Science et Technologie - Le monde minéral et ses trésors cachés : Gypse et ses cristaux monocliniques

Le gypse est un sulfate de calcium. Souvent enchâssé dans des marnes imperméables, il est alors préservé de la dissolution comme c'est le cas à Grozon, dans le Jura. Translucide, il présente ici, à la surface de ses parois, le contour de cristaux monocliniques.

Bruno Cupillard

Science & Technology - Astronomy picture of the day : Celestial Alignment over Sicilian Shore

2019 March 4
Celestial Alignment over Sicilian Shore  
Image Credit & Copyright: Dario Giannobile

Explanation: This was a sunrise to remember. About a month ago, just before the dawn of the Sun, an impressive alignment of celestial objects was on display to the east. Pictured, brightest and closest to the horizon, is the Moon. The Moon's orange glow is caused by the scattering away of blue light by the intervening atmosphere. Next brightest and next closest to the horizon is the planet Venus. Compared to the Moon, Venus appears more blue -- as can (also) be seen in its reflection from the water. Next up is Jupiter, while the bright object above Jupiter is the star Antares. Although this display was visible from almost anywhere on planet Earth, the featured image was taken along a picturesque seashore near the city of Syracuse, on the island of Sicily, in the country of Italy. This month Saturn appears between Venus and Jupiter before sunrise, while Mars is visible just after sunset.

Science et Technologie - Le monde minéral et ses trésors cachés : Gypse noir et blanc aux impuretés contrastées

Le gypse est un minéral très fréquent des terrains sédimentaires. C'est un sulfate hydraté decalcium CaSO4 qui cristallise sous des formes très diverses : concrétions en forme de rose, flèches ou masses de cristaux aux parois accolées.

Les couleurs sont tout autant variées : incolore, blanc, jaune, rose à rouge, gris à noir, etc.

Bruno Cupillard

Science & Technology - Astronomy picture of the day : The Orion Bullets

2019 March 3
The Orion Bullets 
Image Credit: GeMS/GSAOI Team, Gemini Observatory, AURA, NSF;
Processing: Rodrigo Carrasco (Gemini Obs.), Travis Rector (Univ. Alaska Anchorage)

Explanation: Why are bullets of gas shooting out of the Orion Nebula? Nobody is yet sure. First discovered in 1983, each bullet is actually about the size of our Solar System, and moving at about 400 km/sec from a central source dubbed IRc2. The age of the bullets, which can be found from their speed and distance from IRc2, is very young -- typically less than 1,000 years. As the bullets expand out the top of the Kleinmann-Low section of the Orion Nebula, a small percentage of iron gas causes the tip of each bullet to glow blue, while each bullet leaves a tubular pillar that glows by the light of heated hydrogen gas. The detailed image was created using the 8.1 meter Gemini South telescope inChile with an adaptive optics system (GeMS). GeMS uses five laser generated guide stars to help compensate for the blurring effects of planet Earth's atmosphere.

Science & Technology - Astronomy picture of the day : NGC 6302: The Butterfly Nebula

2019 March 2
NGC 6302: The Butterfly Nebula 
Image Credit: NASA, ESA, Hubble, HLA; Reprocessing & Copyright: Robert Eder

Explanation: The bright clusters and nebulae of planet Earth's night sky are often named for flowers or insects. Though its wingspan covers over 3 light-years, NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the dying central star of this particular planetary nebula has become exceptionally hot, shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. This sharp close-up was recorded by the Hubble Space Telescope in 2009. The Hubble image data is reprocessed here, showing off the remarkable details of the complex planetary nebula. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is near the center of this view, almost edge-on to the line-of-sight. Molecular hydrogen has been detected in the hot star's dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius).

Science et Technologie - Le monde minéral et ses trésors cachés : "Pietersite aux reflets chatoyants"

"Pietersite aux reflets chatoyants"

Sid Pieters a découvert cette forme de crocidolite en 1962 sur les terres de sa ferme, en Namibie. En 1964, cette matière a été nommée pietersite. Depuis 1993, une amphibole très fibreuse trouvée en Chine porte la même appellation car elle présente des couleurs et des chatoyances similaires.

Bruno Cupillard

Science & Technology - Astronomy picture of the day : Charioteer's Comet

2019 March 1
A Charioteer's Comet  Image Credit & Copyright: Rolando Ligustri (CARA Project, CAST)

Explanation: Still racing across planet Earth's night skies, Comet Iwamoto (C/2018 Y1) shares this pretty telescopic field of view with stars and nebulae of northern constellation Auriga, the Charioteer. Captured on February 27, Iwamoto's greenish coma and faint tail appear between a complex of reddish emission nebulae and open star cluster M36 (bottom right). The reddish emission is light from hydrogen gas ionized by ultraviolet radiation from hot stars near the region's giant molecular cloud some 6,000 light-years distant. The greenish glow from the comet, less than 5 light-minutes away, is predominantly emission from diatomic carbon molecules fluorescing in sunlight. M36, one of Auriga's more familiar star clusters, is also a background object far beyond the Solar System, about 4,000 light-years away. Comet Iwamoto passed closest to Earth on February 12 and is outward bound in a highly elliptical orbit that will carry it beyond the Kuiper belt. With an estimated orbital period of 1,317 years it should return to the inner Solar System in 3390 AD.

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.