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.

Science & Technology - Astronomy picture - Dragon Aurora over Iceland

Dragon Aurora over Iceland Image Credit & Copyright: Jingyi Zhang & Wang Zheng

Explanation: Have you ever seen a dragon in the sky? Although real flying dragons don't exist, a huge dragon-shaped aurora developed in the sky over Iceland earlier this month. The aurora was caused by a hole in the Sun's coronathat expelled charged particles into a solar wind that followed a changing interplanetary magnetic field to Earth's magnetosphere. As some of those particles then struck Earth's atmosphere, they excited atoms which subsequently emitted light: aurora. This iconic display was so enthralling that the photographer's mother ran out to see it and was captured in the foreground. No sunspots have appeared on the Sun so far in February, making the multiple days of picturesque auroral activity this month somewhat surprising.

Sciences et Technologie - Le monde minéral et ses trésors cachés - "Agate onyx noire à bandes blanches"

"Agate onyx noire à bandes blanches"

Il existe plusieurs types d'agates. L'agate fortifiée présente des dessins angulaires qui évoquent des fortifications. L'agate mousse est translucide. Elle est parcourue d'inclusions à base de chlorite verte. L'agate onyx est noire à bandes blanches, alors que la sardonyx alterne les couches brunes, orangées et blanches.

Bruno Cupillard

Sciences et Technologie - Le monde minéral et ses trésors cachés - "Jaspe orbiculaire de Mahajanga, Madagascar"

"Jaspe orbiculaire de Mahajanga, Madagascar"

Parsemé de cercles concentriques serrés les uns contre les autres, ce jaspe particulièrement esthétique provient de la province de Mahajanga, près de Marovato, au nord-ouest de Madagascar.

Bruno Cupillard

Science & Technology - Shadow of a Martian Robot

Shadow of a Martian Robot  
Image Credit: Mars Exploration Rover Mission, JPL, NASA

Explanation: What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity explored the red planet from 2004 to 2018, finding evidence of ancient water, and sending breathtaking images across the inner Solar System. Pictured here in 2004, Opportunity looks opposite the Sun into Endurance Crater and sees its own shadow. Two wheels are visible on the lower left and right, while the floor and walls of the unusual crater are visible in the background. Caught in a dust storm in 2018, last week NASA stopped try contact Opportunity and declare the ground-breaking mission, originally planned for only 92 days,complete.

Sciences et Technologie - Le monde minéral et ses trésors cachés - "Agate du Brésil"

"Agate du Brésil"

L'agate est une matière composée de silice et colorée par des oxydes. C'est une calcédoine ou quartz polycristallin. En fonction de leur aspect, les agates ont reçu des noms évocateurs : agate mousse, agate rubanée, agate œillée, agate festonnée, agate plume, agate arborisée, agate paysage.

Bruno Cupillard

Science & Tecnology - Astronomy picture of the day : Plane Crossing a Crescent Moon - 2019 February 15

Plane Crossing a Crescent Moon 

Image Credit & Copyright: Olivier Staiger (Binounistan.com)

Explanation: No, this is not a good way to get to the Moon. What is pictured is a chance superposition of an airplane and the Moon. The contrail would normally appear white, but the large volume of air toward the setting Sun preferentially knocks away blue light, giving the reflected trail a bright red hue. Far in the distance, well behind the plane, is a crescent Moon, also slightly reddened. Captured a month ago above Valais, Switzerland, the featured image was taken so soon after sunset that planes in the sky were still in sunlight, as were their contrails. Within minutes, unfortunately, the impromptu sky show ended. The plane crossed the Moon and moved out of sight. The Moon set. The contrail became unilluminated and then dispersed.

Science & Tecnology - Astronomy picture of the day - 2019 February 11 : "New Data: Ultima Thule Surprisingly Flat"

New Data: Ultima Thule Surprisingly Flat  
Illustration Credit: NASA, JHU's APL, SwRI

Explanation: Ultima Thule is not the object humanity thought that it was last month. When the robotic New Horizons spacecraft zoomed past the distant asteroid Ultima Thule (officially 2014 MU69) in early January, early imagesshowed two circular lobes that when most simply extrapolated to 3D were thought to be, roughly, spheres. However, analyses of newly beamed-back images -- including many taken soon after closest approach -- shows eclipsed stars re-appearing sooner than expected. The only explanation possible is that this 30-km long Kuiper belt object has a different 3D shape than believed only a few weeks ago. Specifically, as shown in the featured illustration, it now appears that the larger lobe -- Ultima -- is more similar to a fluffy pancake than a sphere, while the smaller lobe -- Thule -- resembles a dented walnut. The remaining uncertainty in the outlines are shown by the dashed blue lines. The new shape information indicates that gravity -- which contracts more massive bodies into spheres -- played perhaps less of a role in contouring the lobes of Ultima Thule than previously thought. The New Horizons spacecraft continued on to Ultima Thule after passing Pluto in mid-2015. New data and images are still being received.