juliensimon/nasa-apod huggingface dataset:
A Gamma Ray Burst - Supernova Connection (2003-04-14)

New evidence has emerged that a mysterious type of explosion known as a gamma ray burst is indeed connected to a supernova of the type visible in the above image.  Two weeks ago, the orbiting HETE satellite detected gamma-ray burst GRB030329.  The extremely bright burst was found hours later to have an extremely bright afterglow in visible light, and soon set the record for the closest measured distance at redshift 0.17.  The afterglow brightness allows unprecedented coverage of its evolution.  Just this week, as many astronomers suspected would happen, the afterglow began to appear as a fading Type II Supernova.  Type II Supernovas might not appear coincident with gamma-ray bursts, however, when the gamma-ray beam goes in another direction.  The above spiral galaxy, NGC 3184, was home to a Type II Supernova in 1999 at the position of the arrow.  Astronomers are currently pressing hard to find the host galaxy for GRB030329.
A Crescent Nebula Star Field (2003-04-15)

What caused the Crescent Nebula?  Looking like an emerging space cocoon, the Crescent Nebula, visible on the right, was created by the brightest star in its center.  A leading progenitor hypothesis has the Crescent Nebula beginning to form about 250,000 years ago.  At that time, the massive central star had evolved to become a Wolf-Rayet star (WR 136), shedding its outer envelope in a strong stellar wind, ejecting the equivalent of our Sun's mass every 10,000 years.  This wind impacted surrounding gas left over from a previous phase, compacting it into a series of complex shells, and lighting it up.  The Crescent Nebula, also known as NGC 6888, lies about 4,700 light-years away in the constellation of Cygnus.  Star WR 136 will probably undergo a supernova explosion sometime in the next million years.

Image credit: T. A. Rector
Magma Bubbles from Mt. Etna (2003-04-16)

Mt. Etna erupted spectacularly in 2001 June.  Pictured above, the volcano was photographed expelling bubbles of hot magma, some of which measured over one meter across.  One reason planetary geologists study Earth's Mt. Etna is because of its likely similarity to volcanoes on Mars.  Mt. Etna, a basalt volcano, is composed of material similar to Mars, and produces similar lava channels.  Located in Sicily, Italy, Mt. Etna is not only one of the most active volcanoes on Earth, it is one of the largest, measuring over 50 kilometers at its base and rising nearly 3 kilometers high.

Image credit: Stromboli online
M106 in Canes Venatici (2003-04-17)

Close to the Great Bear (Ursa Major) and surrounded by the stars of the Hunting Dogs (Canes Venatici), this celestial nebula was discovered in 1781 by the metric French astronomer Pierre Mechain and later added to the catalog of his friend and colleague Charles Messier as M106. Modern deep telescopic views reveal it to be an island universe -- a spiral galaxy around 30 thousand light-years across located only about 21 million light-years beyond the stars of the Milky Way. Youthful blue star clusters and reddish stellar nurseries trace the striking spiral arms of M106. Seen so clearly in this beautiful image, the galaxy's bright core is also visible across the spectrum from radio to x-rays, making M106 a nearby example of the Seyfert class of active galaxies. The bright core of a Seyfert galaxy is believed to be powered by matter falling into a massive central black hole.
Double Eruptive Prominences (2003-04-18)

Lofted over the Sun on looping magnetic fields, large solar prominences are composed of relatively cool, dense plasma. When seen against the brilliant solar disk they appear as dark filaments, but these enormous magnetic structures are bright themselves when viewed against the blackness of space as they arc above the Sun's edge. In a rare visual treat, these two solar prominences arising from the Sun's southern (lower) hemisphere were captured in extreme ultraviolet light by the EIT camera on board the space-based SOlar and Heliospheric Observatory (SOHO) on March 21. For scale, the pair of plasma loops stretch above the Sun to a height of about twenty times the diameter of planet Earth. In a matter of hours, these prominences apparently erupted away from the Sun's surface and may have been associated with a flare and coronal mass ejection.
Spiral Galaxy In Centaurus (2003-04-19)

Centaurus, the Centaur, is one of the most striking constellations in the southern sky. The lovely Milky Way flows through this large constellation whose celestial wonders also include the closest star to the sun, Alpha Centauri, the largest globular star cluster in our galaxy, Omega Centauri, and the closest active galaxy, Centaurus A. Embraced by tightly wound spiral arms of bright blue star clusters, this gorgeous galaxy - cataloged as ESO 269-57 - also falls within Centaurus' borders. Seen behind a veil of foreground stars which lie within our own galaxy, this face-on spiral galaxy is about 150 million light-years away and 200,000 light-years across. The brighter foreground stars are marked by diffraction spikes caused by the telescope and yellow vertical stripes due to saturated digital camera pixels in the above Very Large Telescope image from the European Southern Observatory. Tantalizing wisps of more distant, faint galaxies are visible in the background.
The Gum Nebula Supernova Remnant (2003-04-20)

Because the Gum Nebula is the closest supernova remnant, it is actually hard to see.  Spanning 40 degrees across the sky, the nebula is so large and faint it is easily lost in the din of a bright and complex background.  The Gum Nebula, highlighted nicely in the above wide angle photograph, is so close that we are much nearer the front edge than the back edge, each measuring 450 and 1500  light years respectively.  The complex nebula lies in the direction of the constellations of Puppis and Vela.  Oddly, much remains unknown about the Gum Nebula, including the timing and even number of supernova explosions that formed it.

Image credit: John Gleason (Celestial Images)
A Halo Around the Moon (2003-04-21)

Tomorrow's picture: North Mars  < | Archive | Index | Search | Calendar | Glossary | Education | About APOD | >  Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Web Site Statements, Warnings, and Disclaimers NASA Official: Jay Norris. Specific rights apply. A service of: LHEA at NASA / GSFC & Michigan Tech. U.

Image credit: Sarah McKay
Springtime on Mars (2003-04-22)

Vast canyons, towering volcanoes, sprawling fields of ice, deep craters, and high clouds can all be seen in this image of the Solar System's fourth planet: Mars.  The orbiting robot Mars Global Surveyor spacecraft took the above mosaic of images as springtime dawned in Northern Mars in 2002 May.  Sprawled across the image bottom is Valles Marinaris, a canyon three times the length of Earth's Grand Canyon, and four times as deep.  On the left are several volcanoes including Olympus Mons, a volcano three times higher than Earth's Mt. Everest.  At the top is the North Polar Cap made of thawing water and carbon-dioxide based ice.  Swirling white clouds and circular impact craters are also visible around Mars.  Two rovers will be launched to Mars this summer and should arrive in 2004 January.
The Stars of NGC 1705 (2003-04-23)

Some 2,000 light-years across, NGC 1705 is small as galaxies go, similar to our Milky Way's own satellite galaxies, the Magellanic Clouds. At a much larger distance of 17 million light-years, the stars of NGC 1705 are still easily resolved in this beautiful image constructed from data taken in 1999 and 2000 with the Hubble Space Telescope. Most of the younger, hot, blue stars in the galaxy are seen to be concentrated in a large central star cluster with the older, cooler, red stars more evenly distributed. Possibly 13 billion years old, NGC 1705 could well have been forming stars through out its lifetime while light from its most recent burst of star formation reached Earth only 30 million years ago. This gradually evolving dwarf irregular galaxy lacks organized structures like spiral arms and is thought to be a nearby analog to the first galaxies to form in the early Universe.
Earth at Twilight (2003-04-24)

No sudden, sharp boundary marks the passage of day into night in this gorgeous view of ocean and clouds over our fair planet Earth. Instead, the shadow line or terminator is diffuse and shows the gradual transition to darkness we experience as twilight. With the Sun illuminating the scene from the right, the cloud tops reflect gently reddened sunlight filtered through the dusty troposphere, the lowest layer of the planet's nurturing atmosphere. A clear high altitude layer, visible along the dayside's upper edge, scatters blue sunlight and fades into the blackness of space. This picture actually is a single digital photograph taken in June of 2001 from the International Space Station orbiting at an altitude of 211 nautical miles.
M17: A Hubble Close-Up (2003-04-25)

Sculpted by stellar winds and radiation, these fantastic, undulating shapes lie within the stellar nursery known as M17, the Omega Nebula, some 5,500 light-years away in the nebula-rich constellation Sagittarius. The lumpy features in the dense cold gas and dust are illuminated by stars off the upper left of the image and may themselves represent sites of future star formation. Colors in the fog of surrounding hotter material indicate M17's chemical make up. The predominately green glow corresponds to abundant hydrogen, with trace sulfur and oxygen atoms contributing red and blue hues. The picture spans about 3 light-years and was released to celebrate the thirteenth year of the Hubble Space Telescope's cosmic voyage of exploration.
Big Blue Marble Earth (2003-04-26)

This reconstructed digital portrait of our planet is reminiscent of the Apollo-era pictures of the "big blue marble" Earth from space. To create it, researchers at Goddard Space Flight Center's Laboratory for Atmospheres combined data from a Geostationary Operational Environmental Satellite (GOES), the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and the Polar Orbiting Environmental Satellites (POES) with a USGS elevation model of Earth's topography. Stunningly detailed, the planet's western hemisphere is cast so that heavy vegetation is green and sparse vegetation is yellow, while the heights of mountains and depths of valleys have been exaggerated by 50 times to make vertical relief visible.  Hurricane Linda is the dramatic storm off North America's west coast. And what about the Moon? The lunar image was reconstructed from GOES data and artistically rescaled for this visualization.
Venus' Once Molten Surface (2003-04-27)

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.
Rollout of a Soyuz TMA-2 Aboard an R7 Rocket (2003-04-28)

It takes a big rocket to go into space.  Last weekend, this huge Russian rocket was launched toward Earth-orbiting International Space Station (ISS), carrying two astronauts who will make up the new Expedition 7 crew.  Seen here during rollout at the Baikonur Cosmodrome, the rocket's white top is actually a Soyuz TMA-2, the most recent version of the longest serving type of human spacecraft.  The base is a Russian R7 rocket, originally developed as a prototype Intercontinental Ballistic Missile in 1957.  The rocket spans the width of a football field and has a fueled mass of about half a million kilograms.  Russian rockets like this will be primary transportation system to the ISS while NASA studies the underlying reasons behind the recent tragic break-up of the Space Shuttle Columbia.
In the Center of the Rosette Nebula (2003-04-29)

In the heart of the Rosette Nebula lies a bright open cluster of stars that lights up the nebula.  The stars of NGC 2244 formed from the surrounding gas only a few million years ago.  This just-released image taken by the CFHT's new MegaPrime camera shows the region in unprecedented detail.  Although the emission nebula is dominated by red hydrogen light, the above image has exaggerated the effect of green light emitted primarily by small amounts of oxygen. A hot wind of particles streams away from the cluster stars and contributes to an already complex menagerie of gas and dust filaments while slowly evacuating the cluster center.  The Rosette Nebula's center measures about 50 light-years across, lies about 4500 light-years away, and is visible with binoculars towards the constellation of Monoceros.

Image credit: MegaPrime Camera,
Canada-France-Hawaii Telescope
A Lenticular Cloud Over New Hampshire (2003-04-30)

Why does this cloud look so strange?  Actually, pictured above are several clouds all stacked up into one striking lenticular cloud.  Normally, air moves much more horizontally than it does vertically.  Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes.  The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance.  The above picture was taken in 1999 over Plymouth, New Hampshire, USA.  The same lenticular cloud also looks strange when photographed from 30 kilometers away.

Image credit: J. D. Rufo, 
J. Koermer, 
Plymouth State College
The Energetic Jet from Centaurus A (2003-05-01)

The center of well-studied active galaxy Centaurus A is hidden from the view of optical telescopes by a cosmic jumble of stars, gas, and dust. But both radio and x-ray telescopes can trace the remarkable jet of high-energy particles streaming from the galaxy's core. With Cen A's central region at the lower right, this composite false-color image shows the radio emission in red and x-rays in blue over the inner 4,000 light-years of the jet. One of the most detailed images of its kind, the picture shows how the x-ray and radio emitting sites are related along the jet, providing a road map to understanding the energetic stream. Extracting its energy from a supermassive black hole at the galaxy's center, the jet is confined to a relatively narrow angle and seems to produce most of its x-rays (bluer colors) at the upper left, farther from the core, where the jet begins to collide with Centaurus A's denser gas.
Five to Mars (2003-05-02)

Come December 2003 - January 2004, an armada of five new invaders from Earth should arrive on the shores of the Red Planet -- the Japanese ( ISAS) Nozomi orbiter, the European Space Agency's Mars Express orbiter carrying the Beagle 2 lander, and NASA's own two Mars Exploration Rovers. While Nozomi began its interplanetary voyage in 1998, the other spacecraft are scheduled for launch windows beginning this June. Clearly, earthdwellers remain intensely curious about Mars and the tantalizing possibility of past or present martian life, with these robotic missions focussing on investigating the planet's atmosphere and the search for water. This mosaic of over 100 Viking 1 orbiter images of Mars was recorded in 1980 and is projected to show the perspective seen from an approaching spacecraft at a distance of 2,000 kilometers. Exceptional views of Mars will be possible from earthbound telescopes in August and September.
Denizen of the Tarantula Nebula (2003-05-03)

The star cluster at lower right, cataloged as Hodge 301, is a denizen of the Tarantula Nebula. An evocative nebula in the southern sky, the sprawling cosmic Tarantula is an energetic star forming region some 168,000 light-years distant in our neighboring galaxy the Large Magellanic Cloud. The stars within Hodge 301 formed together tens of millions of years ago and as the massive ones quickly exhaust their nuclear fuel they explode. In fact, the giant stars of Hodge 301 are rapidly approaching this violent final phase of stellar evolution - known as a supernova. These supernova blasts send material and shock waves back into the nebular gas to create the Tarantula's glowing filaments also visible in this Hubble Space Telescope Heritage image. But these spectacular stellar death explosions signal star birth as well, as the blast waves condense gas and dust to ultimately form the next generation of stars inside the Tarantula Nebula.
A Sonic Boom (2003-05-04)

Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane.  When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom.  As a plane accelerates to just break the sound barrier, however, an unusual cloud might form.  The origin of this cloud is still debated.  A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets.  Above, an F/A-18 Hornet was  photographed just as it broke the sound barrier.  Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.
NGC 1275: A Galactic Collision (2003-05-05)

In NGC 1275, one galaxy is slicing through another.  The disk of the dusty spiral galaxy near the image center is cutting through a large elliptical galaxy, visible predominantly on the lower left.  Galaxies can change significantly during a collision like this, with gravitational tides distorting each galaxy and gas clouds being compressed and lighting up with new star formation.  Galaxy collisions occur in slow motion to the human eye, with a single pass taking as much as 100 million years.  NGC 1275 is a member of the Perseus cluster of galaxies that lies about 230 million light years away toward the constellation of Perseus.  Each galaxy spans about 50,000 light years across.  The above picture is a composite of images taken by the Hubble Space Telescope in 1995 and 2001.
A Chicago Meteorite Fall (2003-05-06)

If you wait long enough, a piece of outer space itself will come right to you.  As Colby Navarro worked innocently on the computer, a rock from space crashed through the roof, struck the printer, banged off the wall, and came to rest near the filing cabinet.  This occurred around midnight on March 26 in Park Forest, Illinois, USA, near Chicago.  The meteorite, measuring about 10 cm across, was one of several that fell near Chicago that day as part of a tremendous fireball.  Pictured above is the resulting hole in the ceiling, while the inset image shows the wall dent and the meteorite itself.  Although the vast majority of meteors is much smaller and burn up in the Earth's atmosphere, the average homeowner should expect to repair direct meteor damage every hundred million years.

Image credit: Ivan and Colby Navarro
The Southern Sky from the International Space Station (2003-05-07)

Look up from Earth's South Pole, and this stellar starscape is what you might see.  Alternatively, this patch of sky is also visible from many southern locations as well as the orbiting International Space Station, where the above image was recently recorded.  To the left of the photograph's center are the four stars that mark the boundaries of the famous Southern Cross.  The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy.  At the lower left is the dark Coal Sack Nebula, and the bright nebula on the far right is the Carina Nebula.  The Southern Cross is such a famous constellation that it is depicted on the national flag of Australia.
Mercury Spotting (2003-05-08)

Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. The Sun was above the horizon during the entire transit for observers in Europe, Africa, Asia, or Australia, and the horizon was certainly no problem for the sun-staring SOHO spacecraft. Seen as a dark spot, Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. The panels' false-colors correspond to different wavelengths in the extreme ultraviolet which highlight regions above the Sun's visible surface. This is the first of 14 transits of Mercury which will occur during the 21st century, but the next similar event will be a transit of Venus in June of 2004. Need help spotting Mercury? Just click on the picture.
International Space Station in Transit (2003-05-09)

A stunning telescopic image of the International Space Station crossing in front of an eight day old Moon, this picture was captured on April 11th. But while Wednesday's leisurely transit of Mercury across the Sun entertained observers all over the dayside of planet Earth, the audience for this lunar transit was more restricted. Like other satellites in low Earth orbit, the space station moves quickly through the sky. Glinting in the sunlight near sunset and sunrise, its path strongly depends on the observer's longitude and latitude. So, well-placed astronomer Tom Laskowski tracked the orbiting space station from a site near South Bend, Indiana, USA and recorded a digital movie of the fleeting, dramatic event. This single frame from the movie has been enhanced to bring out detail in the space station. Seen below the lunar terminator at the lower left, the International Space Station appears here at a distance of just over 400 kilometers, with the Moon nearly 400,000 kilometers away.

Image credit: Tom Laskowski
NGC 7293: The Helix Nebula (2003-05-10)

Will our Sun look like this one day?  The Helix Nebula is the closest example of a planetary nebula created at the end of the life of a Sun-like star.  The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix.  The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce.  The Helix Nebula, given a technical designation of NGC 7293, lies about 650 light-years away towards the constellation of Aquarius and spans about 2.5 light-years.  The above picture is a composite of newly released images from the ACS instrument on the Hubble Space Telescope and wide-angle images from the Mosaic Camera on the WIYN 0.9-m Telescope at Kitt Peak National Observatory.  A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.   News: Today is Astronomy Day!
M83: The Southern Pinwheel Galaxy from VLT (2003-05-11)

M83 is one of the closest and brightest spiral galaxies on the sky. Visible with binoculars in the constellation of Hydra, majestic spiral arms have prompted its nickname as the Southern Pinwheel. Although discovered 250 years ago, only much later was it appreciated that  M83 was not a nearby gas cloud, but a barred spiral galaxy much like our own Milky Way Galaxy.  M83, pictured above in a photograph from a Very Large Telescope, is a prominent member of a group of galaxies that includes Centaurus A and NGC 5253, all of which lie about 15 million light years distant.  To date, six supernova explosions have been recorded in M83.  An intriguing double circumnuclear ring has been discovered at the center of M83.