Astronomy Picture of the Day

Sh2-188: The Shrimp Nebula
Image Credit & Copyright: Pawel Piechnik

Explanation: What causes the swirl in the Shrimp Nebula? Its high speed is likely. What is sure is that Sh2-188 is one of the larger planetary nebulas on the night sky, by angular size, spanning about half the diameter of the Moon. Moreover, the white-dwarf core — leftover from the Sun-like star that shed its outer atmosphere — is moving unusually fast through interstellar space, creating a bow shock most visible on the upper left that is similar to a boat plowing through water. Although faint, the Shrimp Nebula glows also by compressing and brightening gas on its leading edge. The featured image was taken in the light of hydrogen, sulfur, and oxygen by a backyard telescope in Krakow, Poland and then digitally adjusted to approximate the nebula‘s true colors.

Tomorrow’s picture: open space

Astronomy Picture of the Day

Andromeda before Photoshop
Image Credit: Kees Scherer

Explanation: What does the Andromeda galaxy really look like? The featured image shows how our Milky Way Galaxy‘s closest major galactic neighbor really appears in a long exposure through Earth‘s busy skies and with a digital camera that introduces normal imperfections. The picture is a stack of 223 images, each a 300 second exposure, taken from a garden observatory in Portugal during 2019. Obvious image deficiencies include bright parallel airplane trails, long and continuous satellite trails, short cosmic ray streaks, and bad pixels. These imperfections were actually not removed with Photoshop specifically, but rather greatly reduced with a series of computer software packages that included Astro Pixel Processor, DeepSkyStacker, and PixInsight. All of this work was done not to deceive you with a digital fantasy that has little to do with the real likeness of the Andromeda galaxy (M31), but to minimize Earthly artifacts that have nothing to do with the distant galaxy and so better recreate what M31 really does look like.

Tomorrow’s picture: cosmic move

Astronomy Picture of the Day

Mirrored Meteor and Milky Way
Image Credit & Copyright: Jeff Dai (TWAN)

Explanation: On August 15, this perseid meteor streaked through night skies over the Observatorio del Roque de los Muchachos at La Palma, Canary Islands, Spain. The bright and colorful meteor trail was captured next to the central Milky Way, whose dark interstellar dust clouds and luminous starlight reach above the horizon. In the foreground of this tantalizing celestial scene is the 23 meter diameter mirror of the prototype Large-Sized Telescope (LST-1). LST-1 is the first telescope constructed at the northern hemisphere site of the innovative Cherenkov Telescope Array Observatory. With 198 hexagonal mirror segments and a large, high-efficiency, pixelized camera, LST-1 is designed to detect extremely brief, atmospheric visible light flashes. Lasting about a billionth of a second, the visible light flashes are triggered by energetic gamma-rays from cosmic sources such as distant active galaxies and gamma-ray bursts. Of course, on that night some individual mirror segments of LST-1 also reflected the atmospheric flash of the bright perseid meteor.

Tomorrow’s picture: before and after

Astronomy Picture of the Day

Globular Cluster Omega Centauri
Image Credit & Copyright: Javier O. Cadenas Parra

Explanation: Globular star cluster Omega Centauri packs about 10 million stars much older than the Sun into a volume some 150 light-years in diameter. Also known as NGC 5139, at a distance of 15,000 light-years it’s the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. With a yellowish hue, Omega Centauri’s red giant stars are easy to pick out in this sharp telescopic view. A two-decade-long exploration of the dense star cluster with the Hubble Space Telescope has revealed evidence for a massive black hole near the center of Omega Centauri.

Tomorrow’s picture: reflections on a starry night

Astronomy Picture of the Day

Chance Triple Alignment: Plane, Space Station, Sun
Image Credit & Copyright: Petr Horalek / Inst. Physics Opava

Explanation: This shot captured an unexpected silhouette. Which is it? It isn’t the sunspots, the small dark regions caused by concentrated magnetic fields visible around the Sun’s bright disk. Sunspots typically last for weeks and were expected, since these spots were seen previously. It isn’t the International Space Station (ISS), the small dark structure on the middle left.  This is because the featured picture was planned with sub-second timing to record the iconic structure passing before the Sun. It is the airplane. Just as this exposure was taking place in June, from Prasek in the Czech Republic, an airplane began its own miniature partial eclipse. The result is this triply aligned image of our Sun. The photographer estimates that the chance of any random Sun image containing silhouettes of both a space station and an airplane, from that location, is about 30 million to one.

Tomorrow’s picture: open space

Astronomy Picture of the Day

Cocoon Nebula Wide Field
Image Credit & Copyright: Piotr Czerski

Explanation: When does a nebula look like a comet? In this crowded starfield covering over two degrees within the high-flying constellation of the Swan (Cygnus), the eye is drawn to the Cocoon Nebula. A compact star forming region, the cosmic Cocoon punctuates a nebula bright in emission and reflection on the lower right, with a long trail of interstellar dust clouds to the left, making the entire complex appear a bit like a comet. Cataloged as IC 5146, the central bright head of the nebula spans about 10 light years, while the dark dusty tail spans nearly 100 light years. Both are located about 2,500 light years away. A bright star near the colorful nebula’s center likely supplies power and helps clear out a cavity. The long dusty filaments of the tail, although dark in this visible light image, hide stars in the process of formation. The featured image was captured in July from Death Valley, California, USA.

Tomorrow’s picture: triple eclipse

Astronomy Picture of the Day

A Zodiacal Night
Image Credit & Copyright: Neelam and Ajay Talwar (TWAN)

Explanation: Also known as the false dawn, a luminous band of zodiacal light is captured in this dark night skyscape. The serene view was recorded just before the beginning of astronomical twilight during September’s star party at the remote Hanle Dark Sky Reserve, Ladakh, India, planet Earth. At about 4,500 meters altitude, the dark sky reserve presents a haven for hardy stargazing and astrophotography enthusiasts. While meteors streak through the night, bright planet Jupiter appears immersed in the faint zodiacal glow near the eastern horizon. Follow the zodiacal band toward the zenith to find open star cluster M44 and a yellowish tinged planet Mars near the center of the frame. In fact, serendipitous detections of interplanetary dust by NASA’s Juno spacecraft suggest Mars itself is the source of dust that back scatters sunlight and creates zodiacal light in planet Earth’s night.

Tomorrow’s picture: only sunny days

Astronomy Picture of the Day

Messier 33: The Triangulum Galaxy
Image Credit & Copyright: George Chatzifrantzis

Explanation: The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, Messier 33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other’s grand spiral star systems. As for the view from the Milky Way, this sharp telescopic image shows off M33’s blue star clusters and pinkish star forming regions along the galaxy’s loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 5 o’clock position from the galaxy center. Like M31, M33’s population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe.

Tomorrow’s picture: star party weekend

Astronomy Picture of the Day

A Treasure Chest in the Carina Nebula
Image Credit & Copyright: ESA/Webb, NASA & CSA, M. Reiter; Acknowledgement: M. H. Özsaraç
Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: This treasure chest is full of stars. The featured image was obtained with NASA‘s James Webb Space Telescope and shows a dust pilar in the Carina Nebula inside our Galaxy, roughly 7500 light-years away. It is formed by interstellar gas and dust, and shaped by powerful stellar winds and radiation form neighboring stars like the nearby Eta Carinae stellar system which is more luminous than 5 million suns. The star formation inside the pillar is excavating its head, creating the open lid of the chest. Astronomers estimate that there are about 70 stars in a compact cluster inside the pillar. This cluster is now thought to be only around 1.3 million years old. Its bounty of young stars includes a massive star approximately 19 times as massive as the Sun. More massive stars are rarer, shine brighter and evolve faster than less massive stars. They are the shiniest jewels in the treasure chest

Tomorrow’s picture: what’s next?

Astronomy Picture of the Day

A Daytime Eclipse: Moon Occults Venus
Image Credit & Copyright: Arnaud Mariat

Explanation: 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.

Tomorrow’s picture: galactic eye