omnianasa/nasa-apod-metadata huggingface dataset:
M61: Virgo Spiral Galaxy (1998-09-22)
M61 is a barred spiral galaxy located in the nearby Virgo Cluster of Galaxies. Visible in M61 are a host of features common to spiral galaxies: bright spiral arms, a central bar, dust lanes, and bright knots of stars.  M61, also known as NGC 4303, in similar to our own Milky Way Galaxy.  M61 was discovered by telescope in 1779 twice on the same day, but one observer initially mistook the galaxy for a comet. Light from M61 takes about 60 million years to reach us.  Recent observations of M61 have detected unpredicted high velocity gas moving in its halo.
Autumn and the Active Sun (1998-09-23)
As the Sun heads South, crossing the celestial equator today at 1:37 a.m. Eastern Time, Autumn begins for Earth's Northern Hemisphere. This Autumnal Equinox finds an increasingly active Sun steadily approaching a solar cycle maximum expected around the year 2003. The solar activity cycle is driven by a periodic winding up of the Sun's internal magnetic field. This colorized picture is a mosaic of recent ultraviolet images from the orbiting TRACE satellite sensitive to light emitted by highly charged iron atoms. Growing in number, the intricate structures visible are the Sun's hot active regions with temperatures over a million degrees Fahrenheit and their associated magnetic loops.
The North Pole Of Mars (1998-09-24)
The North Pole of Mars is capped by layers likely consisting of ice and dust deposited over millions of years. Imaged on September 12 - early Spring for Northern Mars - by the Mars Global Surveyor's camera, this synthesized wide-angle color view shows the rippled, eroded polar terrain covered with pinkish seasonal carbon dioxide frost. Dark areas bordering the polar cap are fields of sand dunes. This is the last picture scheduled to be taken by Surveyor's camera until it resumes operation in late March 1999. Over the past year of operation, the camera has taken about 2,000 pictures of Mars. Meanwhile, the spacecraft will begin its second round of aerobraking to achieve a circularized martian mapping orbit.
Twin Proto-Planetary Disks (1998-09-25)
Sun-like stars are forming - and probably planets too - hidden inside Lynds 1551, an interstellar cloud of molecular gas and dust in the constellation Taurus. Using new receivers, coordinated radio telescopes at the Very Large Array near Socorro, New Mexico, USA, can now sharply image the dusty proto-planetary disks surrounding these young stars at radio wavelengths. Just announced, this exciting example shows a false-color radio picture of twin disks in a double star system! A yellow bar indicates the scale in astronomical units (AUs) where one AU is the average distance between the Earth and Sun. The stars (unseen near the center of each disk) are about 45 AUs apart, comparable to the radius of the orbit of Pluto. Similar proto-planetary disks have been seen around single stars, but these twin disks are much smaller, each limited in size by the gravity of the nearby companion star.  In fact, if large planets form orbiting near the edges of these disks they may be ejected from the binary system.
Albert Einstein Describes Space and Time (1998-09-27)
Albert Einstein (1879-1955) is considered by many the greatest astrophysicist. He is pictured here in the Swiss Patent Office where he did much of his great work.  Einstein's many visionary scientific contributions include the equivalence of mass and energy (E=mc^2), how the maximum speed limit of light affects measurements of time and space (special relativity), and a more accurate theory of gravity based on simple geometric concepts (general relativity). One reason Einstein was awarded the 1921 Nobel Prize in Physics was to make the prize more prestigious.
A Hurricane in the Gulf (1998-09-28)
Last Friday, Hurricane Georges was photographed from space entering the Gulf of Mexico. This immense storm system, larger than most states, is expected to make landfall today.  Starting as a slight pressure difference, hurricanes grow into large spiraling storm systems of low pressure, complete with high winds and driving rain.  A hurricane is powered by evaporating ocean water, and so typically gains strength over warm water and loses strength over land. Currently offshore in the Atlantic Ocean, Hurricanes Ivan, Jeanne, and Karl swirl, but will likely stay well away from North America.   Recent GOES Satellite Image
A Peculiar Cluster of Galaxies (1998-09-29)
Far across the universe, an unusual cluster of galaxies has been evolving.  A diverse group of galaxies populate this cluster, including, on the left, an unusual galaxy showing an equatorial polar ring and a large spiral.  Above looms a large elliptical galaxy.  The reason for the small size of galaxies on the right is not yet known - these galaxies might be smaller or might just lie even farther in the distance.  Almost every spot in this picture is a galaxy. Studying distant clusters like this may help astronomers better understand when and how these cosmic giants formed.
Spiral Galaxy NGC 1232 (1998-09-30)
Galaxies are fascinating not only for what is visible, but for what is invisible.  Grand spiral galaxy NGC 1232, recently captured in detail by the new Very Large Telescope, is a good example.  The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms rotating about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them.  Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate the dynamics of the inner galaxy.  Invisible are even greater amounts of matter in a form we don't yet know - pervasive dark matter needed to explain the motions of the visible in the outer galaxy.  What's out there?
Happy 40th Birthday, NASA! (1998-10-01)
Happy Birthday, NASA! The National Aeronautics and Space Administration officially began operations on October 1, 1958, absorbing its forerunner organization the National Advisory Committee for Aeronautics, NACA. Its landmark achievements in human spaceflight include the Mercury and Gemini Projects culminating in the Apollo Project moon landings in the 1960s and early 1970s, Apollo-Soyuz and Skylab in the 1970s, and the Space Shuttle program of the 1980s and 1990s. (Pictured is the June 1998 launch of the Space Shuttle Discovery.) NASA's science programs have produced the robotic exploration of our Solar System, views of the Universe across the electromagnetic spectrum, and valuable meteorological and remote-sensing Earth observations. At birth, NASA's priorities were largely driven by the pressures and competitions of the Cold War. But looking back over 40 years, the sum of its accomplishments have produced needed new technologies and a vital new perspective on Planet Earth and the Cosmos.
Magnetar In The Sky (1998-10-02)
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. From a distance of about 20,000 light-years, SGR 1900+14 recently 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.
Sputnik: Traveling Companion (1998-10-03)
Sputnik means "traveling companion". Despite the innocuous sounding name, the launch of the Earth's first "artificial moon", Sputnik 1, by the Soviets on October 4, 1957 shocked the free world, setting 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.
One Small Step (1998-10-04)
On July 20th, 1969, a human first set foot on the Moon. Pictured above is the first lunar footprint. The footprint and distinction of the first person to walk on the Moon belong to Neil Armstrong. It has been estimated that one billion people world-wide watched Armstrong's first step - making the live transmission from a camera mounted on the lunar lander one of the highest rated television shows ever.  Upon setting foot on the moon, Armstrong said: "That's one small step for (a) man, one giant leap for mankind." The Apollo missions to the Moon have been described as the result of the greatest technological mobilization the world has known.
A Sunspot Up Close (1998-10-05)
Sometimes, small regions of the Sun appear unusually dark.  Visible above is a close-up picture of a sunspot, a depression on the Sun's face that is slightly cooler and less luminous than the rest of the Sun. The Sun's complex magnetic field creates this cool region by inhibiting hot material from entering the spot.  Sunspots can be larger than the Earth and typically last for only a few days.  This high-resolution picture also shows clearly that the Sun's face is a bubbling sea of separate cells of hot gas.  These cells are known as granules. A solar granule is about 1000 kilometers across and lasts about 10 minutes. After that, many granules end up exploding.
Comet Williams in 1998 (1998-10-06)
The brightest comet in the sky right now is Comet Williams. Moving slowly though the constellation of Centaurus, Comet Williams, at magnitude 8, is visible to Southern Hemisphere observers with binoculars. In ten days, Comet Williams will reach its closest point to the Sun, although it will still be farther from the Sun than the Earth.  Comet Williams should become visible to many Northern Hemisphere observers in late November.  At magnitude 10, however, it might require a small telescope to see.  Comet Williams was discovered in early August by Peter Williams. The above image was taken August 25th from Australia.
Ocean Planet Pole To Pole (1998-10-07)
The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument onboard the orbiting SeaStar spacecraft can map subtle differences in Earth's ocean color. These North (left) and South Pole projections are based on SeaWiFS measurements made between September 1997 and July 1998. The "color" strongly depends on how sunlight is reflected by free-floating phytoplankton - photosynthesizing organisms which contain chlorophyll. Chlorophyll absorbs blue and red light and reflects green. Since the tiny phytoplankton are tremendously important, forming the beginning of the food chain for sea life, SeaWiFS color maps can help track the activity of ocean planet Earth's biosphere.
Far Side of the Moon (1998-10-08)
Locked in synchronous rotation, the Moon always presents its well-known near side to Earth. But from lunar orbit, Apollo astronauts also grew to know the Moon's far side. This sharp picture from Apollo 16's mapping camera shows the eastern edge of the familiar near side (left) and the strange and heavily cratered far side of the Moon. Surprisingly, the rough and battered surface of the far side looks very different from the near side which is covered with smooth dark lunar maria. The likely explanation is that the far side crust is thicker, making it harder for molten material from the interior to flow to the surface and form the smooth maria.
M27: Not A Comet (1998-10-09)
While searching the skies above 18th century France for comets, astronomer Charles Messier diligently recorded this object as number 27 on his list of things which are definitely not comets. So what is it? Well, 20th century astronomers would classify it as a Planetary Nebula ... but it's not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is now known to be an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light. Known by the popular name of the "Dumbbell Nebula", the beautifully symmetric interstellar gas cloud is about 1,200 light-years away in the constellation Vulpecula. This gorgeous synthetic color picture of M27 was produced during testing of the European Southern Observatory's new Very Large Telescope.
Maria Mitchell Inspires a Generation (1998-10-10)
"Do not look at stars as bright spots only - try to take in the vastness of the universe." October 1st was the 151st anniversary of the day Maria Mitchell swept the sky with her telescope and discovered the comet of 1847 (comet Mitchell 1847VI). Honored and recognized internationally for her discovery, Mitchell, who lived from 1818 to 1889, became one of the most famous American scientists of her day.  Vassar College appointed Mitchell the first woman Professor of Astronomy and she remained the only woman ever elected to the American Academy of Arts and Sciences until 1943.  Mitchell mentored a generation of scientists, and is fondly remembered for her ability to motivate.  "We especially need imagination in science," Maria Mitchell said, "Question everything."
Resolving Mira (1998-10-11)
Most stars appear only as points of light. Early last year, Betelgeuse became the second star, after our Sun, to have it surface resolved.  Later last year, Mira was added to the list. Mira A is a red giant star undergoing dramatic pulsations, causing it to become more than 100 times brighter over the course of a year.  Mira was discovered to be the first variable star 401 years ago today by David Fabricus.  Mira can extend to over 700 times the size of our Sun, and is only 400 light-years away. The above photograph taken by the Hubble Space Telescope shows the true face of Mira. But what are we seeing?  The unusual extended feature off the lower left of the star remains somewhat mysterious.  Possible explanations include gravitational perturbation and/or heating from Mira's white dwarf star companion
The Hubble Deep Field in Infrared (1998-10-12)
Galaxies this faint have never been seen before. In 1996 the Hubble Space Telescope (HST) created one of the most famous pictures of modern astronomy, the Hubble Deep Field (HDF).  Now HST has returned to a piece of the HDF for a long exposure by its new NICMOS camera, sensitive to infrared light. The resulting image, shown above in representative color, shows known galaxies in a new light, and previously unknown galaxies probably farther than anything ever seen before. Galaxies as dim as magnitude 30 are visible. Astronomers are learning from the HDF how different the young universe was from the familiar universe of today.
In the Center of the Dumbbell Nebula (1998-10-13)
Here's part of the Dumbbell Nebula that you can't see through binoculars.   To see this, we suggest a sophisticated spectrograph attached to a telescope with an 8-meter aperture. Pictured above is the central part of the Dumbbell Nebula, also known as M27 and NGC 6853.  The Dumbbell is a planetary nebula created by the aging bright star visible just right of center.  The nebula, located in the constellation Vulpecula, is thousands of years old. Visible in this false-color photograph is glowing hydrogen gas (green) and enigmatical globules of dense molecular gas and dust (red).
The World's Largest Ozone Hole (1998-10-14)
It's back, and it's bigger than ever. The ozone hole that has been a cause of concern in recent years has again reformed over Earth's South Pole.  The seasonal recurrence of the ozone hole was expected, although the size of the hole has never been so large this early in the season.  Ozone is important because it shields us from damaging ultraviolet sunlight. Ozone is vulnerable, though, to CFCs and halons being released into the atmosphere.  The ozone hole's large size is probably related to unusually low temperatures, allowing CFC byproducts like chlorine to react with atmospheric ozone molecules with greater efficiency.  In the above false-color picture taken earlier this month, low ozone levels are shown in blue.
A Great Day For SOHO (1998-10-15)
The last 10 days have been great days for SOHO, the space-based SOlar and Heliospheric Observatory. Contact was completely lost with this international research spacecraft over 3 months ago but recovery teams have reacquired control of SOHO and, beginning October 5th, have been successfully switching on its scientific instruments. This October 13th view of the Sun in the light of ionized Helium atoms was recorded by the restored EIT instrument. It shows bright active regions and lofty prominences above the solar limb. North is toward the left rather than the top as the spacecraft's orientation has not yet been fully adjusted. (For a full Sun / full resolution view, click on the picture!) With the solar cycle approaching a maximum in the coming years, excitement continues to build as it becomes very likely that SOHO will be able to resume its unprecedented exploration of solar phenomena.
Io Aurora (1998-10-16)
Alluring aurora surrounding Io (eye-oh) appear as a ghostly glow while the volcanic moon orbits within Jupiter's dark shadow. Gas giant Jupiter is off to the right of this image, recorded in May by the robot Galileo spacecraft's solid state imaging camera from a distance of about 1.3 million kilometers. Energetic charged particles colliding with Io's atmospheric gases create the vivid colors and produce the red and green glow analogous to the aurora of Earth. The striking blue light is caused by dense volcanic plumes and may indicate regions electrically connected to Jupiter itself.
A Giant Globular Cluster in M31 (1998-10-17)
This cluster of stars, known as G1, is the brightest globular cluster in the whole Local Group of galaxies. Also called Mayall II, it orbits the center of the largest nearby galaxy: M31.  G1 contains over 300,000 stars and is almost as old as the entire universe.  In fact, observations of this globular star cluster show it to be as old as the oldest of the roughly 250 known globular clusters in our own Milky Way Galaxy.  Two bright foreground stars appear in this image of G1 taken with the orbiting Hubble Space Telescope in July of 1994.  It shows detail in the distant cluster comparable to ground-based telescopic views of globular star clusters in our own Galaxy.
Saturn's Rings Seen Sideways (1998-10-18)
Saturn's rings are actually very thin.  This picture from the Hubble Space Telescope was taken on August 6, 1995 when the rings lined up sideways as seen from Earth.  Saturn's largest moon Titan is seen on the left, and Titan's shadow can be seen on Saturn's cloud tops!  Titan itself looks a brownish color because of its thick atmosphere. Four other moons of Saturn can be seen just above the ring plane, which are, from left to right: Mimas, Tethys, Janus, and Enceladus. If you look carefully, you will note that the dark band across the planet is actually the shadow of the rings, and is slightly displaced from the real rings - which are best seen away from the planet.  Saturn's rings are not solid - they are composed of ice chunks which range in size from a grain of sand to a house.
Olympus Mons From Orbit (1998-10-19)
Tomorrow's picture: Infrared Uranus  < 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.
Infrared Uranus (1998-10-20)
The Sun's third largest planet usually looks quite dull.  Uranus typically appears as a featureless small spot in a small telescope or a featureless large orb in a large telescope.  Last August, however, the Hubble Space Telescope was able to photograph Uranus in infrared light, where the distant planet better shows its unusual clouds, rings, and moons.  Recent analysis indicates that clouds seen here in orange appear to circle Uranus at speeds in excess of 500 kilometers per hour.  Comparisons to earlier photographs show a slight precession shift in the brightest of Uranus' rings. Several of Uranus' numerous small moons are visible.
The Case of the Missing Aurora (1998-10-21)
Sometimes, near midnight, auroras suddenly stop. Nobody knows why.  This nightside gap in aurora was confirmed recently by D. Chua (U. Washington) and colleagues in data from the Ultraviolet Imager onboard the Polar spacecraft.  The gap appears from space as a slight break in a more full auroral arc surrounding a magnetic pole of the Earth.  Pictured above are clouds and auroras occurring last August near Wildcat Mountain in Wisconsin.
Jupiter: When Storms Collide (1998-10-22)
Sometime in February, two of three long-lived Jovian storm systems known as "white ovals" apparently collided and merged -- forming what is now likely the second largest storm in the Solar System, after the famous Great Red Spot. The whitish, oval-shaped storms in Jupiter's banded atmosphere have been telescopically studied since the 1930s, but details of this surprising merger are unknown as Jupiter and Earth were on opposite sides of the Sun when it happened. The aftermath is shown in the (top panel) Hubble Space Telescope picture, taken in July as part of the evidence investigators are using to reconstruct the facts of the case. Centered are the swirling white clouds of the newly created storm system which is about as wide as planet Earth. At its left is the remaining smaller white oval which seems to be drifting away from the larger new storm. Atmospheric temperature data from the Galileo spacecraft represented in the (bottom panel) false-color image show the new storm as a dark feature, cooler than its surroundings.
Seyfert Galaxy NGC 7742 (1998-10-23)
This might resemble a fried egg you've had for breakfast, but it's actually much larger. In fact, ringed by blue-tinted star forming regions and faintly visible spiral arms, the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years away in the constellation Pegasus, NGC 7742 is known to be a Seyfert galaxy - a type of active spiral galaxy with a center or nucleus which is very bright at visible wavelengths. Across the spectrum, the tremendous brightness of Seyferts can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores. This beautiful color picture is courtesy of the newly inaugurated Hubble Space Telescope Heritage Project.
The Sun Also Rises (1998-10-24)
Sunrise seen from low Earth orbit by the shuttle astronauts can be very dramatic indeed ( and the authors apologize to Hemingway for using his title!). In this breathtaking view, the Sun is just visible peaking over towering anvil-shaped storm clouds whose silhouetted tops mark the upper boundary of the troposphere, the lowest layer of planet Earth's atmosphere. Sunlight filtering through suspended dust causes this dense layer of air to appear red. In contrast, the blue stripe marks the stratosphere, the tenuous upper atmosphere, which preferentially scatters blue light.