juliensimon/nasa-apod huggingface dataset:
Tutulemma: Solar Eclipse Analemma (2007-10-02)

If you went outside at exactly the same time every day and took a picture that included the Sun, how would the Sun appear to move?  With great planning and effort, such a series of images can be taken.   The figure-8 path the Sun follows over the course of a year is called an analemma.  With even greater planning and effort, the series can include a total eclipse of the Sun as one of the images. Pictured is such a total solar eclipse analemma or Tutulemma - a term coined by the photographers based on the Turkish word for eclipse. The composite image sequence was recorded from Turkey starting in 2005. The base image for the sequence is from the total phase of a solar eclipse as viewed from Side, Turkey on 2006 March 29. Venus was also visible during totality, toward the lower right.

Image credit: Tunc
Tezel
and
Cenk E. Tezel
Comet Encke's Tail Ripped Off (2007-10-03)

Swinging inside the orbit of Mercury, on April 20th periodic comet Encke encountered a blast from the Sun in the form of a Coronal Mass Ejection (CME). When CMEs, enormous clouds of energetic particles ejected from the Sun, slam into Earth's magnetosphere, they often trigger auroral displays. But in this case, the collison carried the tail of the comet away. The tail was likely ripped off by interacting magnetic fields rather than the mechanical pressure of the collision. Clicking on the two panel image will play a movie gif of the remarkable event as recorded by the Heliospheric Imager onboard the STEREO A spacecraft. In the movie, the time between frames is about 45 minutes, while the frames span about 14x20 million kilometers at the distance of the comet. Of course, similar collisions have happened before as the ancient comet loops through its 3.3 year solar orbit. So don't worry, Encke's tail grows back!
50th Anniversary of Sputnik: Traveling Companion (2007-10-04)

Sputnik means "traveling companion". Despite the innocuous sounding name, the launch of planet Earth's first artificial moon, Sputnik 1, by the Soviet Union on October 4, 1957, changed the world and set in motion events which resulted in the creation of NASA and the race to the Moon. Sputnik 1 was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded earthbound audience for 23 days. A short month later, on November 3, the Soviet Union followed this success by launching a dog into orbit aboard Sputnik 2.
Starburst Cluster in NGC 3603 (2007-10-05)

A mere 20,000 light-years from the Sun lies NGC 3603, a resident of the nearby Carina spiral arm of our Milky Way Galaxy. NGC 3603 is well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies. Surrounding the cluster are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years.
X-ray Stars of Orion (2007-10-06)

The stars of Orion shine brightly in visible light in planet Earth's night sky. The constellation harbors the closest large stellar nursery, the Great Nebula of Orion, a mere 1,500 light-years away. In fact, the apparently bright clump of stars near the center of this false color Chandra x-ray telescope picture are the massive stars of the Trapezium - the young star cluster which powers much of the nebula's visible-light glow. The stars shown in blue and orange are young sun-like stars; prodigious sources of x-rays thought to be produced in hot stellar coronae and surface flares in a young star's strong magnetic field. Our middle-aged Sun itself was probably thousands of times brighter in x-rays when, like the Trapezium stars, it was only a few million years old. The x-ray image spans about 2.5 light-years across the central region of the Orion Nebula.
Two Million Galaxies (2007-10-07)

Our universe is filled with galaxies.  Galaxies -- huge conglomerations of stars, gas, dust -- and mysterious  dark matter are the basic building blocks of the large-scale universe.   Although distant galaxies move away from each other as the universe expands, gravity attracts neighboring galaxies to each other, forming galaxy groups, clusters of galaxies, and even larger expansive filaments.  Some of these structures are visible on one of the most comprehensive maps of the sky ever made in galaxies: the APM galaxy survey map completed in the early 1990s.  Over 2 million galaxies are depicted above in a region 100 degrees across centered toward our Milky Way Galaxy's south pole.  Bright regions indicate more galaxies, while bluer colors denote larger average galaxies.  Dark ellipses have been cut away where bright local stars dominate the sky.  Many scientific discoveries resulted from analyses of the map data, including that the universe was surprisingly complex on large scales.

Image credit: S. Maddox 
(Nottingham U.) et al.
APM Survey, 
Astrophys. Dept. Oxford U.
Galaxy NGC 474: Cosmic Blender (2007-10-08)

What's happening to galaxy NGC 474? The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images.  The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years.  Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy to the right of NGC 474 is causing density waves to ripple though the galactic giant.  Regardless of the actual cause, the above image dramatically highlights the increasing consensus that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies.  The halo of our own Milky Way Galaxy is one example of such unexpected complexity. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish Pisces.

Image credit: Mischa Schirmer
Aurora, Stars, Meteor, Lake, Alaska (2007-10-09)

Sometimes, after your eyes adapt to the dark, a spectacular sky appears. In this case, a picturesque lake lies in front of you, beautiful green aurora flap high above you, brilliant stars shine far in the distance, and, for a brief moment, a bright meteor streaks by.  This digitally fused breathtaking panorama was captured late last month across one of the Chena Lakes in North Pole, Alaska, USA, and includes the Pleiades open cluster of stars on the image right.  The shot is unusual not only for the many wonders it has captured simultaneously, but because lakes this far north tend to freeze and become non-reflecting before a sky this dark can be photographed.

Image credit: Bud Kuenzli
The Strange Trailing Side of Saturn's Iapetus (2007-10-10)

What has happened to Saturn's moon Iapetus?  Vast sections of this strange world are dark as coal, while others are as bright as ice.  The composition of the dark material is unknown, but infrared spectra indicate that it possibly contains some dark form of carbon.  Iapetus also has an unusual equatorial ridge that makes it appear like a walnut.  To help better understand this mysterious moon, NASA directed the robotic Cassini spacecraft orbiting Saturn to swoop within 2,000 kilometers just last month. Pictured above, from about 75,000 kilometers out, Cassini's trajectory allowed unprecedented imaging of the hemisphere of Iapetus that is always trailing.  A huge impact crater seen in the south spans a tremendous 450 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike.  Close inspection indicates that the dark coating typically faces the moon's equator.  Whether Iapetus' colors are the result of unusual episodes of internal volcanism or external splattering remains unknown.  This and other images from Cassini's Iapetus flyby are being studied for even greater clues.
Bright Planets, Crescent Moon (2007-10-11)

rly risers are currently enjoying the sight of dazzling Venus, near the eastern horizon as the morning star. Recorded on October 7, this predawn skyview does feature Venus at the upper right. It also includes a crescent Moon and Saturn (lower left). In fact, holding your fist at arms length would have easily covered both planets and the Moon in this 5 degree wide field. Earthshine, sunlight reflected from planet Earth's dayside, illuminates features on the lunar nightside. A close inspection of Saturn itself reveals a nearby pinpoint of light corresponding to Saturn's large moon Titan. Though the Moon has moved on, the tight triangle formed by Venus, Saturn, and Regulus (top), alpha star in the constellation Leo, will continue to look impressive in early morning skies over the next few days. Early bird astrophotographer Jay Ouellet also described Mars as a "brilliant red diode" in his dark country sky east of Quebec City, Canada.   Count the Stars: The Great World Wide Star Count

Image credit: Jay Ouellet
The Whale and The Hockey Stick (2007-10-12)

NGC 4631 is a big beautiful spiral galaxy seen edge-on (top right) only 25 million light-years away towards the small northern constellation Canes Venatici. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. Either way, it is similar in size to our own Milky Way. In this gorgeous color image, the Whale's dark interstellar dust clouds, yellowish core, and young blue star clusters are easy to spot. A companion galaxy, the small elliptical NGC 4627, appears above the Whale Galaxy. At the lower left is another distorted galaxy, the hockey stick-shaped NGC 4656. The distortions and mingling trails of gas detected at other wavelengths suggest that all three galaxies have had close encounters with each other in their past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in x-rays.   Count the Stars: The Great World Wide Star Count

Image credit: Josef Poepsel,
Stefan Binnewies
(Capella Observatory)
Enceladus Ice Geysers (2007-10-13)

Ice geysers erupt on Enceladus, bright and shiny inner moon of Saturn. Shown in this false-color image, a backlit view of the moon's southern limb, the majestic, icy plumes were discovered by instruments on the Cassini Spacecraft during close encounters with Enceladus in November of 2005. Eight source locations for these geysers have now been identified along substantial surface fractures in the moon's south polar region. Researchers suspect the geysers arise from near-surface pockets of liquid water with temperatures near 273 kelvins (0 degrees C). That's hot when compared to the distant moon's surface temperature of 73 kelvins (-200 degrees C).  The cryovolcanism is a dramatic sign that tiny, 500km-diameter Enceladus is surprisingly active. Enceladus ice geysers also likely produce Saturn's faint but extended E ring.
NGC 3132: The Eight Burst Nebula (2007-10-14)

It's the dim star, not the bright one, near the center of NGC 3132 that created this odd but beautiful planetary nebula.  Nicknamed the Eight-Burst Nebula and the Southern Ring Nebula, the glowing gas originated in the outer layers of a star like our Sun.  In this representative color picture, the hot blue pool of light seen surrounding this binary system is energized by the hot surface of the faint star.  Although photographed to explore unusual symmetries, it's the asymmetries that help make this planetary nebula so intriguing.  Neither the unusual shape of the surrounding cooler shell nor the structure and placements of the cool filamentary dust lanes running across NGC 3132 are well understood.
Jupiter's Clouds from New Horizons (2007-10-15)

The New Horizons spacecraft took some stunning images of Jupiter earlier this year while on the way out to Pluto. Famous for its Great Red Spot, Jupiter is also known for its regular, equatorial cloud bands, visible through even modest sized telescopes. The above image was taken near Jupiter's terminator, and shows that the Jovian giant possibly has the widest diversity of cloud patterns in our Solar System.  On the far left are clouds closest to Jupiter's south pole.  Here turbulent whirlpools and swirls are seen in a dark region, dubbed a belt, that rings the planet.  Even light colored regions, called zones, show tremendous structure, complete with complex wave patterns.   The energy that drives these waves likely comes from below.  New Horizons is the fastest space probe ever launched, and is zipping through the Solar System on track to reach Pluto in 2015.
SN 2005ap: The Brightest Supernova Yet Found (2007-10-16)

What could cause a bang this big?  This supernova explosion was so inherently bright that it could be seen nearly 5 billion light years away (a redshift of 0.28) even with a small telescope. Specific colors emitted during SN 2005ap indicate that it was a Type II supernova, a breed of stellar explosion that results when a high mass star begins fusing heavy elements in or near its core.  Type II supernovas may be more powerful than their Type Ia cousins, but they are not currently more useful cosmologically because astronomers don't understand how to accurately recover their intrinsic brightnesses.  It is therefore dimmer Type Ia supernovas that are used by astronomers to calibrate the distance scale of the nearby universe.  Were Type II supernova better understood, astronomers might be able to probe distances further into the universe, and so probe the stability of the strange dark energy that dominates the present universe. Pictured above in a digitally compressed image, the bright supernova SN 2005ap is visible on the right where no exploding star had been seen on the left less than three months before.
I Zwicky 18: The Case of the Aging Galaxy (2007-10-17)

How old is this galaxy?  The galaxy on the left, I Zwicky 18, was once thought to be one of the youngest galaxies on record since its bright stars indicated an age of only 500 million years.  The galaxy was also intriguing because it resembled galaxies forming in the very early universe, but mysterious since it is so nearby -- only 59 million light years away -- and surrounded by galaxies that are significantly older.  Recent images of I Zwicky 18 by the Hubble Space Telescope have helped resolve this mystery, discovering a population of old faint stars intermixed with the bright star population. Therefore I Zwicky 18 is now thought to be just as old as its neighbors, roughly 10 billion years old, but with an intense episode of relative new star formation. Possibly the trigger for this recent episode of bright star formation is the changing gravitational influence of  I Zwicky 18's smaller companion galaxy, visible at the upper right.
The Elephant's Trunk in IC 1396 (2007-10-18)

Like an illustration in a galactic Just So Story, the Elephant's Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Of course, this cosmic elephant's trunk is over 20 light-years long. The false-color view was recorded through narrow band filters that transmit the light from hydrogen (in green), sulfur (in red), and oxygen (in blue) atoms in the region. The resulting composite highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within the obscuring cosmic dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning about 5 degrees. This dramatic close-up covers a 1/2 degree wide field, about the size of the Full Moon.

Image credit: Brian Lula
IC 5067 in the Pelican Nebula (2007-10-19)

The prominent ridge of emission featured in this dramatic skyscape is cataloged as IC 5067. Part of a larger emission nebula with a distinctive shape, popularly called The Pelican Nebula, the ridge spans about 10 light-years following the curve of the cosmic pelican's head and neck. This false color view also translates the pervasive glow of narrow emission lines from atoms in the nebula to a color palette made popular in Hubble Space Telescope images of star forming regions. Fantastic, dark shapes inhabiting the 1/2 degree wide field are clouds of cool gas and dust sculpted by the winds and radiation from hot, massive stars. Close-ups of some of the sculpted clouds show clear signs of newly forming stars. The Pelican Nebula, itself cataloged as IC 5070, is about 2,000 light-years away. To find it, look northeast of bright star Deneb in the high flying constellation Cygnus.   A new APOD RSS feed is available here, or from the link line below.

Image credit: Antonio Fernandez
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.

Image credit: Larry Landolfi
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.

Image credit: Lynette Cook
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.

Image credit: Anthony Ayiomamitis
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.

Image credit: Babak Tafreshi