juliensimon/nasa-apod huggingface dataset:
Comet ATLAS Breaks Up (2020-04-16)

Cruising through the inner solar system, Comet ATLAS (C/2019 Y4) has apparently fragmented. Multiple separate condensations within its diffuse coma are visible in this telescopic close-up from April 12, composed of frames tracking the comet's motion against trailing background stars. Discovered at the end of December 2019, this comet ATLAS showed a remarkably rapid increase in brightness in late March. Northern hemisphere comet watchers held out hope that it would become a bright naked-eye comet as it came closer to Earth in late April and May. But fragmenting ATLAS is slowly fading in northern skies. The breakup of comets is not uncommon though. This comet ATLAS is in an orbit similar to the Great Comet of 1844 (C/1844 Y1) and both may be fragments of a single larger comet.

Image credit: NAO Rozhen
The Windmill and the Star Trails (2020-04-17)

Stars can't turn these old wooden arms, but it does look like they might in this scene from a rotating planet. The well-composed night skyscape was recorded from Garafia, a municipality on the island of La Palma, Canary Islands, planet Earth. The center of the once working windmill, retired since 1953, is lined-up with the north celestial pole, the planet's rotation axis projected on to the northern sky. From a camera fixed to a tripod, the star trails are a reflection of the planet's rotation traced in a digital composite of 39 sequential exposures each 25 seconds long. Brought out by highlighting the final exposure in the sequence, the stars themselves appear at the ends of their short concentric arcs. A faint band of winter's Milky Way and even a diffuse glow from our neighboring Andromeda Galaxy also shine in the night.

Image credit: Antonio Gonzalez
Just Another Day on Aerosol Earth (2020-04-18)

It was just another day on aerosol Earth. For August 23, 2018, the identification and distribution of aerosols in the Earth's atmosphere is shown in this dramatic, planet-wide digital visualization. Produced in real time, the Goddard Earth Observing System Forward Processing (GEOS FP) model relies on a combination of Earth-observing satellite and ground-based data to calculate the presence of types of aerosols, tiny solid particles and liquid droplets, as they circulate above the entire planet. This August 23rd model shows black carbon particles in red from combustion processes, like smoke from the fires in the United States and Canada, spreading across large stretches of North America and Africa. Sea salt aerosols are in blue, swirling above threatening typhoons near South Korea and Japan, and the hurricane looming near Hawaii. Dust shown in purple hues is blowing over African and Asian deserts. The location of cities and towns can be found from the concentrations of lights based on satellite image data of the Earth at night.   Celebrate: Earth Day at Home
Cassini Approaches Saturn (2020-04-19)

What would it look like to approach Saturn in a spaceship? One doesn't have to just imagine -- the Cassini spacecraft did just this in 2004, recording thousands of images along the way, and hundreds of thousands more since entering orbit. Some of Cassini's early images have been digitally tweaked, cropped, and compiled into the featured inspiring video which is part of a larger developing IMAX movie project named In Saturn's Rings.  In the concluding sequence, Saturn looms increasingly large on approach as cloudy Titan swoops below. With Saturn whirling around in the background, Cassini is next depicted flying over Mimas, with large Herschel Crater clearly visible. Saturn's majestic rings then take over the show as Cassini crosses Saturn's thin ring plane. Dark shadows of the ring appear on Saturn itself. Finally, the enigmatic ice-geyser moon Enceladus appears in the distance and then is approached just as the video clip ends. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 was directed to enter Saturn's atmosphere, where it surely melted.

Image credit: Cassini Imaging Team,
ISS,
JPL,
ESA,
NASA,
S. Van Vuuren et al.;
Music:
Adagio for Strings
(NY Philharmonic)
IC 2944: The Running Chicken Nebula (2020-04-20)

To some, it looks like a giant chicken running across the sky. To others, it looks like a gaseous nebula where star formation takes place. Cataloged as IC 2944, the Running Chicken Nebula spans about 100 light years and lies about 6,000 light years away toward the constellation of the Centaur (Centaurus).  The featured image, shown in scientifically assigned colors, was captured recently in a 12-hour exposure. The star cluster Collinder 249 is visible embedded in the nebula's glowing gas.  Although difficult to discern here, several dark molecular clouds with distinct shapes can be found inside the nebula.

Image credit: Juan Filas
Eye on the Milky Way (2020-04-21)

Have you ever had stars in your eyes? It appears that the eye on the left does, and moreover it appears to be gazing at even more stars. The featured 27-frame mosaic was taken last July from Ojas de Salar in the Atacama Desert of Chile.  The eye is actually a small lagoon captured reflecting the dark night sky as the Milky Way Galaxy arched overhead. The seemingly smooth band of the Milky Way is really composed of billions of stars, but decorated with filaments of light-absorbing dust and red-glowing nebulas. Additionally, both Jupiter (slightly left the galactic arch) and Saturn (slightly to the right) are visible.  The lights of small towns dot the unusual vertical horizon.  The rocky terrain around the lagoon appears to some more like the surface of Mars than our Earth.

Image credit: Miguel Claro
Planet Earth at Twilight (2020-04-22)

No sudden, sharp boundary marks the passage of day into night in this gorgeous view of ocean and clouds over our fair planet Earth. Instead, the shadow line or terminator is diffuse and shows the gradual transition to darkness we experience as twilight. With the Sun illuminating the scene from the right, the cloud tops reflect gently reddened sunlight filtered through the dusty troposphere, the lowest layer of the planet's nurturing atmosphere. A clear high altitude layer, visible along the dayside's upper edge, scatters blue sunlight and fades into the blackness of space. This picture was taken in June of 2001 from the International Space Station orbiting at an altitude of 211 nautical miles. Of course from home, you can check out the Earth Now.  Celebrate: Today is Earth Day
Lyrid Meteor Streak (2020-04-23)

rth's annual Lyrid Meteor Shower peaked before dawn yesterday, as our fair planet plowed through debris from the tail of long-period comet Thatcher. In crisp, clear and moonless predawn skies over Brown County, Indiana this streak of vaporizing comet dust briefly shared a telephoto field of view with stars and nebulae along the Milky Way. Alpha star of the constellation Cygnus, Deneb lies near the bright meteor's path along with the region's dark interstellar clouds of dust and the recognizable glow of the North America nebula (NGC 7000). The meteor's streak points back to the shower's radiant, its apparent point of origin on the sky. That would be in the constellation Lyra, near bright star Vega and off the top edge of the frame.   Celebrate the Night: International Dark Sky Week

Image credit: Zolt Levay
Around the World at Night (2020-04-24)

Watch this video.  In only a minute or so you can explore the night skies around planet Earth through a compilation of stunning timelapse sequences.  The presentation will take you to sites in the United States, Germany, Russia, Iran, Nepal, Thailand, Laos and China. You might even catch the view from a small island in the southeastern Pacific Ocean. But remember that while you're home tonight, the night sky will come to you. Look up and celebrate the night during this International Dark Sky Week.

Image credit: Jeff Dai
Hubble's Cosmic Reef (2020-04-25)

These bright ridges of interstellar gas and dust are bathed in energetic starlight. With its sea of young stars, the massive star-forming region NGC 2014 has been dubbed the Cosmic Reef. Drifting just off shore, the smaller NGC 2020, is an expansive blue-hued structure erupting from a single central Wolf-Rayet star, 200,000 times brighter than the Sun. The cosmic frame spans some 600 light-years within the Large Magellanic Cloud 160,000 light-years away, a satellite galaxy of our Milky Way. A magnificent Hubble Space Telescope portrait, the image was released this week as part of a celebration to mark Hubble's 30th year exploring the Universe from Earth orbit.
Edwin Hubble Discovers the Universe (2020-04-26)

How big is our universe? This very question, among others, was debated by two leading astronomers 100 years ago today in what has become known as astronomy's Great Debate.  Many astronomers then believed that our Milky Way Galaxy was the entire universe.  Many others, though, believed that our galaxy was just one of many.  In the Great Debate, each argument was detailed, but no consensus was reached.  The answer came over three years later with the detected variation of single spot in the Andromeda Nebula, as shown on the original glass discovery plate digitally reproduced here. When Edwin Hubble compared images, he noticed that this spot varied, and so wrote "VAR!" on the plate.  The best explanation, Hubble knew, was that this spot was the image of a variable star that was very far away. So M31 was really the Andromeda Galaxy -- a galaxy possibly similar to our own.  The featured image may not be pretty, but the variable spot on it opened a door through which humanity gazed knowingly, for the first time, into a surprisingly vast cosmos.   Centennial Celebration: Astronomy's Great Debate was  100 Years Ago Today

Image credit: Carnegie Institution for Science
Fresh Tiger Stripes on Saturn's Enceladus (2020-04-27)

How will humanity first learn of extraterrestrial life? One possibility is to find it under the icy surface of Saturn's moon Enceladus. A reason to think that life may exist there are long features -- dubbed tiger stripes -- that are known to be spewing ice from the moon's icy interior into space. These surface cracks create clouds of fine ice particles over the moon's South Pole and create  Saturn's mysterious E-ring.  Evidence for this has come from the robot Cassini spacecraft that orbited Saturn from 2004 to 2017.  Pictured here, a high resolution image of Enceladus is shown from a close flyby.  The unusual surface tiger stripes are shown in false-color blue.  Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead. A recent analysis of ejected ice grains has yielded evidence that complex organic molecules exist inside Enceladus. These large carbon-rich molecules bolster -- but do not prove -- that oceans under Enceladus' surface could contain life. Another Solar System moon that might contain underground life is Europa.    Experts Debate: How will humanity first discover ET life?
The Kepler-90 Planetary System (2020-04-28)

Do other stars have planetary systems like our own? Yes -- one such system is Kepler-90. Cataloged by the  Kepler satellite that operated from Earth orbit between 2009 and 2018,  eight planets were discovered, giving Kepler-90 the same number of known planets as our Solar System. Similarities between Kepler-90 and our system include a G-type star comparable to our Sun, rocky planets comparable to our Earth, and large planets comparable in size to Jupiter and Saturn. Differences include that all of the known Kepler-90 planets orbit relatively close in -- closer than Earth's orbit around the Sun -- making them possibly too hot to harbor life. However, observations over longer time periods may discover cooler planets farther out. Kepler-90 lies about 2,500 light years away, and at magnitude 14 is visible with a medium-sized telescope toward the constellation of the Dragon (Draco).  The exoplanet-finding mission TESS was launched in 2018, while missions with exoplanet finding capability planned for launch in the next decade include NASA's JWST and WFIRST.   Experts Debate: How will humanity first discover extraterrestrial life?
The Ion Tail of New Comet SWAN (2020-04-29)

Newly discovered Comet SWAN has already developed an impressive tail.  The comet came in from the outer Solar System and has just passed inside the orbit of the Earth. Officially designated C/2020 F8 (SWAN), this outgassing interplanetary iceberg will pass its closest to the Earth on May 13, and closest to the Sun on May 27.  The comet was first noticed in late March by an astronomy enthusiast looking through images taken by ESA's and NASA's Sun-orbiting SOHO spacecraft, and is named for this spacecraft's Solar Wind Anisotropies (SWAN) camera. The featured image, taken from the dark skies in Namibia in mid-April, captured Comet SWAN's green-glowing coma and unexpectedly long, detailed, and blue ion-tail.   Although the brightness of comets are notoriously hard to predict, some models have Comet SWAN becoming bright enough to see with the unaided eye during June.    Experts Debate: How will humanity first discover extraterrestrial life?

Image credit: Gerald Rhemann
Andromeda Island Universe (2020-04-30)

The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy some two and a half million light-years away. But without a telescope, even this immense spiral galaxy - spanning over 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda. In contrast, a bright yellow nucleus, dark winding dust lanes, expansive blue spiral arms and star clusters are recorded in this stunning telescopic image. While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers debated this fundamental concept 100 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes", distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations of M31 in favor of Andromeda, island universe.    Experts Debate: How will humanity first discover extraterrestrial life?

Image credit: Yuzhe Xiao
A View Toward M106 (2020-05-01)

Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The nearly two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy's remarkable maser, or microwave laser emission. Very rare but naturally occurring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years, but the bright spiky stars are in the foreground, well inside our own Milky Way galaxy. Even the existence of galaxies beyond the Milky Way was questioned 100 years ago in astronomy's Great Debate.   Experts Debate: How will humanity first discover extraterrestrial life?

Image credit: Joonhwa Lee
Radio, The Big Ear, and the Wow! Signal (2020-05-02)

Since the early days of radio and television we have been freely broadcasting signals into space. For some time now, we have been listening too. A large radio telescope at Ohio State University known as affectionately The Big Ear was one of the first listeners. The Big Ear was about the size of three football fields and consisted of an immense metal ground plane with two fence-like reflectors, one fixed and one tiltable. It relied on the Earth's rotation to help scan the sky. This photo, taken by former Big Ear student volunteer Rick Scott, looks out across the ground plane toward the fixed reflector with the radio frequency receiver horns in the foreground. Starting in 1965, the Big Ear was used in an ambitious survey of the radio sky. In the 1970s, it became the first telescope to continuously listen for signals from extraterrestrial civilizations. For an exciting moment during August 1977 a very strong, unexpected signal, dubbed the Wow! Signal, was detected by the Big Ear. But alas, heard only once, the source of the signal could not be determined. In May 1998 the final pieces of the Big Ear were torn down.   Experts Debate: How will humanity first discover extraterrestrial life?

Image credit: Rick Scott
A Message from Earth (2020-05-03)

What are these Earthlings trying to tell us?  The featured message was broadcast from Earth towards the globular star cluster M13 in 1974.  During the dedication of the Arecibo Observatory - still one of the largest single radio telescopes in the world - a string of 1's and 0's representing the diagram was sent.   This attempt at extraterrestrial communication was mostly ceremonial - humanity regularly broadcasts radio and television signals out into space accidentally.  Even were this message received, M13 is so far away we would have to wait almost 50,000 years to hear an answer.   The featured message gives a few simple facts about humanity and its knowledge: from left to right are numbers from one to ten, atoms including hydrogen and carbon, some interesting molecules, DNA, a human with description, basics of our Solar System, and basics of the sending telescope.  Several searches for extraterrestrial intelligence are currently underway, including one where you can use your own home computer.    Experts Debate: How will humanity first discover ET life?
Earth Flyby of BepiColombo (2020-05-04)

What it would look like to approach planet Earth?  Such an event was recorded visually in great detail by ESA's and JAXA's robotic BepiColombo spacecraft last month as it swung back past Earth on its journey in to the planet Mercury.  Earth can be seen rotating on approach as it comes out from behind the spacecraft's high-gain antenna in this nearly 10-hour time-lapse video.  The Earth is so bright that no background stars are visible.  Launched in 2018, the robotic BepiColombo used the gravity of Earth to adjust its course, the first of nine planetary flybys over the next seven years -- but the only one involving Earth. Scheduled to enter orbit in 2025, BepiColombo will take images and data of the surface and magnetic field of Mercury in an effort to better understand the early evolution of our Solar System and its innermost planet.    New: APOD now available through Instagram in Portuguese
Carina in Perspective (2020-05-05)

You need to be in the south, looking south, to see such a sky.  And only then if you're lucky.  Just above the picturesque tree is the impressive Carina Nebula, one of the few nebulas in the sky that is visible to the unaided eye.  The featured image had to be taken from a very dark location to capture the Carina Nebula with such perspective and so near the horizon.  The Great Nebula in Carina, cataloged as NGC 3372, is home to the wildly variable star Eta Carinae that sometimes flares to become one of the brightest stars in the sky.  Above Carina is IC 2944, the Running Chicken Nebula, a nebula that not only looks like a chicken, but contains impressive dark knots of dust.  Above these red-glowing emission nebulas are the bright stars of the Southern Cross, while on the upper left of the image is the dark Coalsack Nebula. This image was composed from six consecutive exposures taken last summer from Padre Bernardo, Goiás, Brazil.  Even with careful planning, the astrophotographer felt lucky to get this shot because clouds -- some still visible near the horizon -- kept getting in the way.    Almost Hyperspace: Random APOD Generator

Image credit: Carlos Kiko Fairbairn
LDN 1471: A Windblown Star Cavity (2020-05-06)

What is the cause of this unusual parabolic structure?  This illuminated cavity, known as LDN 1471, was created by a newly forming star, seen as the bright source at the peak of the parabola.  This protostar is experiencing a stellar outflow which is then interacting with the surrounding material in the Perseus Molecular Cloud, causing it to brighten.  We see only one side of the cavity -- the other side is hidden by dark dust.  The parabolic shape is caused by the widening of the stellar-wind blown cavity over time. Two additional structures can also be seen either side of the protostar, these are known as Herbig-Haro objects, again caused by the interaction of the outflow with the surrounding material.  What causes the striations on the cavity walls, though, remains unknown.  The featured image was taken by NASA and ESA’s Hubble Space Telescope after an original detection by the Spitzer Space Telescope.
Analemma of the Moon (2020-05-07)

An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day for one year. But the trick to imaging an analemma of the Moon is to wait bit longer. On average the Moon returns to the same position in the sky about 50 minutes and 29 seconds later each day. So photograph the Moon 50 minutes 29 seconds later on successive days. Over one lunation or lunar month it will trace out an analemma-like curve as the Moon's actual position wanders due to its tilted and elliptical orbit. To create this composite image of a lunar analemma, astronomer Gyorgy Soponyai chose a lunar month from March 26 to April 18 with a good stretch of weather and a site close to home near Mogyorod, Hungary. Crescent lunar phases too thin and faint to capture around the New Moon are missing though. Facing southwest, the lights of Budapest are in the distance of the base image taken on March 27.

Image credit: Gyorgy Soponyai
Long Tailed Comet SWAN (2020-05-08)

Blowing in the solar wind the spectacular ion tail of Comet SWAN (C/2020 F8) extends far across this 10 degree wide telephoto field of view. Captured on May 2 its greenish coma was about 6 light-minutes from Earth. The pretty background starfield lies near the border of the constellations Cetus and Aquarius. This comet SWAN was discovered at home by Australian amateur Michael Mattiazzo by checking images from the Sun-staring SOHO spacecraft's SWAN (Solar Wind ANisotropies) camera. The comet has now become just visible to the naked-eye as it sweeps from southern to northern skies. Appearing in morning twilight near the eastern horizon, Comet SWAN will make its closest approach to planet Earth on May 12 and reach perihelion on May 27.

Image credit: D. Peach
Full Flower Moonrise (2020-05-09)

Rising as the Sun set, the Moon was bright and full in planet Earth skies on May 7 and known to some as a Flower Moon. Near the horizon it does seem to take on rose pink hues of reddened sunlight in this reflective twilight scene. In fact one of the brighter Full Moons of the year, this month's full lunar phase occurred within about 32 hours of perigee. That's the closest point in the Moon's elliptical orbit. Flooded field and ruined church tower are near the municipality of Casaleggio Novara, Piedmont Region of northern Italy.

Image credit: Tiziano Boldrini