Η Αστρονομική Εικόνα της Ημέρας από τη NASA
Star Trails over One-Mile Radio Telescope
13/09/2025
The steerable 60 foot diameter dish antenna of the One-Mile Telescope at Mullard Radio Astronomy Observatory, Cambridge, UK, is pointing skyward in this evocative night-skyscape. To capture the dramatic scene, consecutive 30 second exposures were recorded over a period of 90 minutes. Combined, the exposures reveal a background of gracefully arcing star trails that reflect planet Earth's daily rotation on its axis. The North Celestial Pole, the extension of Earth's axis of rotation into space, points near Polaris, the North Star. That's the bright star that creates the short trail near the center of the concentric arcs. But the historic One-Mile Telescope array also relied on planet Earth's rotation to operate. Exploring the universe at radio wavelengths, it was the first radio telescope to use Earth-rotation aperture synthesis. That technique uses the rotation of the Earth to change the relative orientation of the telescope array and celestial radio sources to create radio maps of the sky at a resolution better than that of the human eye.
Copyright: Joao Yordanov Serralheiro
Προηγούμενες Αστρονομικές Εικόνες της Ημέρας από τη NASA
Dawn of the Crab
08/08/2025
One of the all-time historic skyscapes occured in July 1054, when the Crab Supernova blazed into the dawn sky. Chinese court astrologers first saw the Guest Star on the morning of 4 July 1054 next to the star Tianguan (now cataloged as Zeta Tauri). The supernova peaked in late July 1054 a bit brighter than Venus, and was visible in the daytime for 23 days. The Guest Star was so bright that every culture around the world inevitably discovered the supernova independently, although only nine reports survive, including those from China, Japan, and Constantinople. This iPhone picture is from Signal Hill near Tucson on the morning of 26 July 2025, faithfully re-creates the year 1054 Dawn of the Crab, showing the sky as seen by Hohokam peoples. The planet Venus, as a stand-in for the supernova, is close to the position of what is now the Crab Nebula supernova remnant. Step outside on a summer dawn with bright Venus, and ask yourself "What would you have thought in ancient times when suddenly seeing the Dawn of the Crab?"
Copyright: NASA
The Double Cluster in Perseus
07/08/2025
This stunning starfield spans about three full moons (1.5 degrees) across the heroic northern constellation of Perseus. It holds the famous pair of open star clusters, h and Chi Persei. Also cataloged as NGC 869 (right) and NGC 884, both clusters are about 7,000 light-years away and contain stars much younger and hotter than the Sun. Separated by only a few hundred light-years, the clusters are both 13 million years young based on the ages of their individual stars, evidence that both clusters were likely a product of the same star-forming region. Always a rewarding sight in binoculars or small telescopes, the Double Cluster is even visible to the unaided eye from dark locations.
Copyright: Ron Brecher
Meteor before Galaxy
06/08/2025
What's that green streak in front of the Andromeda galaxy? A meteor. While photographing the Andromeda galaxy in 2016, near the peak of the Perseid Meteor Shower, a small pebble from deep space crossed right in front of our Milky Way Galaxy's far-distant companion. The small meteor took only a fraction of a second to pass through this 10-degree field. The meteor flared several times while braking violently upon entering Earth's atmosphere. The green color was created, at least in part, by the meteor's gas glowing as it vaporized. Although the exposure was timed to catch a Perseid meteor, the orientation of the imaged streak seems a better match to a meteor from the Southern Delta Aquariids, a meteor shower that peaked a few weeks earlier. Not coincidentally, the Perseid Meteor Shower peaks next week, although this year the meteors will have to outshine a sky brightened by a nearly full moon.
Copyright: Fritz Helmut Hemmerich
NGC 6072: A Complex Planetary Nebula from Webb
05/08/2025
Why is this nebula so complex? The Webb Space Telescope has imaged a nebula in great detail that is thought to have emerged from a Sun-like star. NGC 6072 has been resolved into one of the more unusual and complex examples of planetary nebula. The featured image is in infrared light with the red color highlighting cool hydrogen gas. Study of previous images of NGC 6072 indicated several likely outflows and two disks inside the jumbled gas, while the new Webb image resolves new features likely including one disk's edge protruding on the central left. A leading origin hypothesis holds that the nebula's complexity is caused or enhanced by multiple outbursts from a star in a multi-star system near the center.
Copyright: NASA
Blue Arcs Toward Andromeda
04/08/2025
What are these gigantic blue arcs near the Andromeda Galaxy (M31)? Discovered in 2022 by amateur astronomers, the faint arcs -- dubbed SDSO 1 -- span nearly the same angular size as M31 itself. At first, their origin was a mystery: are they actually near the Andromeda Galaxy, or alternatively near to our Sun? Now, over 550 hours of combined exposure and a collaboration between amateur and professional astronomers has revealed strong evidence for their true nature: SDSO 1 is not intergalactic, but a new class of planetary nebula within our galaxy. Dubbed a Ghost Planetary Nebula (GPN), SDSO 1 is the first recognized member of a new subclass of faded planetary nebulas, along with seven others also recently identified. Shown in blue are extremely faint oxygen emission from the shock waves, while the surrounding red is a hydrogen-emitting trail that indicates the GPN's age.
Copyright: Ogle et al.
Milky Way and Exploding Meteor
03/08/2025
In about a week the Perseid Meteor Shower will reach its maximum. Grains of icy rock will streak across the sky as they evaporate during entry into Earth's atmosphere. These grains were shed from Comet Swift-Tuttle. The Perseids result from the annual crossing of the Earth through Comet Swift-Tuttle's orbit, and are typically the most active meteor shower of the year. Although it is hard to predict the level of activity in any meteor shower, in a clear dark sky an observer might see a meteor a minute. This year's Perseids peak just a few days after full moon, and so some faint meteors will be lost to the lunar skyglow. Meteor showers in general are best seen from a relaxing position, away from lights. Featured here is a meteor caught exploding during the 2015 Perseids above Austria next to the central band of our Milky Way Galaxy.
Copyright: Andre van der Hoeven
Fireflies, Meteors, and Milky Way
02/08/2025
Taken on July 29 and July 30, a registered and stacked series of exposures creates this dreamlike view of a northern summer night. Multiple firefly flashes streak across the foreground as the luminous Milky Way arcs above the horizon in the Sierra de Órganos national park of central Mexico, The collection of bright streaks aligned across the sky toward the upper left in the timelapse image are Delta Aquariid meteors. Currently active, the annual Delta Aquarid meteor shower shares August nights though, overlapping with the better-known Perseid meteor shower. This year that makes post-midnight, mostly moonless skies in early August very popular with late night skygazers. How can you tell a Delta Aquariid from a Perseid meteor? The streaks of Perseid meteors can be traced back to an apparent radiant in the constellation Perseus. Delta Aquariids appear to emerge from the more southerly constellation Aquarius, beyond the top left of this frame. Of course, the bioluminescent flashes of fireflies are common too on these northern summer nights. But how can you tell a firefly from a meteor? Just try to catch one.
Copyright: Daniel Korona
Small Dark Nebula
01/08/2025
A small, dark, nebula looks isolated near the center of this telescopic close-up. The wedge-shaped cosmic cloudlet lies within a relatively crowded region of space though. About 7,000 light-years distant and filled with glowing gas and an embedded cluster of young stars, the region is known as M16 or the Eagle Nebula. Hubble's iconic images of the Eagle Nebula include the famous star-forming Pillars of Creation, towering structures of interstellar gas and dust 4 to 5 light-years long. But this small dark nebula, known to some as a Bok globule, is a fraction of a light-year across. The Bok globule stands out in silhouette against the expansive background of M16's diffuse glow. Found scattered within emission nebulae and star clusters, Bok globules are small interstellar clouds of cold molecular gas and obscuring dust that also form stars within their dense, collapsing cores.
Copyright: Peter Bresseler
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.