omnianasa/nasa-apod-metadata huggingface dataset:
Magnetar (1998-05-27)
What do you call a neutron star with a super-strong magnetic field? You guessed it ... a Magnetar. Imagine a star with more mass than the sun, the density of a neutron, and a magnetic field about a thousand trillion (a one followed by 15 zeroes) times stronger than Earth's. It sounds exotic and theoretical, but strong evidence for the existence of magnetars has recently been announced based on data from orbiting X-ray and Gamma-ray observatories. Neutron stars are formed in the violent crucibles of stellar explosions. Some become pulsars with relatively weak magnetic fields, spinning and emitting pulses of electromagnetic radiation as their rotation slows. However, astronomers now believe that some become magnetars, with magnetic fields so intense that the solid neutron star crust buckles and shifts under its influence. The resulting star quakes could repeatedly generate brief flashes of hard X-rays and soft gamma-rays giving rise to the rare but mysterious "soft gamma repeaters" (not to be confused with " gamma-ray bursters"!). This still frame from an animation illustrating a spinning, flashing magnetar emphasizes the looping magnetic field lines embedded in the X-ray hot neutron star surface.
Afterglow (1998-05-28)
This sequence of three false color X-ray pictures from the Italian/Dutch BeppoSAX satellite follows the fading glow from a gamma-ray burster. This burster triggered orbiting gamma-ray observatories on December 14, 1997 and within 6.5 hours the sensitive X-ray cameras onboard BeppoSAX had been turned to record the first image (left) of the afterglow. Each image covers a field about the size of the full moon with the position of the afterglow indicated by the white circle. The first two pictures were taken 6 hours apart, while the final picture was made 2 days after the gamma-ray burst. Initiated by an unknown but immensely powerful explosive event, gamma-ray bursts are thought to be caused by blast waves of particles moving at nearly the speed of light. The expanding cosmic fireball produces seconds-long bursts of gamma-rays and then as it slows and sweeps up surrounding material, generates an afterglow visible for many days at X-ray, optical, and radio energies. Evidence indicates that this burst originated at a distance of 12 billion light-years requiring a fantastic and extreme energy source. What could power a gamma-ray burst?
An Extrasolar Planet? (1998-05-29)
This infrared Hubble Space Telescope view may contain the first ever direct image of a planet outside our own solar system. The picture shows a very young double star located about 450 light-years away toward the constellation of Taurus. Cataloged as TMR-1 (Taurus Molecular Ring star 1), the binary system is still embedded in the dust cloud that formed it. This double star and dust cloud are the brightest grouping in the picture, glowing strongly at infrared wavelengths. A filament extends from the binary system toward the lower left and points toward the spot of light representing the candidate planet. Astronomers believe this planet is a "runaway" object which was gravitationally ejected, the filament tracing the path to its present location at about 1500 times the Earth-Sun distance from the parent star system. Models suggest that the planet and binary system are a mere 300,000 years old, with the planet having a mass of about 2 to 3 Jupiters. Future observations to look for the planet's continued runaway motion and spectral signatures should be able to confirm the nature of this object. While this and other tantalizing discoveries of extrasolar planetary objects and protoplanetary disks don't seem to offer direct examples of solar systems like our own, they do strongly hint that planet formation is a varied and common process.   Update: TMR-1 likely just a background star.
Water World (1998-05-30)
Water (Dihydrogen Oxide, H2O) is a truly remarkable chemical compound, fundamental to life on Earth. Earth is the only planet in the Solar System where the present surface temperature and pressure allow the three forms of water, solid (ice), liquid (ocean), and gas (water vapor condensing in clouds) to exist simultaneously. Water in one of these forms accounts for everything visible in this view of Earth from space looking north at the Bering Sea and the coast of Alaska, USA, around Bristol Bay.
Phobos: Doomed Moon of Mars (1998-05-31)
Phobos is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These Martian moons may well be captured asteroids originating in the asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of the Solar System. In this 1977 Viking orbiter image, the largest moon, Phobos, is seen to be a heavily cratered asteroid-like object. It is about 17 miles across and zips through the Martian sky completing an orbit in less than 8 hours. Phobos orbits so close to Mars, (about 3,600 miles above the surface compared to 250,000 miles for our Moon) that gravitational tidal forces are dragging it down. In 100 million years or so it should crash into the surface or be shattered by stress caused by the relentless tidal forces, the debris forming a ring around Mars.
Solar Flares Cause Sun Quakes (1998-06-01)
An 11th magnitude quake has been recorded on the Sun, immediately following a moderate solar flare.  The quake was the first ever recorded on the Sun, but only because astronomers have only recently figured out when and how to find them using the orbiting SOHO spacecraft. Dark waves from the quake can be seen in the above picture spreading out from an explosive bright flare. The solar ripples are similar in appearance to waves caused by a rock thrown into a pond.  The magnitude and evolution of these quakes gives information about the physical nature of solar flares, the surface of the Sun, and even the Sun's interior.
NGC 6302: The Butterfly Nebula (1998-06-02)
The Butterfly Nebula is only thousands of years old.  As a central star of a binary system aged, it threw off its outer envelopes of gas in a strong stellar wind. The remaining stellar core is so hot it ionizes the previously ejected gas, causing it to glow.  The different colors of this planetary nebula are determined by small differences in its composition.  This bipolar nebula will continue to shine brightly for only a few thousand more years, after which its central star will fade and become a white dwarf star. The above picture is one of the first ever taken by the Very Large Telescope (VLT), a new 8.2-meter telescope located in Chile.
Martian Crater Shows Evidence of Dried Pond (1998-06-03)
Did a pond once exist in this Martian crater? Recent photographs by the spacecraft Mars Global Surveyor, currently in orbit around Mars, show features unusual for Mars yet similar to a dried pond on Earth.  Previously, much evidence suggested the effects of ancient channels of flowing water on Mars, but less evidence had been found for dried pools of water.  Islands and bays on this crater floor indicate an accumulation of some liquid, however, a hypothesis consistent with channels found on the (inset) crater walls.   As it is also possible the features were formed by other mechanisms including flowing lava, future observations and analysis will be needed to say for sure.
Comet SOHO and Nebulae in Orion (1998-06-04)
Astrophotographer Michael Horn captured this gorgeous view of comet SOHO in the dark night sky above Wandibindle, Queensland, Australia on May 23rd. On this date, comet SOHO was moving against the background of the nebula-rich constellation of Orion. South is up in the picture which shows SOHO's bright head or coma and long tail extending past the glowing gas clouds and dark dust lanes of the Flame and Horsehead nebulae.  Alnitak, the bright star above and to the right of the cometary coma, is also known as Zeta Orionis, the eastern-most of the three stars in Orion's belt. Southern Hemisphere observers report that comet SOHO has recently undergone a dramatic increase in brightness.
Neutrinos in the Sun (1998-06-05)
Neutrinos, along with things like electrons and quarks, are fundamental pieces of matter according to physicists' Standard Model. But neutrinos are hard to detect. Readily produced in nuclear reactions and particle collisions, they can easily pass completely through planet Earth without once interacting with any other particle. Constructed in an unused mine in Japan, an ambitious large-scale experiment designed to detect and study neutrinos is known as Super-Kamiokande or "Super-K". Only(!) 500 days worth of data was needed to produce this "neutrino image" of the Sun, using Super-K to detect the neutrinos from nuclear fusion in the solar interior. Centered on the Sun's postion, the picture covers a significant fraction of the sky (90x90 degrees in R.A. and Dec.). Brighter colors represent a larger flux of neutrinos.  News: In a tantalizing recent announcement, an international collaboration of Super-K researchers has now presented evidence that the ghostly neutrinos undergo quantum mechanical oscillations, changing their particle identities and quantum properties over time. Theorists have considered neutrinos to be massless particles but these oscillations would imply that they have a very small (but nonzero) mass. Astrophysicists are taking note because even a small mass for ubiquitous, nearly undetectable neutrinos would make them accountable for a substantial fraction of the total mass of our Universe, influencing and perhaps determining its ultimate fate! A measurable mass for neutrinos would also make them candidates for the mysterious dark matter known to affect the motions of stars and galaxies, while proof of neutrino oscillations would be a step toward resolving the decades old Solar Neutrino Problem. Even skeptical scientists will be waiting impatiently to see if these results are independently confirmed.
M100: A Grand Design (1998-06-06)
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 of M100 was made in 1993 with the Wide Field and Planetary Camera 2. It reveals the bright blue star clusters and intricate winding dust lanes which are hallmarks of this class of galaxies. Studies of stars in M100 have recently played an important role in determining the size and age of the Universe.
The Hubble Deep Field (1998-06-07)
Galaxies like colorful pieces of candy fill the Hubble Deep Field - humanity's most distant yet optical view of the Universe. The dimmest, some as faint as 30th magnitude (about four billion times fainter than stars visible to the unaided eye), are the most distant galaxies and represent what the Universe looked like in the extreme past, perhaps less than one billion years after the Big Bang. To make the Deep Field image, astronomers selected an uncluttered area of the sky in the constellation Ursa Major (the Big Bear) and pointed the Hubble Space Telescope at a single spot for 10 days accumulating and combining many separate exposures. With each additional exposure, fainter objects were revealed. The final result can be used to explore the mysteries of galaxy evolution and the infant Universe.
A Mars Glint (1998-06-08)
Tomorrow's picture: Ice Cusps on Europa  < 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.
Ice Cusps on Europa (1998-06-09)
uropa's icy crust has many unusual features. Pictured above is part of Europa's southern hemisphere photographed by the Galileo spacecraft currently orbiting Jupiter. Europa is one of the largest moons of Jupiter, and is thought to have oceans of water underneath its ice-covered surface. Among many cracks and ridges appear dark cusp-shaped features running from the lower left toward the upper right.  The origin of these features is not known for sure, but their shape is thought to indicate that large portions of Europa's crust move together, similar to tectonic motion of our Earth's crust.
NGC 6070: First Light for Sloan (1998-06-10)
The graceful spiral galaxy NGC 6070, 100 million light-years distant in the constellation Serpens, is helping astronomers celebrate "First Light" (the first test sky images) for an exciting new telescope built to perform the ambitious Sloan Digital Sky Survey. The dedicated survey instrument, located at Apache Point Observatory in Sunspot, New Mexico, USA, will map 1/4 of the entire sky in unprecedented detail with sophisticated digital imaging and data processing technologies. Telescopic observations tend to offer sensitive views of only very small pieces of the universe. Interpreting the results is a bit like watching a baseball game through a a drinking straw and trying to figure out what's going on! But scanning the sky over five years of planned operation, the Sloan Digital Sky Survey will build up a multi-color, 3-dimensional view of a large portion of the visible universe. At the turn of the millennium, this "big picture" will give humanity a critical new and detailed field guide to the cosmos.
SOHO's Twin Sungrazers (1998-06-11)
This four frame animation (courtesy D. Biesecker) shows two comets arcing toward a fatal fiery encounter with the Sun. These discovery images were recorded by the LASCO instrument on board the space-based SOHO solar observatory on June 1-2. A portion of LASCO's circular occulting disk - which blocks the blinding direct sunlight - is seen at the upper left along with a bright solar wind region extending to the right. For scale, the size and position of the Sun's edge are outlined by the white quarter circle on the occulting disk. The Sungrazer comets approach from below and have visible tails. The lower comet's coma is bright enough to cause a horizontal blemish in the digital image, while the tail of the upper comet grows dramatically as it closes with the Sun. The pair are "twins" or at least "siblings" in the sense that they are both likely members of a family of comets thought to result from the breakup of a single large parent comet. Members of the Sungrazer family can pass within 400,000 miles or less of the solar surface and many, like this pair, do not survive.
Orion Nebula: The 2MASS View (1998-06-12)
Few astronomical sights excite the imagination like the nearby stellar nursery known as the Orion Nebula. The Nebula's glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1,500 light-years away. This distinctively detailed image of the Orion Nebula was constructed using data from the 2 Micron All Sky Survey or 2MASS. Now underway with telescopes in the Northern and Southern Hemispheres of planet Earth, the 2MASS project will map the entire sky in infrared light. The wavelength of infrared light is longer than visible light but more easily penetrates obscuring dust clouds. 2MASS cameras are sensitve to near infrared wavelengths around 2 microns or about 0.00008 inches. Visible light has a wavelength of about 0.00002 inches. Survey observations in three infrared bands were translated to blue, green, and red colors to produce this composite image.
Henize 70: A SuperBubble In The LMC (1998-06-13)
Stars with tens of times the mass of the Sun profoundly affect their galactic environment. Churning and mixing the interstellar gas and dust clouds they leave their mark in the compositions and locations of future generations of stars and star systems. Dramatic evidence of this is beautifully illustrated in our neighboring galaxy, the Large Magellanic Cloud (LMC), by the lovely ring shaped nebula, Henize 70. It is actually a luminous "superbubble" of interstellar gas about 300 lightyears in diameter, blown by winds from massive stars and supernova explosions, its interior filled with tenuous hot expanding gas. These superbubbles offer astronomers a chance to explore this crucial connection between the lifecycles of stars and the evolution of galaxies.
Giant Cluster Bends, Breaks Images (1998-06-14)
What are those strange blue objects? Many are images of a single, unusual, beaded, blue, ring-like galaxy which just happens to line-up behind a giant cluster of galaxies. Cluster galaxies here appear yellow and -- together with the cluster's dark matter -- act as a gravitational lens. A gravitational lens can create several images of background galaxies, analogous to the many points of light one would see while looking through a wine glass at a distant street light. The distinctive shape of this background galaxy -- which is probably just forming -- has allowed astronomers to deduce that it has separate images at 4, 8, 9 and 10 o'clock, from the center of the cluster. Possibly even the blue smudge just left of center is yet another image! This spectacular photo from HST was taken in October 1994. The first cluster lens was found unexpectedly by Roger Lynds (NOAO) and Vahe Petrosian (Stanford) in 1986 while testing a new type of imaging device.  Lensed arcs around this cluster, CL0024+1654, were first discovered from the ground by David Koo (UCO Lick) in 1988.
NGC 4314: A Nuclear Starburst Ring (1998-06-15)
Is this old galaxy up to new tricks? The barred spiral galaxy NGC 4314 is billions of years old, but its appearance has changed markedly over just the past few millions of years.  During that time, a nuclear ring of bright young stars has been evolving.  The inset picture of NGC 4314 taken by McDonald Observatory shows the whole galaxy and boxes the small region around the core imaged by the Hubble Space Telescope. This inner region appears much like a miniature spiral galaxy itself, complete with dust lanes and spiral arms, even though it is only a few thousand light-years across.  Further study of NGC 4314 might help astronomers understand how the inner and outer parts of this galaxy interact, and what caused this unusual ring of star formation.
An Active Region of the Sun (1998-06-16)
The Sun is a busy place.  This false-color image depicts an active region near an edge of the Sun.  Hot plasma is seen exploding off the Sun's photosphere and traveling along loops defined by the Sun's magnetic field.  The red regions are particularly hot, indicating that some magnetic field loops carry hotter gas than others.  These active loops were so large that the Earth could easily fit under one. The TRACE satellite was launched in April with plans to continue high-resolution imaging as the Sun passes  Solar Maximum in the next few years.
The Sloan Digital Sky Survey Telescope (1998-06-17)
The Sloan Digital Sky Survey (SDSS) will soon begin.  Pictured above is the 2.5-meter telescope poised to create the most ambitious sky map in the history of astronomy.  SDSS will catalog one quarter of the sky down past 23rd magnitude ( R), obtaining redshifts for galaxies and quasars brighter than magnitude 19.  SDSS is expected to store about 200 Gigabytes of data each night. Astronomers will work to cull from this information an unprecedented three-dimensional view of our local universe.  However, the SDSS may one day be remembered not only for the hundreds of millions of objects which it could see, but for how it indicated the nature and composition of the rest of the universe which it could not see.
Cosmic Rays and Supernova Dust (1998-06-18)
Cosmic Rays are celestial high energy particles traveling at nearly the speed of light, which constantly bombard the Earth. Discovered during high altitude balloon flights in 1912 their source has been a long standing mystery. But a recent theory suggests that cosmic ray particles are atomic nuclei blasted from dust grains formed in supernovae, the death explosions of massive stars. This artist's illustration shows a supernova explosion (at left) and a conical section of the expanding cloud of ejected material. Atoms are torn from the brownish bands of "dust" material by shock waves (represented by orange rings). The shocks in the expanding blast wave then accelerate the atoms to near light speeds firing them into interstellar space like cosmic bullets. The theory is supported by observations indicating that high velocity dust was formed in the nearby supernova 1987A, and that Beryllium, a light element created in Cosmic Ray collisions, is found equally in both old an young stars. NASA's Advanced Composition Explorer (ACE) satellite can also test details of the theory by directly measuring Cosmic Rays.
Good Morning Mars (1998-06-19)
Looking down on the Northern Hemisphere of Mars on June 1, the Mars Global Surveyor spacecraft's wide angle camera recorded this morning image of the red planet. Mars Global Surveyor's orbit is now oriented to view the planet's surface during the morning hours and the night/day shadow boundary or terminator arcs across the left side of the picture. Two large volcanos, Olympus Mons (left of center) and Ascraeus Mons (lower right) peer upward through seasonal haze and water-ice clouds of the Northern Martian Winter. The color image was synthesized from red and blue band pictures and only approximates a "true color" picture of Mars.
Pioneer 10: The First 6 Billion Miles (1998-06-20)
Q: What was made by humans and is 6.5 billion miles away? A: Pioneer 10 - and last year was the 25th anniversary of its launch. More than 9.5 light-hours distant, Pioneer 10 is presently about twice as far from the Sun as Pluto, bound for interstellar space at 28,000 miles per hour. The distinction of being the first human artifact to venture beyond the Solar System is just one in a long list of firsts for this spacefaring ambassador, including; the first spacecraft to travel through the asteroid belt and explore the outer Solar System, the first spacecraft to visit Jupiter, the first to use a planet's gravity to change its course and to reach solar-system-escape velocity, and the first spacecraft to pass beyond the known planets. Pioneer 10's mission is nearing an end - now exploring the distant reaches of the heliosphere it will soon run out of sufficient electrical power to operate science instruments. However, the 570 lb. spacecraft will continue to coast and in 30,000 years or so it will pass within about 3 light years of a nearby star known as Ross 248. Ross 248 is a faint red dwarf just over 10 light years distant in the constellation Taurus. (Note: This year Voyager 1, launched 21 years ago but traveling faster than Pioneer 10, became humanity's most distant spacecraft.)
Edwin Hubble Discovers the Universe (1998-06-21)
No person in history has had greater impact in determining the extent of our universe than Edwin Hubble. From proving that other galaxies existed to proving that galaxies move apart from one another, Hubble's work defined our place in the cosmos.  Hubble lived from 1889 to 1953 and is shown above posing with the 48-inch telescope on Palomar Mountain and his famous pipe. In memory of his great work, the Orbiting Space Telescope was named after him. The rate of the universe's expansion is now parameterized by a quantity known as Hubble's constant. A modern debate on the value of Hubble's constant took place in 1996.