juliensimon/nasa-apod huggingface dataset:
Reflection Nebula vdB1 (2012-10-26)

very book has a first page and every catalog a first entry. And so this lovely blue cosmic cloud begins the van den Bergh Catalog (vdB) of stars surrounded by reflection nebulae. Interstellar dust clouds reflecting the light of the nearby stars, the nebulae usually appear blue because scattering by the dust grains is more effective at shorter (bluer) wavelengths. The same type of scattering gives planet Earth its blue daytime skies. Van den Bergh's 1966 list contains a total of 158 entries more easily visible from the northern hemisphere, including bright Pleiades cluster stars and other popular targets for astroimagers. Less than 5 light-years across, VdB1 lies about 1,600 light-years distant in the constellation Cassiopeia. Also on this scene, two intriguing nebulae at the right show loops and outflow features associated with the energetic process of star formation. Within are extremely young variable stars V633 Cas (top) and V376 Cas.

Image credit: Adam Block
A Halo for NGC 6164 (2012-10-27)

Beautiful emission nebula NGC 6164 was created by a rare, hot, luminous O-type star, some 40 times as massive as the Sun. Seen at the center of the cosmic cloud, the star is a mere 3 to 4 million years old. In another three to four million years the massive star will end its life in a supernova explosion. Spanning around 4 light-years, the nebula itself has a bipolar symmetry. That makes it similar in appearance to more familiar planetary nebulae - the gaseous shrouds surrounding dying sun-like stars. Also like many planetary nebulae, NGC 6164 has been found to have an extensive, faint halo, revealed in this deep telescopic image of the region. Expanding into the surrounding interstellar medium, the material in the halo is likely from an earlier active phase of the O star. The gorgeous skyscape is a composite of narrow-band image data highlighting the glowing gas, and broad-band data of the surrounding starfield. NGC 6164 is 4,200 light-years away in the southern constellation of Norma.

Image credit: Don Goldman
Phobos: Doomed Moon of Mars (2012-10-28)

This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of the Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the Mars Reconnaissance Orbiter, recorded at a resolution of about seven meters per pixel. But Phobos orbits so close to Mars - about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon - that gravitational tidal forces are dragging it down. In 100 million years or so Phobos will likely be shattered by stress caused by the relentless tidal forces, the debris forming a decaying ring around Mars.
The Red Spider Planetary Nebula (2012-10-29)

Oh what a tangled web a planetary nebula can weave.  The Red Spider Planetary Nebula shows the complex structure that can result when a normal star ejects its outer gases and becomes a white dwarf star. Officially tagged NGC 6537, this two-lobed symmetric planetary nebula houses one of the hottest white dwarfs ever observed, probably as part of a binary star system.  Internal winds emanating from the central stars, visible in the center, have been measured in excess of 1000 kilometers per second. These winds expand the nebula, flow along the nebula's walls, and cause waves of hot gas and dust to collide.  Atoms caught in these colliding shocks radiate light shown in the above representative-color picture by the Hubble Space Telescope.  The Red Spider Nebula lies toward the constellation of the Archer (Sagittarius).  Its distance is not well known but has been estimated by some to be about 4,000 light-years.

Image credit: Carlos Milovic,
Hubble Legacy Archive,
NASA
Planetary Nebula PK 164 +31.1 (2012-10-30)

Is this what will become of our Sun? Quite possibly. The bubble of expanding gas pictured above is the planetary nebula PK 164 +31.1, the remnants of the atmosphere of a Sun-like star expelled as its supply of fusion-able core hydrogen became depleted. Visible near the center of the nebula is what remains of the core itself -- a blue-hot white dwarf star.  This particularly photogenic planetary nebula shows intricate shells of gas likely expelled at different times toward the end the star's demise, and whose structure is not fully understood. This deep image of PK 164 +31.1 from the Calar Alto Observatory in Spain shows many other stars from our own Milky Way Galaxy as well as several galaxies far in the distance. PK 164 +31, also known as Jones-Emberson 1, lies about 1,600 light years away toward the constellation of the Wildcat (Lynx). Due to its faintness (magnitude 17) and low surface brightness, the object is only visible with a good-sized telescope. Although the expanding nebula will fade away over the next few thousand years, the central white dwarf may well survive for billions of years -- to when our universe may be a very different place.

Image credit: Descubre Foundation,
CAHA,
OAUV,
DSA,
Vicent Peris (OAUV),
Jack Harvey (SSRO),
PixInsight
VdB 152: A Ghost in Cepheus (2012-10-31)

Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint. Far from your neighborhood on this Halloween Night, the cosmic phantom is nearly 1,400 light-years away. Also catalogued as Ced 201, it lies along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving parts of the nebula a characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. This deep telescopic image of the region spans about 7 light-years.

Image credit: Stephen Leshin
Rigel and the Witch Head Nebula (2012-11-01)

Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula. The suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula spans about 50 light-years and is composed of interstellar dust grains reflecting Rigel's starlight. In this cosmic portrait, the blue color of the Witch Head Nebula and of the dust surrounding Rigel is caused not only by Rigel's intense blue starlight but because the dust grains scatter blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in Earth's atmosphere are molecules of nitrogen and oxygen. Rigel, the Witch Head Nebula, and gas and dust that surrounds them lie about 800 light-years away.

Image credit: Rogelio Bernal Andreo
The Black Hole in the Milky Way (2012-11-02)

At the center of our Milky Way Galaxy, a mere 27,000 light-years away, lies a black hole with 4 million times the mass of the Sun. Fondly known as Sagittarius A* (pronounced A-star), the Milky Way's black hole is fortunately mild-mannered compared to the central black holes in distant active galaxies, much more calmly consuming material around it. From time to time it does flare-up, though. An outburst lasting several hours is captured in this series of premier X-ray images from the orbiting Nuclear Spectroscopic Telescope Array (NuSTAR). Launched last June 13, NuSTAR is the first to provide focused views of the area surrounding Sgr A* at X-ray energies higher than those accessible to Chandra and XMM observatories. Spanning two days of NuSTAR observations, the flare sequence is illustrated in the panels at the far right. X-rays are generated in material heated to over 100 million degrees Celsius, accelerated to nearly the speed of light as it falls into the Miky Way's central black hole. The main inset X-ray image spans about 100 light-years. In it, the bright white region represents the hottest material closest to the black hole, while the pinkish cloud likely belongs to a nearby supernova remnant.
Hunter's Moon over the Alps (2012-11-03)

A Full Moonset can be a dramatic celestial sight, and Full Moons can have many names.  Late October's Full Moon, the second Full Moon after the northern hemisphere autumnal equinox, has been traditionally called the Hunter's Moon. According to lore, the name is a fitting one because this Full Moon lights the night during a time for hunting in preparation for the coming winter months. In this scene, last week's Hunter's Moon shines with a rich yellow light, setting as dawn comes to the Italian Alps. Topping out at over 11,000 feet, the snowy peak known as Rochemelon glows, just catching the first reddened light of the rising Sun.

Image credit: Stefano De Rosa
Lenticular Clouds Over Washington (2012-11-04)

Are those UFOs near that mountain?  No -- they are multilayered lenticular clouds. Moist air forced to flow upward around mountain tops can create lenticular clouds. Water droplets condense from moist air cooled below the dew point, and clouds are opaque groups of water droplets. Waves in the air that would normally be seen horizontally can then be seen vertically, by the different levels where clouds form.  On some days the city of Seattle, Washington, USA, is treated to an unusual sky show when lenticular clouds form near Mt. Rainier, a large mountain that looms just under 100 kilometers southeast of the city. This image of a spectacular cluster of lenticular clouds was taken in 2008 December.

Image credit: Tim Thompson
Saturn's Moon Dione in Slight Color (2012-11-05)

Why does one half of Dione have more craters than the other? Start with the fact that Saturn's moon Dione has one side that always faces Saturn, and one side that always faces away.  This is similar to Earth's Moon. This tidal locking means that one side of Dione always leads as the moon progresses in its orbit, while the other side always trails.  Dione should therefore have undergone a significant number of impacts on its leading half. Strangely, the current leading half of Dione is less cratered than the trailing half.  A leading explanation is that some crater-forming impacts were so large they spun Dione, changing the part that suffered the highest impact rate before the moon's spin again became locked.  The above detailed image of Dione highlighting the moon's subtle hues is a meticulously-constructed mosaic -- by an dedicated amateur -- of pictures taken during the April 2010 flyby of Dione by NASA's robotic Cassini spacecraft.
Methone: Smooth Egg Moon of Saturn (2012-11-06)

Why is this moon shaped like a smooth egg? The robotic Cassini spacecraft completed the first flyby ever of Saturn's small moon Methone in May and discovered that the moon has no obvious craters. Craters, usually caused by impacts, have been seen on every moon, asteroid, and comet nucleus ever imaged in detail -- until now.  Even the Earth and Titan have craters. The smoothness and egg-like shape of the 3-kilometer diameter moon might be caused by Methone's surface being able to shift -- something that might occur were the moon coated by a deep pile of sub-visual rubble. If so, the most similar objects in our Solar System would include Saturn's moons Telesto, Pandora, Calypso, as well as asteroid Itokawa, all of which show sections that are unusually smooth. Methone is not entirely featureless, though, as some surface sections appear darker than others. Although flybys of Methone are difficult, interest in the nature and history of this unusual moon is sure to continue.
Superstorm Sandy From Formation to Landfall (2012-11-07)

It was the largest hurricane ever recorded in the Atlantic Ocean.  The cost of its devastation is still unknown. Pictured above is a movie of Superstorm Sandy taken by the Earth-orbiting GOES-13 satellite over eight days in late October as the hurricane formed, gained strength, advanced across the Caribbean, moved up the Atlantic Ocean along the US east coast, made an unusual turn west, made landfall in New Jersey, turned back to the north over Pennsylvania, and then broke up moving north-east over the northern US and Canada.  Although Sandy's winds were high and dangerous, perhaps even more damaging was the storm surge of water pushed onto land ahead of Sandy, a surge that flooded many coastal areas, streets, and parts of the New York City subway system. Spanning over 1500 kilometers, US states as far west as Wisconsin experienced parts of the storm. Although Hurricane Sandy might have formed at any almost time, concerns are being raised that large storms like Sandy might become more common if water in the Atlantic continues to edge higher in power-enhancing surface temperature.
Arp 188 and the Tadpole's Tail (2012-11-08)

In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper right. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.
Melotte 15 in the Heart (2012-11-09)

Cosmic clouds seem to form fantastic shapes in the central regions of emission nebula IC 1805. Of course, the clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15. About 1.5 million years young, the cluster stars are toward the right in this colorful skyscape, along with dark dust clouds in silhouette against glowing atomic gas. A composite of narrow and broad band telescopic images, the view spans about 30 light-years and includes emission from hydrogen in green, sulfur in red, and oxygen in blue hues. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - The Heart Nebula. IC 1805 is located about 7,500 light years away toward the constellation Cassiopeia.

Image credit: Stefano Cancelli
Polar Ring Galaxy NGC 660 (2012-11-10)

NGC 660 is featured in this cosmic snapshot, a sharp composite of broad and narrow band filter image data from the Gemini North telescope on Mauna Kea. Over 20 million light-years away and swimming within the boundaries of the constellation Pisces, NGC 660's peculiar appearance marks it as a polar ring galaxy. A rare galaxy type, polar ring galaxies have a substantial population of stars, gas, and dust orbiting in rings nearly perpendicular to the plane of the galactic disk. The bizarre-looking configuration could have been caused by the chance capture of material from a passing galaxy by a disk galaxy, with the captured debris eventually strung out in a rotating ring. The violent gravitational interaction would account for the myriad pinkish star forming regions scattered along NGC 660's ring. The polar ring component can also be used to explore the shape of the galaxy's otherwise unseen dark matter halo by calculating the dark matter's gravitational influence on the rotation of the ring and disk. Broader than the disk, NGC 660's ring spans over 50,000 light-years.
Baily's Beads near Solar Eclipse Totality (2012-11-11)

Just before the Sun blacks out, something strange occurs. As the Moon moves to completely cover the Sun in a total solar eclipse -- like the one set to occur over parts of Australia on Tuesday -- beads of bright sunlight stream around the edge of the Moon. This effect, known as Baily's beads, is named after Francis Baily who called attention to the phenomenon in 1836.  Although, the number and brightness of Baily's beads used to be unpredictable, today the Moon is so well mapped that general features regarding Baily's beads are expected. When a single bead dominates, it is called the diamond ring effect, and is typically seen just before totality.  Pictured above, horizontally compressed, a series of images recorded Baily's beads at times surrounding the 2008 total solar eclipse visible from Novosibirsk, Russia. At the end of totality, as the Sun again emerges from behind the moon, Baily's beads may again be visible -- but now on the other side of the Moon.

Image credit: Leonid Durman
Meteor and Moonbow over Wallaman Falls (2012-11-12)

Which feature takes your breath away first in this encompassing panorama of land and sky? The competition is strong with a waterfall, meteor, starfield, and even a moonbow all vying for attention. It is interesting to first note, though, what can't be seen -- a rising moon on the other side of the camera.  The bright moon not only illuminated this beautiful landscape in Queensland, Australia last June, but also created the beautiful moonbow seen in front of Wallaman Falls. Just above the ridge in the above image is the horizontal streak of an airplane. Toward the top of the frame is the downward streak of a bright meteor, a small pebble from across our Solar System that lit up as it entered the Earth's atmosphere. Well behind the meteor are numerous bright stars and nebula seen toward the center of our Galaxy. Finally, far in the background, is the band of our Milky Way Galaxy, running diagonally from the lower left to the upper right in the image but also circling the entire sky.

Image credit: Thierry
A Solar Eclipse Quilt (2012-11-13)

Some people are so inspired by solar eclipses that they quilt.  Pictured above is a resulting textile from one such inspiration. The 38x38 inch quilt offers impressions of a total annular eclipse, when the Moon is too far from the Earth to cover the entire Sun, witnessed in Spain in October of 2005.  Today, however, a full total solar eclipse will occur, although it will only be visible to eclipse chasers and those who live in a thin swath of Australia. For a few minutes, those near the center of the eclipse path will see the entire Sun blocked by the Moon, causing the day to become unusually dark. Just before -- and just after --  totality occurs, sunlight may stream between mountains on the Moon's edge creating a diamond ring effect. The next total eclipse of the Sun will occur in November 2013.

Image credit: CXC
Our Story in One Minute (2012-11-14)

Could you tell the story of human existence in a minute? This thrilling video culls together multiple teasing snippets in an attempt to do just that. And sets it to music. Briefly depicted, from start to finish, is an artistic animation of the Big Bang, a trip across the early universe, the formation of the Earth and Moon, the emergence of multi-celled life and plants, the rise of reptiles and dinosaurs, a devastating meteor strike, the rise of mammals and humans, and finally the rise of modern civilization. The minute movie ends with a flyover of the modern skyscraper and a human standing atop a snow covered mountain. The above video is the latest from the Symphony of Science project.   Gallery: Yesterday's Total Solar Eclipse  Challenge: Can you identify the skyscraper at 1:18 and the snow-covered mountain at 1:25?

Image credit: MelodySheep, 
Symphony of Science, 
John Boswell;
 Music Credit: 
Our Story
Solar Eclipse over Queensland (2012-11-15)

This month's New Moon brought a total solar eclipse to parts of planet Earth on November 13 (UT). Most of the total eclipse track fell across the southern Pacific, but the Moon's dark umbral shadow began its journey in northern Australia on Wednesday morning, local time.  From along the track, this telescopic snapshot captures the Moon's silhouette in skies over Queensland along the Mulligan highway west of Port Douglas. Almost completely covered, the Sun's disk is seen still surrounded by a hint of the faint solar corona. Planet-sized prominences stretch above the active Sun's edge. Sunlight streaming through gaps in the rugged profile of the lunar limb creates the brilliant but fleeting Baily's Beads.

Image credit: Phil Hart
Moon Shadow Sequence (2012-11-16)

On the morning of November 14, the Moon's umbral shadow tracked across northern Australia before heading into the southern Pacific. Captured from a hilltop some 30 miles west of the outback town of Mount Carbine, Queensland, a series of exposures follows the progress of the total solar eclipse in this dramatic composite image. The sequence begins near the horizon. The Moon steadily encroaches on the reddened face of the Sun, rising as the eclipse progresses. At the total phase, lasting about 2 minutes for that location, an otherwise faint solar corona shimmers around the eclipsed disk.  Recorded during totality, the background exposure shows a still sunlit sky near the horizon, just beyond a sky darkened by the shadow of the Moon.

Image credit: Ben
Cooper
Like a Diamond in the Sky (2012-11-17)

A dark Sun hung over Queensland, Australia on Wednesday morning during a much anticipated total solar eclipse. Storm clouds threatened to spoil the view along the northern coast, but minutes before totality the clouds parted. Streaming past the Moon's edge, the last direct rays of sunlight produced a gorgeous diamond ring effect in this scene from Ellis Beach between Cairns and Port Douglas. Winking out in a moment, the diamond didn't last forever though. The area was plunged into darkness for nearly 2 minutes as the Moon's shadow swept off shore toward Australia's Great Barrier Reef and out into the southern Pacific. Ranging from 1/4000 to 1/15 seconds long, five separate exposures were blended in the image to create a presentation similar to the breathtaking visual experience of the eclipse.

Image credit: Terrastro
NGC 6357: Cathedral to Massive Stars (2012-11-18)

How massive can a normal star be?  Estimates made from distance, brightness and standard  solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, nearly making it the record holder.  This star is the brightest object located just above the gas front in the above image.  Close inspection of images taken with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least.  Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record.  Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon.
Leonids Over Monument Valley (2012-11-19)

What's happening in the sky over Monument Valley? A meteor shower. Over the past weekend the Leonid meteor shower has been peaking.  The image -- actually a composite of six exposures of about 30 seconds each -- was taken in 2001, a year when there was a much more active Leonids shower. At that time, Earth was moving through a particularly dense swarm of sand-sized debris from Comet Tempel-Tuttle, so that meteor rates approached one visible streak per second. The meteors appear parallel because they all fall to Earth from the meteor shower radiant -- a point on the sky towards the constellation of the Lion (Leo). Although the predicted peak of this year's Leonid meteor shower is over, another peak may be visible early tomorrow morning. By the way -- how many meteors can you identify in the above image?

Image credit: Sean M. Sabatini