Αστρονομική Εικόνα της Ημέρας από τη NASA

Προηγούμενες Αστρονομικές Εικόνες της Ημέρας από τη NASA

Aurora Slathers Up the Sky

16/05/2026

Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth's limb.

R3 PanSTARRS: An Orion Comet

15/05/2026

Comet R3 PanSTARRS might be best remembered as an Orion comet. A key reason is because Comet C/2025 R3 (PanSTARRS) was near its most spectacular -- in terms of tail visibility -- when passing in front of the iconic constellation. Although rare, other bright comets, too, have ventured across Orion, including Lovejoy in 2015, Hale-Bopp in 1997, and the Great Comet of 1264. Best visible in long duration exposures, the featured image was captured last week from the Craigieburn Mountain Range in New Zealand. Visible in the deep background image are the Orion Nebula, Barnard's Loop, and through R3's tail, the bright star Saiph, the sixth brightest star in the constellation of Orion. Comet R3 PanSTARRS continues to fade as it moves further south, passing into the constellation of the Unicorn (Monoceros) in the next few days. Sky Surprise: What picture did APOD feature on your birthday? (after 1995)

Messier Catalog at Uniform Scale

14/05/2026

What are some of the most interesting astronomical objects you can see in the night sky? Armed with a good pair of binoculars or a small telescope, if you live in the Northern Hemisphere, you can look for the very popular objects in the Messier Catalog. Most of them, but not all, are also visible from the southern half of the Earth. The featured image shows all 110 objects in the catalog at uniform scale -- the same magnification. Charles Messier created the catalog in the 18th century. He was interested in comets, and his catalog was a list of known comet-like "objects to avoid" in the sky when observing or hunting for comets. The deep sky objects in the catalog include a supernova remnant (the Crab Nebula, M1), other galaxies (such as Andromeda, M31), nebulae (e.g. the Orion Nebula, M42, a star-forming region) and stellar clusters (such as the Pleiades, M45, a bright young open cluster).

NGC 188: Old Cluster in the New General Catalog

13/05/2026

The New General Catalog of star clusters and nebulae really isn't so new. In fact, it was published in 1888 - an effort by J. L. E. Dreyer to consolidate the work of astronomers William, Caroline, and John Herschel along with others into a useful single, complete catalog of astronomical discoveries and measurements. Dreyer's work was largely successful and is still important today, as this famous catalog continues to lend its "NGC" to bright clusters, galaxies, and nebulae. Take for example the star cluster known as NGC 188 (item number 188 in the NGC compilation). It lies about 6,000 light-years distant in the northern constellation Cepheus and represents a galactic or open star cluster. With an age of about 7 billion years, NGC 188 is old for an open cluster. Its old, evolved red giant stars have yellowish hues in this colorful, deep sky view. NGC 188 also enjoys the designation Caldwell 1 in a modern compilation of deep sky objects. Located well above the plane of the Milky Way and seen in the direction of planet Earth's north celestial pole, the ancient stellar group is known to some as the Polarissima Cluster.

The Conjunction of Comet R3 PanSTARRS and the Orion Nebula

12/05/2026

Today’s composite image features something old, something new, something borrowed, and something blue! Comet R3 PanSTARRS, streaking across the right of the image, likely originated from the Oort Cloud, meaning it is an old Solar System relic from billions of years ago. It’s bright extended ion tail glows blue as the gas escaping the comet’s core is ionized by sunlight. Astronomers are fascinated by comets for all sorts of reasons: comet compositions are untouched time capsules containing the building blocks of Solar System planets; comets may have delivered water to the young Earth; the behavior of cometary tails shed light on solar wind and radiation interactions. The background mosaic, featuring the Orion Nebula (M42), was taken over two nights of observation with the comet captured on the third night. The Orion Nebula is our nearest stellar nursery and, at about 2 million years old, is our something (relatively) new! Now at around 127.5 million kilometers from Earth, we wave goodbye to the borrowed Comet R3 PanSTARRS as it leaves the Solar System. Growing Gallery: Comet R3 in 2026

Comet R3 PanSTARRS and Orion

10/05/2026

Orion never had a sword like this. As Comet C/2025 R3 (PanSTARRS) heads out of the inner Solar System, it is putting on quite a show for long exposure cameras. Currently seen toward the constellation of Orion the Hunter, the distant Orion Nebula is visible on the upper right. Comet R3 PanSTARRS is now showing two distinct tails: a short dust tail pointing toward the top of the image and a long and wavy ion tail trailing off toward the upper left. The ion tail points away from the Sun and glows blue from excited carbon monoxide. Large particles in the dust tail somewhat resist the radiation pressure that push them away from the Sun and so retain a bit of the comet's orbit. The dust tail shines by reflected sunlight. The featured image was taken a few days ago from France's Reunion Island in the southern Indian Ocean. Growing Gallery: Comet R3 PanSTARRS in 2026

Messier Craters in Stereo

09/05/2026

Many bright nebulae and star clusters in planet Earth's sky are associated with the name of astronomer Charles Messier from his famous 18th century catalog. His name is also given to these two large and remarkable craters on the Moon. Standouts in the dark, smooth lunar Sea of Fertility or Mare Fecunditatis, Messier (left) and Messier A have dimensions of 15 by 8 and 16 by 11 kilometers respectively. Their elongated shapes are explained by the extremely shallow-angle trajectory followed by an impactor, moving left to right, that gouged out the craters. The shallow impact also resulted in two bright rays of material extending along the surface to the right, beyond the picture. Intended to be viewed with red/blue glasses (red for the left eye), this striking stereo picture of the crater pair was recently created from high resolution scans of two images (AS11-42-6304, AS11-42-6305) taken during the Apollo 11 mission to the Moon.

Comet R3 PanSTARRS Before Rigel

08/05/2026

Which way is Comet R3 PanSTARRS going? Not towards the star at the top of the image, because that is Rigel, which, being far in the background, is unrelated to the comet. Not through the nebula in the image middle, because that is the Witch Head Nebula and it, too, is far in the distance -- but not far from Rigel. Not into northern skies because over the past week Comet C/2025 R3 (PanSTARRS) has moved into southern skies and is now best visible in Earth's Southern Hemisphere toward the west after sunset. Angularly, Comet R3 PanSTARRS is slowly moving toward the upper right, night by night, and will soon be in the constellation Orion. Spatially, the comet is now headed out of our Solar System but should remain visible to cameras in southern skies for about a week. The featured image was captured last week near Cerro Paranal in Chile. Growing Gallery: Comet R3 PanSTARRS in 2026

Η Αστρονομική Εικόνα της Ημέρας από τη NASA

NGC 1300: Barred Spiral Galaxy

17/05/2026