juliensimon/nasa-apod huggingface dataset:
Welcome to the Moon Hotel (2001-07-13)

The most detailed proposal so far for a hotel and resort destination on the Moon (!) has been prepared by Dutch architect Hans-Jurgen Rombaut.  The harsh lunar environment posed serious design challenges but the Moon's low, one-sixth-Earth gravity, and the absence of wind were an architectural boon allowing a much more slender and fragile-looking building than would have been possible on Earth. Illustrated here, the structure's two 160 meter high needle-like towers soar over the rim of a deep canyon as planet Earth hangs in the lunar sky. To shield the interior, Rombaut designed 50 centimeter thick walls with two outer layers of Moon rock and a 35 centimeter layer of water held between glass planes. The water absorbs energetic cosmic rays and along with the rock helps keep the temperature constant. Windows are framed as holes in the rock layers. Construction materials are intended to be manufactured on the Moon itself. This Moon Hotel design is welcomed by the international Lunar Explorers Society, LUNEX, who hope to construct a robotic Moon base by 2015, ultimately supporting a lunar village by 2040.

Image credit: Hans-Jurgen Rombaut
(courtesy Carl Koppeschaar's ASTRONET)
Solar System Web Cam (2001-07-14)

Ranging throughout the solar system, these pictures all have something in common. They were taken with an 8 inch diameter telescope, a size popular with amateur astronomy buffs, and slightly modified "web cam" of the type widely used to send images out over the internet. The results are clearly remarkable for such inexpensive and readily available equipment. Each sharp image was produced from 20 to 30 frames which were digitally stacked and processed using free software. Until recently, digital imaging for amateur astronomers required a specialized camera, but the advent of low-light video surveillance cameras and web cams now presents other options for relatively bright solar system objects. Want to try some unconventional web cam astronomy? Geoff Chester, Public Affairs Officer at the U.S. Naval Observatory, offers these images and an account of his own adventures from a suburban front lawn near Washington D.C.

Image credit: Geoff Chester
Io in True Color (2001-07-15)

The strangest moon in the Solar System is bright yellow.  This picture, showing Io's true colors, was taken in 1999 July by the Galileo spacecraft currently orbiting Jupiter.  Io's colors derive from sulfur and molten silicate rock.  The unusual surface of Io is kept very young by its system of active volcanoes.  The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons.  The resulting friction greatly heats Io's interior, causing molten rock to explode through the surface.  Io's volcanoes are so active that they are effectively turning the whole moon inside out.  Some of Io's volcanic lava is so hot it glows in the dark.
Water Found Around Nearby Star CW Leonis (2001-07-16)

Do worlds outside our Solar System have oceans of water like Earth?  An indication that such worlds might exist was bolstered recently by new evidence that nearby star system CW Leonis harbors water.  Recent observations with the Submillimeter Wave Astronomy Satellite (SWAS) found significant detections of light at specific colors emitted by water.  A hypothesis quickly arose that the activity of the central star is vaporizing water from a cloud of comets that surrounds the star -- a cloud that may be similar to the Kuiper Belt of comets that surrounds our own Sun.  The above drawing depicts the CW Leonis system with its hypothesized cloud of water-bearing comets situated to a ring.  The closest comets are depicted as showing tails rich in water vapor pointing away from the star.  Far from the central star, however, comets should not show significant tails and should be more sparsely spaced.  The central star, also known as IRC+10216, is an aging giant star located about 500 light-years away toward the constellation of Leo.
The Carina Nebula in Three Colors (2001-07-17)

Stars, like people, do not always go gentle into that good night.  The above Carina Nebula, also known as the Keyhole Nebula and NGC 3372, results from dying star Eta Carinae's violently casting off dust and gas during its final centuries.  Eta Carinae, one of the most luminous stars known, is visible as the bright star near the center of the nebula.  The above picture was taken in three distinct colors of light: blue light as emitted from hot oxygen, green light as emitted by warm hydrogen, and red light as emitted by cool sulfur.  Eta Carinae faded from being one of the brightest stars in the sky during the 1800s, but is still visible with binoculars in southern skies towards the constellation of Carina.

Image credit: University of Minnesota
Mars from Earth (2001-07-18)

Last month, Mars and Earth were right next to each other in their orbits.  Formally called opposition, the event was highlighted by a very bright Mars for skywatchers and a good photo opportunity for the Hubble Space Telescope.  Above, Hubble snapped the highest resolution picture of Mars ever obtained from the Earth.  Visible on Mars are ice caps over the poles in white, regions covered with sand and gravel in dark brown and orange, and large dust storms in light orange.  A particularly large dust storm can be seen on the lower right pouring out of Hellas Basin.  This storm has since erupted into a huge planet wide storm that continues even today. Pictures like these allow planetary astronomers to continue to compare the weather patterns of Mars and Earth.  When Mars next reaches opposition in 2003, its elliptical orbit will cause it to be even 20 percent closer.
Pulsar Wind in the Vela Nebula (2001-07-19)

The Vela pulsar was born 10,000 years ago at the center of a supernova -- an exploding star. In this Chandra Observatory x-ray image, the pulsar still produces a glowing nebula at the heart of the expanding cloud of stellar debris. The pulsar itself is a neutron star, formed as the stellar core was compacted to nuclear densities. With a strong magnetic field, approximately the mass of the Sun, and a diameter of about 20 kilometers, the Vela pulsar rotates 11 times a second. The sharp Chandra image aids astronomers in understanding such extreme systems as efficient high-voltage generators which drive structured winds of electrically charged particles. An x-ray bright nebula is created as the pulsar winds slam into the surrounding material. This view spans about 6 light-years across the central region of the much larger Vela supernova remnant.
The Elephant's Trunk in IC 1396 (2001-07-20)

Like a picture from a galactic Just So Story, the Elephant's Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Bright swept-back ridges compose the suggestive form, outlining pockets of interstellar dust and gas. Such embedded dark, comet-shaped clouds contain the raw material for star formation. About 3,000 light-years distant, the relatively faint IC 1396 complex covers a much larger region on the sky than shown here, with an apparent width of more than 10 full moons. This close-up telescopic view is a delightful color mosaic of two digital images intended to follow the 'satiable curious cosmic trunk.

Image credit: Robert Gendler
25 Years Ago: Vikings on Mars (2001-07-21)

On July 20, 1976, NASA's Viking 1 lander became the first U.S. spacecraft to land on Mars, followed weeks later by its twin robot explorer, the Viking 2 lander. Operating on the Martian surface into the early 1980s, the Vikings took thousands of pictures, conducted sophisticated chemical searches for life, and studied the martian weather and geology. In the dramatically detailed image above, a field of rocks and boulders is viewed from the Viking 1 landing site on Chryse Planitia (the Plain of Chryse). Viking 1's dusty foot pad is just visible at the lower right. The image was created by combining high resolution black and white images with lower resolution color images of the same area. NASA is continuing its well chronicled martian exploration program as the Mars Odyssey spacecraft is scheduled to arrive at the mysterious Red Planet on October 24th. What's Mars like today?
NGC 1977: Blue Reflection Nebula in Orion (2001-07-22)

The Orion Nebula is visible to the unaided eye as a fuzzy patch near the famous belt of three stars in the Orion.  The above picture captures a part of the Orion Nebula that primarily reflects light from bright Orion stars.  This reflection nebula appears blue because the blue light from the neighboring stars scatters more efficiently from nebula gas than does red light.  The dark lanes are composed of mostly interstellar dust - fine needle-shaped carbon grains.

Image credit: AAO
Atlantis to Orbit (2001-07-23)

Birds don't fly this high.  Airplanes don't go this fast.  The Statue of Liberty weighs less.  No species other than human can even comprehend what is going on, nor could any human just a millennium ago.  The launch of a rocket bound for space is an event that inspires awe and challenges description.  Pictured above, the Space Shuttle Atlantis lifted off to visit the International Space Station during the early morning hours of July 12.  From a standing start, the two million kilogram rocket ship left to circle the Earth where the outside air is too thin to breathe and where there is little noticeable onboard gravity.  Rockets bound for space are now launched from somewhere on Earth about once a week.
The Red Spider Planetary Nebula (2001-07-24)

Oh what a tangled web a planetary nebula can weave.  The Red Spider Planetary Nebula shows the complex structure that can result when a normal star ejects its outer gases and becomes a white dwarf star.  Officially tagged NGC 6537, this two-lobed symmetric planetary nebula houses one of the hottest white dwarfs ever observed, probably as part of binary star system.  Internal winds emanating from the central stars, visible in the center, have been measured in excess of 1000 kilometers per second.  These winds expand the nebula, flow along the nebula's walls, and cause waves of hot gas and dust to collide.  Atoms caught in these colliding shocks radiate light shown in the above representative-color picture.  The Red Spider Nebula lies toward the constellation of Sagittarius.  It's distance is not well known but estimated by some to be about 4000 light-years.
Hot Gas Halo Detected Around Galaxy NGC 4631 (2001-07-25)

Is our Milky Way Galaxy surrounded by a halo of hot gas?  A step toward solving this long-standing mystery was taken recently with Chandra X-ray observations of nearby galaxy NGC 4631.  In the above composite picture, newly resolved diffuse X-ray emission is shown in blue, superposed on an HST image showing massive stars in red.  Since NGC 4631 is similar to the Milky Way, this observation indicates that our own Galaxy is indeed surrounded by a halo of hot X-ray emitting gas, although we are too close to clearly differentiate it from more nearby extended X-ray sources.  The clusters of massive stars probably heat the halo gas.  Exactly how this gas gets ejected into a halo is a topic of continuing research.
Madagascar Totality (2001-07-26)

When the Moon's shadow reached out and touched Earth's southern hemisphere on 2001 June 21, the first total solar eclipse of the 21st century began. Starting in the Atlantic, the dark, central lunar shadow or umbra traced a path which crossed southern Africa and the large island of Madagascar before ending at sunset in the Indian Ocean. Of course, as the lunar disk blocked the Sun the total phase offered splendid views of the elusive outer solar corona. But, as seen in this stunning telescopic view from southern Madagascar, it also revealed an active solar limb bristling with pinkish, planet-sized prominences. Taken as totality began, this image of the last bright rays of sunlight shining through dips and valleys in irregular lunar terrain gives the illusion of a glittering jewel set in a pink celestial ring.

Image credit: Vic & Jen Winter /
ICSTARS Astronomy, Inc.
Martian Dust Storm (2001-07-27)

If you've been unhappy with the weather on Earth, check out Mars, now in the grip of a planet-wide dust storm. Above, observations from the orbiting Mars Global Surveyor (MGS) spacecraft illustrate the storm's progress through July 21. The series of dated frames show measurements from the MGS Thermal Emission Spectrometer which can determine both temperature and amount of atmospheric dust. Dust data has been plotted on maps of the martian surface with blue representing relatively clear atmosphere and red colors indicating increasing concentrations of dust. In mid June, scientists first noticed the beginnings of the storm in Mars' southern hemisphere and have watched it grow to obscure most of the planet. Unfortunately for Mars-watchers, the timing of the storm has hidden the Red Planet's surface from view during its period of close approach to planet Earth.
A Daytime Fireball in 1944 (2001-07-28)

While stationed in  central Africa in December 1944, Norman Appleton witnessed a meteor so bright he remembered it his entire life.  Right before his eyes a tremendous smoking fireball streaked across the daytime sky.  Years later, as an accomplished member of the Guild of Aviation Artists, he recorded his memories in the above painting.  Several days ago, on July 23 at 6:19 pm EDT, a daytime fireball visible from the northeast United States was reported by many personal accounts.  No pictures of this event have yet surfaced, although it is quite possible that a video security camera somewhere caught it serendipitously. The bolide was likely caused by a sofa-sized rocky meteor disintegrating as it fell to Earth, an event that occurs over some unpopulated area almost every day.

Image credit: Norman Appleton
M57: The Ring Nebula (2001-07-29)

cept for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. This planetary nebula's simple, graceful appearance is thought to be due to perspective -- our view from planet Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Astronomers of the Hubble Heritage Project produced this strikingly sharp image from Hubble Space Telescope observations using natural appearing colors to indicate the temperature of the stellar gas shroud. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. Dark, elongated structures can also be seen near the nebula's edge. The Ring Nebula is about one light-year across and 2,000 light-years away in the northern constellation Lyra.
Star Cluster R136 Bursts Out (2001-07-30)

In the center of star-forming region 30 Doradus lies a huge cluster of the largest, hottest, most massive stars known. Known as R136, the cluster's energetic stars are breaking out of the cocoon of gas and dust from which they formed. This disintegrating cocoon, which fills the rest of the recently released above picture by the Hubble Space Telescope, is predominantly ionized hydrogen from 30 Doradus. R136 is composed of thousands of hot blue stars, some about 50 times more massive than our Sun.  R136, also known as NGC 2070, lies in the LMC - a satellite galaxy to our own Milky Way Galaxy.  Although the young ages of stars in R136 make it similar to a Milky Way open cluster, its high density of stars will likely turn it into a low mass globular cluster in a few billion years.
Oceans Under Jupiters Callisto (2001-07-31)

Tomorrow's picture: Flowing Mars  < | 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.
Young Martian Terrain (2001-08-01)

What caused the pits, ridges, and gullies on otherwise smooth Martian terrain?  One hypothesis is water.  The lack of craters at this mid-latitude location indicates that the terrain is quite young by geological standards, perhaps only 100,000 years old.  Were the terrain since saturated by water ice, that ice would soon evaporate into the thin Martian air.  Left over, however, might be fragile cake-like sand that can be broken up by wind into pits and ridges.  Consequences of this hypothesis include that even the Martian equator undergoes epochs of relative wet and dry, and that future spacefarers might be able to find water (ice) in a relatively mild climate near the Martian equator. Pictured above is young-ridged terrain that also shows evidence of a downhill flow.
Burning Tree Sprite (2001-08-02)

This dramatic, garishly colored image was captured with a low-light level camera on 2001 June 7. It shows what appears to be a "burning tree" above the National Cheng Kung University campus in Tainan City, Taiwan ... but the burning tree is actually a fleeting red sprite 300 kilometers away. Red sprites are recently discovered and still poorly understood optical flashes seen dancing at altitudes of 30 to 90 kilometers above thunderstorms. Cousins to lightning bolts, red sprites occur near the edge of the atmosphere and have been glimpsed by astronauts from orbit. What ever their cause, the red sprite flashes usually last only tenths to hundredths of a second and characteristically take on shapes which researchers describe as columns, fingers, trees, or carrots.
Warped Spiral Galaxy ESO 510-13 (2001-08-03)

How did spiral galaxy ESO 510-13 get bent out of shape?  The disks of many spirals are thin and flat, but not solid.  Spiral disks are loose conglomerations of billions of stars and diffuse gas all gravitationally orbiting a galaxy center.  A flat disk is thought to be created by sticky collisions of large gas clouds early in the galaxy's formation.  Warped disks are not uncommon, though, and even our own Milky Way Galaxy is thought to have a small warp.  The causes of spiral warps are still being investigated, but some warps are thought to result from interactions or even collisions between galaxies.  ESO 510-13, pictured above, is about 150 million light years away and about 100,000 light years across.
Neighboring Galaxy: The Large Magellanic Cloud (2001-08-04)

The brightest galaxy visible from our own Milky Way Galaxy is the Large Magellanic Cloud (LMC).  Visible predominantly from Earth's Southern Hemisphere, the LMC is the second closest galaxy, neighbor to the Small Magellanic Cloud, and one of eleven known dwarf galaxies that orbit our Milky Way Galaxy.  The LMC is an irregular galaxy composed of a bar of older red stars, clouds of younger blue stars, and a bright red star forming region visible near the top of the above image called the Tarantula Nebula.  The brightest supernova of modern times, SN1987A, occurred in the LMC.

Image credit: AURA
NGC 2440: Cocoon of a New White Dwarf (2001-08-05)

Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self.  In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! The above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf can be seen as the bright dot near the photo's center.  Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years.  The above false color image and was post-processed by Forrest Hamilton.
The Orbiting Hubble Space Telscope (2001-08-06)

The Hubble Space Telescope (HST) is the largest orbiting public optical telescope in history.  Its 2.4 meter diameter reflecting mirror and its perch above Earth's atmosphere allow it to create exceptionally sharp images.  Originally launched in 1990, HST optics were repaired to their intended accuracy in 1993 by the first of several regular servicing missions.  Astronomers using HST continue to make numerous monumental scientific discoveries, including new estimates of the age and composition of our universe, previously unknown galaxies, evidence of massive black holes in the centers of galaxies, protoplanetary star systems and star forming regions, and a better understanding of physical processes in our universe. A larger Next Generation Space Telescope (NGST) may be launched as early as 2007.
A July Dawn (2001-08-07)

Those up before dawn in late July in the northern hemisphere could see planets, stars, and a spacecraft in a single quick glance before starting their day.  Near the eastern horizon was bright Jupiter, and not far above and to its right was the very bright Venus.  Connecting the dots will point you just right of Saturn.  Far in the distance but near the top right of the frame is the Pleiades star cluster.  Orbiting the Earth well in the foreground, the International Space Station reflected sunlight to cause the faint line segment.  In the very close foreground, the bright red and yellow lines were caused by a passing van.  The above picture was taken on July 26 from Quebec, Canada.  Why are bushes visible through the van?  The van was present for only a few of the 25 seconds of the total exposure.

Image credit: Dominic
Cantin
Farewell Jupiter (2001-08-08)

Tomorrow's picture: Ray Craters  < | 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.
Tycho and Copernicus: Lunar Ray Craters (2001-08-09)

Dazzling in binoculars or a small telescope, the Moon is pocked with impact craters. During partial lunar phases, the craters along the terminator are cast in dramatic relief by strong shadows. But when the Moon is full some craters seem to sprout systems of bright radial lines or rays. This detailed digital close-up of the full Moon features two prominent ray craters, Copernicus (upper left) and Tycho (lower right), each with extensive ray systems of light colored debris blasted out by the crater-forming impacts. In general, ray craters are relatively young as their rays overlay the lunar terrain. In fact, at 85 kilometers wide, Tycho, with its far reaching rays, is the youngest large crater on the nearside. Crater Copernicus, surrounded by dark mare which contrast nicely with its bright rays, is 93 kilometers in diameter.

Image credit: Steve Mandel,
Hidden Valley Observatory
Perseids of Summer (2001-08-10)

Like falling stardust, cast off bits of comet Swift-Tuttle hurtle through the upper atmosphere about this time each year as planet Earth passes near the comet's orbital path. For the northern hemisphere, this regular celestial display is known as the annual Perseid meteor shower -- so named because the meteor trails all appear traceable to a common "radiant point" in the constellation Perseus. This gorgeous wide-angle photo from the 1997 shower captures a 20-degree-long fireball meteor and another, fainter Perseid meteor trail in a rich area of the northern summer Milky Way. A labeled version is available identifying the shower's radiant point, surrounding deep-sky objects, and constellations. Easy to view (just go outside and look up!), the Perseid meteor shower will peak this weekend with maximum rates anticipated early Sunday morning, August 12, for eastern North America. Despite interfering moonlight, last year's faithful Perseid watchers were rewarded with bright meteors and extensive displays of the northern lights.

Image credit: Rick Scott &
Joe Orman