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
The Galactic Center in Radio from MeerKAT
14/04/2025
What's happening at the center of our galaxy? It's hard to tell with optical telescopes since visible light is blocked by intervening interstellar dust. In other bands of light, though, such as radio, the galactic center can be imaged and shows itself to be quite an interesting and active place. The featured picture shows an image of our Milky Way's center by the MeerKAT array of 64 radio dishes in South Africa. Spanning four times the angular size of the Moon (2 degrees), the image is impressively vast, deep, and detailed. Many known sources are shown in clear detail, including many with a prefix of Sgr, since the galactic center is in the direction of the constellation Sagittarius. In our galaxy's center lies Sgr A, found here in the image center, which houses the Milky Way's central supermassive black hole. Other sources in the image are not as well understood, including the Arc, just to the left of Sgr A, and numerous filamentary threads. The inset image shows a small patch recently imaged in infrared light with the James Webb Space Telescope to investigate the effects of magnetic fields on star formation. Open Science: Browse 3,600+ codes in the Astrophysics Source Code Library
Copyright: NASA
An Unusual Hole in Mars
13/04/2025
What created this unusual hole in Mars? Actually, there are numerous holes pictured in this Swiss cheese-like landscape, with all-but-one of them showing a dusty, dark, Martian terrain beneath evaporating, light, carbon dioxide ice. The most unusual hole is on the upper right, spans about 100 meters, and seems to punch through to a lower level. Why this hole exists and why it is surrounded by a circular crater remains a topic of speculation, although a leading hypothesis is that it was created by a meteor impact. Holes such as this are of particular interest because they might be portals to lower levels that extend into expansive underground caves. If so, these naturally occurring tunnels are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore also prime targets for possible future spacecraft, robots, and even human interplanetary explorers.
Copyright: NASA
Moon Near the Edge
12/04/2025
Most of us watch the Moon at night. But the Moon spends nearly as many daylight hours above our horizon, though in bright daytime skies the lunar disk looks pale and can be a little harder to see. Of course in daytime skies the Moon also appears to cycle through its phases, shining by reflected sunlight as it orbits our fair planet. For daytime moonwatchers, the Moon is probably easier to spot when the visible sunlit portion of the lunar disk is large and waxing following first quarter or waning approaching its third quarter phase. And though it might look unusual, a daytime moon is often seen even in urban skies. Captured here in a telephoto snapshot taken on March 12, a waxing daytime Moon is aligned near the edge of a popular observation deck that overlooks New York City's borough of Manahattan.
Copyright: Jordi Coy
The ISS Meets Venus
11/04/2025
Made with a telescope shaded from bright sunlight by an umbrella, on April 5 a well-planned video captured a crescent Venus shining in clear daytime skies from Shoreline, Washington, USA at 11:57AM Pacific Time. It also caught the International Space Station in this single video frame. In close conjunction with the bright planet, the faint outline of the orbital outpost seen at a range of about 400 kilometers appears to be similar in size to the slender planetary crescent. Of course the ISS is much smaller than Venus. Now appearing as planet Earth's brilliant morning star and climbing above the eastern horizon in predawn skies, inner planet Venus was nearly 45 million kilometers from Shoreline.
Copyright: A.J. Smadi
38 Hours with the M81 Group
10/04/2025
From a garden on planet Earth, 38 hours of exposure with a camera and small telescope produced this cosmic photo of the M81 galaxy group. In fact, the group's dominant galaxy M81 is near the center of the frame sporting grand spiral arms and a bright yellow core. Also known as Bode's galaxy, M81 itself spans some 100,000 light-years. Near the top is cigar-shaped irregular galaxy M82. The pair have been locked in gravitational combat for a billion years. Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters. Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in massive star forming regions arrayed along M81's spiral arms. M82 was left with violent star forming regions too, and colliding gas clouds so energetic that the galaxy glows in X-rays. In the next few billion years, their continuing gravitational encounters will result in a merger, and a single galaxy will remain. Another group member, NGC 3077 is below and left of the large spiral M81. Far far away, about 12 million light-years distant the M81 group galaxies are seen toward the northern constellation Ursa Major (the Great Bear). But in the closer foreground the wide-field image is filled with integrated flux nebulae whose faint, dusty interstellar clouds reflect starlight above the plane of our own Milky Way galaxy.
Copyright: Daniel Yang K.
HH 49: Interstellar Jet from Webb
09/04/2025
What's at the tip of this interstellar jet? First let's consider the jet: it is being expelled by a star system just forming and is cataloged as Herbig-Haro 49 (HH 49). The star system expelling this jet is not visible -- it is off to the lower right. The complex conical structure featured in this infrared image by the James Webb Space Telescope also includes another jet cataloged as HH 50. The fast jet particles impact the surrounding interstellar gas and form shock waves that glow prominently in infrared light -- shown here as reddish-brown ridges. This JWST image also resolved the mystery of the unusual object at HH 49's tip: it is a spiral galaxy far in the distance. The blue center is therefore not one star but many, and the surrounding circular rings are actually spiral arms. Jump Around the Universe: Random APOD Generator
Copyright: NASA
Moon Visits Sister Stars
08/04/2025
Sometimes, the Moon visits the Pleiades. Technically, this means that the orbit of our Moon takes it directly in front of the famous Pleiades star cluster, which is far in the distance. The technical term for the event is an occultation, and the Moon is famous for its rare occultations of all planets and several well-known bright stars. The Moon's tilted and precessing orbit makes its occultations of the Seven Sisters star cluster bunchy, with the current epoch starting in 2023 continuing monthly until 2029. After that, though, the next occultation won't occur until 2042. Taken from Cantabria, Spain on April 1, the featured image is a composite where previous exposures of the Pleiades from the same camera and location were digitally added to the last image to bring up the star cluster's iconic blue glow. Jigsaw Challenge: Astronomy Puzzle of the Day
Copyright: NASA
NGC 4414: A Flocculent Spiral Galaxy
07/04/2025
How much mass do flocculent spirals hide? The featured image of flocculent spiral galaxy NGC 4414 was taken with the Hubble Space Telescope to help answer this question. Flocculent spirals -- galaxies without well-defined spiral arms -- are a quite common form of galaxy, and NGC 4414 is one of the closest. Stars and gas near the visible edge of spiral galaxies orbit the center so fast that the gravity from a large amount of unseen dark matter must be present to hold them together. Understanding the matter and dark matter distribution of NGC 4414 helps humanity calibrate the rest of the galaxy and, by deduction, flocculent spirals in general. Further, calibrating the distance to NGC 4414 helps humanity calibrate the cosmological distance scale of the entire visible universe.
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.