omnianasa/nasa-apod-metadata huggingface dataset:
The Milky Road (2007-10-20)
Inspired during a visit to Fort Davis, Texas, home of McDonald Observatory and dark night skies, photographer Larry Landolfi created this tantalizing fantasy view. The composited image suggests the Milky Way is a heavenly extension of a deserted country road. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. At the beginning of the 17th century, Galileo turned his telescope on the Milky Way and announced it to be composed of innumerable stars.
Will the Universe End in a Big Rip? (2007-10-21)
How will our universe end?  Recent speculation now includes a pervasive growing field of mysterious repulsive phantom energy that rips virtually everything apart.  Although the universe started with a Big Bang, analysis of cosmological measurements allows a possibility that it will end with a Big Rip.  As soon as few billion years from now, the controversial scenario holds, dark energy will grow to such a magnitude that our own Galaxy will no longer be able to hold itself together.  After that, stars, planets, and then even  atoms might not be able to withstand the expansive internal force.  Previously, speculation on the ultimate fate of the universe centered on either a re-collapsing Big Crunch or a Big Freeze.  Although the universe's fate is still a puzzle, piecing it together will likely follow from an increased understanding of the nature of dark matter and dark energy.    A new APOD RSS feed is available here, or from the link line below.
Victoria Crater on Mars (2007-10-22)
Scroll right to see the largest crater yet visited by a rover on Mars.  Reaching the expansive Victoria Crater has been a goal for the robotic Opportunity rover rolling across Mars for the past two years.  Victoria crater has about five times the diameter of Endurance Crater, which Opportunity spent six months exploring.  Opportunity reached Victoria last year, and was cautiously probing the edges of the stadium-sized crevice while waiting for large dust storms to clear.  A safe path was found, and Opportunity has slowly entered into Victoria Crater. It is hoped that Victoria Crater will show a deep stack of layers uncovered by the initial impact, and hence new clues into the ancient surface history of Mars. Visible in the distance in the above mosaic is the far rim of Victoria Crater, lying about 800 meters away and rising about 70 meters above the crater floor.   The alcove in front has been dubbed Duck Bay.    A new APOD RSS feed is available here, or from the link line below.
Crescent Saturn (2007-10-23)
Saturn never shows a crescent phase -- from Earth.  But when viewed from beyond, the majestic giant planet can show an unfamiliar diminutive sliver. This image of crescent Saturn in natural color was taken by the robotic Cassini spacecraft in May. The image captures Saturn's majestic rings from the side of the ring plane opposite the Sun -- the unilluminated side -- another vista not visible from Earth. Pictured are many of Saturn's photogenic wonders, including the subtle colors of cloud bands, the complex shadows of the rings on the planet, the shadow of the planet on the rings, and the moons Mimas (2 o'clock), Janus (4 o'clock), and Pandora (8 o'clock). As Saturn moves towards equinox in 2009, the ring shadows are becoming smaller and moving toward the equator.   During equinox, the rings will be nearly invisible from Earth and project only an extremely thin shadow line onto the planet.
Ring Scan (2007-10-24)
Scroll right and cruise above the thin, icy rings of Saturn. This high resolution scan is a mosaic of images presented in natural color and recorded in May, over about 2.5 hours as the Cassini spacecraft passed above the unlit side of the rings. The rings themselves are seen to be composed of many individual ringlets. To help track your progress, the rings are labeled below, along with the distance from the center of the gas giant in kilometers. Major ring gaps are labeled above. The alphabetical designation of Saturn's rings is historical and related to their order of discovery; rings A and B are the bright rings separated by the Cassini division. In order of increasing distance from Saturn, the seven main rings run D,C,B,A,F,G,E. (Faint, outer rings G and E are not imaged here.)
Apogee Moon, Perigee Moon (2007-10-25)
Tonight, those blessed with clear skies can enjoy a glorious Full Moon, (exact full phase at 0452 UT, October 26). In fact, the Moon will reach its full phase within a few hours of perigee, the closest point in its elliptical orbit, making it the largest Full Moon of 2007. On April 3, the Full Moon was within hours of apogee, the farthest point in the lunar orbit, corresponding to the smallest Full Moon of 2007. The difference in apparent size between the largest and smallest Full Moon is quite dramatic and similar to this side by side comparison of the lunar apogee/perigee apparitions from 2006. But seen in the sky many months apart, the change is difficult to notice. Skygazers should also enjoy the Moon on Saturday, October 27, as it encounters the lovely Pleiades star cluster. Because the Moon will be so bright, it will be easiest to spot the Pleiades stars near the Moon with binoculars or a small telescope.
Comet Holmes in Outburst (2007-10-26)
Comet 17P/Holmes stunned comet watchers across planet Earth earlier this week. On October 24, it increased in brightness over half a million times in a matter of hours. The outburst transformed it from an obscure and faint comet quietly orbiting the Sun with a period of about 7 years to a naked-eye comet rivaling the brighter stars in the constellation Perseus. Recorded on that date, this view from Tehran, Iran highlights the comet's (enhanced and circled) dramatic new visibility in urban skies. The inset (left) is a telescopic image from a backyard in Buffalo, New York showing the comet's greatly expanded coma, but apparent lack of a tail. Holmes' outburst could be due to a sudden exposure of fresh cometary ice or even the breakup of the comet nucleus. The comet may well remain bright in the coming days.
The Great Carina Nebula (2007-10-27)
A jewel of the southern sky, the Great Carina Nebula, aka NGC 3372, spans over 300 light-years, one of our galaxy's largest star forming regions. Like the smaller, more northerly Orion Nebula, the Carina Nebula is easily visible to the naked eye, though at a distance of 7,500 light-years it is some 5 times farther away. This stunning telescopic view reveals remarkable details of the region's glowing filaments of interstellar gas and dark cosmic dust clouds. The Carina Nebula is home to young, extremely massive stars, including the still enigmatic variable Eta Carinae, a star with well over 100 times the mass of the Sun.  Eta Carinae is the bright star left of the central dark notch in this field and just below the dusty Keyhole Nebula (NGC 3324).
Noctilucent Clouds Over Sweden (2007-10-28)
Sometimes it's night on the ground but day in the air.  As the Earth rotates to eclipse the Sun, sunset rises up from the ground.  Therefore, at sunset on the ground, sunlight still shines on clouds above.   Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark.   Pictured above last month, a network of noctilucent clouds cast a colorful but eerie glow after dusk near Vallentuna, Sweden.   Although noctilucent clouds are thought to be composed of small ice-coated particles, much remains unknown about them.  Satellites launched to help study these clouds includes Sweden's Odin and NASA's AIM. Recent evidence indicates that at least some noctilucent clouds result from freezing water exhaust from Space Shuttles.
A Telescopic View of Erupting Comet Holmes (2007-10-29)
What's happened to Comet Holmes?  A normally docile comet discovered over 100 years ago, Comet 17P/Holmes suddenly became nearly one million times brighter last week, possibly over just a few hours.  In astronomical terms, the comet brightened from magnitude 17, only visible through a good telescope, to magnitude 3, becoming visible with the unaided eye.   Comet Holmes had already passed its closest to the Sun in 2007 May outside the orbit of Mars and was heading back out near Jupiter's orbit when the outburst occurred.  The comet's sudden brightening is likely due to some sort of sunlight-reflecting outgassing event, possibly related to ice melting over a gas-filled cavern, or possibly even a partial breakup of the comet's nucleus.  Pictured above through a small telescope last Thursday, Comet Holmes appeared as a fuzzy yellow spot, significantly larger in angular size than Earth-atmosphere blurred distant stars. Although Comet Holmes' orbit will place it in northern hemisphere skies for the next two years, whether it will best be viewed through a telescope or sunglasses remains unknown.
Comet Holmes' Coma Expands (2007-10-30)
Go outside tonight and see Comet Holmes. No binoculars or telescopes are needed -- just curiosity and a sky map.  Last week, Comet 17P/Holmes underwent an unusual outburst that vaulted it unexpectedly from obscurity into one of the brightest comets in recent years. Sky enthusiasts from the northern hemisphere have been following the comet's progress closely.  In this animation recorded from Quebec, Canada, the coma of Comet Holmes is seen noticeably expanding over the past few days.  Jupiter has been placed artificially nearby to allow for a comparison of angular sizes and scaled to the size it would appear at the current location of Comet Holmes. How Comet Holmes will further evolve is unknown, with one possibility being that the expanding gas cloud that started from its recent outburst will slowly disperse and fade.
Halloween and the Ghost Head Nebula (2007-10-31)
Halloween's origin is ancient and astronomical.  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.  Another cross-quarter day is Groundhog's Day. Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead.  Perhaps a fitting modern tribute to this ancient holiday is the above-pictured Ghost Head Nebula taken with the Hubble Space Telescope.  Appearing similar to the icon of a fictional ghost, NGC 2080 is actually a star forming region in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way Galaxy.  The Ghost Head Nebula spans about 50 light-years and is shown in representative colors.
Peculiar Arp 87 (2007-11-01)
A cosmic bridge of stars, gas, and dust stretches for over 75,000 light-years and joins this peculiar pair of galaxies cataloged as Arp 87. The bridge is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity. As further evidence, the face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many young blue star clusters produced in a burst of star formation. The twisted edge-on spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and surrounded by a curious polar ring. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the merger of this pair of galaxies into a larger single galaxy of stars. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 87 representing a stage in this inevitable process. The Arp 87 pair are about 300 million light-years distant toward the constellation Leo. The prominent edge-on spiral at the far left appears to be a more distant background galaxy and not involved in the on-going merger.
Three Nebulae in Narrow Band (2007-11-02)
Narrow band filters and a false-color palette give these three nebulae a stunning appearance against the cosmic canvas of the central Milky Way. All three are stellar nurseries about 5,000 light-years or so distant, toward the nebula rich constellation Sagittarius. In the 18th century, astronomer Charles Messier cataloged two of them; colorful M8, above and right of center, and compact M20 at the left. The third, NGC 6559, is at bottom right. Over a hundred light-years across, M8 is also known as the Lagoon Nebula. Divided by obscuring dust lanes, M20's popular moniker is the Trifid. In the composite image, narrow emission lines from sulfur, hydrogen, and oxygen atoms recorded through the filters, are mapped into broader red, green, and blue colors respectively. The color scheme was made popular in Hubble Space Telescope images. But for ground-based telescopes, narrow band filters also make it possible to reject overwhelming light-pollution and capture compelling images of the cosmos from urban skies.
Golden Comet Holmes (2007-11-03)
Surprising Comet Holmes remains easily visible as a round, fuzzy cloud in the northern constellation Perseus. Skywatchers with telescopes, binoculars, or those that just decide to look up can enjoy the solar system's latest prodigy as it glides about 150 million kilometers from Earth, beyond the orbit of Mars. Still expanding, Holmes now appears to be about 1/3 the size of the Full Moon, and many observers report a yellowish tint to the dusty coma. A golden color does dominate this telescopic view recorded on November 1, showing variations across the coma's bright central region. But where's the comet's tail? Like any good comet, Holmes' tail would tend to point away from the Sun. That direction is nearly along our line-of-sight behind the comet, making its tail very difficult to see.
The Closest Galaxy: Canis Major Dwarf (2007-11-04)
What is the closest galaxy to the Milky Way?  The new answer to this old question is the Canis Major dwarf galaxy.  For many years astronomers thought the Large Magellan Cloud (LMC) was closest, but its title was supplanted in 1994 by the Sagittarius dwarf galaxy.  Recent measurements indicate that the Canis Major dwarf is only 42,000 light years from the  Galactic center, about three quarters of the distance to the Sagittarius dwarf and a quarter of the distance to the LMC.  The discovery was made in data from the 2MASS-sky survey, where infrared light allows a better view through our optically opaque Galactic plane.  The labeled illustration above shows the location of the newly discovered Canis Major dwarf and its associated tidal stream of material in relation to our Milky Way Galaxy.  The Canis Major dwarf and other satellite galaxies are slowly being gravitationally ripped apart as they travel around and through our Galaxy.   Note added in 2010: Canis Major's galaxy designation is now disputed.
Comet Holmes Grows a Tail (2007-11-05)
Comet Holmes continues to be an impressive sight to the unaided eye. The comet has diminished in brightness only slightly, and now clearly appears to have a larger angular extent than stars and planets.  Astrophotographers have also noted a distinctly green appearance to the comet's coma over the past week.  Pictured above over Spain in three digitally combined exposures, Comet 17P/Holmes now clearly sports a tail.  The blue ion tail is created by the solar wind impacting ions in the coma of Comet Holmes and pushing them away from the Sun.  Comet Holmes underwent an unexpected and dramatic increase in brightness starting only two weeks ago.  The detail visible in Comet Holmes' tail indicates that the explosion of dust and gas that created this dramatic brightness increase is in an ongoing and complex event. Comet Holmes will move only slightly on the sky over during the next month.
An X Class Flare Region on the Sun (2007-11-06)
Why does the Sun flare?  Unpredictably, our Sun unleashes tremendous flares expelling hot gas into the Solar System that can affect satellites, astronauts, and power grids on Earth.  This close up of an active region on the Sun that produced a powerful X-class flare was captured by the orbiting TRACE satellite. Clicking on the image should bring up a movie that shows the evolution of Active Region 9906 over about four hours.  The glowing gas flowing around the relatively stable magnetic field loops above the Sun's photosphere has a temperature of over ten million degrees Celsius. These flows occurred after violently unstable magnetic reconnection events above the Sun produced the flare.  Many things about solar active regions are not well understood including the presence of dark regions that appear to move inward during the movie.
The Sloan Great Wall: Largest Known Structure? (2007-11-07)
What is the largest structure known? The answer might depend on how one defines "structure." A grouping of galaxies known as the Sloan Great Wall was discovered in the Sloan Digital Sky Survey and is a leading candidate. The Sloan Great Wall can be seen in this digitally recast contour map of galaxies in the Two Degree Field galaxy survey.  Galaxies within one billion light years, a redshift of about 0.1, are depicted.  The labeled Sloan Great Wall spans over one billion light years, longer than any structure ever measured. Critics worry that the Sloan Great Wall should not itself be characterized as a coherent structure because it is not currently gravitationally bound together and parts of it might never become gravitationally bound.  Regardless, the beauty of the local universe of galaxies is evident in the image where several huge superclusters of galaxies -- clusters of galaxy clusters -- can also be seen.  These include the Shapley Supercluster of galaxies, part of the Pisces-Cetus Supercluster, and part of the Horologium-Reticulum Supercluster.
VERITAS and Venus (2007-11-08)
rly morning risers and late to bed astronomers have recently enjoyed bright planets in predawn skies, with brilliant Venus above the eastern horizon. On November 5, Venus was joined by the waning crescent Moon. This self-portrait by astronomer Larry Ciupik captures the lovely pairing of the two brightest celestial beacons on the scene, though the Moon, right of Venus, is strongly over exposed. Included at the far left in the 30 second exposure is the bright streak of the International Space Station still docked with shuttle orbiter Discovery. Together in Earth orbit, the spacefaring combination was momentarily the third brightest sky light in view. In dim silhouette, a multi-mirrored unit of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) is also visible in the foreground. VERITAS operates at the Whipple Observatory near Tucson, Arizona to detect high-energy gamma-rays from the cosmos.
Skyscape with Comet Holmes (2007-11-09)
This gorgeous skyscape spans some 10 degrees across the heroic constellation Perseus, about the size of a generous binocular field of view. The deep exposure includes bright stars, emission nebulae, star clusters, and, of course, the famous Comet Holmes. To identify the celestial landmarks, just place your cursor over the image. The brightest star in view, Alpha Persei, is itself surrounded by a loose cluster of stars - the Alpha Per Moving Cluster - at a distance of about 600 light-years. But, at a distance of a mere 14 light-minutes bright Comet Holmes still dominates the scene with its fluorescing greenish coma and foreshortened blue tail.
A Tale of Comet Holmes (2007-11-10)
A beautiful blue ion tail has become visible in deep telescopic images of Comet Holmes. Pointing generally away from the Sun and also planet Earth, the comet's ion tail is seriously foreshortened by our extreme viewing angle. Still, enthusiastic comet watchers have remarked that on the whole, the compact but tentacled appearance suggests a jellyfish or even a cosmic calamari. This stunning view of the comet's greenish coma and blue tail was recorded on November 4 in clear skies near Budapest, Hungary. The colors are caused by molecules in the tenuous gas, like C2 (green) and CO+ (blue), fluorescing in sunlight. In a more recent development, the dramatic inset is a deep image from L'Aquila in central Italy on November 8, showing the ion tail disconnecting from the comet.
NGC 6888: The Crescent Nebula (2007-11-11)
What caused the Crescent Nebula?  Looking like an emerging space cocoon, the Crescent Nebula, visible in the center of the above image, was created by the brightest star in its center.  A leading progenitor hypothesis has the Crescent Nebula beginning to form about 250,000 years ago.  At that time, the massive central star had evolved to become a Wolf-Rayet star (WR 136), shedding its outer envelope in a strong stellar wind, ejecting the equivalent of our Sun's mass every 10,000 years.  This wind impacted surrounding gas left over from a previous phase, compacting it into a series of complex shells, and lighting it up.  The Crescent Nebula, also known as NGC 6888, lies about 4,700 light-years away in the constellation of Cygnus.  Star WR 136 will probably undergo a supernova explosion sometime in the next million years.
Cosmic Rays from Galactic Centers (2007-11-12)
Where do cosmic rays come from?  A major step toward answering this century old question may have just come in from the Auger Observatory project, the world's premier cosmic ray observatory.  That high energy fundamental particles are barreling through the universe has been known for about a century.  Because ultra high energy cosmic rays are so rare and because their extrapolated directions are so imprecise, no progenitor objects have ever been unambiguously implied. New results from Auger, however, indicate that 12 of 15 ultra high energy cosmic rays have sky directions statistically consistent with the positions of nearby active galactic nuclei.   These galactic centers are already known to emit great amounts of light and are likely powered by large black holes.  The Auger results also indicate that the highest energy cosmic rays are protons, since the electric charge of higher energy nuclei would force the Milky Way Galaxy's magnetic field to deflect and effectively erase progenitor source direction. Pictured above, an artist illustrates a cosmic ray striking the Earth's atmosphere and creating a shower of secondary particles detectable on the surface.   The image of Centaurus A digitally superposed near the top signifies one such active galaxy from which cosmic rays might originate.
The Inner Coma of Comet Holmes (2007-11-13)
What's happening to Comet Holmes? The rare comet remains visible to the unaided eyes of northern observers as an unusual small puff ball in the constellation of Perseus.  A high resolution set of images of the comet's inner coma, taken last week and shown above, reveals significant detail.  Close inspection shows numerous faint streamers that are possibly the result of jets emanating from the comet's nucleus.   Comet Holmes has remained surprisingly bright over the past week, with luminosity estimates ranging from between visual magnitudes 2 to 3, making it brighter than most stars visible on a dark sky.  The above image of Comet Holmes was made with a small automated 0.38-meter telescope hirable over the web for a small fee.