juliensimon/nasa-apod huggingface dataset:
Cepheus: Trunk to Bubble (2010-09-09)

Star clusters, glowing nebulae and dark dust clouds abound in Cepheus, royal constellation of the northern hemisphere. You can follow them in amazing detail across this broad skyscape, a mosaic of telescopic images spanning about 17 degrees. Beginning at the lower left, the large emission nebula is cataloged as IC 1396. Hundreds of light-years across and about 3,000 light-years distant, it contains a dark, winding, tendril-shaped feature popularly known as the Elephant's Trunk. Near the top middle, the bright nebula with an embedded star cluster is NGC 7380. At the upper right lies NGC 7635 (the Bubble Nebula) and star cluster M52. Put your cursor over the picture to see a labeled version of the field. Many of the objects highlighted have a designation from the second version of the Sharpless catalog (Sh2) and the Barnard catalog (B) of dark nebulae. Associated with star formation, the sites are telltale markers along the region's complex of giant molecular clouds.  Take a short survey about viewing astronomy images on mobile devices.

Image credit: Rogelio
Bernal Andreo
Vela Supernova Remnant (2010-09-10)

The plane of our Milky Way Galaxy runs through this complex and beautiful skyscape. At the northwestern edge of the constellation Vela (the Sails) the four frame mosaic is over 10 degrees wide, centered on the glowing filaments of the Vela Supernova Remnant, the expanding debris cloud from the death explosion of a massive star. Light from the supernova explosion that created the Vela remnant reached Earth about 11,000 years ago. In addition to the shocked filaments of glowing gas, the cosmic catastrophe also left behind an incredibly dense, rotating stellar core, the Vela Pulsar. Some 800 light-years distant, the Vela remnant is likely embedded in a larger and older supernova remnant, the Gum Nebula.  Take a short survey about viewing astronomy images on mobile devices.

Image credit: Star Echoes
Star Streams and the Sunflower Galaxy (2010-09-11)

A bright spiral galaxy of the northern sky, Messier 63 is about 25 million light-years distant in the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way. Known by the popular moniker, The Sunflower Galaxy, M63 sports a bright yellowish core and sweeping blue spiral arms, streaked with cosmic dust lanes and dotted with pink star forming regions. This deep exposure also reveals an enormous but dim arc extending far into the halo above the brighter galactic plane. A collaboration of professional and amateur astronomers has shown the arc to be consistent with the stellar stream from a smaller satellite galaxy, tidally disrupted as it merged with M63 during the last 5 billion years. Their discovery is part of an increasing body of evidence that the growth of large spirals by cannibalizing smaller galaxies is commonplace in the nearby Universe.  Take a short survey about viewing astronomy images on mobile devices.

Image credit: R Jay GaBany
Oklo: Ancient African Nuclear Reactors (2010-09-12)

The remnants of nuclear reactors nearly two billion years old were found in the 1970s in Africa.  These reactors are thought to have occurred naturally. No natural reactors exist today, as the relative density of fissile uranium has now decayed below that needed for a sustainable reaction. Pictured above is Fossil Reactor 15, located in Oklo, Gabon. Uranium oxide remains are visible as the yellowish rock.  Oklo by-products are being used today to probe the stability of the fundamental constants over cosmological time and distance scales and to develop more effective means for disposing of human-manufactured nuclear waste.

Image credit: Robert D. Loss
(Curtin U.)
Zodiacal Light Over Namibia (2010-09-13)

An unusual triangle of light is visible this time of year just before dawn, in the northern hemisphere. Once considered a false dawn, this triangle of light is actually zodiacal light, light reflected from interplanetary dust particles.  The bright reflecting triangle is clearly visible on the right of the above horizontally-compressed image taken just after sunset from Namibia in the southern hemisphere in 2009 June. The central band of our Milky Way Galaxy on the left first mirrors the zodiacal band on the right but then curves around the sky.  The faint smudges inside the arch of the Milky Way are the Large and Small Magellanic Clouds. Zodiacal dust orbits the Sun predominantly in the same plane as the planets: the ecliptic.  Zodiacal light is so bright in the north this time of year because the dust band is oriented nearly vertical at sunrise, so that the thick air near the horizon does not block out relatively bright reflecting dust.  Zodiacal light is also bright for people in Earth's northern hemisphere in March and April just after sunset. In the southern hemisphere, zodiacal light is most notable after sunset in late summer, and brightest before sunrise in late spring.

Image credit: Rudi Dobesberger
(Sternfreunde Steyr)
An Extraordinary Spiral from LL Pegasi (2010-09-14)

What created the strange spiral structure on the left?  No one is sure, although it is likely related to a star in a binary star system entering the planetary nebula phase, when its outer atmosphere is ejected.  The huge spiral spans about a third of a light year across and, winding four or five complete turns, has a regularity that is without precedent.  Given the expansion rate of the spiral gas, a new layer must appear about every 800 years, a close match to the time it takes for the two stars to orbit each other. The star system that created it is most commonly known as LL Pegasi, but also AFGL 3068. The unusual structure itself has been cataloged as IRAS 23166+1655. The above image was taken in near-infrared light by the Hubble Space Telescope. Why the spiral glows is itself a mystery, with a leading hypothesis being illumination by light reflected from nearby stars.
Clouds, Birds, Moon, Venus (2010-09-15)

Sometimes the sky above can become quite a show. Last week, for example, the Moon and Venus converged, creating quite a sight by itself for sky enthusiasts around the globe.  From some locations, though, the sky was even more picturesque. In the above image taken last week from Spain, a crescent Moon and the planet Venus, on the far right, were captured during sunset posing against a deep blue sky.  In the foreground, dark storm clouds loom across the image bottom, while a white anvil cloud shape appears above. Black specks dot the frame, caused by a flock of birds taking flight. Very soon after this picture was taken, however, the birds passed by, the storm ended, and Venus and the Moon set.  The Moon and Venus have now separated, although Venus will remain visible at sunset for the rest of this month.

Image credit: Isaac Guti�rrez Pascual (Spain)
The Veil Nebula (2010-09-16)

Delicate in appearance, these filaments of shocked, glowing gas, draped in planet Earth's sky toward the constellation of Cygnus, make up the Veil Nebula. The nebula is a large supernova remnant, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Also known as the Cygnus Loop, the Veil Nebula now spans nearly 3 degrees or about 6 times the diameter of the full Moon. That translates to over 70 light-years at its estimated distance of 1,500 light-years. In fact, the Veil is so large its brighter parts are recognized as separate nebulae, including The Witch's Broom (NGC 6960) at the bottom of this stunning skyview and Pickering's Triangle (NGC 6979) below and right of center. At the top is the haunting IC 1340.  Take a short survey about viewing astronomy images on mobile devices.

Image credit: Martin Pugh
Northern Lights over Prelude Lake (2010-09-17)

Curtains of shimmering green light sprawl across this gorgeous night skyscape. In the foreground lies the peaceful Prelude Lake, located about 30 kilometers east of Yellowknife, Northwest Territories, Canada. From high northern latitudes these mesmerizing northern lights, also known as the aurora borealis, are becoming a more familiar sight. As the September 23rd equinox approaches, nights grow longer and a favorable season for aurora begins. Recorded on September 11, this panoramic scene spans about 180 degrees. Brighter stars peering through the auroral glow at the left form the recognizable northern asterism, the Big Dipper. A more compact Pleiades star cluster shines at the far right.   Take a short survey about viewing astronomy images on mobile devices.

Image credit: Yuichi Takasaka
Opposite the Sun (2010-09-18)

Chances are the brightest star you've seen lately is actually planet Jupiter. Jupiter rules the sky in this labeled view of a starry September night from the Alborz mountains in Iran, complete with the trail of a red flashlight illuminating the mountain road. On September 21st (Universal Time) Jupiter will be at opposition, the point opposite the Sun along its orbit, rising just as the Sun sets. For this opposition, Jupiter will be slightly brighter and closer to planet Earth than in any year since 1963. Much fainter and also approaching its own opposition on September 21st, is the distant planet Uranus. Very near Jupiter on the sky, the fainter planet is easy to spot in binoculars (similar to the inset view), well above and right of brilliant Jupiter and about as bright as one of Jupiter's own Galilean moons. Remarkably close to the opposition of both planets, the point on the sky exactly opposite the Sun on September 23rd is marked the Vernal Equinox. On that date, a Full Moon will join the celestial scene. Of course, any Full Moon is also at opposition.  Tonight: International Observe the Moon Night

Image credit: Babak Tafreshi
Dark Clouds of the Carina Nebula (2010-09-19)

What dark forms lurk in the mists of the Carina Nebula? These ominous figures are actually molecular clouds, knots of molecular gas and dust so thick they have become opaque.  In comparison, however,  these clouds are typically much less dense than Earth's atmosphere.  Pictured above is part of the most detailed image of the Carina Nebula ever taken, a part where dark molecular clouds are particularly prominent.  The image has recently been retaken and then re-colored based on light emitted by oxygen. The entire Carina Nebula spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula.  Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.  Wide-field annotated and zoomable versions of the larger image composite are also available.
Aurora Over Norway (2010-09-20)

Auroras can make spectacular sights. Photographed above last weekend, flowing multi-colored auroras helped illuminate a busy sky above  Troms�, Norway. Besides the spectacular aurora pictured above, the photographer caught three satellites streaks, one airplane streak, and a friend trying to capture the same sight. Although auroras might first appear to be moonlit clouds, they only add light to the sky and do not block background stars from view. Called northern lights in the northern hemisphere, auroras are caused by collisions between charged particles from the magnetosphere and air molecules high in the Earth's atmosphere. If viewed from space, auroras can be seen to glow in X-ray and ultraviolet light as well.  Predictable auroras might occur a few days after a powerful magnetic event has been seen on the Sun.

Image credit: Ole Christian Salomonsen
Starry Night Over the Rhone (2010-09-21)

How can the majesty of the night sky best be captured in a painting? This was a continual challenge for Vincent van Gogh, a famous painter in the late 1800s who pioneered stirring depictions of star filled skies into several of his works. Pictured above is van Gogh's Starry Night Over the Rhone, where the French town of Arles is depicted complete with gas lights reflecting off the Rhone river. van Gogh's night sky appears alive with turbulent stellar images contrasting with lofty dark blue hues.  Above the river, one can discern the stars of the familiar Big Dipper asterism. Following a line connecting the two Big Dipper stars on the right, the North Star Polaris could be easily found, the height of which can then be estimated and actually gives the latitude where the painting was created.
Discovery Rollout Shadow (2010-09-22)

Who goes there?  Although the spotlighted figure in white might not be identifiable by itself, surely the huge shadow behind it makes its identity clear: the space shuttle.  Specifically, it was the space shuttle Discovery being rolled out last March in preparation for launch. As captured above, an unusual monstrous shadow on passing fog was created during a picturesque night unveiling. While on the shuttle Crawler-Transporter, one of the largest tracked vehicles on Earth, the shuttle moved at about 2 km per hour from the main assembly building to the launch pad at NASA's Kennedy Space Center in Florida, USA. About a month later, in its penultimate planned mission, Discovery roared off the launch pad and delivered needed supplies and equipment to the International Space Station. Yesterday, Discovery reached Launch Pad 39A in preparation for its last planned mission.

Image credit: Nancy
Atkinson
(Universe Today)
Equinox and the Iron Sun (2010-09-23)

Today, the Sun crosses the celestial equator heading south at 03:09 Universal Time. Known as an equinox, this astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. Equinox means equal night. With the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, in the north the days continue to grow shorter, the Sun marching lower in the sky as winter approaches. To celebrate the equinox, consider this view of the Sun in extreme ultraviolet light from the Sun staring Solar Dynamics Observatory. Recorded yesterday, the false-color image shows emission from highly ionized iron atoms. Loops and arcs trace the glowing plasma suspended in magnetic fields above solar active regions.
Equinox and the Harvest Moon (2010-09-24)

Did you enjoy the moonlight last night? The Full Moon closest to autumnal equinox and the beginning of Fall is traditionally known as the Harvest Moon, rising opposite the Sun and illuminating fields at harvest time after sunset. This year's northern hemisphere autumnal equinox occurred yesterday, September 23rd, at 03:09 Universal Time. The Moon was at its full phase a mere 6 hours later -- exceptionally close for a Harvest Moon! Of course, the Moon still shines brightly through the night in surrounding days. In this picture from September 22nd, the lunar orb dominates the sky above a ruined church in Zsámbék, Hungary. Shining nearby, the brightest star is actually Jupiter, also opposite the Sun, seen here through thin clouds just left of the church wall.

Image credit: Tamás Ábrahám
Melotte 15 in the Heart (2010-09-25)

Cosmic clouds seem to form fantastic shapes in the central regions of emission nebula IC 1805. Of course, the clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15. About 1.5 million years young, the cluster stars are near the center in this colorful skyscape, along with dark dust clouds silhouetted against glowing atomic gas. A composite of narrow and broad band telescopic images, the view spans about 40 light-years and includes emission from hydrogen in green, sulfur in red, and oxygen in blue hues. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - The Heart Nebula. IC 1805 is located about 7,500 light years away toward the constellation Cassiopeia.

Image credit: Derek Santiago
Arp 188 and the Tadpole's Tidal Tail (2010-09-26)

Why does this galaxy have such a long tail?   In this stunning vista recorded with the Hubble Space Telescope's Advanced Camera for Surveys, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation Draco. Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from left to right in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the lower left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy.
The Dancing Auroras of Saturn (2010-09-27)

What drives auroras on Saturn? To help find out, scientists have sorted through hundreds of infrared images of Saturn taken by the Cassini spacecraft for other purposes, trying to find enough aurora images to correlate changes and make movies. Once made, some movies clearly show that Saturnian auroras can change not only with the angle of the Sun, but also as the planet rotates. Furthermore, some auroral changes appear related to waves in Saturn's magnetosphere likely caused by Saturn's moons. Pictured above, a false-colored image taken in 2007 shows Saturn in three bands of infrared light.  The rings reflect relatively blue sunlight, while the planet itself glows in comparatively low energy red.  A band of southern aurora in visible in green. Inspection of many more Saturnian images may well lead to an even better understanding of both Saturn's and Earth's auroras.
Venus' South Polar Vortex (2010-09-28)

What's happening over the South Pole of Venus?  To find out, scientists have been studying images taken by the robotic Venus Express spacecraft when it passes over the lower spin axis of Earth's overheated twin. Surprisingly, recent images from Venus Express do not confirm previous sightings of a double storm system there, but rather found a single unusual swirling cloud vortex. In the above recently released image sequence taken in infrared light and digitally compressed, darker areas correspond to higher temperatures and hence lower regions of Venus' atmosphere.  Also illuminating are recently released movies, which show similarities between Venus' southern vortex and the vortex that swirls over the South Pole of Saturn. Understanding the peculiar dynamics of why, at times, two eddies appear, while at other times a single peculiar eddy appears, may give insight into how hurricanes evolve on Earth, and remain a topic of research for some time.  In three months, the European Venus Express spacecraft will be joined around Venus by the Japanese Akatsuki satellite.
An Airplane in Front of the Moon (2010-09-29)

If you look closely at the Moon, you will see a large airplane in front of it.  Well, not always. OK, hardly ever.  But if you wait for days with your camera attached to a Moon tracker in a place where airplanes are known to pass, you might catch a good photograph of it.  Well, if you're lucky. OK, extremely lucky.  The above image was taken two weeks ago over South East Queensland, Australia using an exposure time of 1/250th of a second and, in the words of the photographer, "a nerve of steel".

Image credit: Chris Thomas
Coreshine from a Dark Cloud (2010-09-30)

Stars and their planets are born in cold, dark, interstellar clouds of gas and dust. While exploring the clouds at infrared wavelengths, astronomers have made a surprising discovery -- dozens of cases where dense cloud cores shine by reflecting infrared starlight. Based on archival Spitzer Space Telescope data, these panels illustrate the newly described phenomenon, known as coreshine. At longer infrared wavelengths (right) the core of cloud Lynds 183 is dark, but at shorter infrared wavelengths (left) the core clearly shines, scattering light from nearby stars. As seen in these panels, the elongated core covers a mere 1.5 light-years. The scattering requires dust grains that are about 10 times larger than previously thought to exist in the clouds, about 1 micron in size instead of 0.1 micron. For comparison, a human hair is about 100 microns thick. The larger dust grains indicated by coreshine could change models of the early phases of star and planet formation, a still mysterious process hidden within the interstellar clouds. Dark nebula Lynds 183 lies around 325 light-years away in the constellation Serpens.
Zarmina's World (2010-10-01)

A mere 20 light-years away in the constellation Libra, red dwarf star Gliese 581 has received much scrutiny by astronomers in recent years. Earthbound telescopes had detected the signatures of multiple planets orbiting the cool sun, two at least close to the system's habitable zone -- the region where an Earth-like planet can have liquid water on its surface. Now a team headed by Steven Vogt (UCO Lick), and Paul Butler (DTM Carnagie Inst.) has announced the detection of another planet, this one squarely in the system's habitable zone. Based on 11 years of data, their work offers a very compelling case for the first potentially habitable planet found around a very nearby star. Shown in this artist's illustration of the inner part of the exoplanetary system, the planet is designated Gliese 581g, but Vogt's more personal name is Zarmina's World, after his wife. The best fit to the data indicates the planet has a circular 37 day orbit, an orbital radius of only 0.15 AU, and a mass 3.1 times the Earth's. Modeling includes estimates of a planet radius of 1.5, and gravity at the planet's surface of 1.1 to 1.7 in Earth units. Finding a habitable planet so close by suggests there are many others in our Milky Way galaxy.

Image credit: Lynette Cook
Hubble's Lagoon (2010-10-02)

Like brush strokes on a canvas, ridges of color seem to flow across this scene. But here, the canvas is nearly 3 light-years wide and the colors map emission from ionized gas in the Lagoon Nebula, recorded by the Hubble Space Telescope's Advanced Camera for Surveys. Also known as M8, the nebula is a star forming region about 5,000 light-years distant in the constellation Sagittarius. Hubble's remarkably sharp, close-up view reveals undulating shapes sculpted by the energetic light and winds from the region's new born stars. Of course, the Lagoon nebula is a popular target for earthbound skygazers, too. It features a prominent dust lane and bright hourglass shape in small telescopes with wider fields of view.
Io in True Color (2010-10-03)

The strangest moon in the Solar System is bright yellow.  This picture, an attempt to show how Io would appear in the "true colors" perceptible to the average human eye, was taken in 1999 July by the Galileo spacecraft that orbited Jupiter from 1995 to 2003.  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.   Follow APOD on Facebook