Η Αστρονομική Εικόνα της Ημέρας από τη NASA
A Daytime Eclipse: Moon Occults Venus
15/09/2026
There was something behind the clouds. Upon close inspection, it was the Moon, which was hard to see yesterday around noon above the small village of Cessy, France. But soon, it was not only the Moon. As expected, a bright dot suddenly appeared from behind the Moon -- the planet Venus far in the distance. Captured in the single featured exposure, both appeared to show a crescent phase. The Moon's crescent was quite slight -- with only about 10 percent of its face illuminated by the Sun. In contrast, Venus's crescent was more full -- showing about 25 percent illumination. Venus appeared brighter because it is nearer the Sun and because its clouds are more reflective than the dark lunar surface. An occultation of Venus by the Moon is visible to only about 10 percent of the Earth, but in yesterday's event even most of that was experiencing daytime. APOD's main NASA site is moving: From apod.nasa.gov to science.nasa.gov/apod
Copyright: Arnaud Mariat
Προηγούμενες Αστρονομικές Εικόνες της Ημέρας από τη NASA
NGC 2403 in Camelopardalis
03/06/2024
Magnificent island universe NGC 2403 stands within the boundaries of the long-necked constellation Camelopardalis. Some 10 million light-years distant and about 50,000 light-years across, the spiral galaxy also seems to have more than its fair share of giant star forming HII regions, marked by the telltale reddish glow of atomic hydrogen gas. The giant HII regions are energized by clusters of hot, massive stars that explode as bright supernovae at the end of their short and furious lives. A member of the M81 group of galaxies, NGC 2403 closely resembles a galaxy in our own local galaxy group with an abundance of star forming regions, M33, the Triangulum Galaxy. Spiky in appearance, bright stars in this portrait of NGC 2403 are in the foreground, within our own Milky Way. Also in the foreground of the deep, wide-field, telescopic image are the Milky Way's dim and dusty interstellar clouds also known as galactic cirrus or integrated flux nebulae. But faint features that seem to extend from NGC 2403 itself are likely tidal stellar streams drawn out by gravitational interactions with neighboring galaxies.
Copyright: (Team F.A.C.T.)
Rotating Moon from LRO
02/06/2024
No one, presently, sees the Moon rotate like this. That's because the Earth's moon is tidally locked to the Earth, showing us only one side. Given modern digital technology, however, combined with many detailed images returned by the Lunar Reconnaissance Orbiter (LRO), a high resolution virtual Moon rotation movie has been composed. The featured time-lapse video starts with the standard Earth view of the Moon. Quickly, though, Mare Orientale, a large crater with a dark center that is difficult to see from the Earth, rotates into view just below the equator. From an entire lunar month condensed into 24 seconds, the video clearly shows that the Earth side of the Moon contains an abundance of dark lunar maria, while the lunar far side is dominated by bright lunar highlands. Currently, over 32 new missions to the Moon are under active development from multiple countries and companies, including NASA's Artemis program which aims to land people on the Moon again within the next few years.
Copyright: NASA
Stereo Helene
01/06/2024
Get out your red/blue glasses and float next to Helene, small, icy moon of Saturn. Appropriately named, Helene is a Trojan moon, so called because it orbits at a Lagrange point. A Lagrange point is a gravitationally stable position near two massive bodies, in this case Saturn and larger moon Dione. In fact, irregularly shaped ( about 36 by 32 by 30 kilometers) Helene orbits at Dione's leading Lagrange point while brotherly ice moon Polydeuces follows at Dione's trailing Lagrange point. The sharp stereo anaglyph was constructed from two Cassini images captured during a close flyby in 2011. It shows part of the Saturn-facing hemisphere of Helene mottled with craters and gully-like features.
Copyright: NASA
The Nebulous Realm of WR 134
31/05/2024
Made with narrowband filters, this cosmic snapshot covers a field of view over twice as wide as the full Moon within the boundaries of the constellation Cygnus. It highlights the bright edge of a ring-like nebula traced by the glow of ionized hydrogen and oxygen gas. Embedded in the region's expanse of interstellar clouds, the complex, glowing arcs are sections of shells of material swept up by the wind from Wolf-Rayet star WR 134, brightest star near the center of the frame. Distance estimates put WR 134 about 6,000 light-years away, making the frame over 100 light-years across. Shedding their outer envelopes in powerful stellar winds, massive Wolf-Rayet stars have burned through their nuclear fuel at a prodigious rate and end this final phase of massive star evolution in a spectacular supernova explosion. The stellar winds and final supernova enrich the interstellar material with heavy elements to be incorporated in future generations of stars.
Copyright: Xin Long
A Lunar Corona over Paris
30/05/2024
Why does a cloudy moon sometimes appear colorful? The effect, called a lunar corona, is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently. Lunar coronae are one of the few quantum mechanical color effects that can be easily seen with the unaided eye. Solar coronae are also sometimes evident. The featured image was taken last month from Paris, France. The blue beacon emanating from the Eiffel Tower did not affect the colorful lunar corona. Portal Universe: Random APOD Generator
Copyright: Valter Binotto
Stairway to the Milky Way
29/05/2024
What happens if you ascend this stairway to the Milky Way? Before answering that, let's understand the beautiful sky you will see. Most eye-catching is the grand arch of the Milky Way Galaxy, the band that is the central disk of our galaxy which is straight but distorted by the wide-angle nature of this composite image. Many stars well in front of the Milk Way will be visible, with the bright white star just below the stellar arch being Altair, and the bright blue star above it being Vega. The air glows green on the left, just above the yellow cloud deck. The featured image was taken last month on Portugal's Madeira Island in the North Atlantic Ocean. Oh, and what happens after you reach the top of these stairs and admire the amazing sky is, quite probably, that you then descend down the stairs on the other side. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
Copyright: Marcin Rosadziński
Solar X Flare as Famous Active Region Returns
28/05/2024
It's back. The famous active region on the Sun that created auroras visible around the Earth earlier this month has survived its rotation around the far side of the Sun -- and returned. Yesterday, as it was beginning to reappear on the Earth-facing side, the region formerly labeled AR 3664 threw another major solar flare, again in the highest-energy X-class range. The featured video shows the emerging active region on the lower left, as it was captured by NASA's Earth-orbiting Solar Dynamics Observatory yesterday in ultraviolet light. The video is a time-lapse of the entire Sun rotating over 24 hours. Watch the lower-left region carefully at about the 2-second mark to see the powerful flare burst out. The energetic particles from that flare and associated CME are not expected to directly impact the Earth and trigger impressive auroras, but scientists will keep a close watch on this unusually active region over the next two weeks, as it faces the Earth, to see what develops.
Copyright: NASA
Chamaeleon I Molecular Cloud
27/05/2024
Dark markings and bright nebulae in this telescopic southern sky view are telltale signs of young stars and active star formation. They lie a mere 650 light-years away, at the boundary of the local bubble and the Chamaeleon molecular cloud complex. Regions with young stars identified as dusty reflection nebulae from the 1946 Cederblad catalog include the C-shaped Ced 110 just above and right of center, and bluish Ced 111 below it. Also a standout in the frame, the orange tinted V-shape of the Chamaeleon Infrared Nebula (Cha IRN) was carved by material streaming from a newly formed low-mass star. The well-composed image spans 1.5 degrees. That's about 17 light-years at the estimated distance of the nearby Chamaeleon I molecular cloud.
Copyright: Amiel Contuliano
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.