One of the most identifiable nebulas in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1,500 years to reach us from the Horsehead Nebula. The featured image was taken from the Chilescope Observatory in the mountains of Chile.
Copyright: Alex Lin (Chilescope)
Why would a small part of the Sun appear slightly dark? Visible is a close-up picture of sunspots, depressions on the Sun's surface that are slightly cooler and less bright than the rest of the Sun. The Sun's complex magnetic field creates these cool regions by inhibiting hot material from entering the spots. Sunspots can be larger than the Earth and typically last for about a week. Part of active region AR 3297 crossing the Sun in early May, the large lower sunspot is spanned by an impressive light bridge of hot and suspended solar gas. This high-resolution picture also shows clearly that the Sun's surface is a bubbling carpet of separate cells of hot gas. These cells are known as granules. A solar granule is about 1000 kilometers across and lasts for only about 15 minutes. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
Copyright: Mark Johnston
Most photographs don't adequately portray the magnificence of the Sun's corona. Seeing the corona first-hand during a total solar eclipse is unparalleled. The human eye can adapt to see coronal features and extent that average cameras usually cannot. Welcome, however, to the digital age. The featured image digitally combined short and long exposures taken in Exmouth, Australia that were processed to highlight faint and extended features in the corona during the total solar eclipse that occurred in April of 2023. Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields in the Sun's corona. Looping prominences appear bright pink just past the Sun's edge. Images taken seconds before and after the total eclipse show glimpses of the background Sun known as Baily's Beads and diamond ring effect. The next total solar eclipse will cross North America in April of 2024. Total Solar Eclipse of 2023 April Gallery: Notable Submissions to APOD
Copyright: Reinhold Wittich
From afar, the whole thing looks like an eagle. A closer look at the Eagle Nebula, however, shows the bright region is actually a window into the center of a larger dark shell of dust. Through this window, a brightly-lit workshop appears where a whole open cluster of stars is being formed. In this cavity, tall pillars and round globules of dark dust and cold molecular gas remain where stars are still forming. Already visible are several young bright blue stars whose light and winds are burning away and pushing back the remaining filaments and walls of gas and dust. The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of the Serpent (Serpens). This picture involved long and deep exposures and combined three specific emitted colors emitted by sulfur (colored as yellow), hydrogen (red), and oxygen (blue).
Copyright: Gianni Lacroce
What would it be like to fly free in space? At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was living the dream -- floating farther out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured, was floating free in space. During Space Shuttle mission 41-B in 1984, McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk". The MMU worked by shooting jets of nitrogen and was used to help deploy and retrieve satellites. With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was later replaced with the SAFER backpack propulsion unit.
Copyright: NASA
Our fair planet sports a curved, sunlit crescent against the black backdrop of space in this stunning photograph. From the unfamiliar perspective, the Earth is small and, like a telescopic image of a distant planet, the entire horizon is completely within the field of view. Enjoyed by crews on board the International Space Station, only much closer views of the planet are possible from low Earth orbit. Orbiting the planet once every 90 minutes, a spectacle of clouds, oceans, and continents scrolls beneath them with the partial arc of the planet's edge in the distance. But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972. The original photograph, AS17-152-23420, was taken by the homeward bound crew of Apollo 17, on December 17, 1972. For now it is the last picture of Earth from this planetary perspective taken by human hands.
Copyright: NASA
Grains of cosmic dust streaked through night skies in early May. Swept up as planet Earth plowed through the debris streams left behind by periodic Comet Halley, the annual meteor shower is known as the Eta Aquarids. This year, the Eta Aquarids peak was visually hampered by May's bright Full Moon, though. But early morning hours surrounding last May's shower of Halley dust were free of moonlight interference. In exposures recorded between April 28 and May 8 in 2022, this composited image shows nearly 90 Eta Aquarid meteors streaking from the shower's radiant in Aquarius over San Pedro de Atacama, Chile. The central Milky Way arcs above in the southern hemisphere's predawn skies. The faint band of light rising from the horizon is Zodiacal light, caused by dust scattering sunlight near our Solar System's ecliptic plane. Along the ecliptic and entrained in the Zodiacal glow are the bright planets Venus, Jupiter, Mars, and Saturn. Of course Mars itself has recently been found to be a likely source of the dust along the ecliptic responsible for creating Zodiacal light.
Copyright: Petr Horalek
Fomalhaut is a bright star, a 25 light-year voyage from planet Earth in the direction of the constellation Piscis Austrinus. Astronomers first noticed Fomalhaut's excess infrared emission in the 1980s. Space and ground-based telescopes have since identified the infrared emission's source as a disk of dusty debris surrounding the hot, young star related to the ongoing formation of a planetary system. But this sharp infrared image from the James Webb Space Telescope's MIRI camera reveals details of Fomalhaut's debris disk never before seen, including a large dust cloud in the outer ring that is possible evidence for colliding bodies, and an inner dust disk and gap likely shaped and maintained by embedded but unseen planets. An image scale bar in au or astronomical units, the average Earth-Sun distance, appears at the lower left. Fomalhaut's outer circumstellar dust ring lies at about twice the distance of our own Solar System's Kuiper Belt of small icy bodies and debris beyond the orbit of Neptune.
Copyright: NASA
For ten years the stargazer dreamed of taking a picture like this. The dreamer knew that the White Desert National Park in Egypt's Western Desert is a picturesque place hosting numerous chalk formations sculpted into surreal structures by a sandy wind. The dreamer knew that the sky above could be impressively dark on a clear moonless night, showing highlights such as the central band of our Milky Way Galaxy in impressive color and detail. So the dreamer invited an even more experienced astrophotographer to spend three weeks together in the desert and plan the composite images that needed to be taken and processed to create the dream image. Over three days in mid-March, the base images were taken, all with the same camera and from the same location. The impressive result is featured here, with the dreamer -- proudly wearing a traditional Bedouin galabyia -- pictured in the foreground.
Copyright: Amr Abdelwahab
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.