juliensimon/nasa-apod huggingface dataset:
Bound For Mars (1997-05-22)

Two NASA spacecraft, Mars Global Surveyor and Mars Pathfinder, are presently approaching the red planet. Pathfinder is scheduled to land on July 4th and Global Surveyor due to enter orbit in September. Recent studies of the Martian climate, motivated by this impending invasion of spacecraft from Earth, have indicate that Mars weather is more chaotic than previously thought - showing abrupt swings between "hot and dusty" and "cold and cloudy". These Hubble Space Telescope images from March 1997 show the Northern Hemisphere in early Martian summer, with a receding polar cap and whitish water-ice clouds. The left image is centered on Ares Valles, Pathfinder's landing site, while in the right image, towering Tharsis mountains (massive extinct volcanoes) can be seen poking through the clouds. Stretching to the eastern edge of the righthand image (at lower right) is the Valles Marineris, an immense canyon system. Martian weather reports will play an important role in mission planning. Both spacecraft rely on the Martian atmosphere for braking maneuvers and Pathfinder's lander and rover are solar powered.
The Heart Of Orion (1997-05-23)

Newborn stars lie at the heart of the Orion Nebula, hidden from view by the dust and gas of the giant Orion Molecular Cloud number 1 (OMC-1). Sensitive to invisible infrared wavelengths, Hubble's recently installed NICMOS camera can explore the interior of OMC-1 detecting the infrared radiation from infant star clusters and the interstellar dust and atoms energized by their intense starlight. In this false color picture, stars and the glowing dust clouds which also scatter the starlight appear yellowish orange while emission from hydrogen gas is blue. The dramatic image reveals a wealth of details, including many filaments and arcs of gas and dust -- evidence of violent motions stirred-up by the emerging stars. The bright object near the center is the massive young star "BN" (named for its discoverers Becklin and Neugebauer). The pattern of speckles and ripples surrounding BN and other bright stars are image artifacts.
Saturn's Rings Seen Sideways (1997-05-24)

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 moon's 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.
A High Energy Fleet (1997-05-25)

Looking 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 near the date of the famous physicist's 100th birthday (November, 1978) 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.
Old Faithful Meets Hale-Bopp (1997-05-26)

As Comet Hale-Bopp leaves our Northern Skies, it provides us with yet another burst of joy.  On May 11th the fading comet was photographed behind the famous "Old Faithful" water geyser of Yellowstone National Park, Wyoming, USA, Planet Earth.  Perhaps more familiar to Earth Dwellers than the dark geysers on Neptune's moon Triton, the gas geysers on Jupiter's moon Io, and the dirty water geysers hypothesized on Jupiter's moon Europa, Earth's Old Faithful is also reliable - every 60-80 minutes it gushes a plume of water and steam high into the air.  Comet Hale-Bopp will continue to be visible to observers in the Southern Hemisphere as it moves away from the Sun towards the outer Solar System.

Image credit: D. 
Vanderhoff, A. Frazier
Moonrise, Planet Earth (1997-05-27)

During the Astro-1 astronomy mission of December, 1990, Space Shuttle astronauts photographed this stunning view of the full moon rising above the Earth's limb. In the foreground, towering clouds of condensing water vapor mark the extent of the troposphere, the lowest layer of the planet's life-sustaining atmosphere. Strongly scattering blue sunlight, the upper atmospheric layer, the stratosphere, fades dramatically to the black background of space. Moon and clouds are strong visual elements of many well known portraits of Planet Earth, including Ansel Adams' famous "Moonrise, Hernandez, New Mexico", photographed in November of 1941.
Mars: Just The Fiction (1997-05-28)

For centuries, astronomers have observed Mars, patiently compiling many facts and theories. Like a distant mirror of Earth dwellers' hopes and fears for the future, Mars, the fourth planet from the sun, has inspired profound works of fiction as well. Classics of the science fiction genre with visions of Earth's alluring planetary neighbor include H.G. Wells' terrifying "War of the Worlds", Edgar Rice Buroughs' John Carter adventure series (Thuvia, Maid of Mars, The Gods of Mars, A Princess of Mars, The Warlord of Mars),  Robert Heinlein's youthful "Podkayne of Mars", and Ray Bradbury's reflective and philosophical "The Martian Chronicles". Through the years scientific theories about Mars have been disproven, but the sense of wonder and adventure embodied in these works of fiction remain with us. As two spacecraft from Earth now draw close to the red planet- in dreams, desires, and a quest for knowledge - we are once again bound for Mars.
Southern Neptune (1997-05-29)

Neptune, the Solar System's outermost gas giant planet, is 30 times farther from the Sun than Earth. Twelve years after a 1977 launch, Voyager 2 flew by Neptune and found surprising activity on a planet that receives only 3 percent as much sunlight as Jupiter. In its brief but tantalizing close-up glimpse of this dim and distant world, the robot spacecraft recorded pulses of radio emission, zonal cloud bands, and large scale storm systems with up to 1500 mile per hour winds - the strongest measured on any planet. This mosaic of 5 Voyager images shows Neptune's Southern Hemisphere. Cloud bands and the Earth-sized, late "Great Dark Spot" with trailing white clouds located at about 22 degrees southern latitude are clearly visible.  The distance from the Great Dark Spot feature to Neptune's South Pole (image center) is about 17,000 miles.
A Cosmic Snowball (1997-05-30)

Like cosmic snowballs, fluffy comet-like objects the size of houses and composed mostly of water-ice, may be pummeling planet Earth 5 to 30 times a minute. This controversial theory was originally proposed in 1986 by Dr. Louis Frank (U. Iowa) based on data from NASA's Dynamics Explorer 1. It is further supported by recently reported findings from the one year old POLAR spacecraft. Representing a previously unknown class of Solar System objects, these proposed small, icy comets disintegrate in the upper atmosphere at altitudes of 600 to 15,000 miles and so do not pose an impact threat to the Earth's surface or even to spacecraft in low Earth orbit. On breaking up, however, they produce a fleeting trail of clouds of water vapor. Traces of these transient, extremely high altitude clouds can be detected by down looking spacecraft designed to monitor the near-Earth environment. The suspected trail of one such cosmic snowball vaporizing over the Atlantic Ocean and Western Europe at an altitude of 5,000 to 15,000 miles is seen above. It was recorded in a 54 second exposure by POLAR's Visible Imaging System in September of 1996. A map has been added as a background for location reference. If continuous over the history of the Earth's formation, this relatively gentle cosmic snow shower would have been a major source of water for Earth's present life-nurturing oceans and possibly even a source of simple organic compounds.
Saturn with Moons Tethys and Dione (1997-05-31)

Saturn and two of its larger moons - Tethys and Dione - were photographed by the Voyager 1 spacecraft which flew by the planet in November of 1980. This picture gives an indication of Saturn's extensive ring system, which can be seen casting a shadow on the planet, as does Tethys. Saturn's rings are composed of many chunks of ice ranging in size from a pebble to a car. The rings have several large gaps, the largest of which is clearly visible in the picture and is named the Cassini Division, after its discoverer.  Saturn appears brighter than most stars in the sky, and its rings can be discerned with a small telescope. A new spacecraft - Cassini - will visit Saturn and is currently scheduled for launch later in 1997.
M100: A Grand Design (1997-06-01)

Majestic on a truly cosmic scale, M100 is appropriately known as a Grand Design spiral galaxy. A large galaxy of over 100 billion or so stars with well defined spiral arms, it is similar to our own Milky Way. One of the brightest members of the Virgo Cluster of galaxies , M100 (alias NGC 4321) is 56 million light-years distant in the spring constellation of Coma Berenices. This Hubble Space Telescope image of the central region M100 revealing bright stars and intricate winding dust lanes was made in 1993 with the Wide Field and Planetary Camera 2. Studies of stars in M100 have recently played an important role in determining the size and age of the Universe.
Bright Star Knots in NGC4038
Credit: (1997-06-02)

This galaxy is having a bad millennium. In fact, the past 100 million years haven't been so good, and probably the next billion or so should be quite tumultuous.  NGC 4039 was a normal spiral galaxy, minding its own business, when NGC 4038 crashed into it.  The evolving wreckage, known as the "Antennae", is pictured above. As gravity pulls each galaxy apart, clouds of gas slam into each other and bright blue knots are formed. These knots are large clusters of stars imbedded in vast regions of ionized hydrogen gas. The high abundance of relatively dim star clusters is quite unlike our Milky Way's globular cluster system, though.  Perhaps some of these young star clusters will go on to form globular clusters, while others will disperse through close gravitational encounters. The above picture is centered around the larger of the two interacting galaxies: NGC 4038.  The diagonal streak across the upper left is unrelated to the colliding galaxies. The color contrast in the above three-color mosaic was chosen to highlight extended features.

Image credit: AURA
Venus' Once Molten Surface
Credit: (1997-06-03)

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.
Tarantula
Credit: (1997-06-04)

NGC 2070 is an immense star forming region in a nearby galaxy known as the Large Magellanic Cloud. Its spidery appearance is responsible for its popular name, "The Tarantula Nebula", except that this tarantula is about 1,000 light-years across, and 165,000 light-years away in the southern constellation Dorado. If it were at the distance of the Orion Nebula, the nearest stellar nursery to Earth, it would appear to cover about 30 degrees on the sky or about 60 full moons. The spindly arms of the Tarantula Nebula surround the 30 Doradus Star Cluster which contains some of the intrinsically brightest, most massive stars known. This celestial Tarantula is also seen near the site of the closest recent Supernova.
Small Star
Credit: (1997-06-05)

A dim double star system cataloged as Gliese 623 lies 25 light-years from Earth, in the constellation of Hercules. The individual stars of this binary system were distinguished for the first time when the Hubble Space Telescope's Faint Object Camera recorded this image in June 1994. They are separated by 200 million miles - about twice the Earth/Sun distance. On the right, the fainter Gliese 623b is 60,000 times less luminous than the Sun and approximately 10 times less massive. The fuzzy rings around its brighter companion, Gliese 623a, are image artifacts. The lowest mass stars are classified as red dwarf stars, but even red dwarfs are massive enough to trigger hydrogen fusion in their cores to sustain their feeble starlight. Slightly less massive objects, known as brown dwarfs, can shine only briefly as their central temperatures are too low to utilize hydrogen as nuclear fuel. The present estimates of the mass of Gliese 623b are right at this red dwarf/brown dwarf border but future observations should help clarify the nature of one of our Galaxy's small stars. Dim and difficult to detect, an abundance of objects like Gl623b has been proposed as a possible solution to the mystery of "Dark Matter" in the Universe.
Boosting Compton
Credit: (1997-06-06)

ven great observatories need a boost from time to time -- including the orbiting Compton Gamma-Ray Observatory. Sparkling reflections and the bright limb of the Earth are visible in this 1991 window view of Compton's release into orbit by the crew of the Space Shuttle Atlantis. Named after the American Nobel-prize-winning physicist, Arthur Holly Compton, the Compton Observatory has spent the last 6 years making spectacular discoveries while exploring the Universe at extreme gamma-ray energies. From its post over 240 miles above the Earth's surface, the 17 ton satellite still experiences enough atmospheric drag to cause its orbit to deteriorate over time.  But NASA controllers have just completed a complex two month long series of firings of Compton's on-board thrusters which has raised its orbit to an altitude of over 300 miles. This reboost (Compton's second in 6 years) should allow it to continue its voyage of exploration of the distant high-energy Universe until about 2007. What if you could see gamma rays?
Apollo 15: Driving on the Moon (1997-06-07)

Apollo 15 astronaut James Irwin works on the first Lunar Roving Vehicle, before he and fellow astronaut David Scott take it out for a drive. Sloping up behind the lunar module "Falcon" on the left are lunar mountains Hadley Delta and Apennine Front, while about 5 kilometers behind Irwin is St. George Crater. The explorations conducted during the Apollo lunar missions discovered much about our Moon, including that the Moon is made of ancient rock, that the Moon's composition is similar to Earth's, that life is not evident there, that the Moon underwent a great hot melting in its distant past, that the Moon has suffered from numerous impacts as shown by its craters, and that the Moon's surface is covered by a layer of rock fragments and dust.
M101: An Ultraviolet View
Credit: (1997-06-08)

This giant spiral galaxy, Messier 101 (M101), was photographed by the Ultraviolet Imaging Telescope (UIT). UIT flew into orbit as part of the Astro 2 mission on-board the Space Shuttle Endeavour in March 1995. The image has been processed so that the colors (purple to white) represent an increasing intensity of ultraviolet light. Pictures of galaxies like this one show mainly clouds of gas containing newly formed stars many times more massive than the sun, which glow strongly in ultraviolet light. In contrast, visible light pictures of galaxies tend to be dominated by the yellow and red light of older stars. Ultraviolet light, invisible to the human eye, is blocked by ozone in the atmosphere so ultraviolet pictures of celestial objects must be taken from space.
An Auroral Ring on Jupiter (1997-06-09)

Do other planets have aurora?  Terrestrial and spacecraft observations have found evidence for aurora on Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. In the above false-color photograph, a good portion of an auroral ring was captured recently in optical light by the Galileo spacecraft in orbit around Jupiter.  Auroral rings encircle a planet's magnetic pole, and result from charged particles spiraling down magnetic field lines. Although the surroundings near Jupiter are much different than Earth, the auroral rings appear similar.
Hale-Bopp Above the Cinqui Torri Mountains (1997-06-10)

Hale-Bopp may be the most photographed comet in history.  Above, our photogenic giant flying snowball appeared last month as a backdrop to the "Cinque Torri" Mountains near Contina d'Ampezzo, Italy.  Although the comet is still fairly bright, it is fading as it recedes from the Sun, and is now more easily visible from Earth's southern hemisphere.  Having shed a few meters of ice and rock from its surface, Comet Hale-Bopp will coast to the outer Solar System, and return again in another 2400 years.

Image credit: G. Menardi 
 (Col Druscie Obs.,
ACC)
Young Suns (1997-06-11)

The star cataloged as NGC2264 IRS is normally hidden from the inquiring gaze of optical telescopes. It resides in the midst of the obscuring gas and dust of a nearby star forming region popularly known as the Cone Nebula. Imaged in penetrating infrared light by the Hubble Space Telescope's newly operational NICMOS instrument, this young and massive star was found to be surrounded by six "baby" sun-like stars - all within less than a tenth of a light-year of their "big brother". The diffraction spikes and rings surrounding big brother are image artifacts. Astronomers believe that the high speed winds generated by the massive star compressed nearby material causing the formation of the smaller stars in a text book example of triggered star formation. The newly created suns appear to lie along an otherwise invisible boundary where the high speed gas has collided with the wall of a denser molecular cloud. NGC2264 IRS also seems to be the source of the outflow which created the striking cone shape of the optical nebula.
Jupiter's Dry Spots (1997-06-12)

Known for its spectacular images of Jupiter's moons, Io, Ganymede, Callisto, and Europa, the robot spacecraft Galileo has also aggressively explored the Jovian atmosphere. In December of 1995, Galileo's atmospheric probe descended into Jupiter's clouds and reported a surprising absence of water. It is now believed that the probe entered through one of Jupiter's dry spots, similar to the dark region in this image of the swirling Jovian cloud deck. The smallest features visible here are tens of miles in size. These dry regions appear to correspond to locations where winds converge creating downdrafts. The downdrafts generate local cloudless clearings through which Jupiter's deeper warmer layers can be glimpsed. Just as the dark areas are extremely dry, the surroundings are full of moisture. The contrast is analogous to the desert and tropics of Earth.
Streaming From A Black Hole (1997-06-13)

Glowing gas clouds are streaming from the core of galaxy NGC4151 at hundreds of thousands of miles per hour. A powerful tool, the Hubble Space Telescope's new STIS instrument, makes it possible to map out the cloud velocities - producing this false color "velocity map" for the central regions of NGC4151. The horizontal line is light from the intensely bright region near the galaxy nucleus.  Emission at two wavelengths characteristic of Oxygen atoms in the gas clouds is visible along this line. Below the line the emission is displaced to the left, indicating motion toward us (blue shift); above the displacement is to the right indicating a receding motion (red shift). Where do the clouds come from? As evidence mounts, the widely accepted explanation for energetic nuclear activity in galaxies is based on material spiraling into a central black hole with over a million times the mass of our sun. The rotating disk of interstellar debris which develops is thought to blast out high velocity jets along the axis of the disk. Do all galaxies contain supermassive black holes?
The Early Universe (1997-06-14)

What did our universe look like when it was young? To answer this, cosmologists run sophisticated computer programs tracking the locations of millions of particles. The above animated frame is the result of such a calculation and shows how our universe might have looked when it was just a fracton of its current age.  The universe started out very smooth - matter and light are spread almost uniformly. As time progressed, gravity caused slight gatherings of mass to accrete so that ever greater conglomerations formed.  Galaxies and long filaments formed - which are shown by the bright patches and streaks in the above frame. An IMAX movie including hundreds of these frames was nominated for an academy award.
Rockets and Robert Goddard (1997-06-15)

Robert H. Goddard, one of the founding fathers of modern rocketry, was born in Worcester Massachusetts in 1882. As a 16 year old, Goddard read H.G. Wells' science fiction classic "War Of The Worlds" and dreamed of spaceflight. By 1926 he had designed, built, and launched the world's first liquid fuel rocket. During his career he was ridiculed by the press for suggesting that rockets could be flown to the Moon, but he kept up his experiments in rocketry supported in part by the Smithsonian Institution and championed by Charles Lindbergh. Pictured above in 1937 in the desert near Roswell, New Mexico, Goddard examines a nose cone and parachute from one of his test rockets. Widely recognized as a gifted experimenter and engineering genius, his rockets were many years ahead of their time. He died in 1945 holding over 200 patents in rocket technology. A liquid fuel rocket constructed on principles developed by Goddard landed humans on the Moon in 1969.
APOD is Two Years Old Today (1997-06-16)

The first Astronomy Picture of the Day (APOD) appeared two years ago today. Pictured above is a scene surrounding the creation of an early APOD, depicting the famous astronomer Tycho Brahe demonstrating a celestial globe to Emperor Rudolph II.  The image of a possible optical counterpart to a gamma-ray burst appears on the back wall.  In Tycho's day, humanity discovered the nature of the Earth and the geometry of the Solar System.  The times we live in are even more fascinating as we explore the nature of our Solar System and the geometry of our whole universe.  APOD continues to chronicle these events by finding, presenting ,and annotating the most important astronomical pictures of our time, and cataloging them in an indexed and searchable archive. Link to APOD and discover the cosmos! With over five million pages served, we thank NASA,  Michigan Tech, USRA, and most of all our readers, for their continued support.