Science & Technologie - La Terre vue de l'Espace : Guiné Bissau

La Guinée-Bissau est un petit pays en Afrique occidentale. Des différences sédimentaires complexes peuvent être vues dans les eaux peu profondes le long de son littoral, où la vase portée par le fleuve Geba et d'autres fleuves plonge dans l'océan Atlantique.

© USGS, Nasa

Science & Technologie - La Terre vue de l'Espace : Parc national de Canyonlands

Le parc national de Canyonlands est situé dans l'Utah non loin de Moab (États-Unis). Cette image prise par Landsat 7 montre les trois principales parties du parc : Island in the Sky, the Needles et The Maze. Canyonlands offre un paysage minéral aride, façonné par l'érosion provoquée par le fleuve Colorado et la Green River dont les affluents ont creusé et sculpté la roche au cours de milliers d'années, laissant derrière eux des formes extraordinaires et un témoignage géologique unique.

© Nasa

Science & Technology - Astronomy picture of the day : Sharpless-308: The Dolphin Nebula

2020 March 2

Sharpless-308: The Dolphin Nebula
Image Credit & Copyright: Chilesope 2, Pleaides Astrophotography Team (Peking U.)

Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is much larger than the dolphin it appears to be. Cataloged as Sharpless 2-308 it lies some 5,200 light-years away toward the constellation of the Big Dog (Canis Major) and covers slightly more of the sky than a Full Moon. That corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a Wolf-Rayet star, is the bright one near the center of the nebula. Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. Fast winds from this Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The windblown nebula has an age of about 70,000 years. Relatively faint emission captured in the featured expansive image is dominated by the glow of ionized oxygen atoms mapped to a blue hue.

Science & Technology - Astronomy picture of the day : A hole in Mars

A Hole in Mars
Image Credit: NASA, JPL, U. Arizona

Explanation: What created this unusual hole in Mars? The hole was discovered by chance in 2011 on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole, shown in representative color, appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern. Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.

Science & Technologie - Astronomy icture of the day : To Fly Free in Space

2020 February 9 
To Fly Free in Space 

Image Credit: NASA, STS-41B

Explanation: What would it be like to fly free in space? At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was living the dream -- floating farther out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk" during Space Shuttle mission 41-B in1984. The MMU worked by shooting jets of nitrogen and was used to help deploy and retrieve satellites. With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was later replaced with the SAFER backpack propulsion unit.

Science et Technologie - Santé/Médecine - L'hypnose (1/12)

 

L'hypnose est un état psychologique particulier encore mal défini qui revêt certains attributs physiologiques et marqué par le fonctionnement de l'individu à un niveau d'attention autre que l'état de conscience ordinaire. Il peut, sous certaines conditions, donner l'apparence du sommeil ou du somnambulisme sans en partager toutes les caractéristiques.

Cet état est généralement provoqué chez une personne par l'action volontaire d'une autre personne. Ce processus est parfois nommé induction hypnotique.

Il se caractérise selon les individus par une réduction du champ de conscience (hyperfocalisation), une introspection, le développement d'hallucinations, de rêves, un sentiment d'absence, de dissociation, une perte des repères spatio-temporels et d'autres phénomènes variables. L'expérience hypnotique d'une personne dépend de sa personnalité, du contexte, de la méthode employée, des suggestions qui lui sont faites, de la profondeur de l'induction hypnotique, et d'autres paramètres.

Une personne peut également développer une hypnose spontanée ou provoquer soi-même sa propre hypnose. On parle alors d’autohypnose.

Il existe un débat ancien entre ceux qui considèrent l'hypnose comme un état mental spécifique et ceux qui le considèrent comme un jeu de rôle comportemental en réponse pour se conformer à une attente, ainsi que des positions médianes.

Le mot hypnose désigne également les techniques permettant de créer cet état et les pratiques thérapeutiques utilisées pendant cet état.

Science & Technologie - Image astronomique du jour : La galaxie du Sombrero en infrarouge

Crédit : R. Kennicutt (Steward Obs.) et al., SSC, JPL, Caltech, NASA

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Cet anneau en lévitation a la taille d'une galaxie. En fait, c'est une galaxie, du moins une partie : la galaxie du Sombrero, une des plus grandes galaxies du proche amas de la Vierge. La bande sombre de poussière qui en lumière visible obscurcit le plan de la Galaxie du Sombrero se révèle brillante en infrarouge. L'image ci-dessus montre la lueur infrarouge captée par le télescope spatial Spitzer en orbite autour de la Terre, superposée en fausses couleurs à une autre image prise en lumière visible par le télescope spatial Hubble de la NASA. La Galaxie du Sombrero, connue aussi sous le nom de M 104, mesure environ 50 000 années-lumière de diamètre et est située à 28 millions d'années-lumière de la Terre. M104 est visible à l'aide d'un petit instrument dans la direction de la constellation de la Vierge.

Science & Technology - Astronomy picture of the day : Galaxies in the River

2020 January 8

Galaxies in the River
Image Credit & Copyright: Star Shadows Remote Observatory, PROMPT, CTIO

Explanation: Large galaxies grow by eating small ones. Even our own galaxy engages in a sort of galactic cannibalism, absorbing small galaxies that are too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus, The River. Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531 (right of center), a struggle the smaller galaxy will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. Nicely detailed in this sharp image, the NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.

Science & Technology - Astronomy picture of the day : The Fainting of Betelgeuse

2020 January 2

The Fainting of Betelgeuse
Image Credit & Copyright: Jimmy Westlake (Colorado Mountain College)

Explanation: Begirt with many a blazing star, Orion the Hunter is one of the most recognizable constellations. In this night skyscape the Hunter's stars rise in the northern hemisphere's winter sky on December 30, 2019, tangled in bare trees near Newnan, Georgia, USA. Red super giant star Betelgeuse stands out in yellowish hues at Orion's shoulder left of center, but it no longer so strongly rivals the blue supergiant star Rigel at the Hunter's foot. In fact, skygazers around planet Earth can see a strikingly fainter Betelgeuse now, its brightness fading by more than half in the final months of 2019. Betelgeuse has long been known to be a variable star, changing its brightness in multiple cycles with approximate short and long term periods of hundreds of days to many years. The star is now close to its faintest since photometric measurements in 1926/27, likely due in part to a near coincidence in the minimum of short and long term cycles. Betelgeuse is also recognized as a nearby red supergiant star that will end its life in a core collapse supernova explosion sometime in the next 1,000 years, though that cosmic cataclysm will take place a safe 700 light-years or so from our fair planet.

Science & Technology - Astronomy picture of the day : Betelgeuse Imagined

2020 January 1

Betelgeuse Imagined
Illustration Credit: ESO, L. Calcada

Explanation: Why is Betelgeuse fading? No one knows. Betelgeuse, one of the brightest and most recognized stars in the night sky, is only half as bright as it used to be only five months ago. Such variability is likely just normal behavior for this famously variable supergiant, but the recent dimming has rekindled discussion on how long it may be before Betelgeuse does go supernova. Known for its red color, Betelgeuse is one of the few stars to be resolved by modern telescopes, although only barely. The featured artist's illustration imagines how Betelgeuse might look up close. Betelgeuse is thought to have a complex and tumultuous surface that frequently throws impressive flares. Were it to replace the Sun (not recommended), its surface would extend out near the orbit of Jupiter, while gas plumes would bubble out past Neptune. Since Betelgeuse is about 700 light years away, its eventual supernova will not endanger life on Earth even though its brightness may rival that of a full Moon. Astronomers -- both amateur and professional -- will surely continue to monitor Betelgeuse as this new decade unfolds.