Photographie : "Voie lactée en bord de mer"

"Carcans-Plage - Voie Lactée 

en bord de mer" !

Florent Martinez 

Science & Technology - Astronomy picture of the day : Moon Corona, Halo, and Arcs over Manitoba

2020 March 11

Moon Corona, Halo, and Arcs over Manitoba
Image Credit & Copyright: Brent Mckean

Explanation: Yes, but could you get to work on time if the Moon looked like this? As the photographer was preparing to drive to work, refraction, reflection, and even diffraction of moonlight from millions of falling ice crystals turned the familiar icon of our Moon into a menagerie of other-worldly halos and arcs. The featured scene was captured with three combined exposures two weeks ago on a cold winter morning in Manitoba, Canada. The colorful rings are a corona caused by quantum diffraction by small drops of water or ice near the direction of the Moon. Outside of that, a 22-degree halo was created by moonlight refracting through six-sided cylindrical ice crystals. To the sides are moon dogs, caused by light refracting through thin, flat, six-sided ice platelets as they flittered toward the ground. Visible at the top and bottom of the 22-degree halo are upper and lower tangent arcs, created by moonlight refracting through nearly horizontal hexagonal ice cylinders. A few minutes later, from a field just off the road to work, the halo and arcs had disappeared, the sky had returned to normal -- with the exception of a single faint moon dog.

Science & Technology - Astronomy picture of the day : Pic du Midi Panorama

Pic du Midi Panorama
Image Credit & Copyright: Patrick Lécureuil

Explanation: A surreal night skyscape, this panorama stitched from 12 photos looks to the west at an evening winter sky over Pic du Midi Observatory, Pyrenees Mountains, Planet Earth. Telescope domes and a tall communications tower inhabit the rugged foreground. On the right, lights from Tarbes, France about 35 kilometers away impinge on the designated dark sky site though, but more distant terrestrial lights seen toward the left are from cities in Spain. Stars and nebulae of the northern winter's Milky Way arc through the sky above. Known to the planet's night skygazers, the Pleiades and Hyades star clusters still hang over the western horizon near center. Captured in mid February the familiar stars of the constellation Orion are to the left and include the no longer fainting star Betelgeuse.

Science & Technologie - Stelvision : Le ciel du 4 Mars 2020 à 22h40 (centre France)

Repérez facilement les principales étoiles et planètes, et observez que tout le ciel semble tourner autour de l' étoile polaire ! Ainsi, les astres se lèvent et se couchent, et l'aspect du ciel change au long de la nuit...
Utilisation dehors : imprimez cette carte et placez-la au dessus de votre tête, le repère "Horizon NORD" vers le nord. Comparez au ciel observé !

Pourquoi le ciel change-t-il en permanence ? à cause des mouvements de la TerreComme la Terre tourne sur elle-même, nous voyons défiler le ciel comme si nous étions sur un manège : tout le ciel paraît tourner au fil des heures, autour d'un point voisin de l'étoile Polaire (au centre de la carte). Ceci provoque les "levers" et "couchers" des astres. De plus, la course de la Terre autour du Soleil nous fait découvrir une portion de ciel différente selon la période de l'année. En savoir plus.

à cause des mouvements des astres eux-mêmesLe Soleil, la Lune, les planètes, ont un mouvement perceptible au fil des jours (ou des semaines) par rapport au fond des étoiles. A l'inverse, les étoiles à l'extérieur de notre système solaire sont tellement lointaines qu'elles paraissent fixes au cours d'une vie humaine.

Science & Technology - Astronomy picture of the day : The Slow Dance of Galaxies NGC 5394 and 5395

2020 March 4

The Slow Dance of Galaxies NGC 5394 and 5395
Image Credit: Gemini, NSF, OIR Lab, AURA; Text: Ryan Tanner (NASA/USRA)

Explanation: If you like slow dances, then this may be one for you. A single turn in this dance takes several hundred million years. Two galaxies, NGC 5394 and NGC 5395, slowly whirl about each other in a gravitational interaction that sets off a flourish of sparks in the form of new stars. The featured image, taken with the Gemini North 8-meter telescope on Maunakea, Hawaii, USA, combines four different colors. Emission from hydrogen gas, colored red, marks stellar nurseries where new stars drive the evolution of the galaxies. Also visible are dark dust lanes that mark gas that will eventually become stellar nurseries. If you look carefully you will see many more galaxies in the background, some involved in their own slow cosmic dances.

Science & Technologie - La Terre vue de l'Espace : Guiné Bissau

La Guinée-Bissau est un petit pays en Afrique occidentale. Des différences sédimentaires complexes peuvent être vues dans les eaux peu profondes le long de son littoral, où la vase portée par le fleuve Geba et d'autres fleuves plonge dans l'océan Atlantique.

© USGS, Nasa

Science & Technologie - La Terre vue de l'Espace : Parc national de Canyonlands

Le parc national de Canyonlands est situé dans l'Utah non loin de Moab (États-Unis). Cette image prise par Landsat 7 montre les trois principales parties du parc : Island in the Sky, the Needles et The Maze. Canyonlands offre un paysage minéral aride, façonné par l'érosion provoquée par le fleuve Colorado et la Green River dont les affluents ont creusé et sculpté la roche au cours de milliers d'années, laissant derrière eux des formes extraordinaires et un témoignage géologique unique.

© Nasa

Science & Technology - Astronomy picture of the day : Sharpless-308: The Dolphin Nebula

2020 March 2

Sharpless-308: The Dolphin Nebula
Image Credit & Copyright: Chilesope 2, Pleaides Astrophotography Team (Peking U.)

Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is much larger than the dolphin it appears to be. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the featured expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue.

Science & Technology - Astronomy picture of the day : A hole in Mars

A Hole in Mars
Image Credit: NASA, JPL, U. Arizona

Explanation: What created this unusual hole in Mars? The hole was discovered by chance in 2011 on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole, shown in representative color, appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern. Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.

Science & Technologie - Astronomy icture of the day : To Fly Free in Space

2020 February 9 
To Fly Free in Space 

Image Credit: NASA, STS-41B

Explanation: 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. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk" during Space Shuttle mission 41-B in1984. 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.