omnianasa/nasa-apod-metadata huggingface dataset:
A Meteorite From Mars (1996-08-17)
The famous Martian meteorite pictured above houses microscopic structures interpreted by many as fossils of ancient Martian life.  How do you find a meteorite from Mars here on Earth? On a typical day, several large rocks fall to Earth from space, usually winding up in the oceans. If they do not burn up in the Earth's atmosphere they are called meteorites. (Danger from falling meteorites is rare: the average person would have to repair meteorite damage to their home about every 100 million years.) Most meteorites falling on land are never located or identified - appearing similar to other rocks to the untrained eye. In certain places in Antarctica, however, meteorites stand out from the white frozen ice and snow beneath them, as if they were just left yesterday. When the above meteorite was found in Antarctica, it was considered unusual because of its grey color. So far, about 12 Martian meteorites of similar mineral compostion have been found. One of these contains minute pockets of gases identical in isotopic composition to the Martian atmosphere as determined from the Viking measurements - implying the rocks indeed originated on Mars. These Martian meteorites are typically 1.3 billion years old or less, however, the one containing the potential microfossils appears to have an age of about 4.5 billion years.
A Milestone Quasar (1996-08-18)
Here is a rather typical quasar. But since quasars are so unusual it is quite atypical of most familiar objects. Of the two bright objects in the center of this photo, the quasar is on the left. The bright image to quasar's right is a star, the faint object just above the quasar is an elliptical galaxy, with an apparently interacting pair of spiral galaxies near the top. Quasars appear as unresolved points of light, as do stars, and hence quasars were thought to be a type of star until the 1960s. We now know that the brightest quasars lie far across the visible universe from us, and include the most distant objects known. Quasars may occupy the centers of galaxies and may even be much brighter than their host galaxies. In fact, the centers of many nearby galaxies have similarities to quasars - including the center of our own Milky Way Galaxy. The exact mechanism responsible for a quasar's extreme brightness is unknown, but thought to involve  supermassive black holes. This picture represents a milestone for the six-year-old Hubble Space Telescope as it was picture number 100,000, taken on June 22, 1996.
Welcome to Planet Earth (1996-08-19)
Welcome to Planet Earth, the third planet from a star named the Sun. The Earth is shaped like a sphere and composed mostly of rock. Over 70 percent of the Earth's surface is water.  The planet has a relatively thin atmosphere composed mostly of nitrogen and oxygen.  Earth has a single large Moon which is about 1/4 of its diameter and, from the planet's surface, is seen to have almost exactly the same angular size as the Sun. With its abundance of liquid water, Earth supports a large variety of life forms, including potentially intelligent species such as dolphins and humans. Please enjoy your stay on Planet Earth.
A Close-Up of the Lagoon Nebula (1996-08-20)
Ribbons of red-glowing gas and dark dust surround massive young stars in this close-up of the Lagoon Nebula taken by the Hubble Space Telescope. The Lagoon Nebula is relatively close and bright - it appears larger than the Full Moon and is visible even without a telescope. Light takes about 5000 years to reach here from there. The Lagoon Nebula houses the open star cluster M8.  This photograph is combination of exposures taken in the red, green and ultraviolet. The unusual bright central part of the Lagoon Nebula (lower left in this image) is known as the Hourglass Nebula.
A Close-Up of the Lagoon's Hourglass (1996-08-21)
In the central part of the Lagoon Nebula lies the above pictured Hourglass Nebula. In this region of recent star formation, obscuring dark lanes of dust permeate the red-glowing hydrogen gas. Blocking some of the gas cloud from our view, they chance to create a glowing shape that appears from our vantage point like an hourglass. In the upper right of this picture from the Hubble Space Telescope is a bright young blue star from the open cluster NGC 6530 - visible below center in yesterday's APOD. A recent study of the Lagoon Nebula (M8), has shown that this emission nebula houses large magnetic fields and unusually large dust particles.
Arp 230: Two Spirals in One? (1996-08-22)
Is this one galaxy or two? Analysis of Arp 230 has shown evidence that this seemingly single spiral galaxy is actually the result of the recent collision of two spiral galaxies. The slow motion collision took place over about 100 million years and induced a burst of star formation that has begun to subside. The collision apparently had many similarities to the colliding galaxy sequence in the IMAX movie "Cosmic Voyage."
NGC 3293: A Bright Young Open Cluster (1996-08-23)
Hot Blue stars shine brightly in this beautiful, recently formed galactic or "open" star cluster. Open cluster NGC 3293 is located in the constellation Carina, lies at a distance of about 8000 light years, and has a particularly high abundance of these young bright stars. A study of NGC 3293 implies that the blue stars are only about 6 million years old, whereas the cluster's dimmer, redder stars appear to be about 20 million years old. If true, star formation in this open cluster took at least 15 million years. Even this amount of time is short, however, when compared with the billions of years stars like our Sun live, and the over-ten billion year lifetimes of many galaxies and our universe. NGC 3293 appears just in front dense dust lane emanating from the Carina Nebula.
Why is QSO 1229+204 so Bright? (1996-08-24)
What causes the center of this barred spiral galaxy to light up brighter than almost anything in the universe? The quasar there is a good fraction of the way across our observable universe but appears so bright that astronomers had to use the high resolving power of the Hubble Space Telescope (HST) just to see the host galaxy.  HST then resolved something very interesting. Not only was QSO 1229+204 at the core of an unusual barred spiral galaxy, but this galaxy was in the process of colliding with a dwarf galaxy.  Gas from this collision quite possibly fuels a supermassive black hole causing QSO 1229+204 to shine so brightly.
Luna 9: First Soft Lander (1996-08-25)
The Luna 9 spacecraft above performed the first soft landing on another planetary body. Following a series of failures, the Soviet probe touched down in the Moon's Oceanus Procellarum region February 3, 1966. It accomplished this milestone in lunar exploration only shortly after the death of Sergei Korolev, the father of the Soviet Space Program. Reportedly, Korolev's colleagues wished to dedicate the Luna 9 mission to him but were unable to as his role as the Chief Designer was still a state secret. A pole, just visible extending at the lower left, sensed the impact with the lunar surface, triggering the spacecraft to eject the weighted, egg-shaped capsule (upper right). The 250 pound capsule then struck the surface, rolled upright, unfolded four spring actuated petals to steady itself, and transmitted the first views from the lunar surface back to Earth.
A Wolf-Rayet Star Bubble (1996-08-26)
What's a Wolf-Rayet star, and how did it create that spherical bubble and sweeping arc? A Wolf-Rayet star is a star that originated with a mass over 40 times that of our Sun. An extremely hot, luminous star, it has since expelled shells of material through its strong stellar wind which could account for the bubble shaped nebula that surrounds it. But astronomers are unsure how the central Wolf-Rayet created both the bubble and the arc seen above, and even whether it acted alone in doing so. Together, this bubble and the arc are known as NGC 2359.
Galileo Zooms in on Jupiter's Red Spot (1996-08-27)
What does the largest storm system ever recorded look like close-up? This storm system is Jupiter's Great Red Spot and it was captured recently in detail by the robot spacecraft Galileo now in orbit around Jupiter. Using real images from three color filters, the Galileo team was able to compute what a person would see if able to float just above this ancient rotating cloud system.  But don't get too close - remember that Jupiter's Great Red Spot is a cold, high pressure area more than twice as wide as planet Earth.
NGC 5882: A Small Planetary Nebula (1996-08-28)
Will most stars one day look like this? Pictured above is the planetary nebula NGC 5882, captured by the Hubble Space Telescope.  Although planetary nebulae can appear similar to planets like Uranus and Neptune, they are actually gas clouds surrounding stars typically hundreds of light years away. Planetary nebula form when a typical star completes fusion in its core and ejects an outer envelope of gas - usually about 10 percent of the star's initial mass. This gas shell dims in about 50,000 years - short compared to the lifetimes of stars.  Therefore, although only about 1000 planetary nebula are known in our Galaxy, it is thought that most stars go through this phase.  Green light is emitted when oxygen ions acquire electrons from the surrounding gas.
M17: The Majestic Swan Nebula (1996-08-29)
What unusual eggs have been laid by this majestic swan?  The star forming region above, known as Swan Nebula, is the home of hot red-glowing gas, dark lanes of dust, bright young stars and -- what are those?  Of the few stars visible in the Swan Nebula, several have quite unusual colors and are  hypothesized to be very young stars still shrouded by gas from the cloud that formed them. The Swan Nebula is quite large and massive as it contains roughly 1000 times the mass of our Sun. The bright central region is about 15 light years across lies about 5000 light years away toward the constellation of Sagittarius. The distinctive shape causes this region to have several other names, including the Omega Nebula, the Horseshoe Nebula, and the Lobster Nebula.
Galileo Demonstrates the Telescope (1996-08-30)
Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky. Galileo quickly discovered that our Moon had craters, that Jupiter had it's own moons, that the Sun has spots, and that Venus has phases like our Moon. Galileo, who lived from 1564 to 1642, made many more discoveries.  Galileo claimed that his observations only made sense if all the planets revolved around the Sun, as championed by Aristarchus and Copernicus, not the Earth, as was commonly believed then. The powerful Inquisition made Galileo publicly recant this conclusion, but today we know he was correct.
Kepler Discovers How Planets Move (1996-08-31)
Johannes Kepler used simple mathematics to describe how planets move. Kepler was an assistant to the most accurate astronomical observer of the time, Tycho Brahe.  Kepler was able to use Brahe's data to show that planets move in ellipses around the Sun (Kepler's First Law), that planets move proportionally faster in their orbits when they are nearer the Sun (Kepler's Second Law), and that more distant planets take proportionally longer to orbit the Sun (Kepler's Third Law). Kepler lived from 1571 to 1630, during the time of discovery of the telescope. Kepler was one of the few vocal supporters of Galileo's discoveries and the Copernican system of planets orbiting the Sun instead of the Earth.
VLT: A New Largest Optical Telescope (1996-09-01)
What is the largest telescope in the world? In the optical, this title was long held by the Hale 200-inch, and is presently held by the Keck telescopes in Hawaii. But an even larger optical telescope is being built. Dubbed the Very Large Telescope (VLT), the European Southern Observatory (ESO) is building four 8.2-meter mirrors in Chile which together will act as a single telescope with a mirror diameter of over 16-meters. The first of these telescopes should be completed in 1997, and all four should be completed and working together sometime in the year 2000. The VLT will use active optics to create sub-arcsecond resolution. This, combined with the enormous light-gathering power, will allow astronomers to explore dim objects in our Galaxy and the early universe.
Sirius: The Brightest Star in the Night (1996-09-02)
Sirius is the brightest star in the night sky. Intrinsically, Sirius is over 20 times brighter than our Sun and over twice as massive. As Sirius is 8.7 light years distant, it is not the closest star system -- the Alpha Centauri system holds this distinction. Sirius is called the Dog Star because of its prominence in the constellation of Canis Majoris (Big Dog). In 1862, Sirius was discovered to be a binary star system with a companion star, Sirius B, 10,000 times dimmer than the bright primary, Sirius A. Sirius B was the first white dwarf star discovered, a type of star first understood by Subrahmanyan Chandrasekhar in 1930. While studying Sirius in 1718, Edmond Halley discovered that stars move with respect to each other. The Sirius system is shown above captured in X-ray light.
The Pleiades Star Cluster (1996-09-03)
It is the most famous star cluster on the sky. The Pleiades can be seen without binoculars from even the depths of a light-polluted city.  Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and most easily visible open clusters on the sky. The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across. Quite evident in the above photograph is the blue reflection nebula that surrounds the bright cluster stars. Low mass, faint, brown dwarfs have recently been found in the Pleiades.
IRTF: Scanning the Infrared Skies (1996-09-04)
Above, NASA's Infrared Telescope Facility (IRTF) poses in front of a starry background. Located on top of Hawaii's towering volcano Mauna Kea, the IRTF is the premier telescope for observing in near infrared light. This 3-meter telescope was established in 1979 and spends about half its time observing Solar System objects. In 1994, for example, the IRTF recorded pieces of the famous comet Shoemaker-Levy 9 plunge into Jupiter. Last year, the IRTF recorded an outburst of a volcano on Jupiter's moon Io. IRTF's observational successes outside our Solar System include understanding the infrared emission of dust and Pre-Main Sequence stars and even the identification of faint galaxies.
Watch Galaxies Form (1996-09-05)
 Snips and snails and puppy dog tails, is that what galaxies were  made of? In a  report  released yesterday and soon to be published in  Nature,  astronomers have imaged an interesting  distant patch of sky  with the orbiting  Hubble Space Telescope. They found many merging groups of  stars and  gas which have been  dubbed "pre-galactic blobs." A particularly dense bunch of  these small blue merging objects are visible in the above picture. This may be a snapshot of  galaxies actually being formed!  Although peculiar by present standards of  galaxies, these blobs may have been normal in the distant past, many billions of  years ago. This adds evidence that  galaxies  formed from the  conglomeration of smaller objects instead of the  fragmentation of larger objects.
The Largest Impact Crater (1996-09-06)
 What is the largest known impact crater in the Solar System? Over 1300 miles across, the South Pole-Aitken Basin on the farside of Earth's Moon holds that distinction. Circled above in a false color mosaic of Clementine images it was caused when an asteroid or comet sized object crashed into the surface, penetrating the lunar mantle.  In general, the rocky terrestrial planets and moons are scarred and battered from frequent repeated bombardment by large objects during our Solar System's early years. On Earth, continuous geological activity has hidden much of the damage, but the surface of the smaller, less active Moon bears testimony to a shared history of fierce and frequent impacts. At the present time in the vicinity of Earth, the bombardment continues - fortunately at a greatly reduced rate.
Two Billion Years After the Big Bang (1996-09-07)
 What did the  universe look like two billion years after the  Big Bang? According to  this computer model, the universe was filled with irregular looking objects like the ones shown above.  The simulation then predicts that these blobs of stars and gas collide to form galaxies more similar to the ones we see today. In fact, this simulation bears much resemblance to  recent pictures of distant galaxies taken by the  Hubble Space Telescope.  Galaxy formation is a complex phenomena which only now is becoming understood. Did most galaxies form 5 billion years ago - or 10 billion? Did galaxies fragment from larger sheets of matter, or are they conglomerations of many smaller clumps? Simulations like this one are helping to determine the answer.
Volcano Euboea Fluctus On Io (1996-09-08)
Jupiter's moon  Io is turning out to be our  Solar System's geologic powerhouse. The churning moon was photographed again just recently on June 27th and again shows signs of violent activity.  Shown above are photographs of the volcano Euboea Fluctus taken at different times. The black and white photograph on the upper left was taken by the  Voyager 1 spacecraft when it flew by in 1979, the upper right and lower left photographs were taken in 1996 by the  Galileo spacecraft, while the lower right photograph is a color image taken by Voyager 2, also in 1979. The upper right Galileo picture has been artifically changed to simulate the color sensitivity of the  Voyager 2 mission. The marked difference in the two images is highlighted by new red and yellow deposits. These markings may indicate that Euboea Fluctus erupts in an unusual fashion, possibly caused by an obstruction near the volcanic vent.
The High Energy Crab Nebula (1996-09-09)
 This is the mess that is left when a star explodes. The  Crab Nebula  is so energetic that it glows in  every kind of light known.  Shown above are images of the  Crab Nebula from visible light to the  X-ray band. NUV stands for "near  ultraviolet" light, FUV means "far  ultraviolet" light, and VIS means visible light. In the center of the  Crab Nebula lies the powerful  Crab pulsar - a spinning  neutron star with mass comparable to our  Sun but with the diameter of only a  small town.  The pulsar expels particles and radiation in a beam that sweeps past the  Earth 30 times a second.  The  supernova that created the  Crab Nebula was seen by  ancient  Chinese astronomers and possibly even the  Anasazi Indians  -- in 1054 AD, perhaps glowing for a week as bright as the  full moon. The Crab  still presents mysteries today as the total mass of the nebula and pulsar appears much less than the mass of the original pre-supernova star!
M77: Spiral with a Strange Glow (1996-09-10)
 Why is M77 surrounded by an ultraviolet glow?  M77, also called NGC 1068, appears at first sight to be a relatively normal  barred spiral galaxy. But when photographed in the  ultraviolet (UV), as  shown above in false color, the galaxy sports an ultraviolet halo - shown as violet in the photograph. The blue spiral structure closer to the picture's center indicates normal ultraviolet emission from bright young stars that have recently formed there.  Astronomers now hypothesize that the outer glow arises from UV light emitted from the galaxy's active center and reflected to us from clouds of  gas and  dust. These same gas and dust clouds obscure the active center of this  Seyfert galaxy - where an ultramassive  black hole is thought to live.
In the Center of Spiral M77 (1996-09-11)
 What is happening in the center of nearby spiral galaxy M77? To find out, astronomers used the  Hubble Space Telescope to peer deep into the  dusty chaos of this  active galactic nucleus in 1994.  They found a network of filamentary gas and opaque dust that provides only clues as to what central monster had left this mess. Due to the presence of hot ionized gas clouds near the core, changes in brightness that can take less than a week, and the  ultraviolet halo surrounding the whole galaxy, the leading hypothesis is that a supermassive  black hole lies at the center of this  Seyfert Type 2 galaxy.  Also known as  NGC 1068, this galaxy lies only about 50 million light years distant and is visible with only a small telescope.
Mercury: A Cratered Inferno (1996-09-12)
 Mercury's surface looks similar to our Moon's. Each is heavily  cratered and made of rock.  Mercury's diameter is about 4800 km, while the  Moon's is slightly less at about 3500 km (compared with about 12,700 km for the  Earth). But  Mercury is unique in many ways.  Mercury is the closest planet to the  Sun, orbiting at about 1/3 the radius of the  Earth's orbit. As  Mercury slowly rotates, its surface temperature varies from an unbearably cold -180 degrees  Celsius to an unbearably hot 400 degrees  Celsius. The place nearest the  Sun in  Mercury's orbit changes slightly each orbit - a fact used by  Albert Einstein to help verify the correctness of his then newly discovered theory of gravity:  General Relativity.   The above picture was taken by the only spacecraft ever to pass  Mercury:  Mariner 10 in 1974.
Southwest Mercury (1996-09-13)
 The planet Mercury resembles a moon.  Mercury's old surface is heavily  cratered like many moons.  Mercury is larger than most moons but smaller than  Jupiter's moon  Ganymede and  Saturn's moon  Titan. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the  Earth is the only planet more dense. A visitor to  Mercury's surface would see some strange sights. Because  Mercuryrotates exactly three times every two orbits around the  Sun, and because  Mercury's orbit is so elliptical, a visitor to  Mercury might see the  Sun rise, stop in the sky, go back toward the rising  horizon, stop again, and then set quickly over the other horizon.  From  Earth, Mercury's proximity to the  Sun cause it to be  visible only for a short time just after sunset or just before sunrise.
Aristarchus' Unbelievable Discoveries (1996-09-14)
 Here lived one of the greatest thinkers in human history.   Aristarchus lived on the Greek island of Samos, a small island in the center of the  above picture  that can be identified with a  good map. Aristarchus, who lived from 310 BC to 230 BC, postulated that the planets orbited the  Sun - not the  Earth -- over a thousand years before  Copernicus and  Galileo made similar arguments.  Aristarchus used clear logic to  estimate the size of the Earth, the size and distance to our  Moon, the size and distance to our Sun, the  the even deduced that the points of light we see at night are not dots painted on some celestial sphere but  stars like our Sun at enormous distances.  Aristarchus' discoveries remained truly unbelievable to the people of his time but stand today as pillars of deductive reasoning.
Tycho Brahe Measures the Sky (1996-09-15)
 Tycho Brahe was the most meticulous astronomical observer of his time.  Brahe, who lived between 1546 and 1601, set out to solve the day's most pressing astronomical problem: to determine whether the  Earth or the  Sun was at the center of the  Solar System. To do this he and his assistants created the first major astronomical observatory where they devised and used the most accurate pre-telescopic astronomical instuments.  Tycho Brahe thus compiled tables of precise measurements of the positions and brightnesses of planets and stars.  Brahe never solved the Solar System problem himself - but left data so impressively accurate his assistant  Johannes Kepler was able to develop definitive laws.  Brahe is also  remembered for witnessing a supernova in 1572, showing that the Great Comet of 1577 was not an atmospheric phenomena, and for his  metal nose.