Αστρονομική Εικόνα της Ημέρας από τη NASA

Προηγούμενες Αστρονομικές Εικόνες της Ημέρας από τη NASA

Perseid Meteors from Durdle Door

20/08/2025

What are those curved arcs in the sky? Meteors -- specifically, meteors from this year's Perseid meteor shower. Over the past few weeks, after the sky darkened, many images of Perseid meteors were captured separately and merged into a single frame, taken earlier. Although the meteors all traveled on straight paths, these paths appear slightly curved by the wide-angle lens of the capturing camera. The meteor streaks can all be traced back to a single point on the sky called the radiant, here just off the top of the frame in the constellation of Perseus. The same camera took a deep image of the background sky that brought up the central band of our Milky Way galaxy running nearly vertically through the featured image's center. The limestone arch in the foreground in Dorset, England is known as Durdle Door, a name thought to survive from a thousand years ago.

Giant Galaxies in Pavo

19/08/2025

Over 500,000 light years across, NGC 6872 (bottom left) is a truly enormous barred spiral galaxy. At least 5 times the size of our own large Milky Way, NGC 6872 is the largest known spiral galaxy. About 200 million light-years distant toward the southern constellation Pavo, the Peacock, the appearance of this giant galaxy's stretched out spiral arms suggest the wings of a giant bird. So its popular moniker is the Condor galaxy. Lined with massive young, bluish star clusters and star-forming regions, the extended and distorted spiral arms are due to NGC 6872's past gravitational interactions with the nearby smaller galaxy IC 4970, visible here below the giant spiral galaxy's core. Other members of the southern Pavo galaxy group are scattered through this magnificent galaxy group portrait, with the dominant giant elliptical galaxy, NGC 6876, above and right of the soaring Condor galaxy.

NGC 1309: A Useful Spiral Galaxy

18/08/2025

This galaxy is not only pretty -- it's useful. A gorgeous spiral some 100 million light-years distant, NGC 1309 lies on the banks of the constellation of the River (Eridanus). NGC 1309 spans about 30,000 light-years, making it about one third the size of our larger Milky Way galaxy. Bluish clusters of young stars and dust lanes are seen to trace out NGC 1309's spiral arms as they wind around an older yellowish star population at its core. Not just another pretty face-on spiral galaxy, observations of NGC 1309's two recent supernovas and multiple Cepheid variable stars contribute to the calibration of the expansion of the Universe. Still, after you get over this beautiful galaxy's grand design, check out the array of more distant background galaxies also recorded in this sharp image from the Hubble Space Telescope.

Asperitas Clouds Over New Zealand

17/08/2025

What kind of clouds are these? Although their cause is presently unknown, such unusual atmospheric structures, as menacing as they might seem, do not appear to be harbingers of meteorological doom. Formally recognized as a distinct cloud type only last year, asperitas clouds can be stunning in appearance, unusual in occurrence, and are relatively unstudied. Whereas most low cloud decks are flat bottomed, asperitas clouds appear to have significant vertical structure underneath. Speculation therefore holds that asperitas clouds might be related to lenticular clouds that form near mountains, or mammatus clouds associated with thunderstorms, or perhaps a foehn -- a type of dry downward wind that flows off mountains. Clouds from such a wind called the Canterbury arch stream toward the east coast of New Zealand's South Island. The featured image, taken above Hanmer Springs in Canterbury, New Zealand in 2005, shows great detail partly because sunlight illuminates the undulating clouds from the side.

Moonlight, Planets, and Perseids

15/08/2025

In the predawn sky on August 13, two planets were close. And despite the glare of a waning gibbous Moon, bright Jupiter and even brighter Venus were hard to miss. Their brilliant close conjunction is posing above the eastern horizon in this early morning skyscape. The scene was captured in a single exposure from a site near Gansu, China, with light from both planets reflected in the still waters of a local pond. Also seen against the moonlight were flashes from the annual Perseid Meteor Shower, known for its bright, fast meteors. Near the much anticipated peak of activity, the shower meteors briefly combined with the two planets for a celestial spectacle even in moonlit skies.

M13: The Great Globular Cluster in Hercules

14/08/2025

In 1716, English astronomer Edmond Halley noted, "This is but a little Patch, but it shews itself to the naked Eye, when the Sky is serene and the Moon absent." Of course, M13 is now less modestly recognized as the Great Globular Cluster in Hercules, one of the brightest globular star clusters in the northern sky. Sharp telescopic views like this one reveal the spectacular cluster's hundreds of thousands of stars. At a distance of 25,000 light-years, the cluster stars crowd into a region 150 light-years in diameter. Approaching the cluster core, upwards of 100 stars could be contained in a cube just 3 light-years on a side. For comparison with our neighborhood of the Milky Way, the closest star to the Sun is over 4 light-years away. Early telescopic observers of the great globular cluster also noted a curious convergence of three dark lanes with a spacing of about 120 degrees, seen here just below the cluster center. Known as the propeller in M13, the shape is likely a chance optical effect of the distribution of stars viewed from our perspective against the dense cluster core.

Trapezium: In the Heart of Orion

13/08/2025

What lies in the heart of Orion? Trapezium: four bright stars, that can be found near the center of this sharp cosmic portrait. Gathered within a region about 1.5 light-years in radius, these stars dominate the core of the dense Orion Nebula Star Cluster. Ultraviolet ionizing radiation from the Trapezium stars, mostly from the brightest star Theta-1 Orionis C powers the complex star forming region's entire visible glow. About three million years old, the Orion Nebula Cluster was even more compact in its younger years and a dynamical study indicates that runaway stellar collisions at an earlier age may have formed a black hole with more than 100 times the mass of the Sun. The presence of a black hole within the cluster could explain the observed high velocities of the Trapezium stars. The Orion Nebula's distance of some 1,500 light-years make it one of the closest candidate black holes to Earth.

Perseids from Perseus

12/08/2025

Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is the constellation of Perseus. That is why the meteor shower that peaks tonight is known as the Perseids -- the meteors all appear to come from a radiant toward Perseus. In terms of parent body, though, the sand-sized debris that makes up the Perseids meteors come from Comet Swift-Tuttle. The comet follows a well-defined orbit around our Sun, and the part of the orbit that approaches Earth is superposed in front of Perseus. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Perseus. Featured here, a composite image taken over six nights and containing over 100 meteors from 2024 August Perseids meteor shower shows many bright meteors that streaked over the Bieszczady Mountains in Poland. This year's Perseids, usually one of the best meteor showers of the year, will compete with a bright moon that will rise, for many locations, soon after sunset.

Η Αστρονομική Εικόνα της Ημέρας από τη NASA

Nebulas and Clusters in Sagittarius

17/09/2025