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.

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