PRATIQUE - Nettoyer les phares au dentifrice

 

ASTRONOMY - A Phoenix Aurora over Iceland

 2021 January 3

A Phoenix Aurora over Iceland
Image Credit & Copyright: Hallgrimur P. Helgason; Rollover Annotation: Judy Schmidt

Explanation: All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night's auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the Earth's atmosphere once again. This time, surprisingly, pareidoliacally, the night lit up with an amazing shape reminiscent of a giant phoenix. With camera equipment at the ready, two quick sky images were taken, followed immediately by a third of the land. The mountain in the background is Helgafell, while the small foreground river is called Kaldá, both located about 30 kilometers north of Iceland's capital Reykjavík. Seasoned skywatchers will note that just above the mountain, toward the left, is the constellation of Orion, while the Pleiades star cluster is also visible just above the frame center. The 2016 aurora, which lasted only a minute and was soon gone forever -- would possibly be dismissed as an fanciful fable -- were it not captured in the featured, digitally-composed, image mosaic.

MUSIC - Anastasiya Petryshak - Bach

 

SPACE ART - Saturne vue de Titan

Si Lucien Rudaux est considéré comme le “grand-père” du Space art, Chelsey Bonestell est bien le père de la discipline. L’Américain a démarré sa carrière comme architecte, en participant notamment à l’élaboration de la façade du Chrysler Building à New York ou du bâtiment de la Cour suprême des États-Unis. Il se spécialise ensuite dans les effets spéciaux à Hollywood, par exemple pour les films Le bossu de Notre-Dame (1939) ou Citizen Kane (1941).

Toutefois, passionné depuis toujours par l’astronomie, Chesley Bonestell décide d’utiliser ses compétences afin de créer des œuvres entrant dans la catégorie du Space art. Ainsi, il s’inspire très largement de Lucien Rudaux, et associe miniatures d’argile, astuces photographiques et techniques de peinture pour élaborer des tableaux au réalisme saisissant. C’est en 1944 dans le magazine Life que paraît sa première grande réalisation : une série de représentations de Saturne vue de ses lunes.

Saturne vue de Titan. Crédit : Chesley Bonestell

ASTRONOMY - 21st Century Wet Collodion Moon

 2021 January 2

21st Century Wet Collodion Moon
Image Credit & Copyright: Mike Smolinsky

Explanation: In the mid 19th century, one of the first photographic technologies used to record the lunar surface was the wet-plate collodion process, notably employed by British astronomer Warren De la Rue. To capture an image, a thick, transparent mixture was used to coat a glass plate, sensitized with silver nitrate, exposed at the telescope, and then developed to create a negative image on the plate. To maintain photographic sensitivity, the entire process, from coating to exposure to developing, had to be completed before the plate dried, in a span of about 10 to 15 minutes. This modern version of a wet-plate collodion image celebrates lunar photography's early days, reproducing the process using modern chemicals to coat a glass plate from a 21st century hardware store. Captured last November 28 with an 8x10 view camera and backyard telescope, it faithfully records large craters, bright rays, and dark, smooth mare of the waxing gibbous Moon. Subsequently digitized, the image on the plate was 8.5 centimeters in diameter and exposed while tracking for 2 minutes. The wet plate's effective photographic sensitivity was about ISO 1. In your smart phone, the camera sensor probably has a photographic sensitivity range of ISO 100 to 6400 (and needs to be kept dry ...).

ASTRONOMY - Galaxies and the South Celestial Pole

 2021 January 1

Galaxies and the South Celestial Pole
Image Credit & Copyright: Petr Horalek, Josef Kujal

Explanation: The South Celestial Pole is easy to spot in star trail images of the southern sky. The extension of Earth's axis of rotation to the south, it's at the center of all the southern star trail arcs. In this starry panorama streching about 60 degrees across deep southern skies the South Celestial Pole is somewhere near the middle though, flanked by bright galaxies and southern celestial gems. Across the top of the frame are the stars and nebulae along the plane of our own Milky Way Galaxy. Gamma Crucis, a yellowish giant star heads the Southern Cross near top center, with the dark expanse of the Coalsack nebula tucked under the cross arm on the left. Eta Carinae and the reddish glow of the Great Carina Nebula shine along the galactic plane near the right edge. At the bottom are the Large and Small Magellanic clouds, external galaxies in their own right and satellites of the mighty Milky Way. A line from Gamma Crucis through the blue star at the bottom of the southern cross, Alpha Crucis, points toward the South Celestial Pole, but where exactly is it? Just look for south pole star Sigma Octantis. Analog to Polaris the north pole star, Sigma Octantis is little over one degree fom the the South Celestial pole.

ASTRONOMY - Trail of the Returner

 2020 December 31

Trail of the Returner
Image Credit & Copyright: Zhuoxiao Wang

Explanation: Familiar stars of a northern winter's night shine in this night skyview, taken near Zhangye, Gansu, China and the border with Inner Mongolia. During the early hours of December 17 Orion is near center in the single exposure that captures a fireball streaking across the sky, almost as bright as yellowish Mars shining on the right. Splitting Gemini's twin bright stars Castor and Pollux near the top of the frame, the fireball's trail and timing are consistent with the second skipping atmospheric entry of the Chang'e 5 mission's returner capsule. The returner capsule was successfully recovered after landing in Inner Mongolia, planet Earth with about 2 kilograms of lunar material on board. The lunar sample is thought to contain relatively young material collected near the Mons Rumker region of the Moon's Oceanus Procellarum. Launched on November 23 UT, China's Chang'e 5 mission is the first lunar sample return mission since the Soviet Union’s Luna 24 mission in 1976.

PRATIQUE - Comment faire des symboles sur un clavier

 

METAPHYSIQUE - Sommes-nous tout seuls dans l'Univers ?

 

ASTRONOMY - Earth During a Total Solar Eclipse

 2020 December 29

Earth During a Total Solar Eclipse
Video Credit: GOES-16, ABI, NOAA, NASA

Explanation: What does the Earth look like during a total solar eclipse? It appears dark in the region where people see the eclipse, because that's where the shadow of the Moon falls. The shadow spot rapidly shoots across the Earth at nearly 2,000 kilometers per hour, darkening locations in its path -- typically for only a few minutes -- before moving on. The featured video shows the Earth during the total solar eclipse earlier this month. The time-lapse sequence, taken from a geostationary satellite, starts with the Earth below showing night but the sun soon rises at the lower right. Clouds shift as day breaks over the blue planet. Suddenly the circular shadow of the Moon appears on the left and moves rapidly across South America, disappearing on the lower right. The video ends as nightfall begins again. The next total solar eclipse will occur next December -- but be visible only from parts of Antarctica.