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
Comet G3 ATLAS over Uruguay
28/01/2025
Comets can be huge. When far from the Sun, a comet's size usually refers to its hard nucleus of ice and rock, which typically spans a few kilometers -- smaller than even a small moon. When nearing the Sun, however, this nucleus can eject dust and gas and leave a thin tail that can spread to an enormous length -- even greater than the distance between the Earth and the Sun. Pictured, C/2024 G3 (ATLAS) sports a tail of sunlight-reflecting dust and glowing gas that spans several times the apparent size of a full moon, appearing even larger on long duration camera images than to the unaided eye. The featured image shows impressive Comet ATLAS over trees and a grass field in Sierras de Mahoma, San Jose, Uruguay about a week ago. After being prominent in the sunset skies of Earth's southern hemisphere, Comet G3 ATLAS is now fading as it moves away from the Sun, making its impressive tails increasingly hard to see. Gallery: Comet ATLAS (G3)
Copyright: Mauricio Salazar
Pleiades over Half Dome
27/01/2025
Stars come in bunches. The most famous bunch of stars on the sky is the Pleiades, a bright cluster that can be easily seen with the unaided eye. The Pleiades lies only about 450 light years away, formed about 100 million years ago, and will likely last about another 250 million years. Our Sun was likely born in a star cluster, but now, being about 4.5 billion years old, its stellar birth companions have long since dispersed. The Pleiades star cluster is pictured over Half Dome, a famous rock structure in Yosemite National Park in California, USA. The featured image is a composite of 28 foreground exposures and 174 images of the stellar background, all taken from the same location and by the same camera on the same night in October 2019. After calculating the timing of a future juxtaposition of the Pleiades and Half Dome, the astrophotographer was unexpectedly rewarded by an electrical blackout, making the background sky unusually dark. Astrophysicists: Browse 3,500+ codes in the Astrophysics Source Code Library
Copyright: Dheera Venkatraman
The Many Tails of Comet G3 ATLAS
26/01/2025
Why does this comet have so many tails? C/2024 G3 (ATLAS) has developed several long and intricate tails visible from Earth's southern hemisphere over the past two weeks. Many observers reported seeing the impressive comet without any optical aid above the western horizon just after sunset. At least six different tails appear in the featured image captured five days ago from the dark skies above Paranal Observatory in Chile. One possible cause for the multiple tails is dust and gas being expelled from the comet's rotating nucleus. The outward push of the Sun's complex solar wind may also play a role. The huge iceberg-like nucleus of Comet ATLAS appears to have broken up near its closest approach to the Sun two weeks ago. Unfortunately, Comet ATLAS and its tails are expected to fade significantly over the coming weeks. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
Copyright: Martin Mašek (FZU, Czech Academy of Sciences) & Jakub Kuřák
Stardust in the Perseus Molecular Cloud
25/01/2025
Clouds of stardust drift through this deep skyscape, across the Perseus molecular cloud some 850 light-years away. Dusty nebulae reflecting light from embedded young stars stand out in the nearly 4 degree wide field of view. With a characteristic bluish color reflection nebula NGC 1333 is prominent near center. Hints of contrasting red emission from Herbig-Haro objects, the jets and shocked glowing gas emanating from recently formed stars, are scattered across the dusty expanse. While many stars are forming in the molecular cloud, most are obscured at visible wavelengths by the pervasive dust. The chaotic environment surrounding NGC 1333 may be similar to one in which our own Sun formed over 4.5 billion years ago. At the estimated distance of the Perseus molecular cloud, this cosmic scene would span about 80 light-years. Growing Gallery: Comet ATLAS (G3)
Copyright: Jeff Schilling
Comet G3 ATLAS: a Tail and a Telescope
24/01/2025
Comet C/2024 G3 ATLAS has made a dramatic appearance in planet Earth's skies. A visitor from the distant Oort Cloud, the comet reached its perihelion on January 13. On January 19, the bright comet was captured here from ESO Paranal Observatory in the Atacama desert in Chile. Sporting spectacular sweeping dust tails, this comet ATLAS is setting in the southern hemisphere twilight and was clearly visible to the unaided eye. In the foreground is the closed shell of one of the observatory's famous auxiliary telescopes. Still wowing southern hemisphere observers, the comet's bright coma has become diffuse, its icy nucleus apparently disintegrating following its close approach to the Sun. Growing Gallery: Comet ATLAS (G3)
Copyright: Yuri Beletsky
NGC 7814: Little Sombrero
23/01/2025
Point your telescope toward the high flying constellation Pegasus and you can find this cosmic expanse of Milky Way stars and distant galaxies. NGC 7814 is centered in the sharp field of view that would almost be covered by a full moon. NGC 7814 is sometimes called the Little Sombrero for its resemblance to the brighter more famous M104, the Sombrero Galaxy. Both Sombrero and Little Sombrero are spiral galaxies seen edge-on, and both have extensive halos and central bulges cut by a thin disk with thinner dust lanes in silhouette. In fact, NGC 7814 is some 40 million light-years away and an estimated 60,000 light-years across. That actually makes the Little Sombrero about the same physical size as its better known namesake, appearing smaller and fainter only because it is farther away.
Copyright: Mike Selby
The North America Nebula
22/01/2025
The North America nebula on the sky can do what the North America continent on Earth cannot -- form stars. Specifically, in analogy to the Earth-confined continent, the bright part that appears as the east coast is actually a hot bed of gas, dust, and newly formed stars known as the Cygnus Wall. The featured image shows the star forming wall lit and eroded by bright young stars and partly hidden by the dark dust they have created. The part of the North America nebula (NGC 7000) shown spans about 50 light years and lies about 1,500 light years away toward the constellation of the Swan (Cygnus). Jigsaw Challenge: Astronomy Puzzle of the Day
Copyright: Dimitris Valianos
Comet ATLAS over Brasília
21/01/2025
What's that in the sky? Above the city, above most clouds, far in the distance: it's a comet. Pictured, the impressive tail of Comet C/2024 G3 (ATLAS) was imaged from Brasília, Brazil four days ago. Last week the evolving comet rounded the Sun well inside the orbit of planet Mercury, going so close there was early concern that it might break up -- and recent evidence that it really did. At one point near perihelion, Comet ATLAS was so bright that sightings were even reported during the day -- over the bright sky near the Sun -- by careful observers. Over the past few days, Comet ATLAS has developed a long tail that has been partly visible with unaided eyes after sunset, most notably in Earth's southern hemisphere. Growing Gallery: Comet ATLAS (G3)
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.