juliensimon/nasa-apod huggingface dataset:
Near the Nucleus of Hyakutake (1996-03-28)

NASA's Hubble Space Telescope captured this image of the near-nuclear region of Comet Hyakutake on March 25 as the comet approached within 9.3 million miles of the Earth. It covers a relatively "small" 2,000 mile wide area with the sunward direction toward the lower right (tailward is upper left). The image shows large amounts of dust jetting from the sunward side of the nucleus as the sun heats the surface of this dirty "orbiting iceberg". Pressure from sunlight eventually pushes the dust tailward and as the dust production increases, the already visually impressive tail will grow even brighter! The actual size of the nucleus is uncertain but is estimated to be 5-10 miles, similar to Comet Halley. As seen here, the brightest point is probably the tip of the strongest dust jet rather than the nucleus itself. A dramatic dust jet feature also appears to arise from the nightside but its true angle to our line of sight is difficult to judge. Some large fragments which have broken away from the comet nucleus are visible in the upper left of the image, producing dust tails of their own. Comet dust may represent primordial material from the formation of the solar system and NASA has plans for a comet dust sample return mission.   Latest Comet Hyakutake images: JPL, Crni Vrh Observatory, Slovenia, Fayetteville Observer-Times, NASA's Night of the Comet
The Colors of Comet Hyakutake (1996-03-29)

The colors of Comet Hyakutake are caused by the action of sunlight on the dust and gas produced by the warming nucleus. The microscopic dust particles reflect sunlight while the sun's ultraviolet radiation excites and ionizes the gas molecules causing them to glow or fluoresce in a range of visible colors. This enhanced color picture reveals subtle color changes across the cometary coma and a faint multicolored tail. It was made on the night of March 18-19 by combining separate green, red, and blue photographs, each about a 15 minute exposure. Some of the color features in the tail may well represent real changes in its structure from one exposure to the next. The colored star trails, created as the Anglo-Australian Observatory's UK Schmidt Telescope tracked the rapidly moving comet, indicate the order of the separate exposures. The cometary hues revealed here can not be seen directly due to the human eye's lack of color vision at the low light levels involved.  Latest Comet Hyakutake images: JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Crni Vrh Obs., Cent. Mich U.

Image credit: Anglo-Australian Observatory
An Extreme UltraViolet View of the Comet (1996-03-30)

As the Sun floods Comet Hyakutake with ultraviolet light gases in the coma scatter the radiation and fluoresce making the comet a bright source in the ultraviolet sky. The above image made using data from NASA's Extreme UltraViolet Explorer (EUVE) satellite, represents the intensity of the comet in this invisible high energy band in false color. The image is about 3/4 of a degree high and 2 degress wide and offers insights to the composition of this visitor from the distant solar system that can be obtained from the highest energy bands of the ultraviolet spectrum. The International Ultraviolet Explorer (IUE) satellite has also examined ultraviolet light from the comet and now reports the detection of many bands of molecular emission particularly those due to molecular carbon (C2), carbon monoxide (CO) and caron dioxide (C02) ions as well as indications of a rapid increase in the production of water (H20).   Latest Comet Hyakutake images: JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Crni Vrh Obs., Cent. Mich U.
Comet Hyakutake Finder Chart for April (1996-03-31)

During April Comet Hyakutake heads in toward the Sun  after passing the Earth. At this time the comet's orbit places it north of the Earth. Remaining visible in the northern sky as it nears the Sun, it will set progressively earlier in the evening. Early in April, the Moon's glow will diminish viewing of the comet's tail - except during the lunar eclipse on April 3rd! As the comet recedes from the Earth it will appear dimmer even though it is getting intrinsically brighter as it nears the Sun. In late April the intrinsic brightening effect will "win" and the comet will again appear to brighten - possibly getting even brighter than it was last week. At this point the comet will appear near sunset low on the northwestern horizon (see above). So far Comet Hyakutake has exceeded most expectations in brightness and length of tail. If you haven't been impressed by Hyakutake, you probably haven't seen it from a dark location!   Latest Comet Hyakutake images: JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Crni Vrh Obs., Cent. Mich U.
Hyakutake, Big Dipper, and Observatory Dome (1996-04-01)

In one of the more spectacular pictures yet taken, Comet Hyakutake is shown here on March 26 high in the dark Missouri sky. In the foreground is Elmcrest Observatory complete with a dim red light glowing inside the dome. The stars in the background moved slightly during the exposure causing them to appear as streaks instead of points of light. Nevertheless, the constellation of Ursa Major - including the Big Dipper - is visible. Can you spot it? (Hint: Hyakutake's tail flows through the Dipper's handle.) Photographs with both recognizable foreground and background objects visible can be quite striking as they add angular perspective and contrast to the outworldly and unfamiliar comet. Dare anyone try to compete with city lights and capture the Eiffel Tower or the New York skyline in front of the comet?   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich U.

Image credit: Vic 
Winter, Courtesy
ICSTARS
Atlantis Approaches Mir (1996-04-02)

Imagine flying though space and approaching the Mir space station. The crew of the Space Shuttle Atlantis did just this in a mission that ended only two days ago. Mir, now 10 years old, is equipped for  scientific experiments in astronomy, physics, materials, biology and chemistry. The top most module on Mir is an unmanned supply ship used to send food and supplies. The next module with the long boom carries telescopes and essential flight equipment and connects to the core module with living quarters and solar panels.  To the left is the Spektr module carrying solar arrays and scientific equipment while on the right is a scientific module that also carries an airlock. The docking module seen at the bottom is the ultimate destination of Atlantis. The STS-76 mission left astronaut Shannon Lucid for a planned five month stay. Four more shuttle flights are currently planned to Mir, keeping a NASA astronaut continuously in space until late 1997. In late 1997, building on this jointly developed understanding and experience, the US and Russia will launch the first modules of the International Space Station.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich. U.
A Lucky Lunar Eclipse (1996-04-03)

Tonight's full moon would normally washout the spectacle of Comet Hyakutake's lovely tail, even for those far from light polluted skies. Except that tonight comet observers are in luck - the dance of the planets calls for a total lunar eclipse! Lunar eclipses are caused when the Moon passes through the Earth's shadow. Although dimmed, the eclipsed Moon may not appear completely dark. Sunlight scattered into the Earth's shadow after passing around the planet's edge and through its dusty atmosphere can make the Moon take on dramatic shades of red during totality as demonstrated in the above photo of the November 1993 lunar eclipse. Tonight, totality begins at 6:26 p.m. EST and lasts about an hour and a half. Weather permitting, the eclipse will be visible for all those comet and moon watchers lucky enough to be on the Earth's nightside.  Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich. U.

Image credit: Andy Steere
The Keyhole Nebula Near Eta Carinae (1996-04-04)

The dark dusty Keyhole Nebula gets its name from its unusual shape. Designated NGC 3324, the Keyhole Nebula is a smaller region superposed on the bright Eta Carina Nebula. The Eta Carina Nebula is the largest nebula in angular extent on the sky, larger than the famous Orion Nebula, but its southerly location makes it less familiar to Northern Hemisphere skywatchers. The star Eta Carinae itself is extremely variable and has faded in a mere 150 years - formerly one of the brightest in the sky it is now invisible without a telescope. The nebula created by the star's 19th century outburst has been photographed by the Hubble Space Telescope.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich. U.

Image credit: Anglo-Australian Telescope
Board
The Perseus Cluster of Galaxies (1996-04-05)

Here is one of the largest objects that anyone will ever see on the sky. Each of the fuzzy blobs in the above picture is a galaxy, together making up the Perseus Cluster, one of the closest clusters of galaxies. We view the cluster through the foreground of faint stars in our own Milky Way galaxy. It takes light roughly 300 million years to get here from there, so we only see this cluster as it existed during the age of the dinosaurs. Also known as Abell 426, the center of Perseus cluster is a prodigious source of X-ray radiation, and so helps us study how clusters formed and how gas and dark matter interact. The Perseus Cluster of Galaxies is part of the Pisces-Perseus supercluster of galaxies, which spans over 15 degrees and contains over 1000 galaxies.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich. U.

Image credit: STScI, 
AAO, UK-PPARC, ROE
Andromeda Nebula: Var! (1996-04-06)

In the 1920s, using photographic plates made with the Mt. Wilson Observatory's 100 inch telescope, Edwin Hubble determined the distance to the Andromeda Nebula - decisively demonstrating the existence of other galaxies far beyond the Milky Way. His notations are evident on the plate shown above (the image is a negative with stars appearing as black dots against the white background of space). By intercomparing plates, Hubble searched for "novae", stars which underwent a sudden increase in brightness. He found several on this plate and marked them with an "N".  Later he discovered that one was actually a type of variable star known as a cepheid - crossing out the "N" he wrote "Var!" (upper right). Thanks to the work of Harvard astronomer Henrietta Leavitt, cepheids, regularly varying, pulsating stars, could be used as "standard candle" distance indicators. Identifying such a star allowed Hubble to show that Andromeda was not a small cluster of stars and gas within our own galaxy, but a large galaxy in its own right at a substantial distance from the Milky Way. Hubble's discovery is responsible for our modern concept of a Universe filled with galaxies.   Information: The Scale of the Universe Debate in April 1996
Uranus's Moon Umbriel: A Mysterious Dark World (1996-04-07)

Why is Umbriel so dark? This dark moon reflects only half the light of other Uranus' moons such as Ariel. And what is that bright ring at the top?  Unfortunately, nobody yet knows. These questions presented themselves when Voyager 2 passed this satellite of Uranus in January 1986. Voyager found an old surface with unusually large craters, and determined Umbriel's composition to be about half ice and half rock. Umbriel is the fourth largest and third most distant of Uranus' five large moons. Umbriel was discovered in 1851 by William Lassell.  Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich. U.
Uranus's Moon Oberon: Impact World (1996-04-08)

Oberon is the most distant and second largest moon of Uranus. Discovered by William Herschel in 1787, the properties of the world remained relatively unknown until the robot spacecraft Voyager 2 passed it during its flyby of Uranus in January 1986. Compared to Uranus' moons Ariel, Titania, and Miranda, Oberon is heavily cratered, and in this way resembles Umbriel.  Like all of Uranus' large moons, Oberon is composed of roughly half ice and half rock. Note that Oberon has at least one large mountain, visible on the limb at the lower left, that rises 6 km off the surface.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs., Cent. Mich. U.
A Spiral Galaxy Gallery (1996-04-09)

A progression of beautiful spiral galaxies is illustrated above with three photographs from NASA's Ultraviolet Imaging Telescope (UIT). Flying above the Earth's obscuring layer of atmosphere on the Space Shuttle Columbia during the Astro-1 mission in 1990, UIT's cameras were able to image these distant spirals in the ultraviolet light produced by hot, young stars. These bright stars, newly condensed from gas and dust clouds, give away the location of the spiral arms they are born in. Because they are massive (many times the mass of the Sun), they are shortlived. Dying and fading before they move too far from their birth place they make excellent tracers of spiral structure. From left to right the galaxies are known as M33, M74, and M81 and have progressively more tightly wound spiral arms. Astronomers would classify these as Scd, Sc, and Sb type spirals using a galaxy classification scheme first worked out by Edwin Hubble.   Information: The Scale of the Universe Debate in April 1996
Comet Hyakutake and a Tree (1996-04-10)

Comet Hyakutake is still visible as it continues its orbit around the Sun. The comet will brighten again in late April and early May. The above fascinating picture was taken with a three minute exposure. In the middle of the exposure, the photographer cleverly set off a flash, momentarily illuminating the foreground tree. The picture was taken on March 24th from Mount Teide in the Canary Islands, and the recorded tail length was over 50 degrees.  Discoverer Yuji Hyakutake, whose last name means "100 warriors" is an amateur astronomer in Japan. Interested in comets since age 15, he discovered this comet while sitting on a rural mountain top searching dark skies with huge binoculars in early morning hours. Originally intending to check up on a comet he had discovered only one month earlier, Hyakutake was initially worried that the new fuzzy spot he had located was not really yet another comet! One unexpected result of his comet discovery is that now his family has trouble making phone calls because their telephone is always ringing.   Information: The Scale of the Universe Debate in April 1996

Image credit: Nick James, Martin Mobberley and Glyn Marsh,
The Astronomer Online
Unexpected X-rays from Comet Hyakutake (1996-04-11)

The first X-rays ever detected from a comet were discovered from Comet Hyakutake with the ROSAT satellite on March 27th.  The discovery is particularly surprising because there was little previous indication that comets emit any significant X-radiation. As the comet passed the Earth in late March, repeated observations with ROSAT also showed that the X-ray brightness changed over just a few hours. The crescent shape of the X-ray emission is also enigmatic. One possible explanation is that X-rays emitted from the Sun are absorbed by water in the comet's coma causing fluorescence. Another possible explanation involves interaction with the solar wind - fast moving particles streaming away from the Sun.   Information: The Scale of the Universe Debate in April 1996
Man Enters Space (1996-04-12)

Thirty five years ago today, Soviet cosmonaut Yuri Alexseyevich Gagarin became the first human in space. On April 12, 1961, his remotely controlled Vostok 1 spacecraft lofted him to an altitude of 200 miles and carried him once around planet Earth. Strictly a passenger, his onboard controls were locked out by a secret combination - in case of emergency he carried the combination in a sealed envelope. After reentry, Gagarin ejected from the Vostok at an altitude of 20,000 feet and parachuted to Earth. How was the first view from space? He reportedly commented, "The sky is very dark; the Earth is bluish. Everything is seen very clearly". Coupled with other spacefaring accomplishments, this flight seemed to confirm Soviet technological superiority - the first US astronaut would not be launched until almost a month later and then on a comparatively short suborbital flight. Born on March 9, 1934, Gagarin was an air force jet pilot before being chosen for the first group of cosmonauts in 1960. As a result of his historic flight he became an international hero and legend. Killed when his MIG jet crashed during a training flight on March 27, 1968, Gagarin was given a hero's funeral, his ashes interred in the Kremlin Wall.   Information: The Scale of the Universe Debate in April 1996
The Compton Observatory Turns Five (1996-04-13)

rlier this April, NASA's Compton Gamma Ray Observatory, completed its fifth successful year in orbit, exploring the gamma ray sky. Pictured is astronaut Jay Apt perched in the shuttle payload bay below the massive observatory.  Compton is the largest civilian instrument ever flown - the whole observatory is roughly the size of a school bus. Apt and colleague Jerry Ross rescued the spacecraft from an unexpected problem by successfully freeing the stuck high gain antenna in an unplanned space walk. The second of NASA's planned Great Observatories for Space Astrophysics, the first being the Hubble Space Telescope, the Compton Gamma Ray Observatory has exceeded expectations of scientific discovery. Compton continues to search the depths of the universe for such high energy phenomena as gamma-ray bursts, blazars, and pulsars. Compton is still monitoring a new source it discovered just last December - the spectacular "bursting pulsar" near the center of our Galaxy.   Information: The Scale of the Universe Debate in April 1996
The Rotating Jets of Comet Hyakutake (1996-04-14)

Comet Hyakutake will reach its closest point to the Sun on May 1, passing well inside the orbit of Mercury.  At this time, the comet's dust and ion tail will be at their greatest physical length. As the comet nears the Sun, gas and dust are driven off the surface, sometimes being shot off in jets. Although much of this material ends up in the tail, some interesting features can be seen close to the comet's three kilometer nucleus. Because the comet's nucleus rotates, the jets can be seen to form arcs around the comet's center resembling a pinwheel. The above photograph, taken April 8, shows two expanding arcs of cometary material and two source jets. The outermost arc is at a projected distance of 12,000 kilometers from the nucleus. The inner is about 8,000 kilometers from the nucleus. They are expanding from the nucleus at 870 km per hour. The inner arc ends at the brightest of the Comet Hyakutake's many jets.   Information: The Scale of the Universe Debate in April 1996
NASA Mission to MAP the Universe (1996-04-15)

What is our universe made of? How rapidly is our universe expanding? When did galaxies form? These questions, among the most important and baffling to astronomers since the beginning of the modern astronomical era, might well be answered by a new space satellite mission. The Microwave Anisotropy Probe (MAP) is being designed inspect the universe's microwave background radiation in more detail then ever before. MAP will record the frequency, size and temperature of bumps 20 times smaller than COBE. Astronomers have computed what bumps would be expected from several models of our universe, and comparing these results to MAP's data may yield a new understanding of the composition and structure of our universe. MAP has just won approval as a NASA MIDEX class satellite, and is currently scheduled to launch in the year 2000.   Information: The Scale of the Universe Debate in April 1996
Cometary Knots in the Helix Nebula (1996-04-16)

Four hundred fifty light-years from Earth, the wind from a dying, sun-like star produced a planetary nebula popularly known as the Helix. While exploring the Helix's gaseous envelope with the Hubble Space Telescope (HST), astronomers discovered indications of 1,000s of striking "cometary knots" like those shown above. So called because of their resemblence to comets, they are actually much larger - their heads are several billion miles across (roughly twice the size of the our solar system itself) while their tails, pointing radially away from the central star, stretch over 100 billion miles. Previously known from ground based observations, the sheer number of cometary knots found in this single nebula is astonishing. What caused them to form? Hot, fast moving shells of nebular gas overrunning cooler, denser, slower shells ejected by the star during an earlier expansion may produce these droplet-like condensations as the two shells intermix and fragment. An intriguing possibility is that instead of dissipating over time, these objects, could collapse and form pluto-like bodies. If so, these icy worlds created near the end of a star's life, would be numerous in our galaxy.    Information: The Scale of the Universe Debate in April 1996
NGC 7293: The Helix Nebula (1996-04-17)

The Helix nebula (New General Catalog number 7293) is estimated to be a mere 450 light-years from the Sun, in the direction of the constellation Aquarius. At that distance it may well be the closest planetary nebula, offering a dramatic snapshot of a brief final evolutionary stage in the life of a solar-type star. In this color image the nebula glows red in the light of nitrogen and hydrogen atoms energized by the ultraviolet radiation from the central star. The main rings themselves, though faint, have an angular size about half that of the full moon and span about 1.5 light-years. Because it is so close, it is a prime subject for study by astronomers. When the Hubble Space Telescope was focused near the inner edge of the main ring, at about the 12 o'clock position in the above image, it resolved some of the spoke like radial structures visible into intriguing cometary knots.   Information: The Scale of the Universe Debate in April 1996

Image credit: Anglo-Australian Telescope
Board
Hyakutake, Venus, Orion, and Pond (1996-04-18)

Can you find Comet Hyakutake in the above picture? In this gorgeous photo, the starry night sky of April 9th is pictured with its new comet visitor. In the foreground is a pond with the lights of Kansas City, Missouri on the western horizon. On the upper left, the constellation of Orion is visible. At the center, the brightest object in the picture is the planet Venus. Venus's reflection can be seen in the pond. On the right - halfway between Venus and the photograph's edge - can be seen two bright objects fairly close to each other. Of these two, look closely at lower right object. See the tail? Comet Hyakutake is still visible for Northern observers in the Western sky and now has begun to brighten again as it nears the Sun.   Latest Comet Hyakutake images: APOD Hyakutake Archive, JPL, Fayetteville Observer-Times, NASA's Night of the Comet, ICSTARS, Jerry Lodriguss, ScienceWeb, Crni Vrh Obs.,

Image credit: Vic 
Winter, Courtesy
ICSTARS