"Radetzky March"
01/01/2022
ASTRONOMY - Plane Crossing a Crescent Moon
2019 February 12
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.
31/12/2021
ASTRONOMY - JWST on the Road to L2
2021 December 31
Image Credit & Copyright: Malcolm Park (North York Astronomical Association)
Explanation: This timelapse gif tracks the James Webb Space Telescope as it streaks across the stars of Orion on its journey to a destination beyond the Moon. Recorded on December 28, 12 consecutive exposures each 10 minutes long were aligned and combined with a subsequent color image of the background stars to create the animation. About 2.5 days after its December 25 launch, JWST cruised past the altitude of the Moon's orbit as it climbed up the gravity ridge from Earth to reach a halo orbit around L2, an Earth-Sun Lagrange point. Lagrange points are convenient locations in space where the combined gravitational attraction of one massive body (Earth) orbiting another massive body (Sun) is in balance with the centripetal force needed to move along with them. So much smaller masses, like spacecraft, will tend to stay there. One of 5 Lagrange points, L2 is about 1.5 million kilometers from Earth directly along the Earth-Sun line. JWST will arrive at L2 on January 23, 29 days after launch. While relaxing in Earth's surface gravity you can follow the James Webb Space Telescope's progress and complicated deployment online.
30/12/2021
ASTRONOMY - The Further Tail of Comet Leonard
2021 December 30
Image Credit & Copyright: Daniele Gasparri
Explanation: Comet Leonard, brightest comet of 2021, is at the lower left of these two panels captured on December 29 in dark Atacama desert skies. Heading for its perihelion on January 3 Comet Leonard's visible tail has grown. Stacked exposures with a wide angle lens (also displayed in a reversed B/W scheme for contrast), trace the complicated ion tail for an amazing 60 degrees, with bright Jupiter shining near the horizon at lower right. Material vaporizing from Comet Leonard's nucleus, a mass of dust, rock, and ices about 1 kilometer across, has produced the long tail of ionized gas fluorescing in the sunlight. Likely flares on the comet's nucleus and buffeting by magnetic fields and the solar wind in recent weeks have resulted in the tail's irregular pinched and twisted appearance. Still days from its closest approach to the Sun, Comet Leonard's activity should continue. The comet is south of the Solar System's ecliptic plane as it sweeps through the southern constellation Microscopium.
RADIOACITIVITé - CRIIRAD - Qu'est-ce que la radioactivité - 1 -
Les atomes qui nous entourent sont composés d’un noyau central autour duquel gravitent des électrons. Lorsque le noyau est instable, pour atteindre un niveau de plus grand équilibre, il se transforme spontanément en émettant des rayonnements très énergétiques. G1 Ce phénomène est appelé radioactivité.
Composition des atomes
Le noyau contient la quasi-totalité de la masse de l’atome. Les particules qui le composent sont appelées nucléons. On distingue les protons qui portent une charge positive et les neutrons qui sont électriquement neutres. Protons et neutrons ont une masse quasiment identique.
La cohésion du noyau est assurée par les forces nucléaires qui s’opposent à la répulsion électrique entre protons. Les électrons ont une masse 1 840 fois inférieure à celle des nucléons. Ils portent une charge négative et « gravitent » selon des orbites précisément définies. Dans son état normal, l’atome est électriquement neutre car le nombre d’électrons (-) est égal au nombre de protons (+). La force électromagnétique assure la cohésion de l’atome (les électrons chargés négativement sont attirés par le noyau de charge positive).
CRIIRAD
29/12/2021
ASTRONOMY - Giant Storms and High Clouds on Jupiter
2021 December 29
Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill
Explanation: What and where are these large ovals? They are rotating storm clouds on Jupiter imaged last month by NASA's Juno spacecraft. In general, higher clouds are lighter in color, and the lightest clouds visible are the relatively small clouds that dot the lower oval. At 50 kilometers across, however, even these light clouds are not small. They are so high up that they cast shadows on the swirling oval below. The featured image has been processed to enhance color and contrast. Large ovals are usually regions of high pressure that span over 1000 kilometers and can last for years. The largest oval on Jupiter is the Great Red Spot (not pictured), which has lasted for at least hundreds of years. Studying cloud dynamics on Jupiter with Juno images enables a better understanding of dangerous typhoons and hurricanes on Earth.
ART FRACTAL - Kevin R. Johnson, DR - Un arbre brownien né de sulfate de cuivre
SANTE/MEDECINE - Comment mieux dormir - Pas de sport le soir (2)
L’activité sportive est excellente pour la santé, mais mieux vaut programmer son jogging, son cour de gymnastique ou sa séance de natation en matinée ou pendant la pause déjeuner plutôt que le soir. En effet, à partir de 19h, la température du corps commence à baisser, signe que l'organisme se prépare au repos. En augmentant le rythme cardiaque, la pratique sportive maintient une température corporelle plus élevée et réveille l'organisme, perturbant ainsi le rythme biologique. Si votre emploi du temps ne vous permet pas de pratiquer en journée, prenez une douche tiède, et attendez au moins 2 heures après la fin de votre séance pour aller au lit.
Doctissimo
28/12/2021
SANTE/MEDECINE - Comment mieux dormir - Evitez la caféine et la théine (1)
Les fans de café vont être déçus, mieux vaut prendre son dernier expresso après le repas de midi. De même, concernant le thé et les boissons au cola, il est préférable de les arrêter après 16h. Il est en effet prouvé que la caféine rallonge le temps d'endormissement et raccourcit le temps de sommeil. A la place, buvez une tisane de plantes apaisantes (tilleul, verveine, camomille ou fleur d'oranger, mais aussi passiflore, valériane, aubépine et houblon), ou un verre de lait tiède qui exerce un effet sédatif.
Doctissimo
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