make the occasion a very special show from their own vantage point. In fact, in the central panel of this montage of Kranz's telescopic eclipse images, the silhouetted balloon reminds the APOD editors of a remarkably well-fed exclamation mark!

Image credit: Thilo Kranz