Science & Technologie - Astronomie - La lune - 1

Située en moyenne à 384 400 kilomètres, la Lune est le seul satellite naturel de notre planète Terre. Avec ses 3 470 kilomètres de diamètre et parce qu’elle est très proche de nous comparés aux autres astres du ciel, la Lune offre de nombreuses choses à voir au curieux : forme changeante, détails de surface, rapprochements esthétiques avec d’autres astres… mais aussi quelques surprises qui font travailler l’imaginaire !

Croissant, quartier, pleine lune…

Si on voit aussi bien la Lune, il faut remercier le Soleil : c’est en effet lui qui l’éclaire et qui la rend visible à nos yeux. Vous aurez sans doute remarqué qu’au fil du temps, la Lune change de forme : parfois en fin croissant, puis en quartier, voire davantage, entièrement ronde ou même invisible ! Pourquoi ces changements ? Tout simplement parce que notre satellite tourne autour de la Terre en 28 jours environ et que depuis le point où nous l’observons, la partie éclairée par le Soleil n’est pas toujours la même.
sTELVISION

Science & Technologie - La Terre vue de l'Espace : Culture du raisin le long du fleuve Orange

Le fleuve Orange est le plus long fleuve d'Afrique du Sud (2.160 km) et sert en partie de frontière avec la Namibie voisine. À une centaine de kilomètres en amont de l'embouchure vers l'océan Atlantique, des programmes d'irrigation installés sur les rives de l'Orange profitent de cette source d'eau douce ainsi que des riches terres des plaines inondables. Ces rectangles aux différentes nuances de vert contrastent avec le reste du paysage désertique. La Namibie est le pays le plus aride de l'Afrique au sud du désert du Sahara et la majeure partie de son territoire est impropre à l'agriculture. C'est la culture du raisin qui domine dans cette région. Les conditions climatiques locales permettent au raisin de Namibie d'être récoltable deux à trois semaines avant celui qui est produit dans la région du Cap en Afrique du Sud. Remarque : rotation de l'image 90° à droite. 

© Nasa

Science & Technologie - Astronomy picture of the day : The Traffic in Taurus - 2020 April 03

The Traffic in Taurus

Image Credit & Copyright: Lionel Majzik

Explanation: There's a traffic jam in Taurus lately. On April 1, this celestial frame from slightly hazy skies over Tapiobicske, Hungary recorded an impressive pile up toward the zodiacal constellation of the Bull and the Solar System's ecliptic plane. Streaking right to left the International Space Station speeds across the bottom of the telescopic field of view. Wandering about as far from the Sun in planet Earth's skies as it can get, inner planet Venus is bright and approaching much slower, overexposed at the right. Bystanding at the upper left are the sister stars of the Pleiades. No one has been injured in the close encounter though, because it really isn't very close. Continuously occupied since November 2000, the space station orbits some 400 kilometers above the planet's surface. Venus, currently the brilliant evening star, is almost 2/3 of an astronomical unit away. A more permanent resident of Taurus, the Pleiades star cluster is 400 light-years distant.

Science & Technology - Astronomy picture of the day : The Galactic Center from Radio to X-ray - 2020 march 31

The Galactic Center from Radio to X-ray
Image Credit: X-Ray: NASA, CXC, UMass, D. Wang et al.; Radio: NRF, SARAO, MeerKAT

Explanation: In how many ways does the center of our Galaxy glow? This enigmatic region, about 26,000 light years away toward the constellation of the Archer (Sagittarius), glows in every type of light that we can see. In the featured image, high-energy X-ray emission captured by NASA's orbiting Chandra X-Ray Observatory appears in green and blue, while low-energy radio emission captured by SARAO's ground-based MeerKAT telescope array is colored red. Just on the right of the colorful central region lies Sagittarius A (Sag A), a strong radio source that coincides with Sag A*, our Galaxy's central supermassive black hole. Hot gas surrounds Sag A, as well as a series of parallel radio filaments known as the Arc, seen just left of the image center. Numerous unusual single radio filaments are visible around the image. Many stars orbit in and around Sag A, as well as numerous small black holes and dense stellar cores known as neutron stars and white dwarfs. The Milky Way's central supermassive black hole is currently being imaged by the Event Horizon Telescope.

Science & Technology - Astronomy picture of the day : Andromeda Station

2020 march 26

Andromeda Station
Composite Image Credit & Copyright: Ralf Rohner

Explanation: This surreal picture isn't from a special effects sci-fi movie. It is a digital composite of frames of the real Andromeda Galaxy, also known as M31, rising over a real mountain. Exposures tracking the galaxy and background stars have been digitally combined with separate exposures of the foreground terrain. All background and foreground exposures were made back to back with the same camera and telephoto lens on the same night from the same location. In the "Deepscape" combination they produce a stunning image that reveals a range of brightness and color that your eye can't quite see on its own. Still, it does look like you could ride a cable car up this mountain and get off at the station right next to Andromeda. But at 2.5 million light-years from Earth the big beautiful spiral galaxy really is a little out of reach as a destination. Don't worry, though. Just wait 5 billion years and the Andromeda Galaxy will come to you. This Andromeda Station is better known as Weisshorn, the highest peak of the ski area in Arosa, Switzerland.

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.