Science et Technologie - Le monde minéral et ses trésors cachés : Calcédoine aux mille couleurs

Calcédoine aux mille couleurs

On qualifie d'agates les calcédoines présentant plusieurs couleurs. Ces colorations peuvent se présenter en zones parallèles, concentriques ou se répartir dans la masse de façon irrégulière. À noter ici la finesse des lignes colorées et les tubes d'échappement de gaz dans cette agate du Brésil.

Bruno Cupillard

Science & Technology - Astronomy picture of the day : Sharpest Ultima Thule

2019 February 28
Sharpest Ultima Thule 
Image Credit: NASA, Johns Hopkins University APL, Southwest Research Institute, National Optical Astronomy Observatory

Explanation: On January 1, New Horizons swooped to within 3,500 kilometers of the Kuiper Belt world known as Ultima Thule. That's about 3 times closer than its July 2015 closest approach to Pluto. The spacecraft's unprecedented feat of navigational precision, supported by data from ground and space-based observing campaigns, was accomplished 6.6 billion kilometers (over 6 light-hours) from planet Earth. Six and a half minutes before closest approach to Ultima Thule it captured the nine frames used in this composite image. The most detailed picture possible of the farthest object ever explored, the image has a resolution of about 33 meters per pixel, revealing intriguing bright surface features and dark shadows near the terminator. A primitive Solar System object, Ultima Thule's two lobes combine to span just 30 kilometers. The larger lobe, referred to as Ultima, is recently understood to be flattenedlike a fluffy pancake, while the smaller, Thule, has a shape that resembles a dented walnut.

Science & Tecnology - Astronomy picture of the day : Magnetic Orion

2019 February 27
Magnetic Orion 
Image Credit & Copyright: NASA, SOFIA, D. Chuss et al. & ESO, M. McCaughrean et al.

Explanation: Can magnetism affect how stars form? Recent analysis of Orion data from the HAWC+ instrument on the airborne SOFIA observatory indicate that, at times, it can. HAWC+ is able to measure the polarization of far-infrared light which can reveal the alignment of dust grains by expansive ambient magnetic fields. In the featured image, these magnetic fields are shown as curvy lines superposed on an infrared image of the Orion Nebula taken by aVery Large Telescope in Chile. Orion's Kleinmann-Low Nebula is visible slightly to the upper right of the image center, while bright stars of the Trapezium cluster are visible just to the lower left of center. The Orion Nebula at about l300 light years distant is the nearest major star formation region to the Sun.

Science et Technologies - Le monde minéral et ses trésors cachés : "Agate de Chine aux formes surréalistes"

"Agate de Chine aux formes surréalistes"

Comme dans la peinture surréaliste de Joan Miró, cette agate de Chine présente une construction de signes et de formes colorées.

 Bruno Cupillard

Science & Technology - Astronomy picture of the day : Simulation TNG50: A Galaxy Cluster Forms

2019 February 26
Simulation TNG50: A Galaxy Cluster Forms Video Credit: IllustrisTNG Project; Visualization: Dylan Nelson (Max Planck Institute for Astrophysics) et al.
Music: Symphony No. 5 (Ludwig van Beethoven), via YouTube Audio Library

Explanation: How do clusters of galaxies form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. A recent effort is TNG50 from IllustrisTNG, an upgrade of the famous Illustris Simulation. The first part of the featured video tracks cosmic gas (mostly hydrogen) as it evolves into galaxies and galaxy clusters from the early universe to today, with brighter colors marking faster moving gas. As the universe matures, gas falls into gravitational wells, galaxies forms, galaxies spin, galaxies collide and merge, all while black holes form in galaxy centers and expel surrounding gas at high speeds. The second half of the video switches to tracking stars, showing a galaxy cluster coming together complete with tidal tails and stellar streams. The outflow from black holes in TNG50 is surprisingly complex and details are being compared with our real universe. Studying how gas coalesced in the early universe helps humanity better understand how our Earth, Sun, and Solar System originally formed.

Science & Technology - Astronomy picture of the day : Red Sprite Lightning over Kununurra

2019 February 25
Red Sprite Lightning over Kununurra 

Image Credit & Copyright: Ben Broady

Explanation: What are those red filaments in the sky? It is a rarely seen form of lightning confirmed only about 30 years ago: red sprites. Recent research has shown that following a powerful positive cloud-to-ground lightning strike,red sprites may start as 100-meter balls of ionized air that shoot down from about 80-km high at 10 percent the speed of light and are quickly followed by a group of upward streaking ionized balls. The featured image, taken just over a week ago in Kununurra, Western Australia, captured some red sprites while shooting a time-lapse sequence of a distant lightning storm. Pictured, green trees cover the foreground, dark mountains are seen on the horizon, ominousstorm clouds hover over the distant land, while red sprites appear in front of stars far in the distance. Red sprites take only a fraction of a second to occur and are best seen when powerful thunderstorms are visible from the side.

Science et Technologie - Le monde minéral et ses trésors cachés : "Rhodochrosite de Capillitas issue d'une stalactite

"Rhodochrosite de Capillitas issue d'une stalactite"

Cette rhodochrosite provient de la mine de Capillitas, en Argentine. Ce carbonate de manganèsedoit son nom au grec « rhodon » signifiant « rose » et « khrozo », « coloré ». Le site de Capillitas se présente sous la forme de cavités dotées de stalactites impressionnantes dont certaines mesurent plus d'un mètre. Ici la coupe de cette stalagmite alterne des festons rosés, blancs et carmins aux tonalités pâles à soutenues.

Bruno Cupillard

Science & Technologie - Le monde minéral et ses trésors cachés : "Agate aux couleurs flamboyantes"

"Agate aux couleurs flamboyantes"

Bruno Cupillard

Science & Tecnology - Astronomy picture : Doomed Star Eta Carinae

2019 February 20
Doomed Star Eta Carinae  Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt

Explanation: Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 170 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only starcurrently thought to emit natural LASER light. This featured image brings out details in the unusual nebula that surrounds this rogue star. Diffraction spikes, caused by the telescope, are visible as bright multi-colored streaks emanating from Eta Carinae's center. Two distinct lobes of the Homunculus Nebula encompass the hot central region, while some strange radial streaks are visible in red extending toward the image right. The lobes are filled with lanes of gas anddust which absorb the blue and ultraviolet light emitted near the center. The streaks, however, remain unexplained.

Sciences et Technologie - Le monde minéral et ses trésors cachés - "Jaspe orbiculaire aux allures de lagon bleu"

"Jaspe orbiculaire aux allures de lagon bleu"

Le jaspe orbiculaire est une calcédoine (silice) plus ou moins opaque créée suite à l'apport d'argileet de pigments divers. Ici, les vides d'une coulée de rhyolite se sont emplis, accueillant un choix étonnant de couleurs et de formes.