juliensimon/nasa-apod huggingface dataset:
Magnetar In The Sky (2000-01-22)

Indicated on this infrared image of the galactic center region is the position of SGR 1900+14 - the strongest known magnet in the galaxy. SGR 1900+14 is believed to be a city-sized, spinning, super-magnetic neutron star, or Magnetar. How strong is a Magnetar's magnetic field? The Earth's magnetic field which deflects compass needles is measured to be about 1 Gauss, the strongest fields sustainable in Earth-based laboratories are about 100,000 Gauss, yet the Magnetar's monster magnetic field is estimated to be 1,000,000,000,000,000 Gauss. A magnet this strong, located at about half the distance to the Moon would easily erase your credit cards and suck pens out of your pocket. In 1998, from a distance of about 20,000 light-years, SGR 1900+14 generated a powerful flash of gamma-rays detected by many spacecraft. That blast of high-energy radiation is now known to have had a measurable effect on Earth's ionosphere. At the surface of the Magnetar, its powerful magnetic field is thought to buckle and shift the neutron star crust generating the intense gamma-ray flares.
A Message From Earth (2000-01-23)

What are these Earthlings trying to tell us?  The above message was broadcast from Earth towards the globular star cluster M13 in 1974.  During the dedication of the Arecibo Observatory - still the largest radio telescope in the world - a string of 1's and 0's representing the above diagram was sent.   This attempt at extraterrestrial communication was mostly ceremonial - humanity regularly broadcasts radio and television signals out into space accidentally.  Even were this message received, M13 is so far away we would have to wait almost 50,000 years to hear an answer.   The above message gives a few simple facts about humanity and its knowledge: from left to right are numbers from one to ten, atoms including hydrogen and carbon, some interesting molecules, DNA, a human with description, basics of our Solar System, and basics of the sending telescope.  Several searches for extraterrestrial intelligence are currently underway, including Project Phoenix and one where you can use your own home computer.
NGC 2392 from the Newly Fixed Hubble (2000-01-24)

In 1787, astronomer William Herschel discovered  NGC 2392.  From the ground, NGC 2392 resembles a person's head surrounded by a parka hood.  In 2000, just after being fixed, the Hubble Space Telescope imaged  NGC 2392.   From space, the nebula displays gas clouds so complex they are not fully understood.   NGC 2392 is clearly a planetary nebula, and the gas seen above composed the outer layers of a Sun-like star only 10,000 years ago.  The inner filaments visible above are being ejected by strong wind of particles from the central star.  The outer disk contains unusual light-year long orange filaments.  NGC 2392 lies about 5000 light-years away and is visible with a small telescope in the constellation of Gemini.
A Lunar Eclipse in Three Exposures (2000-01-25)

Our Moon turned red last week.  The reason was that during the night of January 20, a total lunar eclipse occurred.  The above digitally superimposed photographs captured the Moon three times during this lunar eclipse, once just as the Moon entered the Earth's shadow, once when the Moon was near the middle of the shadow, and once just before the Moon exited.  The red tint of the eclipsed Moon is created by sunlight first passing through the Earth's atmosphere, which preferentially scatters blue light (making the sky blue) but passes and refracts red light, before reflecting back off the Moon.  Differing amounts of clouds and volcanic dust in the Earth's atmosphere make each lunar eclipse appear differently.

Image credit: Stephen Barnes
A Lunar Eclipse Over Time (2000-01-26)

During last week's lunar eclipse, our Moon appeared to disappear.  As the Earth moved between the Moon and the Sun, the Earth's shadow fell on the moon, making it quite dark.  In the above photograph, the Earth's rotation caused the Moon and stars to appear as streaks during this four-hour exposure.  In the foreground is the abbey of the Benedictive monastery of Sant Llorenc del Munt, a structure in Girona, Spain that has stood since the eleventh century.  As the Earth's shadow engulfed the Moon, the Moon streak became less and less bright, practically disappearing during totality.   At this time, the Moon, which normally shines by reflecting direct sunlight, shone only by sunlight refracted through the Earth's atmosphere.  Later, clouds obscured the re-appearing Moon.

Image credit: Juan Carlos Casado
Spiral Galaxy In Centaurus (2000-01-27)

Centaurus, the Centaur, is one of the most striking constellations in the southern sky. The lovely Milky Way flows through this large constellation whose celestial wonders also include the closest star to the sun, Alpha Centauri, the largest globular star cluster in our galaxy, Omega Centauri, and the closest active galaxy, Centaurus A. Embraced by tightly wound spiral arms of bright blue star clusters, this gorgeous galaxy - cataloged as ESO 269-57 - also falls within Centaurus' borders. Seen behind a veil of foreground stars which lie within our own galaxy, this face-on spiral galaxy is about 150 million light-years away and 200,000 light-years across. The brighter foreground stars are marked by diffraction spikes caused by the telescope and yellow vertical stripes due to saturated digital camera pixels in the above Very Large Telescope image from the European Southern Observatory. Tantalizing wisps of more distant, faint galaxies are visible in the background.
Astronomy From An F-18 (2000-01-28)

In an era of blossoming ground and space-based observatories, astronomers are also pushing the envelope with airborne instrumentation - successfully capturing an asteroid occultation from a high performance jet aircraft. This blinking animation represents two digitized frames from inflight data of asteroid number 308, Polyxo, passing in front of or occulting a faint star near the center of the field. The camera used, known as the SouthWest Ultraviolet Imaging System (SWUIS) -A, was mounted in the cockpit of a NASA F/A-18 jet (inset lower left). A former US Navy fighter aircraft, the F/A-18 was able to maneuver to the precise position to record the occultation while cruising above clouds and much of Earth's obscuring atmosphere. Using the SWUIS-A data to time the occultation will reveal the size of the asteroid which is otherwise too small to be imaged by even the orbiting Hubble Space Telescope. Future SWUIS-A airborne missions may include a hunt for Vulcanoids, a suspected population of small asteroids circling the Sun inside the orbit of Mercury.
Natural Saturn On The Cassini Cruise (2000-01-29)

What could you see approaching Saturn aboard an interplanetary cruise ship? Your view would likely resemble this subtly shaded image of the gorgeous ringed gas giant. Processed by the Hubble Heritage project, the picture intentionally avoids overemphasizing color contrasts and presents a natural looking Saturn with cloud bands, storms, nearly edge-on rings, and the small round shadow of the moon Enceladus near the center of the planet's disk. Of course, seats were not available on the only ship currently enroute - the Cassini spacecraft, launched in 1997 and scheduled to arrive at Saturn in the year 2004. After an extended cruise to a world 1,400 million kilometers from the Sun, Cassini will tour the Saturnian system, conducting a remote, robotic exploration with software and instruments designed by denizens of planet Earth. But where is Cassini now? Still about 980 million kilometers from Saturn, last Sunday the spacecraft flew by asteroid 2685 Masursky.
The Milky Way in Infrared (2000-01-30)

At night, from a dark location, part of the clear sky looks milky.  This unusual swath of dim light is generally visible during any month and from any location.  Until the invention of the telescope, nobody really knew what the "Milky Way" was.  About 300 years ago telescopes caused a startling revelation: the Milky Way was made of stars.  Only 70 years ago, more powerful telescopes brought the further revelation that the Milky Way is only one galaxy among many.  Now telescopes in space allow yet deeper understanding.  The above picture was taken by the COBE satellite and shows the plane of our Galaxy in infrared light. The thin disk of our home spiral galaxy is clearly apparent, with stars appearing white and interstellar dust appearing red.
Snowstorm on Planet Earth (2000-01-31)

rth is an ocean planet. From low Earth orbit, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument onboard NASA's SeaStar spacecraft globally maps ocean color, tracking changes in the climate and biosphere of our water world. Richly detailed SeaWiFS images can also follow color changes in Earth's landmasses as illustrated in this close-up picture of the planet. Taken on January 27, it covers the Great Lakes region and Atlantic coastal areas of the North American continent. The space-based perspective splendidly reveals the extent of fractal white seasonal solid phase H20 recently sprinkled over the Northeastern and Midatlantic US. Unanticipated and intense, the snowstorm delighted school children but caused serious disruptions in many locales.
Abell 2218: A Galaxy Cluster Lens (2000-02-01)

Gravity can bend light.  Almost all of the bright objects in this recently released Hubble Space Telescope image are galaxies in the cluster known as Abell 2218.  The cluster is so massive and so compact that its gravity bends and focuses the light from galaxies that lie behind it.  As a result, multiple images of these background galaxies are distorted into long faint arcs - a simple lensing effect analogous to viewing distant street lamps through a glass of wine.  The cluster of galaxies Abell 2218 is itself about three billion light-years away in the northern constellation Draco.
Aeolian Mars (2000-02-02)

Mars' atmosphere is relatively thin, still when martian winds blow they weather and shape its surface. Like familiar aeolian features on Earth, this field of dunes within Mars' Rabe crater exhibits graceful undulating ridges which can shift as windblown material is deposited on the dunes' windward face and falls away down the steeper leeward slopes. Indicated by the arrow, the dark trails are signs that the martian sand has avalanched down the steep slopes in the recent past. Rippling patterns of smaller dunes are also visible in this sharp high-resolution view along with criss-crossing dark trails which may be evidence of local dust-devil windstorms. The image is about 3 kilometers across and was recorded in March of 1999 by the orbiting Mars Global Surveyor spacecraft.
Colorful Clouds Of Carina (2000-02-03)

Tumultuous clouds of the Carina Nebula, 8000 light-years away, glow in planet Earth's southern sky. Striking and detailed, this close-up of a portion of the famous nebula is a combination of exposures through six different filters taken with the Hubble Space Telescope's Wide Field Planetary Camera 2 in April of 1999. Dramatic dark dust knots and complex features revealed are sculpted by the winds and radiation of Carina's massive and energetic stars. But how were this picture's colors generated? Astronomical images produced from Hubble Space Telescope data can be composed of exposures made using relatively narrow filters which don't match the color responses of the human eye. Some of the filters even transmit wavelengths of light outside the visible spectrum. Exposures made with different narrow filters, as in this case, are translated to a visible color where shorter wavelengths are assigned bluer and longer wavelengths assigned redder colors. This color scheme represents a "chromatically ordered" way of presenting the data rather than a natural color image.
X-Ray Stars Of Orion (2000-02-04)

The stars of Orion shine brightly in northern winter skies where the constellation harbors the closest large stellar nursery, the Great Nebula of Orion, a mere 1500 light-years away. In fact, the apparently bright clump of stars near the center of this Chandra X-ray telescope picture of a portion of the nebula are the massive stars of the Trapezium - the young star cluster which powers much of the nebula's visible-light glow. But the sheer number of other stars seen in this X-ray image, which spans about 10 light-years, has surprised and delighted astronomers and this picture was recently touted as the richest field of X-ray sources ever recorded in a single observation. The picture does dramatically illustrate that young stars are prodigious sources of X-rays, thought to be produced in hot stellar coronas 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 dark lines through the image are instrumental artifacts.
NEAR to Asteroid Eros (2000-02-05)

On December 23, 1998 the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew by asteroid 433 Eros.  The robotic spacecraft was intended to brake and orbit Eros, but an unexpected shutdown of its main engine caused this plan to be aborted. Now closing with the asteroid again, NEAR will make another attempt to enter Eros' orbit on February 14th ... Valentine's Day, of course! A successful encounter would make NEAR the first spacecraft ever to orbit an asteroid. This image sequence was taken as NEAR approached Eros in 1998.  The rotation of the asteroid is visible in the successive frames. While cruising through the solar system, NEAR has also been hunting for gamma-ray bursts as part of the operational Interplanetary Network.
The Mysterious Rings of Supernova 1987A (2000-02-06)

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. Meanwhile, astronomers have just reported the possible appearance of a new ring feature.
The W4 Chimney (2000-02-07)

A huge chimney venting hot clouds of gas out from the plane of our Milky Way Galaxy has recently been imaged in radio waves.  The Canadian Galactic Plane Survey team used an array of radio telescopes to survey an ionized gas region known as W4.  At the bottom of W4 and in the center of the above image is a very young open cluster of stars known as OCl 352.  Research continues into how these stars created the W4 superbubble.  Possible explanations include supernova explosions or strong stellar winds from these stars.  It does appear clear, however, that hot gas is expanding outwards, being funneled by relatively cool and dense gas in a chimney-like fashion.  The W4 chimney, which lies 6500 light-years from Earth and spans 250 light-years across, is visible as the comparatively dark area extending toward the top of the above image.
Rings Around Beta Pictoris (2000-02-08)

Tomorrow's picture: Galaxy Wars  < | Archive | Index | Search | Calendar | Glossary | Education | About APOD | >  Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.
Galaxy Wars: M81 Versus M82 (2000-02-09)

In the left corner, wearing a red nucleus surrounded by blue spiral arms, is M81.  In the right corner, sporting light stars and dark dust lanes, is M82.  These two mammoth galaxies have been locked in gravitational combat for the past billion years.   The gravity from each galaxy dramatically affects the other during each hundred million-year pass.  Last go-round, M82's gravity likely raised circulating density waves rippling around M81 resulting in the richness of M81's spiral arms.  M81, though, left M82 a messy pulp of exploded stars and colliding gas so violent it emits bright X-rays.  In both galaxies, colliding gas has created a recent abundance of bright new stars.  In a few billion years only one galaxy will remain.

Image credit: Robert Gendler
Eros Encounter Nears (2000-02-10)

After an unanticipated extra trip around the Sun, the NEAR spacecraft is now politely approaching asteroid 433, Eros, at a respectful relative speed of about 20 miles per hour. Still nearly 2,000 miles distant, NEAR will close to within approximately 200 miles by February 14th - Valentine's Day. If all goes well, the spacecraft will then be captured by the gentle attraction of Eros' gravity, becoming the first artificial moon of an asteroid. While Eros is not round it is certainly not heart-shaped either as seen in this series of frames showing the roughly 20 x 8 x 8 mile asteroid during its 5.27 hour rotation period. Different perspectives clearly show a gouge or saddle and a large impact crater with a raised rim near the asteroid's narrow waist. The frames were recorded by the NEAR spacecraft's multi-spectral imager on February 4th from a range of 4,600 miles.
XMM-Newton First Light: X-Rays From The LMC (2000-02-11)

Recently the European Space Agency released this and other spectacular "first light" pictures from its new orbiting x-ray observatory, christened XMM-Newton. A churning region of star birth and death in our small neighboring galaxy, the Large Magellanic Cloud (LMC), this field was one of several chosen to test out XMM-Newton's x-ray imaging capabilities. The picture is a false-colour one in which low energy x-rays are translated to red, medium energy to green, and high energy to blue. Image colours therefore represent the relative million degree temperatures of the x-ray emitting regions, red being the coolest and blue the hottest. Remains of the star that exploded as Supernova 1987a appear here as the white x-ray source at the lower right, while another supernova remnant, cataloged as N157D is the brightest source at the upper left. The bluish arc (near center) also appears to be a supernova remnant whose expanding debris cloud is interacting with the LMC's local interstellar gas.
Stereo Saturn (2000-02-12)

Get out your red/blue glasses and launch yourself into this stereo picture of Saturn! The picture is actually composed from two images recorded weeks apart by the Voyager 2 spacecraft during its visit to the Saturnian System in August of 1981. Traveling at about 35,000 miles per hour, the spacecraft's changing viewpoint from one image to the next produced this exaggerated but pleasing stereo effect. Saturn is the second largest planet in the Solar System, after Jupiter. Its spectacular ring system is so wide that it would span the space between the Earth and Moon. Although they look solid here, Saturn's rings consist of individually orbiting bits of ice and rock ranging in size from grains of sand to barn-sized boulders.
Southwest Mercury (2000-02-13)

The planet Mercury resembles a moon. Mercury's old surface is heavily cratered like many moons.  Mercury is larger than most moons but smaller than Jupiter's moon Ganymede and Saturn's moon Titan.  Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth is the only planet more dense.  A visitor to Mercury's surface would see some strange sights.  Because Mercury rotates exactly three times every two orbits around the Sun, and because Mercury's orbit is so elliptical, a visitor to Mercury might see the Sun rise, stop in the sky, go back toward the rising horizon, stop again, and then set quickly over the other horizon.   From Earth, Mercury's proximity to the Sun cause it to be visible only for a short time just after sunset or just before sunrise.
An Unexpected Asteroid Valentine (2000-02-14)

Maybe the Moon owns our hearts, but this won't stop the occasional asteroid from sending us a valentine.  Friday, to the surprise of many, the NEAR mission on approach to asteroid 433 EROS photographed what appears to be a heart-shaped depression.  After NEAR reaches the asteroid today, NASA plans a series of maneuvers to make the robot spacecraft the first ever to orbit an asteroid. More detailed pictures will soon be taken of the 33 kilometer long asteroid EROS and this 5 kilometer long depression.  Most likely, fortuitous lighting and viewing angles accentuate the apparent heart shape -- but don't tell the Moon.
M106: A Spiral Galaxy with a Strange Core (2000-02-15)

What's happening at the center of spiral galaxy M106? A swirling disk of stars and gas, M106's appearance is dominated by two bright spiral arms and dark dust lanes near the nucleus.  Bright newly formed stars near their outer tips distinguish the spiral arms in the above photograph. The core of M106 glows brightly in radio waves and X-rays where  twin jets have been found running the length of the galaxy.  An unusual central glow makes M106 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole.  M106, also designated NGC 4258, is a relatively close 25 million light years away, spans 30 thousand light years across, and can be seen with a small telescope towards the constellation of Canes Venatici.
Eros From Orbit (2000-02-16)

On February 14th, the NEAR spacecraft became the first artificial moon of an asteroid. Captured by the gentle gravity of a 20 mile long slipper-shaped mountain of rock, NEAR recorded this premier image while orbiting asteroid 433 Eros at a distance of about 200 miles. The image shows features as small as 100 feet across in a view dominated by a 3 mile wide crater near Eros' narrow waist. Enticing layers and grooves are visible within the crater rim along with an enormous 170 foot boulder lying on the crater floor (near picture center). Although Eros is a large S-type near-earth asteroid, it is still not massive enough for its own gravity to have shaped it into a planet-like spherical form. By comparison, Eros has less than a thousandth Earth's gravity, so a 100 pound object on Earth would weigh about 1 ounce on Eros. A baseball thrown at 22 miles per hour would completely escape into space. The weak gravity and irregular shape make orbiting Eros a delicate challenge for NEAR's controllers who plan a year long exploration program with possible close approaches to the asteroid's surface.
New Shocks For Supernova 1987A (2000-02-17)

In February of 1987, astronomers witnessed the brightest supernova of modern times - supernova 1987A in the Large Magellanic Cloud. Mysterious rings of material surrounding the expanding stellar debris were soon emitting a visible glow excited by intense light from the explosion. After fading over the intervening years, the interior ring has just been seen to sprout four new hotspots, as illustrated in these two versions of a Hubble Space Telescope image recorded on February 2nd. The abrupt appearance of the new features suggests that matter from the stellar blast wave itself has begun to slam into the ring in earnest, shock-heating the gas and producing the bright hotspots. The left-hand picture shows the glowing ring, initially excited by light from the explosion, along with the shocked hotspots. The right-hand picture has been further computer enhanced to emphasize the hotspots. The brightest spot at the right was first observed in 1997, while the four spots on the left half of the ring are new. Astronomers now eagerly anticipate a dramatic rejuvenation of the glowing ring as the bulk of the blast wave material, traveling at about 60 million kilometers per hour, continues to plow into it.