Η Αστρονομική Εικόνα της Ημέρας από τη NASA
Saturn's Iapetus: Painted Moon
05/07/2026
What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as snow. To help better understand this unusually tinted moon, in 2007 NASA directed the robotic Cassini spacecraft then orbiting Saturn to swoop within 2,000 kilometers. Pictured here, from about 75,000 kilometers out, is the hemisphere of Iapetus that is always trailing. A large impact crater seen in the south spans 500 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. A leading hypothesis is that the dark material is mostly a form of carbon-rich soil leftover from when relatively warm but dirty ice sublimates. An initial coating of this dark material may have been effectively painted on by the accretion of meteor-liberated debris from other moons. Jigsaw Moon: Astronomy Puzzle of the Day
Copyright: NASA
Προηγούμενες Αστρονομικές Εικόνες της Ημέρας από τη NASA
Pathfinder on Mars
04/07/2026
On July 4th, 1997, using its own array of fireworks, a parachute, and a cocoon of airbags, the Mars Pathfinder spacecraft bounced like a giant beach ball at least 15 times before it came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. After its then novel airbag-assisted landing sequence was completed, Pathfinder transmitted this color mosaic to mission operators on Earth. In the scene from another world, the Mars Sojourner robot rover is visible in the foreground, crouched on top of the unfolded Pathfinder. About the size of a large house cat, the six-wheeled, solar-powered Sojourner became the first successful Martian rover. Surrounding Pathfinder are deflated airbags and the rock-strewn terrain of the Ares Vallis floodplain. In the distance Martian hills appear against a dusty brownish sky. The Pathfinder lander was subsequently renamed the Carl Sagan Memorial Station.
Copyright: NASA
Three Galaxies in Pavo
03/07/2026
Some 190 million light-years away, far beyond the bright stars and nebulae of the Milky Way, these three galaxies are drawn together by gravity in a mesmerizing cosmic dance. Clearly distorted by galactic-scale gravitational interactions, large spiral galaxies NGC6769 and NGC6770 are seen face-on, with luminous galactic disks scarred by obscuring interstellar dust lanes. Their young blue star clusters along drawn out spiral arms are spawned in star forming regions that result from collisions of massive molecular clouds. Below, spiral NGC6771 presents a more edge-on perspective, its boxy central bulge due to tidal star streams. Of course, in the distant future a merger of the three galaxies is inevitable. At the estimated distance of this galaxy trio, known to some as the Devil's Mask, the sharp telescopic frame spans over 300 thousand light-years within the boundaries of the far southern constellation Pavo.
Copyright: Mike Selby
Sibling Supernova Remnants
02/07/2026
What happens when one of the stars in a binary goes supernova? This image combines visible (yellow), ultraviolet (purple) and infrared light (cyan, red and orange) to show two supernova remnants and their surrounding environment, about 6,000 light-years away. The younger one is the well-known Jellyfish Nebula in the center (mostly in yellow). If we could see it by eye, it would appear larger than the full moon in the sky. The filament shown in purple is part of an older, overlapping supernova remnant, G189.6+3.3. A new study used data from NASA's Fermi Gamma-ray Space Telescope to piece together their story. Astronomers believe that there were two stars in a binary system, then the first one exploded as a supernova, kicking away its companion, which also exploded as a supernova tens of thousands of years later, creating the superimposed supernova remnants we see today. The bright star on the right is actually a triple star system named Propus.
Copyright: NASA
The Cotton Candy Clouds of Rho Ophiuchi
01/07/2026
Although they look like cotton candy, you cannot eat these clouds! Taken in Cádiz, Spain, today's image features the Rho Ophiuchi complex, a rich tapestry of young and old astronomical phenomena. This colorful cloud complex is a nearby star-forming region containing hundreds of young stellar objects, including protostars and T Tauri stars. Light from the triple star system at its center reflects off of small dust grains to create the blue reflection nebula. Ultraviolet light from hot stars ionizes the surrounding hydrogen gas, creating the red emission nebula. Antares, a red supergiant big enough to engulf the Solar System’s asteroid belt, lights up the yellow region. Dark interstellar dust blocks some of the complex’s color. Recent JWST observations exhibit shadows cast by hidden circumstellar disks, the beginning stages of planet formation. Messier 4, a globular cluster almost as old as the universe, sits in the bottom right and witnesses yet another chaotic burst of youth in the Milky Way.
Copyright: Ángel Molina Text: Keighley Rockcliffe (NASA GSFC, UMBC CSST, CRESST II)
Unusually Smooth Sections of Asteroid Itokawa
30/06/2026
Why are parts of this asteroid's surface so smooth? The answer seems likely to do with the dynamics of an asteroid that is a loose pile of rubble rather than a solid rock. The unusual asteroid Itokawa was visited by the Japanese spacecraft Hayabusa in 2005 which imaged and documented its unusual structure and mysterious lack of craters. Analyses of the border regions between smooth and rugged sections indicate that jostling of the asteroid might be creating segregation between large and small rocks near the surface, like the Brazil nut effect. The robotic Hayabusa actually touched down on one of the smooth patches, dubbed the MUSES Sea, and collected soil samples. These samples were returned to Earth and are not only giving clues to the ancient history of this unusual asteroid, but also about the early years of our entire Solar System. Computer simulations show that 500-meter asteroid Itokawa may impact the Earth within the next few million years. Rocking Space: Today is Asteroid Day
Copyright: NASA
M82: Galaxy with a Supergalactic Wind
29/06/2026
Why is the Cigar Galaxy billowing red smoke? M82, as this starburst galaxy is also known, was stirred up by a recent pass near large spiral galaxy M81. This doesn't fully explain the source of the red-glowing outwardly expanding gas and dust, however. Evidence indicates that this gas and dust is being driven out by the combined emerging particle winds of many stars, together creating a galactic superwind. The dust particles are thought to originate in M82's interstellar medium and are actually similar in size to particles in cigar smoke. The featured photographic mosaic combines images taken in visible light from the Hubble Space Telescope and images taken in infrared light from James Webb Space Telescope. It shows the light-colored central galaxy nearly edge on across the image center with tremendous orange and red colored filaments of gas and dust extending both up and down. The filaments extend for over 10,000 light years. The 12-million light-year distant Cigar Galaxy is the brightest galaxy in the sky in infrared light and can be seen in visible light with a small telescope towards the constellation of the Great Bear (Ursa Major).
Copyright: NASA
AR 4478: Giant Sunspot Group
28/06/2026
Right now, one of the largest sunspot groups in recent history is crossing the Sun. Active Region 4478 is not only big -- it's violent, showing tangled magnetic fields capable of throwing off huge clouds of particles into the Solar System. Some of these CMEs might impact the Earth. At the extreme, these solar storms could cause some Earth-orbiting satellites to malfunction, the Earth's atmosphere to slightly distort, and electrical power grids to surge. When impacting Earth's upper atmosphere, these particles can produce beautiful auroras. Pictured here, AR 4478 and its dark sunspots were captured in visible light a few days ago from Barcelona, Spain. Almost as large as AR 3664 was in 2024, the AR 4478 sunspot group is so big that it is visible just with glasses specially designed to view solar eclipses. This week, skygazing enthusiasts all over the globe will not only be tracking AR 4478 during the day -- but keenly watching night skies for its corresponding bright auroras. Sky Surprise: What picture did APOD feature on your birthday? (after 1995)
Copyright: Alfredo Vidal Pérez
Mars Marathon by Perseverance
27/06/2026
In this recent HiRISE view from the Mars Reconnaissance Orbiter, the little green dot indicated on the surface of the big Red Planet is the Perseverance Mars rover. Recorded on June 13, the car-sized, six-wheeled robot was imaged a day before completing a Martian marathon, traveling a total distance of 26.218 miles (42.195 kilometers) since it began exploring the surface of Mars. That equivalent marathon distance was achieved by Perseverance on its mission sol (Martian day) 1,890, after about 5 Earth years and 4 Earth months of driving. Perseverance is continuing to hunt for biosignatures. In the HiRISE image, the Mars rover's tracks can be seen leading to its location in an area west of its landing site in Jezero crater near an ancient river delta.
Copyright: NASA
Η Αστρονομική Εικόνα της Ημέρας από τη NASA (NASA Astronomy Picture of the Day) είναι μια δωρεάν υπηρεσία που παρέχει καθημερινά μια εντυπωσιακή εικόνα από το σύμπαν, την λήψη της οποίας έχει πραγματοποιήσει κάποιος από τους αστρονόμους της NASA ή από κάποιον από τους δορυφόρους ή τα τηλεσκόπια που η NASA λειτουργεί. Οι εικόνες που εμφανίζονται καλύπτουν μια ευρεία γκάμα από θέματα, συμπεριλαμβανομένων των αστερισμών, των γαλαξιών, των πλανητικών συστημάτων, των κομητών, των αστρικών σωμάτων και των παρατηρητηρίων. Κάθε εικόνα συνοδεύεται από μια σύντομη εξήγηση και πληροφορίες σχετικά με το τι παρατηρείται στην εικόνα.