omnianasa/nasa-apod-metadata huggingface dataset:
Sunrise by Season (2005-12-21)
Does the Sun always rise in the same direction?  No. As the seasons change, the direction toward the rising Sun will change, too.  The Sun will always rise and set furthest to the south during the day of Winter Solstice, and furthest to the north during Summer Solstice.  Today is Winter Solstice, the day of least sunlight in the Northern Hemisphere and of most sunlight in the Southern Hemisphere.  In many countries, the Winter Solstice brings a change in season, as it is the first day of winter in the North.   The solar heating and stored energy in the Earth's surface and atmosphere is near its lowest during winter, making it usually the coldest months of the year.  On the brighter side in the north, daylight hours will increase every day from now until June.  Pictured above are the different directions of the rising sun throughout the year above a small town in Greece.
Andromeda Island Universe (2005-12-22)
The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy some two million light-years away. But without a telescope, even this immense spiral galaxy - spanning over 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda. In contrast, a bright yellow nucleus, dark winding dust lanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital mosaic with a cumulative exposure of over 90 hours. While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers seriously debated this fundamental concept only 80 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations of M31 in favor of Andromeda, island universe.
Hydrogen and Dust in the Rosette Nebula (2005-12-23)
At the edge of a large molecular cloud in Monoceros, some 3,000 light years away, dark filaments of dust are silhouetted by luminous hydrogen gas. The close up view of the Rosette Nebula dramatically suggests that star formation is an on going process in the region, with dark filaments sculpted by winds and radiation from hot, young stars. Ultraviolet radiation from the young stars also strips electrons from the surrounding hydrogen atoms. As electrons and atoms recombine they emit longer wavelength, lower energy light in a well known characteristic pattern of bright spectral lines. At visible wavelengths, the strongest emission line in this pattern is in the red part of the spectrum and is known as "Hydrogen-alpha" or just H-alpha. Part of IPHAS, a survey of H-alpha emission in our Milky Way Galaxy, this image spans about 25 light-years.
Earthrise (2005-12-24)
In December of 1968, the Apollo 8 crew flew from the Earth to the Moon and back again. Frank Borman, James Lovell, and William Anders were launched atop a Saturn V rocket on December 21, circled the Moon ten times in their command module, and returned to Earth on December 27. The Apollo 8 mission's impressive list of firsts includes: the first humans to journey to the Earth's Moon, the first manned flight using the Saturn V, and the first to photograph the Earth from deep space.  As the Apollo 8 command module rounded the farside of the Moon, the crew could look toward the lunar horizon and see the Earth appear to rise, due to their spacecraft's orbital motion. The famous picture that resulted, of a distant blue Earth above the Moon's limb, was a marvelous gift to the world.
The Mysterious Cone Nebula (2005-12-25)
Sometimes the simplest shapes are the hardest to explain.  For example, the origin of the mysterious cone-shaped region seen on the far left remains a mystery.   The interstellar formation, dubbed the Cone Nebula, is located about 2700 light years away. Other features in the image include red emission from diffuse  interstellar hydrogen, wispy filaments of dark dust, and bright star S Monocerotis, visible on the far right.  Blue reflection nebulae surround the brighter stars.  The dark Cone Nebula region clearly contains much dust which blocks light from the emission nebula and open cluster NGC 2264 behind it.  One hypothesis holds that the Cone Nebula is formed by wind particles from an energetic source blowing past the Bok Globule at the head of the cone.
SN 1006: Supernova Remnant in X-Rays (2005-12-26)
This huge puff ball was once a star.  One thousand years ago, in the year 1006, a new star was recorded in the sky that today we know was really an existing star exploding.  The resulting expanding gas from the supernova is still visible with telescopes today, continues to expand, and now spans over 70 light years.  SN 1006 glows in every type of light.  The above image of SN 1006 was captured by the orbiting Chandra Observatory in X-ray light.  Even today, not everything about the SN 1006 is understood, for example why particle shocks that produce the bright blue filaments are only visible at some locations.  SN 1006 is thought to have once been a white dwarf that exploded when gas being dumped onto it by its binary star companion caused it to go over the Chandrasekhar limit.  Foreground stars are visible that have nothing to do with the supernova.
IC 2118: The Witch Head Nebula (2005-12-27)
Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula.  This 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 glows primarily by light reflected from Rigel, located just outside the top right corner of the above image. Fine dust in the nebula reflects the light.  The blue color is caused not only by Rigel's blue color but because the dust grains reflect 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.  The nebula lies about 1000 light-years away.
Smooth Sections on Asteroid Itokawa (2005-12-28)
Why are parts of this asteroid's surface so smooth?  No one is yet sure, but it may have to do with the dynamics of an asteroid that is a loose pile of rubble rather than a solid rock.  The unusual asteroid is currently being visited by the Japanese spacecraft Hayabusa that is documenting its unusual structure and mysterious lack of craters.  Last month, Hayabusa actually touched down on one of the smooth patches, dubbed the MUSES Sea, and collected soil samples that will eventually be returned to Earth for analysis.  Unfortunately, the robot Hayabusa craft has been experiencing communications problems and so its departure for Earth has been delayed until 2007.   Computer simulations show that 500-meter asteroid Itokawa may impact the Earth within the next few million years.
The Iris Nebula from CFHT (2005-12-29)
Like delicate cosmic petals, these clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula and dutifully cataloged as NGC 7023, this is not the only nebula in the sky to evoke the imagery of flowers. Still, this beautiful digital image shows off the Iris Nebula's range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a massive, hot, young star in its formative years. Central filaments of cosmic dust glow with a reddish photoluminescence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Yet the dominant color of the nebula is blue, characteristic of dust grains reflecting starlight. Dark, obscuring clouds of dust and cold molecular gas are also present and can lead the eye to see other convoluted and fantastic shapes. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. As shown here, the Iris Nebula is about 6 light-years across.
The Perseus Cluster of Galaxies (2005-12-30)
Here is one of the largest objects that anyone will ever see on the sky.  Each of these fuzzy blobs is a galaxy, together making up the Perseus Cluster, one of the closest clusters of galaxies.  The cluster is seen through a foreground of faint stars in our own Milky Way Galaxy.  Near the cluster center, roughly 250 million light-years away, is the cluster's dominant galaxy NGC 1275, seen here just left of picture center. A prodigious source of x-rays and radio emission, NGC 1275 accretes matter as gas and galaxies fall into it. The Perseus Cluster of Galaxies is part of the Pisces-Perseus supercluster spanning over 15 degrees and containing over 1,000 galaxies. At the distance of NGC 1275, this view covers about 1.5 million light-years.
A Year at Saturn (2005-12-31)
Arriving at Saturn in July of 2004, the Cassini spacecraft has now spent a year and a half exploring the magnificent rings and moons of the distant gas giant. The year 2005 began with Cassini's Huygens probe landing on Saturn's large moon Titan. Cassini's continuing series of close flybys also revealed details and discoveries across the surface of the smog shrouded moon. In fact, with a ringside seat throughout 2005, Cassini's cameras have made spectacular pictures of Titan along with Saturn's other moons and rings almost common place. But often, Saturn itself provided the most dramatic backdrop. In this view, Saturn's moon Dione lies in front of edge-on rings and the gas giant's cloud tops draped with broad ring shadows. Dione is 1,118 kilometers across and lies about 300,000 kilometers from the ring's edge.
NGC 6960: The Witch's Broom Nebula (2007-01-01)
Ten thousand years ago, before the dawn of recorded human history, a new light must suddenly have appeared in the night sky and faded after a few weeks.  Today we know this light was an exploding star and record the colorful expanding cloud as the Veil Nebula.  Pictured above is the west end of the Veil Nebula known technically as NGC 6960 but less formally as the Witch's Broom Nebula.  The rampaging gas gains its colors by impacting and exciting existing nearby gas.  The supernova remnant lies about 1400 light-years away towards the constellation of Cygnus.  This Witch's Broom actually spans over three times the angular size of the full Moon.  The bright star 52 Cygnus is visible with the unaided eye from a dark location but unrelated to the ancient supernova.
Light from the First Stars (2007-01-02)
What were the first stars like? No one is yet sure.  Our Sun is not a first-generation star.  It is not even second generation.  The first stars to appear in the universe likely came and went about 13 billion years ago. However, deep observations by the Spitzer Space Telescope in infrared light have detected a diffuse glow, possibly from first generation stars hundreds of times more massive than our Sun.  The above image shows infrared background light with bright patches that might have originated from clusters of these first objects.   Gray areas depict places where nearby foreground stars from our Milky Way Galaxy were digitally removed.
Twenty Full Moons (2007-01-03)
In celebration of tonight's Full Moon, the first of 2007, consider this grid of twenty Full Moons. From upper left to lower right, the images represent every lunation from May 2005 through December 2006. The consecutive Full Moons are all shown at the same scale, so unlike the famous Moon Illusion the change in apparent size seen here is real. (For example, compare early and late 2006 Full Moons.) The change is caused by the variation in lunar distance due to the Moon's significantly non-circular orbit. A subtler change in appearance can also be noticed on close examination, as the Moon seems to wobble and rock slightly from one Full Moon to the next. This effect, known as libration, is more dramatic and easier to see in a twenty frame movie comparing these twenty Full Moons.
Central Cygnus (2007-01-04)
Supergiant star Gamma Cygni lies at the center of the Northern Cross, famous asterism in the constellation Cygnus the Swan. Known by the proper name Sadr, the bright star also lies at the center of this gorgeous skyscape, featuring a complex of stars, dust clouds, and glowing nebulae along the plane of our Milky Way galaxy. The field of view spans over 3 degrees (six Full Moons) on the sky and includes emission nebula IC 1318 and open star cluster NGC 6910. Left of Gamma Cyg and shaped like two glowing cosmic wings divided by a long dark dust lane, IC 1318's popular name is understandably the Butterfly Nebula. Above and left of Gamma Cyg, are the young, still tightly grouped stars of NGC 6910. Some distance estimates for Gamma Cyg place it at around 1,800 light-years while estimates for IC 1318 and NGC 6910 range from 2,000 to 5,000 light-years.
Comet McNaught Heads for the Sun (2007-01-05)
rly morning risers with a clear and unobstructed eastern horizon can enjoy the sight of Comet McNaught (C/2006 P1) in dawn skies over the next few days. Discovered in August by R. H. McNaught (Siding Spring Survey) the comet has grown bright enough to see with the unaided eye but will soon be lost in the glare of the Sun. Still, by January 11 sun-staring spacecraft SOHO should be able to offer web-based views as the comet heads toward a perihelion passage inside the orbit of Mercury. This image captures the new naked-eye comet at about 2nd magnitude in twilight skies near sunset on January 3rd. After rounding the Sun and emerging from the solar glare later this month, Comet McNaught could be even brighter.
The Orion Deep Field (2007-01-06)
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. But even fainter filaments of glowing gas are easily traced throughout the region in this stunning composite image 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. A magnificent emission region, the Orion Nebula (aka M42) lies at the upper right of the picture. Immediately to its left are a cluster 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 left of center. Alnitak is the easternmost star in Orion's belt and 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.  Completing the trio of Orion's belt stars, bluish Alnilam and Mintaka form a line with Alnitak, extending to the upper left.
The Mysterious Rings of Supernova 1987A (2007-01-07)
What's causing those odd rings in supernova 1987A?  In 1987, the brightest supernova in recent history occurred in the Large Magellanic Clouds.  At the center of the picture is an object central to the remains of the violent stellar explosion. When the Hubble Space Telescope was pointed at the supernova remnant in 1994, however, the existence of  curious rings was confirmed.  The origins of these rings still remains a mystery.  Speculation into the cause of the rings includes beamed jets emanating from a dense star left over from the supernova, and a superposition of two stellar winds ionized by the supernova explosion.
The Big Dipper (2007-01-08)
Do you see it?  This common question frequently precedes the rediscovery of one of the most commonly recognized configurations of stars on the northern sky: the Big Dipper.  This grouping of stars is one of the few things that has likely been seen, and will be seen, by every generation.   The Big Dipper is not by itself a constellation.  Although part of the constellation of the Great Bear (Ursa Major), the Big Dipper is an asterism that has been known by different names to different societies. Five of the Big Dipper stars are actually near each other in space and were likely formed at nearly the same time.  Connecting two stars in the far part of the Big Dipper will lead one to Polaris, the North Star, which is part of the Little Dipper.   Relative stellar motions will cause the Big Dipper to slowly change its apparent configuration over the next 100,000 years.
McNaught Now Brightest Comet in Decades (2007-01-09)
The brightest comet in decades is unexpectedly now visible. The most optimistic predictions have Comet McNaught (C/2006 P1) shortly becoming one of the brightest comets of the past century. For the next few days, its short tail and bright coma can be spotted with the unaided eye close to the Sun and near the horizon in both evening and morning skies. This dramatic picture of the comet shining through cloudy skies was taken near sunset on January 7 from Bad Mergentheim, Germany.
NGC 602 and Beyond (2007-01-10)
Near the outskirts of the Small Magellanic Cloud, a satellite galaxy some 200 thousand light-years distant, lies 5 million year young star cluster NGC 602. Surrounded by natal gas and dust, NGC 602 is featured in this stunning Hubble image of the region. Fantastic ridges and swept back shapes strongly suggest that energetic radiation and shock waves from NGC 602's massive young stars have eroded the dusty material and triggered a progression of star formation moving away from the cluster's center. At the estimated distance of the Small Magellanic Cloud, the picture spans about 200 light-years, but a tantalizing assortment of background galaxies are also visible in the sharp Hubble view. The background galaxies are hundreds of millions of light-years or more beyond NGC 602.
The Eagle Nebula in Infrared (2007-01-11)
In visible light, the whole thing looks like an eagle.  The region was captured recently in unprecedented detail in infrared light by the robotic orbiting Spitzer Space Telescope (SSC). Shown above, the infrared image allows observers to peer through normally opaque dust and so better capture the full complexity of the Eagle Nebula star forming region. In particular, the three famous pillars near the image center are seen bathed in dust likely warmed by a supernova explosion.  The warm dust is digitally assigned the false color of red. Also visible, near the bottom of the image, is ten light-year long pillar sometimes dubbed the Fairy of Eagle Nebula. The greater Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of Serpens.
Collinder 399: The Coat Hanger (2007-01-12)
Is this coat hanger a star cluster or an asterism?  This cosmic hang-up has been debated over much of last century, as astronomers wondered whether this binocular-visible object is really a physically associated open cluster or a chance projection. Chance star projections are known as asterisms, an example of which is the popular Big Dipper.  Recent precise measurements from different vantage points in the Earth's orbit around the Sun have recently uncovered discrepant angular shifts indicating that the Coat Hanger is better described as an asterism. Known more formally as Collinder 399, this bright stellar grouping can be seen spanning more than a full moon toward the direction of the constellation of the Fox (Vulpecula).  On the far right of the above image is the open cluster of stars NGC 6802.
Comet Over Krakow (2007-01-13)
Bright Comet McNaught (C/2006 P1) graced the twilight this week, seen by many and often described with superlatives. Watching the skies over Krakow, Poland, Andrzej Sawow recorded this view on Wednesday - with an ordinary handheld digital camera. He notes that "... astronomy is really for everyone who loves to look at the night sky. And fortunately (sometimes) the sky generously rewards its observer". Now very close to the Sun, Comet McNaught (along with Mercury) is visible in realtime images from the SOHO spacecraft. Otherwise, skywatchers will find the comet hard to see this weekend. But southern hemisphere observers could be rewarded next week as Comet McNaught begins to climb higher in southern skies.
Sgr A*: Fast Stars Near the Galactic Center (2007-01-14)
Why are these stars moving so fast?  Shown above is a time-lapse movie in infrared light detailing how stars in the central light-year of our Galaxy have moved over the past eight years.  The yellow mark at the image center represents the location of a peculiar radio source named Sgr A*.  If these fast stars are held to the Galactic Center by gravity, then the central object exerting this gravity must be both compact and massive.  Analysis of the stellar motions indicates that over one million times the mass of our Sun is somehow confined to a region less than a fifth of a light-year across.  Astronomers interpret these observations as strong evidence that the center of our Galaxy is home to a very massive black hole.
Comet McNaught Over Catalonia (2007-01-15)
This past weekend Comet McNaught peaked at a brightness that surpassed even Venus.  Fascinated sky enthusiasts in the Earth's northern hemisphere were treated to an instantly visible comet head and a faint elongated tail near sunrise and sunset.  Recent brightness estimates had Comet McNaught brighter than magnitude -5 (minus five) over this past weekend, making it the brightest comet since Comet Ikeya-Seki in 1965, which was recorded at -7 (minus seven). The Great Comet of 2007 reached its brightest as it rounded the Sun well inside the orbit of Mercury. Over the next week Comet McNaught will begin to fade as it moves south and away from the Sun.  The unexpectedly bright comet should remain visible to observers in the southern hemisphere with unaided eyes for the rest of January.  The above image, vertically compressed, was taken at sunset last Friday from mountains above Catalonia, Spain.
Kepler's Supernova Remnant in X-Rays (2007-01-16)
What caused this mess? Some type of star exploded to create the unusually shaped nebula known as Kepler's supernova remnant, but which type? Light from the stellar explosion that created this energized cosmic cloud was first seen on planet Earth in October 1604, a mere four hundred years ago. The supernova produced a bright new star in early 17th century skies within the constellation Ophiuchus. It was studied by astronomer Johannes Kepler and his contemporaries, with out the benefit of a telescope, as they searched for an explanation of the heavenly apparition.  Armed with a modern understanding of stellar evolution, early 21st century astronomers continue to explore the expanding debris cloud, but can now use orbiting space telescopes to survey Kepler's supernova remnant (SNR) across the spectrum.  Recent X-ray data and images of Kepler's supernova remnant taken by the orbiting Chandra X-ray Observatory has shown relative elemental abundances more typical of a Type Ia supernova, indicating that the progenitor was a white dwarf star that exploded when it accreted too much material and went over Chandrasekhar's limit. About 13,000 light years away, Kepler's supernova represents the most recent stellar explosion seen to occur within our Milky Way galaxy.
Comet McNaught from New STEREO Satellite (2007-01-17)
The brightest comet of recent decades was a surprising first sight for a new camera in space.  The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument onboard the Solar TErrestrial RElations Observatory (STEREO) satellite had just opened up on January 11 when it snapped the above image of Comet McNaught.  Visible was a spectacular view of the ion tail of Comet McNaught being swept away from the Sun by the solar wind in filamentary rays.   The comet tail is seen to extend at least seven degrees across the above image, while the central coma is so bright it saturates. Comet McNaught is now reportedly so bright that it is visible even in broad daylight by blocking out the Sun with your hand.   Comet McNaught has rounded the Sun and will slowly fade away for observers in Earth's Southern Hemisphere as it recedes from the Sun.