juliensimon/nasa-apod huggingface dataset:
Illustris Simulation of the Universe (2014-05-12)

How did we get here? Click play, sit back, and watch.  A new computer simulation of the evolution of the universe -- the largest and most sophisticated yet produced -- provides new insight into how galaxies formed and new perspectives into humanity's place in the universe.  The Illustris project -- the largest of its type yet -- exhausted 20 million CPU hours following 12 billion resolution elements spanning a cube 35 million light years on a side as it evolved over 13 billion years. The simulation is the first to track matter into the formation of a wide variety of galaxy types. As the virtual universe evolves, some of the matter expanding with the universe soon gravitationally condenses to form filaments, galaxies, and clusters of galaxies. The above video takes the perspective of a virtual camera circling part of this changing universe, first showing the evolution of dark matter, then hydrogen gas coded by temperature (0:45), then heavy elements such as helium and carbon (1:30), and then back to dark matter (2:07). On the lower left the time since the Big Bang is listed, while on the lower right the type of matter being shown is listed.  Explosions (0:50) depict galaxy-center supermassive black holes expelling bubbles of hot gas. Interesting discrepancies between Illustris and the real universe do exist and are being studied, including why the simulation produces an overabundance of old stars.
CG4: A Ruptured Cometary Globule (2014-05-13)

Can a gas cloud grab a galaxy?  It's not even close.  The "claw" of this odd looking "creature" in the above photo is a gas cloud known as a cometary globule.  This globule, however, has ruptured.  Cometary globules are typically characterized by dusty heads and elongated tails.  These features cause cometary globules to have visual similarities to comets, but in reality they are very much different.  Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not completely known.  The galaxy to the left of the globule is huge, very far in the distance, and only placed near CG4 by chance superposition.   Best Space Images: Free APOD Lecture in Paris on June 17

Image credit: Jason Jennings
(cosmicphotos)
A Live View from the International Space Station (2014-05-14)

If you were floating above the Earth right now, this is what you might see. Two weeks ago, the robotic SpaceX Dragon capsule that delivered supplies to the Earth-orbiting International Space Station (ISS) also delivered High Definition Earth Viewing (HDEV) cameras that take and transmit live views of Earth. Pictured above, when working, is the live video feed that switches between four cameras, each pointed differently. Watch white clouds, tan land, and blue oceans drift by.  The above video will appear black when it is nighttime on the Earth below, but the space station's rapid 90-minute orbit compresses this dark time into only 45 minutes.  The present location of the ISS above the Earth can be found on the web. If the video appears gray, this indicates that the view is either being switched between cameras, or communications with the ISS is temporarily unavailable.  As the HDEV project continues, video quality will be monitored to assess the effects of high energy radiation, which types of cameras work best, and which Earth views are the most popular. Although this feed will eventually be terminated, lessons learned will enable better cameras to be deployed to the ISS in the future, likely returning even more interesting live feeds.
Voyager's Neptune (2014-05-15)

Cruising through the outer solar system, the Voyager 2 spacecraft made its closest approach to Neptune on August 25, 1989, the only spacecraft to visit the most distant ice giant planet. Based on the images recorded during its close encounter and in the following days, this inspired composited scene covers the dim outer planet, largest moon Triton, and faint system of rings. From just beyond Neptune's orbit, the interplanetary perspective looks back toward the Sun, capturing the planet and Triton as thin sunlit crescents. Cirrus clouds and a dark band circle Neptune's south polar region, with a cloudy vortex above the pole itself. Parts of the very faint ring system along with the three bright ring arcs were first imaged by Voyager during the fly-by, though the faintest segments are modeled in this composited picture. Spanning 7.5 degrees, the background starfield is composed from sky survey data centered on the constellation Camelopardalis, corresponding to the outbound Voyager's view of the magnificent Neptunian system.

Image credit: Rolf Olsen
Opportunity's Mars Analemma (2014-05-16)

Staring up into the martian sky, the Opportunity rover captured an image at 11:02 AM local mean time nearly every 3rd sol, or martian day, for 1 martian year. Of course, the result is this martian analemma, a curve tracing the Sun's motion through the sky in the course of a year (668 sols) on the Red Planet. Spanning Earth dates from July, 16, 2006 to June 2, 2008 the images are shown composited in this zenith-centered, fisheye projection. North is at the top surrounded by a panoramic sky and landscape made in late 2007 from inside Victoria crater. The tinted martian sky is blacked out around the analemma images to clearly show the Sun's positions. Unlike Earth's figure-8-shaped analemma, Mars' analemma is pear-shaped, because of its similar axial tilt but more elliptical orbit. When Mars is farther from the Sun, the Sun progresses slowly in the martian sky creating the pointy top of the curve. When close to the Sun and moving quickly, the apparent solar motion is stretched into the rounded bottom. For several sols some of the frames are missing due to rover operations and dust storms.
Hubble's Jupiter and the Amazing Shrinking Great Red Spot (2014-05-17)

Gas giant Jupiter is the solar system's largest world with about 320 times the mass of planet Earth. It's also known for a giant swirling storm system, the Great Red Spot, featured in this sharp Hubble image from April 21. Nestled between Jupiter-girdling cloud bands, the Great Red Spot itself could still easily swallow Earth, but lately it has been shrinking. The most recent Hubble observations measure the spot to be about 10,250 miles (16,500 kilometers) across. That's the smallest ever measured by Hubble and particularly dramatic when compared to 14,500 miles measured by the Voyager 1 and 2 flybys in 1979, and historic telescopic observations from the 1800s indicating a width of about 25,500 miles on its long axis. Current indications are that the rate of shrinking is increasing for the long-lived Great Red Spot.
Jupiter's Great Red Spot from Voyager 1 (2014-05-18)

What will become of Jupiter's Great Red Spot?  Recorded as shrinking since the 1930s, the rate of the Great Red Spot's size appears to have accelerated just in the past few years. A hurricane larger than Earth, the Great Red Spot has been raging at least as long as telescopes could see it. Like most astronomical phenomena, the Great Red Spot was neither predicted nor immediately understood after its discovery. Although small eddies that feed into the storm system seem to play a role, a more full understanding of the gigantic storm cloud remains a topic of continued research, and may result in a better understanding of weather here on Earth. The above image is a digital enhancement of an image of Jupiter taken in 1979 by the Voyager 1 spacecraft as it zoomed by the Solar System's largest planet. NASA's Juno spacecraft is currently heading toward Jupiter and will arrive in 2016.    Poll: Do you like APOD's leading question?
Meteors, Planes, and a Galaxy over Bryce Canyon (2014-05-19)

Sometimes land and sky are both busy and beautiful. The landscape pictured in the foreground encompasses Bryce Canyon in Utah, USA, famous for its many interesting rock structures eroded over millions of years. The skyscape above, photogenic in its own right, encompasses the arching central disk of our Milky Way Galaxy, streaks that include three passing airplanes and at least four Eta Aquariid meteors, and bright stars that include the Summer Triangle. The above image is a digital panorama created from 12 smaller images earlier this month on the night May 6.  If you missed the recent Eta Aquariids meteor shower though, don't fret -- you may get an unexpected reprieve.  Sky enthusiasts are waiting to see if a new meteor shower develops in the early morning hours of Saturday, May 24, when the Earth moves through a possibly dense cloud of dust and debris ejected by Comet 209P/LINEAR.   See for yourself: Bryce Canyon National Park Astronomy Festival June 25-28  Best space images: Free APOD Lecture in Paris on June 17

Image credit: Dave Lane
In the Center of Spiral Galaxy M61 (2014-05-20)

M61 is a barred spiral galaxy located in the nearby Virgo Cluster of Galaxies.  Visible in M61 are a host of features common to spiral galaxies: bright spiral arms, a central bar, dust lanes, and bright knots of stars.  M61, also known as NGC 4303, in similar to our own Milky Way Galaxy.  M61 was discovered by telescope in 1779 twice on the same day, but one observer initially mistook the galaxy for a comet.  Light from M61 takes about 55 million years to reach us.  The above image of the central regions of M61 was taken with the Hubble Space Telescope and adapted for release as part of the Hubble's Hidden Treasures image processing competition.
A Supercell Storm Cloud Forming over Wyoming (2014-05-21)

How do supercell storm clouds form? Pictured above is a time-lapse video taken last Sunday detailing the formation of one such violent supercell in eastern Wyoming, USA. Starting as part of a large and dark thunderstorm complex, the supercell comes together along with a large rotating updraft of air known as a mesocyclone. Mesocyclones form during rapid changes in wind speed and direction with height and can produce torrential rain, damaging hail, swirling winds, and sometimes tornadoes.  Storm watchers are seen studying, imaging, and ultimately running from the developing storm cloud during the video.  During the middle part of the video, the kilometer-wide supercell can be seen swirling ominously with a nearly flat bottom. Toward the end of the video, another swirling supercell cloud forms but then quickly dissipates.    Poll: Have you seen this video before?
A Halo for NGC 6164 (2014-05-22)

Beautiful emission nebula NGC 6164 was created by a rare, hot, luminous O-type star, some 40 times as massive as the Sun. Seen at the center of the cosmic cloud, the star is a mere 3 to 4 million years old. In another three to four million years the massive star will end its life in a supernova explosion. Spanning around 4 light-years, the nebula itself has a bipolar symmetry. That makes it similar in appearance to more common and familiar planetary nebulae - the gaseous shrouds surrounding dying sun-like stars. Also like many planetary nebulae, NGC 6164 has been found to have an extensive, faint halo, revealed in this deep telescopic image of the region. Expanding into the surrounding interstellar medium, the material in the halo is likely from an earlier active phase of the O star. The gorgeous skyscape is a composite of extensive narrow-band image data, highlighting glowing atomic hydrogen gas in red and oxygen in blue hues, with broad-band data for the surrounding starfield. NGC 6164 is 4,200 light-years away in the right-angled southern constellation of Norma.

Image credit: Martin Pugh
Rosetta's Target Comet (2014-05-23)

The Rosetta spacecraft captured this remarkable series of 9 frames between March 27 and May 4, as it closed from 5 million to 2 million kilometers of its target comet. Cruising along a 6.5 year orbit toward closest approach to the Sun next year, periodic comet 67P/Churyumov-Gerasimenko is seen moving past a distant background of stars in Ophiuchus and globular star cluster M107. The comet's developing coma is actually visible by the end of the sequence, extending for some 1300 km into space. Rosetta is scheduled for an early August rendezvous with the comet's nucleus. Now clearly active, the nucleus is about 4 kilometers in diameter, releasing the dusty coma as its dirty ices begin to sublimate in the sunlight. The Rosetta lander's contact with the surface of the nucleus is anticipated in November.  Meteor Shower Hunt Tonight: Looking for the Camelopardalids
A Circumhorizontal Arc Over Ohio (2014-05-24)

Why would clouds appear to be different colors? The reason here is that ice crystals in distant cirrus clouds are acting like little floating prisms.  Sometimes known as a fire rainbow for its flame-like appearance, a circumhorizon arc lies parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present.  Furthermore, the numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner.  Therefore, circumhorizontal arcs are quite unusual to see.  This circumhorizon display was photographed through a polarized lens above Dublin, Ohio in 2009.

Image credit: Todd Sladoje
Camelopardalids and ISS (2014-05-25)

From a camp on the northern shores of the Great Lake Erie, three short bright meteor streaks were captured in this composited night skyscape. Recorded over the early morning hours of May 24, the meteors are elusive Camelopardalids. Their trails point back to the meteor shower's radiant near Polaris, in the large but faint constellation Camelopardalis the camel leopard, or in modern terms the Giraffe. While a few meteors did appear, the shower was not an active one as the Earth crossed through the predicted debris trail of periodic comet 209P/LINEAR. Of course, the long bright streak in the image did appear as predicted. Early on May 24, the International Space Station made a bright passage through northern skies.

Image credit: Malcolm Park
An ALMA Telescope Array Time-Lapse (2014-05-26)

It is the most expensive and complex ground-based astronomy project ever -- what will it see tonight? The Atacama Large Millimeter Array (ALMA) project consists of 66 dishes, many the size of a small house, situated in the high altitude Atacama Desert in Northern Chile. Together, ALMA observes the skies in high-frequency radio light, a band usually used only for local communication due to considerable absorption by humid air.  The thin atmosphere and low humidity above ALMA, however, enable it to see deep into our universe in new and unique ways that allow, for example, explorations of the early universe for chemicals involved in star formation, and observing local star systems for signs of disks that form planets.   The above time-lapse video shows the course of four ALMA antennas over one night. The Moon sets early in the video, while three dishes repoint in unison. Background stars continually rotate up, the central band of our Milky Way Galaxy pivots around and eventually exits off to the right, while halfway through the Small and Large Magellanic Clouds -- satellite galaxies near our Milky Way -- rise up from below the horizon.  Car headlights momentarily illuminate the dishes, while an occasional Earth-orbiting satellite crosses overhead. Daylight ends the video but not ALMA observations -- which typically run both all night and all day.    Best space images: Free APOD Lecture in Paris on June 17
Star Factory Messier 17 (2014-05-27)

What's happening at the center of this nebula? Sculpted by stellar winds and radiation, the star factory known as Messier 17 lies some 5,500 light-years away in the nebula-rich constellation Sagittarius. At that distance, this degree wide field of view spans almost 100 light-years. The sharp, composite, color image utilizing data from space and ground based telescopes, follows faint details of the region's gas and dust clouds against a backdrop of central Milky Way stars. Stellar winds and energetic light from hot, massive stars formed from M17's stock of cosmic gas and dust have slowly carved away at the remaining interstellar material producing the cavernous appearance and undulating shapes. M17 is also known as the Omega Nebula or the Swan Nebula.

Image credit: Subaru
Telescope  
(NAOJ), 
Hubble Space
Telescope; 
 Processing: 
Robert Gendler &
Roberto Colombari
The Cone Nebula from Hubble (2014-05-28)

Stars are forming in the gigantic dust pillar called the Cone Nebula. Cones, pillars, and majestic flowing shapes abound in stellar nurseries where natal clouds of gas and dust are buffeted by energetic winds from newborn stars. The Cone Nebula, a well-known example, lies within the bright galactic star-forming region NGC 2264. The Cone was captured in unprecedented detail in this close-up composite of several observations from the Earth-orbiting Hubble Space Telescope. While the Cone Nebula, about 2,500 light-years away in Monoceros, is around 7 light-years long, the region pictured here surrounding the cone's blunted head is a mere 2.5 light-years across. In our neck of the galaxy that distance is just over half way from the Sun to its nearest stellar neighbor, the Alpha Centauri star system. The massive star NGC 2264 IRS, seen by Hubble's infrared camera in 1997, is the likely source of the wind sculpting the Cone Nebula and lies off the top of the image. The Cone Nebula's reddish veil is produced by glowing hydrogen gas.
Millions of Stars in Omega Centauri (2014-05-29)

Globular star cluster Omega Centauri, also known as NGC 5139, is some 15,000 light-years away. The cluster is packed with about 10 million stars much older than the Sun within a volume about 150 light-years in diameter, the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. This astronomically sharp color image of the classic globular cluster was recorded in March under Chilean skies from Hacienda Los Andes.

Image credit: CEDIC Team
Planetary Nebula Abell 36 (2014-05-30)

The gorgeous, gaseous shroud of a dying sunlike star, planetary nebula Abell 36 lies a mere 800 light-years away in the constellation of Virgo. At that distance it spans over 1.5 light-years in this sharp telescopic view. Shrugging off its outer layers, the nebula's central star is contracting and becoming hotter, evolving towards a final white dwarf phase. In fact, in Abell 36, the central star is estimated to have a surface temperature of over 73,000 K, compared to the Sun's present 6,000 K temperature. As a result, the intensely hot star is much brighter in ultraviolet light, compared to its visual appearance here. The invisible ultraviolet light ionizes hydrogen and oxygen atoms in the nebula and ultimately powers the beautiful visible light glow.

Image credit: Adam Block
Satellite Station and Southern Skies (2014-05-31)

This clear night skyscape captures the colorful glow of aurora australis, the southern lights, just outside the port city of Hobart, Tasmania, Australia, planet Earth. As if staring into the dreamlike scene, the Tasmanian Earth Resources Satellite Station poses in the center, illuminated by nearby city lights. Used to receive data from spacebased Earth observing instruments, including NASA's MODIS and SeaWiFS, the station was decommissioned in 2011 and dismantled only recently, shortly after the picture was taken on April 30. Still shining in southern skies though, the central bulge of our Milky Way galaxy and two bright satellite galaxies the Large and Small Magellanic Clouds appear in the frame. The Small Magellanic Cloud shines through the fainter red auroral band.

Image credit: James Garlick
Halo of the Cat's Eye (2014-06-01)

The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its haunting symmetries are seen in the very central region of this stunning false-color picture, processed to reveal the enormous but extremely faint halo of gaseous material, over three light-years across, which surrounds the brighter, familiar planetary nebula. Made with data from the Nordic Optical Telescope in the Canary Islands, the composite picture shows extended emission from the nebula. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. Only much more recently however, have some planetaries been found to have halos like this one, likely formed of material shrugged off during earlier active episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years.

Image credit: R. Corradi (Isaac Newton Group),
Nordic Optical Telescope
The Space Station Captures a Dragon Capsule (2014-06-02)

The space station has caught a dragon. Specifically, in mid-April, the International Space Station captured the unmanned SpaceX Dragon capsule sent to resupply the orbiting outpost. Pictured above, the station's Canadarm2 had just grabbed the commercial spaceship. The Dragon capsule was filled with over 5000 lbs (2260 kilos) of supplies and experiments to be used by the current band of six ISS astronauts who compose Expedition 39, as well as the six astronauts who compose Expedition 40.  After docking with the ISS, the Dragon capsule was unloaded and eventually released, splashing down in the Pacific Ocean on May 18. The current Expedition 40 crew, now complete, will apply themselves to many tasks including the deployment of the Napor-mini RSA experiment which will use phased array radar and a small optical telescope to monitor possible emergency situations on the Earth below.
WR 104: A Pinwheel Star System (2014-06-03)

Might this giant pinwheel one-day destroy us?  Probably not, but investigation of the unusual star system Wolf-Rayet 104 has turned up an unexpected threat.  The unusual pinwheel pattern has been found to be created by energetic winds of gas and dust that are expelled and intertwine as two massive stars orbit each other. One system component is a Wolf-Rayet star, a tumultuous orb in the last stage of evolution before it explodes in a supernova -- an event possible anytime in the next million years. Research into the spiral pattern of the emitted dust, however, indicates the we are looking nearly straight down the spin axis of the system -- possibly the same axis along which a powerful jet would emerge were the supernova accompanied by a gamma-ray burst.  Now the WR 104 supernova itself will likely be an impressive but harmless spectacle.  Conversely, were Earth really near the center of the powerful GRB beam, even the explosion's 8,000 light year distance might not be far enough to protect us. Currently, neither WR 104 nor GRB beams are understood well enough to know the real level of danger.   Best space images: Free APOD Lecture in Paris on June 17

Image credit: P. Tuthill 
(U. Sydney) & 
J. Monnier 
(U. Michigan), 
Keck Obs.,
ARC,
NSF
A Green Flash from the Sun (2014-06-04)

Many think it is just a myth.  Others think it is true but its cause isn't known.  Adventurers pride themselves on having seen it.  It's a green flash from the Sun.  The truth is the green flash does exist and its cause is well understood.  Just as the setting Sun disappears completely from view, a last glimmer appears startlingly green.  The effect is typically visible only from locations with a low, distant horizon, and lasts just a few seconds. A green flash is also visible for a rising Sun, but takes better timing to spot.  A dramatic green flash, as well as an even more rare red flash, was caught in the above photograph recently observed during a sunset visible from the Observatorio del Roque de Los Muchachos in the Canary Islands, Spain.  The Sun itself does not turn partly green or red -- the effect is caused by layers of the Earth's atmosphere acting like a prism.

Image credit: Daniel L�pez
(El Cielo de Canarias)