omnianasa/nasa-apod-metadata huggingface dataset:
To Fly Free in Space (2005-03-22)
At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was further out than anyone had ever been before.  Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured above, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk" during Space Shuttle mission 41-B in 1984.  The MMU works by shooting jets of nitrogen and has since been used to help deploy and retrieve satellites.  With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was replaced with the SAFER backpack propulsion unit.
A Dust Devil Swirling on Mars (2005-03-23)
What is that wisp on the horizon?  Scientists think that the slight white apparition is actually a Martian dust devil that was caught swirling across Mars.  The above image was taken earlier this month by the robotic rover Spirit.  The swirling cloud was found by comparing the above image to a previous image of the same area.  Fresh dust devil tracks have been seen on Mars before, but actually seeing one up close was a surprise.  The most similar phenomena to Martian dust devils on Earth are terrestrial dust devils, tornadoes and waterspouts.  The ultimate cause of Martian dust devils remains unknown, but might be related to rising air heated by sun-warmed rocks and soil.  Just the previous day, Spirit's power acquisition increased unexpectedly, possibly the result of a dust devil passing near or over the Spirit rover and effectively cleaning its solar panels.
Simeis 147: Supernova Remnant (2005-03-24)
It's easy to get lost following the intricate filaments in this detailed image of faint supernova remnant Simeis 147. Seen towards the constellation Taurus it covers nearly 3 degrees (6 full moons) on the sky corresponding to a width of 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. The color composite image includes eight hours of exposure time with an H-alpha filter, transmiting only the light from recombining hydrogen atoms in the expanding nebulosity and tracing the regions of shocked, glowing gas. This supernova remnant has an apparent age of about 100,000 years - meaning light from the massive stellar explosion first reached Earth 100,000 years ago - but this expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star's core.
Huygens Discovers Luna Saturni (2005-03-25)
In 1655, three hundred fifty years ago on this date, Dutch astronomer Christiaan Huygens discovered Luna Saturni - now known as Saturn's moon Titan. To celebrate, consider this intriguing picture of his telescope lens, all that remains of the instrument he used, designed and constructed in collaboration with his brother, Constantijn Huygens. The lens itself measures 57 millimeters (just over 2 inches) in diameter and is inscribed along the border "X 3 FEBR. MDCLV": its focal length (10 Rhineland feet) and the date of its final polishing, 3 February 1655. It also bears a verse from the Roman poet Ovid, "Admovere Oculis Distantia Sidera Nostris" (They brought the distant stars closer to our eyes). Huygens used the verse as part of an anagram announcing his discovery. The use of an anagram, a practice common in his time, established a date for his discovery but kept its details secret until he wished to reveal them. Decoded and translated, his anagram reads "A moon revolves around Saturn in 16 days and 4 hours.", a good agreement with the modern value for Titan's orbital period.
Composite Crab (2005-03-26)
The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this composite image of the inner region of the well-known Crab Nebula. The spectacular picture combines optical data (red) from the Hubble Space Telescope and x-ray images (blue) from the Chandra Observatory, also used in the popular Crab Pulsar movies. Like a cosmic dynamo the pulsar powers the x-ray and optical emission from the nebula, accelerating charged particles and producing the eerie, glowing x-ray jets. Ring-like structures are x-ray emitting regions where the high energy particles slam into the nebular material. The innermost ring is about a light-year across. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of a massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054.
The Einstein Cross Gravitational Lens (2005-03-27)
Most galaxies have a single nucleus -- does this galaxy have four?  The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image.  The central cloverleaf is rather light emitted from a background quasar.  The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images.  The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident.  The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross.  Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.
A Tether in Space (2005-03-28)
One of the greatest unrequited legends of outer space is the tether.  Tethers, long strands of material, hold the promise of stabilizing satellites, generating electricity, and allowing easy transportation.  Possibly the most extreme vision of the space tether is the space elevator popularized by Arthur C. Clarke, where a tether is constructed that connects the ground to geosynchronous orbit.  One problem is strength - it is difficult to make a long useful tether that does not snap.  To help realize more of the tremendous potential of space tethers, NASA and the SpaceWard Foundation have issued the Centennial Tether Challenge, promising a monetary reward for the best space tether that exceeds a minimum standard.  Pictured above is the deployment of the Tethered Satellite System 1 (TSS-1) by the space shuttle Altantis in 1992.  Like other tested tethers, TSS-1 failed to live up to its promise, although many valuable lessons were learned.
Crescents of Titan and Dione (2005-03-29)
What would it be like to see a sky with many moons?  Such is the sky above Saturn.  When appearing close to each other, moons will show a similar phase. A view with two of the more famous moons of Saturn in crescent phase was captured last month by the robot spacecraft Cassini now orbiting Saturn.  Titan, on the lower left, is among the largest moons in the Solar System and is perpetually shrouded in clouds.  Recently, the Huygens probe landed on Titan and gave humanity its first view of its unusual surface.  Dione, on the upper right, has less than a quarter of Titan's diameter and has no significant atmosphere.  Dione, although appearing smaller, was only half the distance to Titan when the above image was taken.
ULXs in M74 (2005-03-30)
In visual appearance, M74 is a nearly perfect face-on spiral galaxy, about 30 million light-years away toward the constellation Pisces.  The red blotches seen in this composite view are ultraluminous x-ray sources (ULXs) mapped by the Chandra X-ray Observatory. The ULXs are so called because they actually do radiate 10 to 1,000 times more x-ray power than "ordinary" x-ray binary stars, which harbor a neutron star or stellar mass black hole. In fact, watching these ULXs change their x-ray brightness over periods of 2 hours or so, astronomers conclude that ULXs could well be intermediate mass black holes -- black holes with masses 10,000 times or so greater than the Sun, but still much less than the million solar mass black holes which lurk in the centers of large spiral galaxies. How did these intermediate mass black holes get there? One intriguing suggestion is that they are left over from the cores of much smaller galaxies that are merging with spiral galaxy M74.
Gamma-Ray Earth (2005-03-31)
The pixelated planet above is actually our own planet Earth seen in gamma rays - the most energetic form of light. In fact, the gamma rays used to construct this view pack over 35 million electron volts (MeV) compared to a mere two electron volts (eV) for a typical visible light photon. The Earth's gamma-ray glow is indeed very faint, and this image was constructed by combining data from seven years of exposure during the life of the Compton Gamma Ray Observatory, operating in Earth orbit from 1991 to 2000. Brightest near the edge and faint near the center, the picture indicates that the gamma rays are coming from high in Earth's atmosphere. The gamma rays are produced as the atmosphere interacts with high energy cosmic rays from space, blocking the harmful radiation from reaching the surface.  Astronomers need to understand Earth's gamma-ray glow well as it can interfere with observations of cosmic gamma-ray sources like pulsars, supernova remnants, and distant active galaxies powered by supermassive black holes.   APOD Update: APOD mirror now on-line from the Beijing Planetarium in Chinese.
Water On Mars (2005-04-01)
Can you help discover water on Mars?  Finding water on different regions on Mars has implications for understanding its complex geologic history, the possible existence of past life and the sustenance of potential future astronauts.  Many space missions have taken photographs of the surface of the red planet, and some of them might show a subtle clue pointing to water on Mars that has been missed.  By close inspection of images, following curiosity, applying scientific principles, applying knowledge about features on the Martian surface, and applying principles of planetary geology, such clues might be brought to light.  In the meantime, happy April Fool's Day from the folks at APOD!
Cyg X-1: Can Black Holes Form in the Dark? (2005-04-02)
The formation of a black hole from the collapsing core of a massive star is thought to be heralded by a spectacular supernova explosion. Such an extremely energetic collapse is also a leading explanation for the mysterious cosmic gamma-ray bursts. But researchers now suggest that the Milky Way's most famous black hole, Cygnus X-1, was born when a massive star collapsed -- without any supernova explosion at all. Their dynamical evidence is summarized in this color image of a gorgeous region in Cygnus, showing Cyg X-1 and a cluster of massive stars (yellow circles) known as Cygnus OB3. Arrows compare the measured direction and speed of Cyg X-1 and the average direction and speed of the massive stars of Cyg OB3. The similar motions indicate that Cyg X-1's progenitor star was itself a cluster member and that its path was not altered at all when it became a black hole. In contrast, if Cyg X-1 were born in a violent supernova it would have likely received a fierce kick, changing its course. If not a supernova, could the formation of the Cyg X-1 black hole have produced a dark gamma-ray burst in the Milky Way?
The Galactic Center Radio Arc (2005-04-03)
What causes this unusual structure near the center of our Galaxy? The long parallel rays slanting across the top of the above radio image are known collectively as the Galactic Center Radio Arc and jut straight out from the Galactic plane.  The Radio Arc is connected to the Galactic center by strange curving filaments known as the Arches.  The bright radio structure at the bottom right likely surrounds a black hole at the Galactic center and is known as Sagittarius A*.  One origin hypothesis holds that the Radio Arc and the Arches have their geometry because they contain hot plasma flowing along lines of constant magnetic field.  Recent images from the Chandra X-ray Observatory appear to show this plasma colliding with a nearby cloud of cold gas.
NGC 1316: After Galaxies Collide (2005-04-04)
How did this strange-looking galaxy form?  Astronomers turn detectives when trying to figure out the cause of unusual jumbles of stars, gas, and dust like NGC 1316.   A preliminary inspection indicates that NGC 1316 is an enormous elliptical galaxy that includes dark dust lanes usually found in a spiral.  The above image taken by the Hubble Space Telescope shows details, however, that help in reconstructing the history of this gigantic jumble.  Close inspection finds fewer low mass globular clusters of stars toward NGC 1316's center. Such an effect is expected in galaxies that have undergone collisions or merging with other galaxies in the past few billion years.  After such collisions, many star clusters would be destroyed in the dense galactic center.  The dark knots and lanes of dust indicate that one or more of the devoured galaxies were spiral galaxies.  NGC 1316 spans about 60,000 light years and lies about 75 million light years away toward the constellation of the Furnace.
Light From A Distant Planet (2005-04-05)
Light emitted by a planet far beyond our Solar System has been identified for the first time.  The planet, illustrated in the above drawing, had its light detected by comparing the brightness of only the parent star, when the planet was behind the star, to the light emitted when both the planet and its parent star were visible.   The Earth-trailing Spitzer Space Telescope made the observation in infrared light, where the intrinsic glow of the planet outshines the light it reflects from its central star.  The direct observation of light allowed a measurement of both the temperature and size of the planet: HD 209458b.  Planet HD 209458b was confirmed to be larger than expected for its mass and on an orbit around its parent star that was unexpectedly close to a circle.
The M7 Open Star Cluster in Scorpius (2005-04-06)
M7 is one of the most prominent open clusters of stars on the sky.  The cluster, dominated by bright blue stars, can be seen with the naked eye in a dark sky in the tail of the constellation of Scorpius.  M7 contains about 100 stars in total, is about 200 million years old, spans 25 light-years across, and lies about 1000 light-years away.   This color picture was taken recently at the Kitt Peak National Observatory in Arizona, USA as part of the Advanced Observers Program. The M7 star cluster has been known since ancient times, being noted by Ptolemy in the year 130 AD.  Also visible is a dark dust cloud near the bottom of the frame, and literally millions of unrelated stars towards the Galactic center.
Solar Eclipse in View (2005-04-07)
Friday's solar eclipse will be a rare hybrid - briefly appearing as either an annular eclipse or a total eclipse when viewed from along the narrow track of the Moon's shadow. Unfortunately that track, never more than about 30 kilometers wide, lies mostly across the Pacific Ocean, beginning south of New Zealand and just ending in Venezuela. Skywatchers along the beginning and end of the shadow track will see an annular eclipse of the Sun, with the Moon's silhouette briefly surrounded by a bright ring of fire, while observers along the middle of the track will witness a total eclipse phase. But the good news is that over a much broader region of the globe, including New Zealand and much of South and North America, a partial eclipse can be seen as the Moon appears to take a bite out of the Sun. If you want to view the eclipse, take care to do it safely, and check the times for your specific location. So, what location is this solar eclipse view from? The picture above was recorded in November of 2003 from within the track of the Moon's shadow across Antarctica, of course.
Sideways Galaxy NGC 3628 (2005-04-08)
Dark dust lanes cutting across the middle of this gorgeous island universe strongly hint that NGC 3628 is a spiral galaxy seen sideways. About 35 million light-years away in the northern springtime constellation Leo, NGC 3628 also bears the distinction of being the only member of the well known Leo triplet of galaxies not in Charles Messier's famous catalog. Otherwise similar in size to our Milky Way galaxy, the disk of NGC 3628 is clearly seen to fan out near the galaxy's edge. A faint arm of material also extends up and to the left in this deep view of the region. The distorted shape and tidal tail suggest that NGC 3628 is interacting gravitationally with the other spiral galaxies in the Leo triplet, M66 and M65.  News: Solar Eclipse Today
Inside the Elephant's Trunk (2005-04-09)
In December of 2003, the world saw spectacular first images from the Spitzer Space Telescope, including this penetrating interior view of an otherwise opaque dark globule known as the Elephant's Trunk Nebula. Seen in a composite of infrared image data recorded by Spitzer's instruments, the intriguing region is embedded within the glowing emission nebula IC 1396 at a distance of 2,450 light-years toward the constellation Cepheus. Previously undiscovered protostars hidden by dust at optical wavelengths appear as bright reddish objects within the globule. Shown in false-color, winding filaments of infrared emission span about 12 light-years and are due to dust, molecular hydrogen gas, and complex molecules called polycyclic aromatic hydrocarbons or PAHs. The Spitzer Space Telescope was formerly known as the Space Infrared Telescope Facility (SIRTF) and is presently exploring the Universe at infrared wavelengths. Spitzer follows the Hubble Space Telescope, the Compton Gamma-ray Observatory, and the Chandra X-ray Observatory as the final element in NASA's space-borne Great Observatories Program.
Venus' Once Molten Surface (2005-04-10)
If you could look at Venus with radar eyes - this is what you might see. This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft.  Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above.  Volcanism is thought to have created the domes, although the precise mechanism remains unknown.  Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.
Clouds, Plane, Sun, Eclipse (2005-04-11)
How can part of the Sun just disappear?  When that part is really hiding behind the Moon.  Last Friday, the first partial solar eclipse of 2005 and the last total eclipse of the Sun until March 2006 was visible.  During a solar eclipse, the Sun, Moon and Earth are aligned.  The total solar eclipse was primarily visible from the Southern Pacific Ocean, while a partial solar eclipse was discoverable across South America and lower North America.  The above image composite was taken with a handheld digital camera last Friday.  After a day of rain in Mt. Holly, North Carolina, USA, a partially eclipsed Sun momentarily peeked through a cloudy sky.  After taking a sequence of images, the best eclipse shot was digitally combined with a less good eclipse shot that featured a passing airplane.
Earth or Mars? (2005-04-12)
Which image is Earth, and which is Mars?  One of the above images was taken by the robot Spirit rover currently climbing Husband Hill on Mars.  The other image was taken by a human across the desert south of Morocco on Earth.  Both images show vast plains covered with rocks and sand.  Neither shows water or obvious signs of life.  Each planet has a surface so complex that any one image does not do that planet justice.  Understanding either one, it turns out, helps understand the other.  Does the one on the left look like home?  Possibly not, but it is Earth.
A Window to the Once Secret Sky (2005-04-13)
If there were a window nearby to the distant universe -- would you look through it?  Quite possibly, there is, in the form of a small telescope.  A local skykeeper could be a relative or a stranger and is frequently proud to show off the sky free of charge.  Through a window called an eyepiece, on a dark cloudless night, you can see clusters of stars, rings around Saturn, glowing nebulas of gas, craters on the Moon, and galaxies across the universe. The technology to create this window -- and the secret sky it reveals -- was unknown only 400 years ago.  Modern sky opportunities may occur this Saturday, Astronomy Day, at local amateur astronomy clubs, universities, science centers, or planetariums.  Pictured above is a small telescope being deployed at picturesque Hohe Wand, about 50 kilometers south of Vienna, Austria.  The spin of the Earth is visible in the above photo as the long star trails.
April's Moon and the Pleiades (2005-04-14)
After parting with the Sun late last week, April's moon graced the early evening sky. Its slender, three-day-old crescent shares this lovely telescopic skyview with the nearby Pleiades star cluster. Here, the Moon's sunlit crescent is overexposed while the lunar terminator, or boundary between lunar night and day, is jagged with craters and mountains. Lunar surface features can also be seen in the dim lunar night illuminated by earthshine - light from sunlit planet Earth. The sister stars of the Pleiades are grouped at the right, but their alluring blue reflection nebulae, usually highlighted in telescopic images of the cluster, are washed-out in the much brighter moonlight.
RCW 79: Stars in a Bubble (2005-04-15)
A cosmic bubble of gas and dust, RCW 79 has grown to about 70 light-years in diameter, blown by the winds and radiation from hot young stars. Infrared light from the dust embedded in the nebula is tinted red in this gorgeous false-color view from the Spitzer Space Telescope. A good 17 thousand light-years away in the grand southern constellation Centaurus, the expanding nebula itself has triggered star formation as it plows into the gas and dust surrounding it. In fact, this penetrating infrared picture reveals groups of new stars as yellowish points scattered along the bubble's edge. One remarkable group still lies within its own natal bubble at about 7 o'clock (lower left), while another can be seen near the upper gap at about 3 o'clock (right) from the bubble's center.
Celebrating Hubble With NGC 6751 (2005-04-16)
Planetary nebulae can look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope have become well known for showing these fluorescent gas shrouds of dying Sun-like stars to possess a staggering variety of detailed symmetries and shapes. This composite color Hubble image of NGC 6751 is a beautiful example of a classic planetary nebula with complex features. It was selected in April of 2000, to commemorate the tenth anniversary of Hubble in orbit. The colors were chosen to represent the relative temperature of the gas - blue, orange, and red indicating the hottest to coolest gas. Winds and radiation from the intensely hot central star (140,000 degrees Celsius) have apparently created the nebula's streamer-like features. The nebula's actual diameter is approximately 0.8 light-years or about 600 times the size of our solar system. NGC 6751 is 6,500 light-years distant in the high-flying constellation Aquila.