juliensimon/nasa-apod huggingface dataset:
An Orion Deep Field (2006-10-15)

Adrift 1,500 light-years away in one of the night sky's most recognizable constellations, the glowing Orion Nebula and the dark Horsehead Nebula are contrasting cosmic vistas. They both appear in this stunning composite digital image assembled from over 20 hours of data that includes exposures filtered to record emission from hydrogen atoms. The view reveals extensive nebulosities associated with the giant Orion Molecular Cloud complex, itself hundreds of light-years across. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right of the picture. Immediately to its left are a cluster of of prominent bluish reflection nebulae sometimes called the Running Man. The Horsehead nebula appears as a dark cloud, a small silhouette notched against the long red glow at the lower left. Alnitak is the easternmost star in Orion's belt and is seen as the brightest star to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes.  Fainter tendrils of glowing hydrogen gas are easily traced throughout the region in this Orion deep field.

Image credit: Robert Gendler
In the Shadow of Saturn (2006-10-16)

In the shadow of Saturn, unexpected wonders appear. The robotic Cassini spacecraft now orbiting Saturn recently drifted in giant planet's shadow for about 12 hours and looked back toward the eclipsed Sun.  Cassini saw a view unlike any other.  First, the night side of Saturn is seen to be partly lit by light reflected from its own majestic ring system.  Next, the rings themselves appear dark when silhouetted against Saturn, but quite bright when viewed away from Saturn and slightly scattering sunlight, in the above exaggerated color image. Saturn's rings light up so much that new rings were discovered, although they are hard to see in the above image.  Visible in spectacular detail, however, is Saturn's E ring, the ring created by the newly discovered ice-fountains of the moon Enceladus, and the outermost ring visible above.  Far in the distance, visible on the image left just above the bright main rings, is the almost ignorable pale blue dot of Earth.
Clouds and Sand on the Horizon of Mars (2006-10-17)

If you could stand on Mars -- what might you see?  Like the robotic Opportunity rover rolling across the red planet, you might well see vast plains of red sand, an orange tinted sky, and wispy light clouds.  The Opportunity rover captured just such a vista after arriving at Victoria Crater earlier this month, albeit in a completely different direction from the large crater.  Unlike other Martian vistas, few rocks are visible in this exaggerated color image mosaic.  The distant red horizon is so flat and featureless that it appears similar to the horizon toward a calm blue ocean on Earth.  Clouds on Mars can be composed of either carbon dioxide ice or water ice, and can move quickly, like clouds move on Earth.  The red dust in the Martian air can change the sky color above Mars from the blue that occurs above Earth toward the red, with the exact color depending on the density and particle size of the floating dust particles.
NGC 7635: The Bubble (2006-10-18)

What created this huge space bubble? Blown by the wind from a star, this tantalizing, ghostly apparition is cataloged as NGC 7635, but known simply as The Bubble Nebula. Astronomer Eric Mouquet's striking view utilizes a long exposure with hydrogen alpha light to reveal the intricate details of this cosmic bubble and its environment. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Seen here above and right of the Bubble's center is a bright hot star embedded in reflecting dust. A fierce stellar wind and intense radiation from the star, which likely has a mass 10 to 20 times that of the Sun, has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia.

Image credit: Eric Mouquet
SWAN Meets Galaxy (2006-10-19)

This cosmic portrait recorded October 9th features the lovely blue-green coma of Comet SWAN posing with spiral galaxy NGC 5005 in the northern constellation Canes Venatici. At the time the comet (center) was in the close foreground, a mere 9 light-minutes from planet Earth, with the galaxy a more substantial 60 million light-years distant. Not actually related to a bird, Comet SWAN (C/2006 M4) was so named as it was first spotted in image data from the SWAN (Solar Wind ANisotropies) camera aboard the sun-staring SOHO spacecraft. Having rounded the Sun, this comet is headed for interstellar space, but first it will make its closest approach to Earth on October 24. With binoculars, northern hemisphere observers can now spot the comet above the northwestern horizon, near the handle of the Big Dipper in the early evening sky.

Image credit: Andrea Tamanti
IC 4628: The Prawn Nebula (2006-10-20)

South of Antares, in the tail of the nebula-rich constellation Scorpius, lies emission nebula IC 4628. Nearby hot, massive stars, millions of years young, radiate the nebula with invisible ultraviolet light, stripping electrons from atoms. The electrons eventually recombine with the atoms to produce the visible nebular glow. This narrow band image adopts a typical false-color mapping of the atomic emission, showing hydrogen emission in green hues, sulfur as red and oxygen as blue. At an estimated distance of 6,000 light-years, the region shown is about 250 light-years across. The nebula is also cataloged as Gum 56 for Australian astronomer Colin Stanley Gum, but seafood-loving astronomers might know this cosmic cloud as The Prawn Nebula.

Image credit: Martin Pugh
Tombaugh 4 (2006-10-21)

Clyde Tombaugh discovered planet Pluto in 1930 while surveying the skies with the 13-inch Lawrence Lowell Telescope. But the skilled and careful astronomer also went on to discover star clusters, comets, asteroids, and clusters of galaxies. For example, pictured is galactic or open star cluster Tombaugh 4 in the northern constellation Cassiopeia. Published in 1941, Tombaugh's description, based on his photographic images from the Lowell 13-inch, indicates the cluster is small and faint, and comprised of about 30 stars. Using the apparent brightness of the cluster stars he estimated the distance to be 20 to 30 thousand light-years, making Tombaugh 4 over 10 light-years in diameter. This deep color image, made with a modern ccd camera and another 13-inch telescope, includes the region's foreground stars and faint nebulosities.

Image credit: Dean Rowe
Star EGGs in the Eagle Nebula (2006-10-22)

Where do stars form?  One place, star forming regions known as "EGGs", are uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16).  EGGs, short for evaporating gaseous globules, are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas - revealing yet more EGGs and more young stars.  This picture was taken by the Wide Field and Planetary Camera on board the Hubble Space Telescope.
Orionid Meteors Over Turkey (2006-10-23)

Meteors have been flowing out from the constellation Orion.  This was expected, as mid-October is the time of year for the Orionids Meteor Shower.  Pictured above, over a dozen meteors were caught in successively added exposures over three hours taken this past weekend from a town near Bursa, Turkey.  The above image shows brilliant multiple meteor streaks that can all be connected to a single point in the sky just above the belt of Orion, called the radiant.  The Orionids meteors started as sand sized bits expelled from Comet Halley during one of its trips to the inner Solar System.  Comet Halley is actually responsible for two known meteor showers, the other known as the Eta Aquarids and visible every May. Next month, the Leonids Meteor Shower from Comet Tempel-Tuttle might show an even more impressive shower from some locations.

Image credit: Tunc Tezel
The Antennae Galaxies in Collision (2006-10-24)

Two galaxies are squaring off in Corvus and here are the latest pictures.  When two galaxies collide, however, the stars that compose them usually do not.  This is because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space.  During the slow, hundred million year collision, however, one galaxy can rip the other apart gravitationally, and dust and gas common to both galaxies does collide.  In the above clash of the titans, dark dust pillars mark massive molecular clouds are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.
Help Search for Interstellar Dust (2006-10-25)

What caused that hole?  The hole in question appears as a small dark circle on the far right.  If the above image of aerogel seems dull and uninteresting, then welcome to one aspect of real world science.  The interesting part is that something created that dark hole, and it might well be one of the first pieces of matter ever captured from outside our Solar System.  Whatever created that hole was captured by the aerogel of the robotic Stardust spacecraft that flew across our Solar System for years and then returned a capsule to Earth.  Scientists are now poring over the aerogel, looking to see what particles have become trapped.  Many particles are surely from local Comet Wild 2, which Stardust flew past in 2004.  Just a few particles, though, perhaps 10 or less, are expected to be from outside our Solar System.  It is so difficult to find them that the Stardust team has created a downloadable interactive microscope program to allow anyone with a standard computer to help inspect aerogel slices and look for interstellar dust tracks.  Good candidate tracks will later be inspected in great detail by members of the Stardust team.

Image credit: Stardust@Home Project,
Space Science Lab., 
 U. C. Berkeley,
NASA
Composite Crab (2006-10-26)

The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from the death explosion of a massive star. This intriguing false-color image combines data from space-based observatories, Chandra, Hubble, and Spitzer, to explore the debris cloud in x-rays (blue-purple), optical (green), and infrared (red) light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.
The Spider and The Fly (2006-10-27)

Star clusters and nebulae abound in the ancient northern constellation Auriga - a region that includes the interesting pair NGC 1931 (lower left) and IC 417. In this gorgeous color image, an imaginative eye toward the expansive IC 417 and diminutive NGC 1931 suggests a cosmic spider and fly. About 10,000 light-years distant, both are young open star clusters formed in interstellar clouds and still embedded in glowing hydrogen gas. The more compact NGC 1931 is about 10 light-years across with contrasting blue hues characteristic of dust reflected starlight.

Image credit: Steve
Cannistra
(StarryWonders)
Comet SWAN Outburst (2006-10-28)

Near its closest approach to planet Earth, comet SWAN (C/2006 M4) brightened unexpectedly earlier this week, becoming visible to naked-eye observers under dark night skies. Telescopic observers also noticed dramatic changes in the comet's colorful coma and tail, seen in this view recorded on October 25th. To make the picture, images totaling eight minutes in exposure time were stacked and centered on the comet as it moved relatively quickly against the background star field. The picture covers about 1 degree on the sky. Northern hemisphere observers should still find the comet an easy binocular target in the early evening, even though moonlight will increase the overall sky brightness in the next few days. Look toward the northwestern horizon and the constellation Hercules.

Image credit: Paolo Candy
The Sun Puffs (2006-10-29)

Our Earth endures bursts of particles from the Sun.  On 1997 April 7, at 10 am (EDT), ground monitors of the SOHO spacecraft, which continually monitors the Sun, noticed a weak spot in the solar corona was buckling again, this time letting loose a large, explosive Coronal Mass Ejection (CME).  Almost simultaneously, NASA's WIND spacecraft began detecting bursts of radio waves from electrons involved in this magnetic storm.  Supersonic waves rippled though the solar corona as a puff of high energy gas shot out into the Solar System.  The above image shows two photographs of the Sun taken about 15 minutes apart and subtracted, highlighting the explosion.  CME's are not unusual.  The CME gas had little lasting effect on the Earth, but likely created fleeting, if not picturesque, Earth auroras.
Crescent Venus and Moon (2006-10-30)

There's something behind these clouds.  Those faint graceful arcs, upon inspection, are actually far, far in the distance.  They are the Earth's Moon and the planet Venus.  Both the Moon and Venus are bright enough to be seen during the day, and both are quite capable of showing a crescent phase.   To see Venus, which appears quite small, in a crescent phase requires binoculars or a telescope. In the above dramatic daytime image taken from Budapest, Hungary, the Moon and Venus shared a similar crescent phase a few minutes before the Moon eclipsed the larger but more distant world.   About an hour later, Venus reappeared.

Image credit: Iv�n �der
SH2 136: A Spooky Nebula (2006-10-31)

The dark nebula SH2-136 appears to be celebrating Halloween all of the time.  The complex process of star formation create dust clouds of many shapes and sizes -- it is human perception that might identify a ghoulish creature, on the right of the above image, chasing humans.  Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead.  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. Other cross-quarter markers include  Groundhog Day and Walpurgis Night.
McMurdo Panorama from Mars (2006-11-01)

This was Spirit's view on Martian-day 1,000 of its 90-Martian-day mission.   The robotic Spirit rover has stayed alive so long on Mars that it needed a place to wait out the cold and dim Martian winter.  Earth scientists selected Low Ridge hill, a place with sufficient slant to give Spirit's solar panels enough sunlight to keep powered up and making scientific observations.  From its Winter Haven, Spirit has been able to build up the above 360-degree panorama, which has been digitally altered to exaggerate colors and compressed horizontally to fit your screen.  The long winter is finally ending in the south of Mars, and with the increasing sunlight plans are now being made for Spirit to further explore the rocky Columbia Hills inside intriguing Gusev crater.
Messier 76 (2006-11-02)

"Nebula at the right foot of Andromeda ... " begins the description for the 76th object in Charles Messier's 18th century Catalog of Nebulae and Star Clusters. In fact, M76 is one of the fainter objects on the Messier list and is also known by the popular name of the "Little Dumbbell Nebula". Like its brighter namesake M27 (the Dumbbell Nebula), M76 is recognized as a planetary nebula - a gaseous shroud cast off by a dying sunlike star. The nebula itself is thought to be shaped more like a donut, while its box-like appearance is due to our nearly edge-on view. Gas expanding more rapidly away from the donut hole produces the faint loops of far flung material. The nebula's dying star can be picked out in this sharp color image as the bottom, blue-tinted member of the double star near the center of the box-like shape. Distance estimates place M76 about 3 to 5 thousand light-years away, making the nebula over a light-year in diameter.

Image credit: Stefan Seip
V838 Mon: Echoes from the Edge (2006-11-03)

Variable star V838 Monocerotis lies near the edge of our Milky Way Galaxy, about 20,000 light-years from the Sun. Still, ever since a sudden outburst was detected in January 2002, this enigmatic star has taken the center of an astronomical stage. As astronomers watch, light from the outburst echoes across pre-existing dust shells around V838 Mon, progressively illuminating ever more distant regions. This stunning image of swirls of dust surrounding the star was recorded by the Hubble Space Telescope in September of this year. The picture spans about 14 light-years. Astronomers expect the expanding echoes to continue to light up the dusty environs of V838 Mon for at least the rest of the current decade. Researchers have now found that V838 Mon is likely a young binary star, but the cause of its extraordinary outburst remains a mystery.
Paranal Moonset (2006-11-04)

Just before the rising Sun fully illuminated the 2,635 meter summit of Cerro Paranal in northern Chile, Gordon Gillet captured this stunning moonset. In the telephoto picture, a nearly full October Moon is silhouetting the impressive array of telescopes at ESO's Paranal Observatory. Most prominent from left to right are the four enclosures of the 8.2 meter very large telescopes christened Antu, Kueyen, and Yepun almost hiding Melipal. Fans of Paranal will also note the VLT Survey Telescope at the far right and the small, white auxilliary telescope domes. Antu, Kueyen, Yepun, and Melipal are names taken from the Mapuche language. Fittingly they translate to Sun, Moon, Evening Star, and Southern Cross.

Image credit: Gordon Gillet
A Galaxy Collision in NGC 6745 (2006-11-05)

Galaxies don't normally look like this.  NGC 6745 actually shows the results of two galaxies that have been colliding for only hundreds of millions of years.  Just off the above photograph to the lower right is the smaller galaxy, moving away.  The larger galaxy, pictured above, used to be a spiral galaxy but now is damaged and appears peculiar.  Gravity has distorted the shapes of the galaxies.  Although it is likely that no stars in the two galaxies directly collided, the gas, dust, and ambient magnetic fields do interact directly. In fact, a knot of gas pulled off the larger galaxy on the lower right has now begun to form stars.  NGC 6745 spans about 80 thousand light-years across and is located about 200 million light-years away.
The Ghostly Tail of Comet SWAN (2006-11-06)

What causes the structure in Comet SWAN's tail?  Comet SWAN, which unexpectedly flared up to naked-eye brightness last week, has been showing detail in its ion tail that might be described as ghostly.  The ion tail is made of ionized gas, energized by ultraviolet light from the Sun and pushed outward by the solar wind.  The solar wind itself is quite structured and sculpted by the Sun's complex and ever changing magnetic field.  Following the wind, structure in Comet SWAN's tail can be seen to move outward from the Sun even alter its wavy appearance over time.  The blue color of the ion tail is dominated by recombining carbon monoxide atoms.   The color of the coma surrounding the head of the comet is tinged green by slight amounts of the molecule cyanogen.  The above image was taken last week from California, USA. This week may be the best remaining chance for northern hemisphere observers to see the fading interplanetary snowball.   SWAN has now passed both the Earth and the Sun and will fade as it moves away from the Earth and heads out into the vast space between the stars.

Image credit: Ray Gralak
Janus: Potato Shaped Moon of Saturn (2006-11-07)

Janus is one of the stranger moons of Saturn.  First, Janus travels in an unusual orbit around Saturn where it periodically trades places with its sister moon Epimetheus, which typically orbits about 50 kilometers away.   Janus, although slightly larger than Epimetheus, is potato-shaped and has a largest diameter of about 190 kilometers.  Next, Janus is covered with large craters but strangely appears to lack small craters.  One possible reason for this is a fine dust that might cover the small moon, a surface also hypothesized for Pandora and Telesto.   Pictured above, Janus was captured in front of the cloud tops of Saturn in late September.
Simulated Transit of Mercury (2006-11-08)

Mercury, the solar system's innermost planet, will spend about five hours crossing in front of the Sun today - beginning at 1912 UT (2:12pm EST), November 8. Specially equipped telescopes are highly recommended to safely spot the planet's diminutive silhouette however, as Mercury should appear about 200 times smaller than the enormous solar disk. This simulated view is based on a filtered solar image recorded on November 3rd. It shows active regions and the Mercury transit across the Sun at six positions from lower left to middle right. Depending on your location, the Sun may not be above the horizon during the entire transit, but webcasts of the event are planned - including one using images from the sun-staring SOHO spacecraft. This is the second of 14 transits of Mercury during the 21st century. The next similar event will be a transit of Venus in June of 2012.

Image credit: Greg Piepol
Halo and Hexagons (2006-11-09)

As a bright November Moon lit up the night sky last week, Gil Esquerdo spotted this lovely Moon halo overhead at the Whipple Observatory on Mt. Hopkins, Arizona. In the foreground, the structure and individual component mirrors of Whipple's 10 meter gamma-ray telescope actually block direct light from the lunar disk, emphasizing the halo in this dramatic view. The halo was caused by ice crystals in the thin high clouds above the observatory - crystals that are hexagonal in shape and produce the characteristic ring of light with a 22 degree radius. In fact, the ice crystal shapes are much like the flat, hexagonal mirrors of the specialized telescope in the picture. Used together the mirrors can collect brief flashes of optical light caused by high-energy gamma-rays impacting Earth's atmosphere.

Image credit: Gil Esquerdo
(Whipple
Observatory)
Mercury and the Chromosphere (2006-11-10)

joying Wednesday's transit of Mercury from Dallas, Texas, astronomer Phil Jones recorded this detailed image of the Sun. Along with a silhouette of the innermost planet, a network of cells and dark filaments can be seen against a bright solar disk with spicules and prominences along the Sun's edge. The composited image was taken through a telescope equiped with an H-alpha filter that narrowly transmits only the red light from hydrogen atoms. Such images emphasize the solar chromosphere, the region of the Sun's atmosphere immediately above its photosphere or normally visible surface. Left of center, the tiny disk of Mercury seems to be imitating a small sunspot that looks a little too round. But in H-alpha pictures, sunspot regions are usually dominated by bright splotches (called plages) on the solar chromosphere.

Image credit: Phil Jones