juliensimon/nasa-apod huggingface dataset:
Gamma-rays and Comet Dust (2016-08-20)

Gamma-rays and dust from periodic Comet Swift-Tuttle plowed through planet Earth's atmosphere on the night of August 11/12. Impacting at about 60 kilometers per second the grains of comet dust produced this year's remarkably active Perseid meteor shower. This composite wide-angle image of aligned shower meteors covers a 4.5 hour period on that Perseid night. In it the flashing meteor streaks can be traced back to the shower's origin on the sky. Alongside the Milky Way in the constellation Perseus, the radiant marks the direction along the perodic comet's orbit. Traveling at the speed of light, cosmic gamma-rays impacting Earth's atmosphere generated showers too, showers of high energy particles. Just as the meteor streaks point back to their origin, the even briefer flashes of light from the particles can be used to reconstruct the direction of the particle shower, to point back to the origin on the sky of the incoming gamma-ray. Unlike the meteors, the incredibly fast particle shower flashes can't be followed by eye. But both can be followed by the high speed cameras on the multi-mirrored dishes in the foreground. Of course, the dishes are MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes, an Earth-based gamma-ray observatory on the Canary Island of La Palma.

Image credit: El Cielo de Canarias
Map of Total Solar Eclipse Path in 2017 August (2016-08-21)

Would you like to see a total eclipse of the Sun?  If so, do any friends or relatives live near the path of next summer's eclipse?  If yes again, then you might want to arrange a visit for one year from today. Next year on this exact date, the path of a total solar eclipse will cut right across the center of the contiguous USA.  All of North America and part of South America will experience, at the least, a partial solar eclipse.  Featured here is a map of the path of totality, computed by eclipse expert Fred Espenak of NASA's GSFC.  Many people who have seen a total solar eclipse tell stories about it for the rest of their lives.  The last path of solar totality that included any part of the contiguous USA was in 1979, and the next two will be in 2024 and  2044.   Zoom in: An interactive map of the eclipse path.
Tutulemma: Solar Eclipse Analemma (2016-08-22)

If you went outside at exactly the same time every day and took a picture that included the Sun, how would the Sun's position change?  With great planning and effort, such a series of images can be taken.  The figure-8 path the Sun follows over the course of a year is called an analemma.  At the Winter Solstice in Earth's northern hemisphere, the Sun appears at the bottom of the analemma. Analemmas created from different latitudes appear at least slightly different, as well as analemmas created at a different time each day. With even greater planning and effort, the series can include a total eclipse of the Sun as one of the images. Pictured is such a total solar eclipse analemma or Tutulemma - a term coined by the photographers based on the Turkish word for eclipse. The featured composite image sequence was recorded from Turkey starting in 2005. The base image for the sequence is from the total phase of a solar eclipse as viewed from Side, Turkey on 2006 March 29. Venus was also visible during totality, toward the lower right. If you want to create your own USA-based tutulemma ending at next August's total solar eclipse, now would be good time to start.    Free Download: APOD 2017 Calendar: NASA Images

Image credit: Cenk E. Tezel and
Tunç Tezel
(TWAN)
Gigantic Jet Lightning over China (2016-08-23)

That's no meteor. While watching and photographing this year's Perseid Meteor Shower, something unexpected happened: a gigantic jet erupted from a nearby cloud. The whole thing was over in a flash -- it lasted less than a second -- but was fortunately captured by an already-recording digital camera. Gigantic jets are a rare form of lightning recognized formally only a few years ago. The featured high resolution color image, taken near the peak of Shikengkong mountain in China, may be the best image yet of this unusual phenomenon.  The same event appears to have been captured simultaneously by another photographer, further away. The gigantic jet appears to start somewhere in a nearby thundercloud and extend upwards towards Earth's ionosphere.  The nature of gigantic jets and their possible association with other types of Transient Luminous Events (TLEs) such as blue jets and red sprites remains an active topic of research.    Free Download: APOD 2017 Calendar: NASA Images

Image credit: Phebe
Pan
Curiosity at Murray Buttes on Mars (2016-08-24)

What are these unusual lumps on Mars?  As NASA's robotic Curiosity rover continues rolling across Mars, it is now approaching Murray Buttes. Several of the 15-meter high buttes are visible ahead in this horizontally compressed 360-degree across image taken inside Gale Crater earlier this month.  The buttes are thought similar to Earth buttes in that they are capped with dense rock that is relatively resistant to erosion. In the image center is Curiosity's "arm" and "hand" used to examine rocks up close, drill into rocks, and collect samples.  Curiosity has reached its four year anniversary on Mars and has been cleared to spend the next two years further exploring the slopes of Mount Sharp, the peak of which is the distant light-colored structure visible on the far left.    Interactive View: YouTube 360-degree tilt and scroll image version
Closest Star has Potentially Habitable Planet (2016-08-25)

The star closest to the Sun has a planet similar to the Earth. As announced yesterday, recent observations confirmed that this planet not only exists but inhabits a zone where its surface temperature could allow liquid water, a key ingredient for life on Earth. It is not yet known if this planet, Proxima b, has any life. Even if not, its potential ability to sustain liquid water might make it a good first hop for humanity's future trips out into the Milky Way Galaxy.  Although the planet's parent star, Proxima Centauri, is cooler and redder than our Sun, one of the other two stars in the Alpha Centauri star system is very similar to our Sun. The featured image shows the sky location of Proxima Centauri in southern skies behind the telescope that made many of the discovery observations: ESO's 3.6-meter telescope in La Silla, Chile.  The discovered planet orbits close in -- so close one year there takes only 11 days on Earth.  The planet was discovered by the ESO's Pale Red Dot collaboration.  Although seemingly unlikely, if Proxima b does have intelligent life, at 4.25 light years distance it is close enough to Earth for two-way communication.
The Milky Way Sets (2016-08-26)

Under dark skies the setting of the Milky Way can be a dramatic sight. Stretching nearly parallel to the horizon, this rich, edge-on vista of our galaxy above the dusty Namibian desert stretches from bright, southern Centaurus (left) to Cepheus in the north (right). From early August, the digitally stitched, panoramic night skyscape captures the Milky Way's congeries of stars and rivers of cosmic dust, along with colors of nebulae not readily seen with the eye. Mars, Saturn, and Antares, visible even in more luminous night skies, form the the bright celestial triangle just touching the trees below the galaxy's central bulge.  Of course, our own galaxy is not the only galaxy in the scene. Two other major members of our local group, the Andromeda Galaxy and the Triangulum Galaxy, lie near the right edge of the frame, beyond the arc of the setting Milky Way.

Image credit: Juan Carlos Casado
Lunar Orbiter Earthset (2016-08-27)

August 10th was the 50th anniversary of the launch of Lunar Orbiter 1. It was the first of five Lunar Orbiters intended to photograph the Moon's surface to aid in the selection of future landing sites. That spacecraft's camera captured the data used in this restored, high-resolution version of its historic first image of Earth from the Moon on August 23, 1966 while on its 16th lunar orbit. Hanging almost stationary in the sky when viewed from the lunar surface, Earth appears to be setting beyond the rugged lunar horizon from the perspective of the orbiting spacecraft. Two years later, the Apollo 8 crew would record a more famous scene in color: Earthrise from lunar orbit.
Abell 370: Galaxy Cluster Gravitational Lens (2016-08-28)

What is that strange arc? While imaging the cluster of galaxies Abell 370, astronomers had noted an unusual arc to the right of many cluster galaxies.  Although curious, one initial response was to avoid commenting on the arc because nothing like it had ever been noted before.  In the mid-1980s, however, better images allowed astronomers to identify the arc as a prototype of a new kind of astrophysical phenomenon -- the gravitational lens effect of entire cluster of galaxies on background galaxies. Today, we know that this arc actually consists of two distorted images of a fairly normal galaxy that happened to lie far behind the huge cluster.  Abell 370's gravity caused the background galaxies' light -- and others -- to spread out and come to the observer along multiple paths, not unlike a distant light appears through the stem of a wine glass. In mid-July of 2009, astronomers used the then just-upgraded Hubble Space Telescope to image Abell 370 and its gravitational lens images in unprecedented detail.  Almost all of the yellow images featured here are galaxies in the Abell 370 cluster. An astute eye can pick up many strange arcs and distorted arclets, however, that are actually images of more distant galaxies. Studying Abell 370 and its images gives astronomers a unique window into the distribution of normal and dark matter in galaxy clusters and the universe.    Free Download: APOD 2017 Calendar: NASA Images
Young Suns of NGC 7129 (2016-08-29)

Young suns still lie within dusty NGC 7129, some 3,000 light-years away toward the royal constellation Cepheus. While these stars are at a relatively tender age, only a few million years old, it is likely that our own Sun formed in a similar stellar nursery some five billion years ago. Most noticeable in the sharp image are the lovely bluish dust clouds that reflect the youthful starlight. But the compact, deep red crescent shapes are also markers of energetic, young stellar objects. Known as Herbig-Haro objects, their shape and color is characteristic of glowing hydrogen gas shocked by jets streaming away from newborn stars. Paler, extended filaments of reddish emission mingling with the bluish clouds are caused by dust grains effectively converting the invisible ultraviolet starlight to visible red light through photoluminesence. Ultimately the natal gas and dust in the region will be dispersed, the stars drifting apart as the loose cluster orbits the center of the Galaxy. The processing of this remarkable composite image has revealed the faint red strands of emission at the upper right. They are recently recognized as a likely supernova remnant and are currently being analyzed by Bo Reipurth (Univ. Hawaii) who obtained the image data at the Subaru telescope. At the estimated distance of NGC 7129, this telescopic view spans over 40 light-years.  Photo Gallery: Jupiter & Venus Conjunction of 2016 August

Image credit: Robert Gendler
Aurora over Icelandic Fault (2016-08-30)

Admire the beauty but fear the beast.  The beauty is the aurora overhead, here taking the form of great green spiral, seen between picturesque clouds with the bright Moon to the side and stars in the background.  The beast is the wave of charged particles that creates the aurora but might, one day, impair civilization. Exactly this week in 1859, following notable auroras seen all across the globe, a pulse of charged particles from a coronal mass ejection (CME) associated with a solar flare impacted Earth's magnetosphere so forcefully that they created the Carrington Event. A relatively direct path between the Sun and the Earth might have been cleared by a preceding CME.  What is sure is that the Carrington Event compressed the Earth's magnetic field so violently that currents were created in telegraph wires so great that many wires sparked and gave telegraph operators shocks. Were a Carrington-class event to impact the Earth today, speculation holds that damage might occur to global power grids and electronics on a scale never yet experienced. The featured aurora was imaged last week over Thingvallavatn Lake in Iceland, a lake that partly fills a fault that divides Earth's large Eurasian and North American tectonic plates.   Free Download: APOD 2017 Calendar: NASA Images

Image credit: Juan Carlos Casado
(TWAN,
Earth and Stars)
Annular Solar Eclipse over New Mexico (2016-08-31)

What is this person doing?  In 2012 an annular eclipse of the Sun was visible over a narrow path that crossed the northern Pacific Ocean and several western US states.  In an annular solar eclipse, the Moon is too far from the Earth to block out the entire Sun, leaving the Sun peeking out over the Moon's disk in a ring of fire.  To capture this unusual solar event, an industrious photographer drove from Arizona to New Mexico to find just the right vista. After setting up and just as the eclipsed Sun was setting over a ridge about 0.5 kilometers away, a person unknowingly walked right into the shot. Although grateful for the unexpected human element, the photographer never learned the identity of the silhouetted interloper. It appears likely, though, that the person is holding a circular device that would enable them to get their own view of the eclipse.  The shot was taken at sunset on 2012 May 20 at 7:36 pm local time from a park near Albuquerque, New Mexico, USA. Tomorrow another annular solar eclipse will become visible, this time along a path crossing Africa and Madagascar.    Free Download: APOD 2017 Calendar: NASA Images

Image credit: Colleen Pinski
Light at the End of the Road (2016-09-01)

The bright light at the end of this country road is actually a remarkably close conjunction of two planets. After sunset on August 27 brilliant Venus and Jupiter almost appear as a single celestial beacon in the night skyscape taken near Lake Wivenhoe, Queensland, Australia. A spectacular vertical panorama from the southern hemisphere, it shows the central Milky Way near zenith, posed on top of a pillar of Zodiacal light along the ecliptic plane. Of course Mars and Saturn are near the ecliptic too, just below the galaxy's central bulge. Above and left of a tree on the horizon, fleeting planet Mercury also adds to the light at the end of the road.

Image credit: Josh Calcino
Little Planet Astro Camp (2016-09-02)

Day and night on this little planet look a lot like day and night on planet Earth. In fact, the images used to construct the little planet projection, a digitally warped and stitched mosaic covering 360x180 degrees, were taken during day and night near Tarján, Hungary, planet Earth. They span a successful 33-hour-long photo experiment at July's Hungarian Astronomical Association Astro Camp. The time-series composite follows the solar disk in 20 minute intervals from sunrise to sunset and over six hours of star trails in the northern night sky centered on the North Celestial Pole near bright star Polaris. The orbiting International Space Station traced the offset arc across the northern night.  Below the little planet's nightside horizon, red light lamps of fellow astro-campers left the night-long, dancing trails.

Image credit: György Soponyai
Reunion Island Eclipse (2016-09-03)

The New Moon's dark shadow crossed planet Earth on September 1. In silhouette the Moon didn't quite cover the Sun though, creating an an annular solar eclipse. The shadow's narrow central path was about 100 kilometers wide at maximum eclipse. Beginning in the South Atlantic, it tracked toward the east across Africa, ending in the Indian Ocean.  Waiting on the Indian Ocean's Reunion Island, eclipse watchers enjoyed a view just north of the eclipse centerline, the annular phase lasting a few minutes or less. Clouds threaten the nearly eclipsed Sun but create a dramatic sky in this wide-angle and telephoto composite at a partial phase from the northern side of the 50 kilometer wide island.

Image credit: Stephane Moser
Io over Jupiter from Voyager 1 (2016-09-04)

Back in 1979, NASA's Voyager 1 spacecraft flew past Jupiter and its moons.  The images in this mosaic, featuring the moon Io against a background of gas giant Jupiter's diffuse swirling cloud bands, were recorded by Voyager's camera from a distance of about 8.3 million kilometers.  The Io image from this mosaic may be the first to show curious round features on Io's surface with dark centers and bright rims more than 60 kilometers across.  Now known to be volcanic in origin, these features were then thought likely to be impact craters, commonly seen on rocky bodies throughout the Solar System.  But as Voyager continued to approach Io, close-up pictures revealed a bizarre world devoid of impact craters, frequently resurfaced by volcanic activity.  Earlier this year a new robotic spacecraft, NASA's Juno, began to orbit Jupiter and last week made a pass within 5,000 kilometers of Jupiter's clouds. During the next two years, it is hoped that Juno will discover new things about Jupiter, for example what's in Jupiter's core.    Free Download: APOD 2017 Calendar: NASA Images
Spiral Meteor through the Heart Nebula (2016-09-05)

What is this meteor doing? Dynamically, the unusually short and asymmetric train may indicate that the sand-sized grain at the center of the glow is momentarily spinning as it ablates, causing its path to be slightly spiral.  Geographically, the meteor appears to be going through the Heart Nebula, although really it is in Earth's atmosphere and so is about one quadrillion times closer. Taken last month on the night of the peak, this meteor is likely from the Perseid meteor shower. The Perseids radiant, in the constellation of Perseus, is off the frame to the upper right, toward the direction that the meteor streak is pointing. The Heart Nebula was imaged in 18 one-minute exposures, of which the unusual meteor streak appeared on just one.  The meteor train is multicolored as its glow emanates from different elements in the heated gas.   Transparent Science: Browse 1,300+ codes in the Astrophysics Source Code Library

Image credit: Roger N. Clark
The Whirlpool Galaxy and Beyond (2016-09-06)

Follow the handle of the Big Dipper away from the dipper's bowl, until you get to the handle's last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (left), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the human eye, the above long-exposure, deep-field image taken earlier this year shows much of the faint complexity that actually surrounds the smaller galaxy. Thousands of the faint dots in background of the featured image are actually galaxies far across the universe.   Follow APOD on: Facebook,  Google Plus,  Instagram, or Twitter

Image credit: �lvaro Ib��ez P�rez
Eclipse to Sunset (2016-09-07)

September's eclipse of the Sun is documented in the 68 frames of this timelapse composite. Starting at 1pm local time a frame every 4 minutes follow's the progress of the New Moon across the solar disk. Taken near the centerline of the narrow eclipse path, the series of exposures ends with a golden sunset. Balanced rock cairns in the foreground line a beach on the southern side of Reunion Island in the Indian Ocean, near the village of Etang-Salé. Of course, the close balance in apparent size creates drama in eclipses of the Sun by the Moon as seen from planet Earth. In an annular eclipse, the Moon's silhouette is just small enough to show the solar disk as a narrow ring-of-fire at maximum eclipse phase.

Image credit: Luc Perrot
Mars in the Clouds (2016-09-08)

Wandering through this stunning field of view, Mars really is in front of these colorful cosmic clouds. The mosaic contructed from telescopic images is about 5 degrees (10 full moons) across. It captures the planet's position on August 26, over 7 light-minutes from Earth and very near the line-of-sight to bright star Antares and the Rho Ophiuchi cloud complex. In the exposure yellow-hued Mars, above and left, is almost matched by Antares, also known as Alpha Scorpii, below center. Globular star cluster M4 shines just right of Antares, but M4 lies some 7,000 light-years away compared to Antares' 500 light-year distance. Slightly closer than Antares, Rho Ophiuchi's bluish starlight is reflected by the dusty molecular clouds near the top of the frame.

Image credit: Sebastian Voltmer
The Wide and Deep Lagoon (2016-09-09)

Ridges of glowing interstellar gas and dark dust clouds inhabit the turbulent, cosmic depths of the Lagoon Nebula. Also known as M8, the bright star forming region is about 5,000 light-years distant. But it still makes for a popular stop on telescopic tours of the constellation Sagittarius, toward the center of our Milky Way Galaxy. Dominated by the telltale red emission of ionized hydrogen atoms recombining with stripped electrons, this stunning, deep view of the Lagoon is nearly 100 light-years across.  Right of center, the bright, compact, hourglass shape is gas ionized and sculpted by energetic radiation and extreme stellar winds from a massive young star. In fact, the many bright stars of open cluster NGC 6530 drift within the nebula, just formed in the Lagoon several million years ago.

Image credit: Michael Miller
The Launch of OSIRIS-REx (2016-09-10)

Near sunset on Thursday, clear skies saw the launch of the OSIRIS-REx spacecraft. Sporting a single solid rocket booster, its Atlas V vehicle blasts off from Cape Canaveral's Complex 41 in this low, wide-angle view toward launch pad and setting Sun. OSIRIS-REx is bound for Bennu, scheduled to encounter the mountain-sized asteroid in 2018. First the spacecraft will swing back by home world planet Earth though, for a gravity assist maneuver to boost it on its way. After a detailed survey of Bennu OSIRIS-REx will collect a sample from the asteroid's surface in 2020 and bring it home, returning to Earth in 2023. If all goes well it will be the largest sample returned by a space mission since the Apollo era.
All the Water on Planet Earth (2016-09-11)

How much of planet Earth is made of water? Very little, actually. Although oceans of water cover about 70 percent of Earth's surface, these oceans are shallow compared to the Earth's radius. The featured illustration shows what would happen if all of the water on or near the surface of the Earth were bunched up into a ball. The radius of this ball would be only about 700 kilometers, less than half the radius of the Earth's Moon, but slightly larger than Saturn's moon Rhea which, like many moons in our outer Solar System, is mostly water ice. How even this much water came to be on the Earth and whether any significant amount is trapped far beneath Earth's surface remain topics of research.   Poll: Have you seen today's APOD image before?

Image credit: Woods Hole Oceanographic Institution