Nombre total de pages vues

06/12/2022

AVIATION IMAGINEE - Les femmes pilotes d'avions : impensable à l'époque

Cette illustration américaine de 1900-1910 est tout à fait audacieuse. Elle représente une femme au volant. Pour rappel, le 19e amendement, qui permit aux femmes de voter aux États-Unis, ne fut passé qu'en 1920 !

© Harry Grant Dart pour All stroy magazine

ASTRONOMIE - Occultation de Mars (8 décembre 2022)

Le 8 décembre 2022 se produit une occultation de Mars par la Lune : un phénomène rare ! La planète rouge étant à l’opposition, c’est aussi l’occasion d’un alignement parfait et peu courant, entre le Soleil, la Terre, la Lune et Mars.

Combien de temps dure l’occultation de Mars par la Lune ?

Alors que le temps d’une nuit, le mouvement de la planète Mars est quasiment imperceptible sur le fond de ciel étoilé, celui de la Lune est beaucoup plus important. En effet, avec son orbite autour de la Terre qui dure 27 jours, cela signifie qu’en l’espace d’une heure, la Lune se décale d’environ un demi-degré sur le fond de ciel étoilé, soit à peu près un diamètre lunaire. Voilà pourquoi Mars est occulté pendant une heure environ le 8 décembre si sa trajectoire derrière la Lune est centrale. La durée est en revanche plus courte si cette trajectoire est très décalée par rapport au centre de notre satellite.

Stelvision

ASTRONOMY - M16: A Star Forming Pillar from Webb

 2022 December 6

The featured image shows a large golden-brown pillar 
of dust surrounded by a few smaller pillars. 
Please see the explanation for more detailed information.

M16: A Star Forming Pillar from Webb
Image Credit: NASAESACSASTScIProcessing & Copyright: Mehmet Hakan Özsaraç

Explanation: What’s happening inside this interstellar mountain? Stars are forming. The mountain is actually a column of gas and dust in the picturesque Eagle Nebula (M16). A pillar like this is so low in density that you could easily fly though it -- it only appears solid because of its high dust content and great depth. The glowing areas are lit internally by newly formed stars. These areas shine in red and infrared light because blue light is scattered away by intervening interstellar dust. The featured image was captured recently in near-infrared light in unprecedented detail by the James Webb Space Telescope (JWST), launched late last year. Energetic light, abrasive winds, and final supernovas from these young stars will slowly destroy this stellar birth column over the next 100,000 years.

05/12/2022

ASTRONOMY - Pleiades: The Seven Sisters Star Cluster

 2022 December 5

The featured image shows many blue stars clustered 
together in blue-glowing gas and dust.
Please see the explanation for more detailed information.

Pleiades: The Seven Sisters Star Cluster
Image Credit & Copyright: Blake Estes (iTelescope Siding Spring Obs.) & Christian Sasse

Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as large and clear as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen with the unaided eye even from the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured 11-hour exposure, taken from the Siding Spring Observatory in Australia, covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six of the sister stars visible to the unaided eye. The actual number of Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.

04/12/2022

MICROPHOTOGRAPHIE - Marek Miś - L'acide malique : le plein de goût

HOOC-CH2-CHOH-COOH. C'est la formule de l'acide malique. On en trouve dans beaucoup de végétaux. Dans les pommes, les poires et le raisin, notamment. C'est aussi lui qui donne une saveur si particulière à la rhubarbe. Et un goût acidulé au vin. Il est largement utilisé comme additif alimentaire. Nom de code E296. Car l'acide malique donne un goût agréable et ralentit le brunissement des aliments. Il présente également une fonction antibactérienne et antioxydante.

C'est lui que l'on retrouve sur cette microphotographie prise en lumière polarisée et avec un grossissement de 100 fois. Sous la forme de cristaux aux reflets dorés dont l'aspect rappelle vaguement celui de quelques haches préhistoriques. Comme un clin d'œil au fait que l'acide malique -- en mélange avec l'acide citrique -- est couramment employé pour acidifier les bonbons de nos enfants, pour leur donner du peps... ou pour détartrer les cafetières !

Cliché réalisé à l'aide d'un microscope Olympus BH-2 et d'un appareil Pentax K1.

© Marek Miś.
FuturaSciences

ASTRONOMY -Video: Powers of Ten

 2022 December 4

Video: Powers of Ten
Video Credit & Copyright: Charles & Ray Eames (Eames Office)

Explanation: How different does the universe look on very small scales? On very large scales? The most famous short science film of its generation gives breathtaking comparisons. That film, Powers of Ten, originally created in the 1960s, has been officially posted to YouTube and embedded here. From a picnic blanket near Chicago out past the Virgo Cluster of Galaxies, every ten seconds the film zooms out to show a square a factor of ten times larger on each side. The 9-minute video then reverses, zooming back in a factor of ten every two seconds and ends up inside a single proton. The Powers of Ten sequence is actually based on the book Cosmic View by Kees Boeke in 1957, as is a similar but mostly animated film Cosmic Zoom that was also created in the late 1960s. The changing perspectives are so enthralling and educational that sections have been recreated using more modern computerized techniques, including the first few minutes of the movie ContactRay and husband Charles Eames, the film's creators, were known as quite visionary spirits and even invented their own popular chair.

03/12/2022

AVIATION IMAGINEE - Influencée par les frères Montgolfier

 

Cette carte, datant de 1890-1900, propose une vision de l’aviation future similaire à celle de 1800, un siècle plus tôt. L’influence des frères Montgolfier a encore frappé ! © Romanet & Cie, collection 476, 2e série

FuturaSciences

ASTRONOMY - Stereo Mars near Opposition

 2022 December 3

See Explanation.  Clicking on the picture will download
the highest resolution version available.

Stereo Mars near Opposition
Image Credit & Copyright: Marco Lorenzi

Explanation: Mars looks sharp in these two rooftop telescope views captured in late November from Singapore, planet Earth. At the time, Mars was about 82 million kilometers from Singapore and approaching its opposition, opposite the Sun in planet Earth's sky on December 8. Olympus Mons, largest of the volcanoes in the Tharsis Montes region (and largest known volcano in the Solar System), is near Mars' western limb. In both the images it's the whitish donut-shape at the upper right. The dark area visible near center is the Terra Sirenum region while the long dark peninsula closest to the planet's eastern limb is Sinus Gomer. Near its tip is Gale crater, the Curiosity rover's landing site in 2012. Above Sinus Gomer, white spots are other volcanoes in the Elysium region. At top of the planet is the north polar cap covered with ice and clouds. Taken about two days apart, these images of the same martian hemisphere form a stereo pair. Look at the center of the frame and cross your eyes until the separate images come together to see the Red Planet in 3D.

02/12/2022

ASTRONOMY - Merging Galaxy Pair IIZw096

 2022 December 2

See Explanation.  Clicking on the picture will download
the highest resolution version available.

Merging Galaxy Pair IIZw096
Image Credit: ESA/Webb, NASA & CSA, L. Armus, A. Evans

Explanation: Bright at infrared wavelengths, this merging galaxy pair is some 500 million light-years away toward the constellation Delphinus. The cosmic mashup is seen against a background of even more distant galaxies, and occasional spiky foreground stars. But the galaxy merger itself spans about 100,000 light-years in this deep James Webb Space Telescope image. The image data is from Webb's Near-InfraRed Camera (NIRCam) and Mid-InfraRed Instrument (MIRI). Their combined, sharp infrared view follows galactic scale restructuring in the dusty merger's wild jumble of intense star forming regions and distorted spiral arms

01/12/2022

ASTRONOMY - Artemis 1: Flight Day 13

 2022 December 1

See Explanation.  Clicking on the picture will download
the highest resolution version available.

Artemis 1: Flight Day 13
Image Credit: NASAArtemis 1

Explanation: On flight day 13 (November 28) of the Artemis 1 mission the Orion spacecraft reached its maximum distance from Earth. In fact, over 430,000 kilometers from Earth its distant retrograde orbit also put Orion nearly 70,000 kilometers from the Moon. In the same field of view in this video frame from flight day 13, planet and large natural satellite even appear about the same apparent size from the uncrewed spacecraft's perspective. Today (December 1) should see Orion depart its distant retrograde orbit. En route to planet Earth it will head toward a second powered fly by of the Moon. Splashdown on the home world is expected on December 11.

ASTRONOMY - The Local Fluff

 2024 December 22 The Local Fluff Illustration Credit:  NASA ,  SVS ,  Adler ,  U. Chicago ,  Wesleyan Explanation:  The stars are not alone...