juliensimon/nasa-apod huggingface dataset:
Disorder in Stephan's Quintet (2000-11-13)

What are four closely grouped galaxies doing in this image?  The grouping composes a majority of the large galaxies in Stephan's Quintet, with the fifth prominent galaxy located off the above image to the lower right. Three of these four galaxies show nearly the same redshift, indicating that they reside at the same distance from us.  These three galaxies are in the midst a titanic collision, each ripping the others apart with gravitational tidal forces. The large bluish spiral below and left of center is a foreground galaxy much closer than the others and hence not involved in the cosmic battle.  Most of Stephan's Quintet lies about 300 million light-years away towards the constellation of Pegasus.
The Yardangs Of Mars (2000-11-14)

OK, fans of classic science fiction might be disappointed. The yardangs are not barsoomian warriors in a newly discovered Edgar Rice Burroughs tale of adventure and conquest on the Red Planet. In fact yardangs, geologists' term for narrow, wind-eroded ridges, are common land features in the desert regions of planet Earth. Such Eolian (wind related) landforms are common on Mars too, and this recently released Mars Global Surveyor picture shows long, sculpted yardangs in the eastern Aeolis region of southern Elysium Planitia. These martian yardangs may have formed in deposits of volcanic ash. Covering a swath of the martian surface 2.5 kilometers high, this composite image does offer special effects, though. If you have red/blue glasses (red for the left eye) you can view the yardangs of Mars in astounding 3-D!
Coronal Rain, Solar Storm (2000-11-15)

In this picture, the Sun's surface is quite dark. A frame from a movie recorded on November 9th by the orbiting TRACE telescope, it shows coronal loops lofted over a solar active region. Glowing brightly in extreme ultraviolet light, the hot plasma entrained above the Sun along arching magnetic fields is cooling and raining back down on the solar surface. Hours earlier, on November 8th, astronomers had watched this particular active region produce a not so spectacular solar flare. Still, the M-class flare spewed forth an intense storm of particles, suddenly showering satellites near the Earth with high energy protons. The flare event was also associated with a large coronal mass ejection, a massive cloud of material which impacted our fair planet's magnetic field about 31 hours later. The result ... a strong geomagnetic storm.
A Daytime Fireball in 1944 (2000-11-16)

While stationed in  central Africa in December 1944, Norman Appleton witnessed a meteor so bright he remembered it his entire life.  Right before his eyes a tremendous smoking fireball streaked across the daytime sky.  Years later, as an accomplished member of the Guild of Aviation Artists, he recorded his memories in the above painting.  Tonight and tomorrow mark the peak of this year's Leonid meteor shower.  Although any individual observer is unlikely to see a fireball as spectacular as this one, observers in dark locations might witness as many as hundreds of transient streaks of light emanating from the constellation of Leo across a morning moonlit sky.

Image credit: Norman Appleton
Leonid Sunrise (2000-11-17)

Such beautiful things begin as grains of sand. Locked in an oyster a granule grows into an iridescent pearl, lustrous and lovely to behold. While hurtling through the atmosphere at 70 kilometers per second, a cosmic sand grain becomes an awe-inspiring meteor, its transient beauty displayed for any who care to watch. Framed perfectly between orange clouds at sunrise, this bright meteor trail was photographed from the Joshua Tree National Park in California, USA during the 1998 Leonid Meteor Shower. Appropriately titled "Leonid Sunrise", the picture was recorded on high-speed film (ASA 3200) with a 35mm camera. Its striking colors and grainy, textured appearance suggest a painting on canvas. Of course, you could see Leonid meteors at sunrise for yourself. With clear skies, your next chance is coming up ... tomorrow morning.

Image credit: Wally Pacholka
Jupiter And Family (2000-11-18)

Tomorrow's picture: Dusty Universe  < | 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.

Image credit: Galileo Project,
Voyager Project,
JPL,
NASA
Our Dusty Universe (2000-11-19)

What's black & white and red all over?  Add our universe to this list.  Adrift in a vast sea of darkness are not only familiar bright stars but dust that glows predominantly in far-infrared light.  This cosmological dust was recently discovered in data taken previously by the COBE satellite, and visible as a diffuse glow visible in the above image.  The amount of dust in the universe is important because it is a measure of the number of stars that created it, of the number of stars that are cloaked by it, and of the amount of distortion created in measurements of the distant universe.
A 2000 Leonid Through Orion (2000-11-20)

The Leonid Meteor Shower this year could be described as good but not great.  During November 17 and 18 the Earth crossed through several streams of sand-sized grit left orbiting the Sun by Comet Tempel-Tuttle.  Several distinct peaks in meteor activity were reported, with rates approaching 400 meteors per hour for brief periods for some dark locations.  Pictured above, a Leonid meteor was caught from Florida streaking through the constellation of Orion on the morning of 2000 November 18.  Visible as a red-tinged smudge to the left of the three nearly linear stars that compose Orion's belt is the picturesque star-forming region known as the Orion Nebula.  Next year, the Leonids Meteor Shower is expected by many to be much more active.

Image credit: Doug Murray
Fire on Earth (2000-11-21)

Sometimes, regions of planet Earth can be seen lit up with fire. Since fire is the rapid acquisition of oxygen, and since oxygen is a key indicator of life, fire on any planet would be an indicator of life on that planet. Most of the Earth's land has been scorched by fire at some time in the past.  Although causing many a tragedy, fire is considered part of a natural ecosystem cycle.  The year 2000 fire season in the continental United States has been one of the most active on record, burning an area similar in size to New Jersey. Large forest fires on Earth are usually caused by lightning and can be visible from orbit. Above, stunned Elk avoid a fire sweeping through Montana's Bitterroot Valley by standing in a river.
The Orion Nebula in Hydrogen (2000-11-22)

The Great Nebula in Orion can be found just below and to the left of the easily identifiable belt of three stars in the popular constellation Orion.  This fuzzy patch, visible to the unaided eye, contains one of the closest stellar nurseries, lying at a distance of about 1500 light years.  The above picture highlights red light emitted by the nebula's hydrogen gas. Dark dust filaments punctuate regions of this glowing hydrogen gas and reflect light from the nebula's brightest stars.  Recent observations of the Orion Nebula by the Hubble Space Telescope have located solar-system sized regions that are thought to be planet-forming circumstellar disks.

Image credit: Robert Gendler
Cassini At Jupiter: Red Spot Movie (2000-11-23)

verything is big on Jupiter, the solar system's reigning gas giant. For example, Jupiter's Great Red Spot is a hurricane-like storm system at least twice the diameter of planet Earth. Approaching Jupiter in early October the Cassini spacecraft recorded the images used in this excellent movie of the swirling storm system and planet-circling cloud bands. Seven mosaicked frames make up the movie sequence, each separated by one or two rotation periods (Jupiter rotates about once every 10 hours). The sequence is viewed as a simple cylindrical map projection spanning 50 degrees north to 50 degrees south of the Jovian equator. Can you see the small bright "clouds" which seem to suddenly appear west (left) of the Red Spot? Data from the Galileo spacecraft, orbiting Jupiter since 1996, suggest that these features are large lightning storms. Saturn-bound, the Cassini spacecraft will take a few months to fly by Jupiter, coordinating Jovian explorations with Galileo and picking up speed for the final leg of its interplanetary journey.
Long Leonid (2000-11-24)

Just last week this long lovely Leonid shower meteor arced through the night. Captured on November 17/18 by photographer Bob Yen, the meteor trail spans about 70 times the apparent diameter of the full moon in the skies above Mt. Wilson, California, USA. The Leonid's path flashes from the outskirts of constellation Gemini to the triangle-shaped head of Taurus (lower right). Of course, the trail points back toward Leo, the shower's eponymous radiant, while passing near such night sky notables as galactic star cluster M35 (upper left) and Taurus's brightest star, red giant Aldebaran. Though the sky was ruled by a bright but waning Moon and brilliant Jupiter, the Leonid meteor shower still awed observers at dark sky locations with peak rates of hundreds of meteors per hour.

Image credit: Bob Yen
A High Energy Fleet (2000-11-25)

Like a fleet of futuristic starcruisers, NASA's highly successful series of High Energy Astrophysical Observatory (HEAO) spacecraft appear poised over planet Earth. Labeled A, B, and C in this vintage illustration, the spacebased telescopes were known as HEAO-1, HEAO-2, and HEAO-3 respectively. HEAO-1 and HEAO-2 were responsible for revealing to earthlings the wonders of the x-ray sky, discovering 1,000s of celestial sources of high-energy radiation. HEAO-2, also known as the Einstein Observatory, was launched in November 1978, near the date of the famous physicist's 100th birthday and was the first large, fully imaging x-ray telescope in space. HEAO-3, the last in the series, was launched in 1979 and measured high energy cosmic-ray particles and gamma-rays. These satellite observatories were roughly 18 feet long and weighed about 7,000 pounds. Their missions completed, all have fallen from orbit and burned up harmessly in the atmosphere.
Leonids Above Torre de la Guaita (2000-11-26)

Last year, the 1999 Leonids Meteor Shower came to a tremendous crescendo.  Observers in Europe observed a sharp peak in the number of meteors visible around 0210 UTC during the early morning hours of November 18.   Meteor counts then exceeded 1000 per hour - the minimum needed to define a true meteor storm.  At other times and from other locations around the world, observers typically reported respectable rates of between 30 and 100 meteors per hour.  This year, the 2000 Leonids were somewhat less impressive, although many astronomers hold much hope for the Leonids in 2001 and 2002. The above photograph is a 20-minute exposure ending just before the main Leonids peak of 1999 began.  Visible are at least five Leonids meteors streaking high above the Torre de la Guaita, an observation tower used during the 12th century in Gorina, Spain.

Image credit: Juan Carlos Casado
Earth at Night (2000-11-27)

This is what the Earth looks like at night.  Can you find your favorite country or city?  Surprisingly, city lights make this task quite possible.  Human-made lights highlight particularly developed or populated areas of the Earth's surface, including the seaboards of Europe, the eastern United States, and Japan.  Many large cities are located near rivers or oceans so that they can exchange goods cheaply by boat.  Particularly dark areas include the central parts of South America, Africa, Asia, and Australia.  The above image is actually a composite of hundreds of pictures made by the orbiting DMSP satellites. (Editor's note: Contrary to some recent press reports, this site does not have a rotating screensaver version of the above image. Also, unfortunately, we do not sell prints.  However, a high-resolution digital version of the image is available (click here or here) and an Earth at Night poster similar to this image can be ordered (click here) from other web sites.
BZ Cam Bow Shock (2000-11-28)

BZ Cam is a binary star system that is not well understood.  In most cataclysmic variables, matter from a normal star accumulates on the surface of the companion white dwarf star, eventually causing a nova-like flare as the material becomes hot enough to ignite nuclear fusion.  In BZ Cam, however, light appears to flicker unpredictably, and an unusually large wind of particles is being expelled.  Pictured above, BZ Cam's wind creates a large bow-shock as the system moves through surrounding interstellar gas.  BZ Cam lies about 2500 light-years away toward the constellation of Camelopardalis.
Leonids from Orbit (2000-11-29)

Here is what a meteor shower looks like from orbit.  During the peak of the 1997 Leonid Meteor Shower, the MSX satellite imaged from above 29 meteors over a 48 minute period entering the Earth's atmosphere.  From above, meteors create short bright streaks.  Visible beneath the meteors are clouds lit by reflected moonlight, while visible above is the constellation of Aries.  The directions of the meteor streaks are nearly parallel, confirming that the meteors  all originate from the same meteor stream.  Recent analysis of the 2000 Leonids meteor shower indicates to many astronomers that the 2001 Leonids may develop into a real meteor storm, with meteor rates perhaps exceeding one per second visible from parts of Asia.
Palomar 13's Last Stand (2000-11-30)

Globular star cluster Palomar 13 has roamed the halo of our Milky Way Galaxy for the last 12 billion years. The apparently sparse cluster of stars just left of center in this composite color digital image, it is one of the smallest, faintest globular clusters known. (The bright foreground star near bottom is unrelated and creates the spiky imaging artifacts.) Observations spanning forty years indicate that Palomar 13's galactic halo orbit is a highly eccentric one which, every one or two billion years, brings it relatively close to the galactic center. With each close approach to the Milky Way's central regions, gravitational tidal forces strip away the delicately bound cluster stars. In fact, detailed present day studies offer evidence for a dramatic end to this dwindling cluster's tidal tug of war. Palomar 13's latest close approach was only about 70 million years ago. But, when Palomar 13 again approaches the galaxy, it could well turn out to be the cluster's last stand.
A Frosty Crater On Mars (2000-12-01)

In the martian southern hemisphere, autumn has arrived. As on planet Earth, the cooler temperatures bring a seasonal frost to the landscape. Of course on Mars, the surface temperatures can be really cool, reaching below minus 100 degrees C. This detailed Mars Global Surveyor synthesized color image of Lowell crater at 52 degrees south martian latitude was recorded on October 17. Whitish frost has begun to accumulate on floor of the 201 kilometer wide crater. The crater's weathered walls suggest Lowell is relatively old. In striking contrast, two smaller, sharp-rimmed young craters are clearly superimposed on the older features near Lowell's outer rim.
SN 1006: Pieces of the Cosmic Ray Puzzle (2000-12-02)

Research balloon flights conducted in 1912 by Austrian physicist Victor Hess revealed that the Earth was constantly bombarded by high energy radiation from space - which came to be called "Cosmic Rays".  What are Cosmic Rays and where do they come from? They are now known to be mostly subatomic particles - predominantly protons and electrons - but their origin is a long standing mystery. After almost a century of study, this cosmic puzzle may have been at least partially solved by X-ray images and spectra from the ASCA satellite observatory. Pieced together to show the region around a star observed to go supernova in 1006 AD, the overlapping X-ray snapshots above (seen in false color) reveal the bright rims of the exploded star's still expanding blast wave. These ASCA observations showed for the first time that the energy spectrum of the bright regions is like that produced by extremely high energy electrons streaming through a magnetic field at nearly the speed of light. If (as expected) high energy protons are associated with these energetic electrons then supernova remnants like SN 1006 are sources of Hess' puzzling Cosmic Rays.
Earth's North Magnetic Pole (2000-12-03)

A magnetic compass does not point toward the true North Pole of the Earth.  Rather, it more closely points toward the North Magnetic Pole of the Earth.  The North Magnetic Pole is currently located in northern Canada.  It wanders in an elliptical path each day, and moves, on the average, more than forty meters northward each day.  Evidence indicates that the North Magnetic Pole has wandered over much of the Earth's surface in the 4.5 billion years since the Earth formed.  The Earth's magnetic field is created by Earth's partially ionized outer core, which rotates more rapidly than the Earth's surface.  Indicated in the above picture is Ellef Ringnes Island, the current location of Earth's North Magnetic Pole.
The Circinus Galaxy (2000-12-04)

Powerful forces are at play in the nearby Circinus Galaxy.  Hot gas, colored pink, is being ejected out of the spiral galaxy from the central region.  Much of Circinus' tumultuous gas, however, is concentrated in two rings.  The outer ring, located about 700 light-years from the center, appears mostly red and is home to tremendous bursts of star formation.  A previously unseen inner ring, inside the green disk above, is visible only 130 light years from the center on this recently released, representative color image taken by the Hubble Space Telescope.  At the very center is an active galactic nucleus, where matter glows brightly before likely spiraling into a massive black hole.  Although only 15 million light years distant, the Circinus Galaxy went unnoticed until 25 years ago because it is so obscured by material in the plane of our own Galaxy.  The galaxy can be seen with a small telescope, however, in the constellation of Circinus.
Layered Mars: An Ancient Water World? (2000-12-05)

Pictured above, layers upon layers stretch across the floor of West Candor Chasma within the immense martian Valles Marineris. Covering an area 1.5 by 2.9 kilometers, the full image from the Mars Global Surveyor spacecraft shows over 100 individual beds. Each strikingly uniform layer is smooth, hard enough to form steep edges, and is 10 to 11 meters thick. In a press conference yesterday scientists Michael Malin and Ken Edgett presented this and other new images which show that the layered patterns exist at widespread locations near the martian equator. Their results indicate that some of the layered regions may be 3.5 billion years old. On planet Earth, layered patterns like these are formed from sediment deposited over time by large bodies of water. Likewise, the layered beds on Mars may be sedimentary rock formed in ancient lakes and seas. The researchers caution, however, that other uniquely martian processes may be responsible for the layering. Did life arise on ancient Mars? Because of their possible association with water, a prime location for future searches for fossil remains of martian life would be within these layers of Mars.
Reflecting Merope (2000-12-06)

Tomorrow's picture: Faulty Earth  < | 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.
Earth's San Andreas Fault (2000-12-07)

The Earth's surface is broken.  Cracks in the Earth's crust known as faults can run for hundreds of kilometers.  These faults are frequently the sites of major earthquakes as the tectonic plates that cover the surface of the Earth shift. Pictured above is San Andreas Fault in California, one of the longest and most active faults.  Visible as the linear feature to the right of the mountains, San Andreas Fault reaches 15 kilometers deep and is about 20 million years old.  The above exaggerated-height image was created by combining radar deployed by the Space Shuttle Endeavour in February with a true-color Landsat picture.  Along San Andreas Fault, the titanic Pacific Plate is shifting relative to the huge North American Plate by an average of a few centimeters per year.  At that rate, in a few million years, the Earth's surface will look quite different than it does today.
Abell 1795: A Galaxy Cluster's Cooling Flow (2000-12-08)

Throughout the Universe, galaxies tend to swarm in groups ranging from just a handful of members to casts of thousands. Astronomers have realized since the early 1970s that the larger swarms, immense clusters of galaxies millions of light-years across, are immersed within tenuous clouds of hot gas which glow strongly in x-rays.  These clouds may have been heated by their collapse in the early Universe, but in many galaxy clusters, the gas appears to be cooling. This Chandra Observatory x-ray image reveals a striking cooling flow in the central regions of the galaxy cluster cataloged as Abell 1795. Brighter pixels in the false-color image represent higher x-ray intensities. The bright filament down the center indicates gas condensing and cooling -- rapidly loosing energy by radiating x-rays. At the very top of the filament is a large, x-ray bright galaxy. As it moved through the cluster gas cloud, the massive galaxy's gravitational influence seems to have created this cosmic wake of denser, cooling gas. Continuing to cool, the cluster gas will ultimately provide raw material to form future generations of stars.
Apollo 17 Lunarscape: A Magnificent Desolation (2000-12-09)

Buzz Aldrin, Apollo 11 Lunar Module pilot and the second human to walk on the Moon, described the lunar landscape as "a magnificent desolation". Dramatic pictures from the Apollo missions to the lunar surface testify to this apt turn of phrase. Near the Apollo 17 landing site, Family Mountain (center background) and the edge of South Massif (left) frame the lunarscape in this photo of astronaut Harrison Schmitt working alongside the lunar roving vehicle. Schmitt and fellow astronaut Eugene Cernan were the last to walk on this magnificent desolation.
Too Close to a Black Hole (2000-12-10)

What would you see if you went right up to a black hole?  Above are two computer generated images highlighting how strange things would look.  On the left is a normal star field containing the constellation Orion.  Notice the three stars of nearly equal brightness that make up Orion's Belt.  On the right is the same star field but this time with a black hole superposed in the center of the frame.  The black hole has such strong gravity that light is noticeably bent towards it - causing some very unusual visual distortions. In the distorted frame, every star in the normal frame has at least two bright images - one on each side of the black hole.  In fact, near the black hole, you can see the whole sky - light from every direction is bent around and comes back to you.  Black holes are thought to be the densest state of matter, and there is indirect evidence for their presence in stellar binary systems and the centers of globular clusters, galaxies, and quasars.

Image credit: Robert Nemiroff
(MTU)