ASTRONOMY - Venus in Ultraviolet from Akatsuki

 2023 July 3

Venus in Ultraviolet from Akatsuki
Image Credit & Copyright: JAXA, Planet-C Project Team; h/t: Mehmet Hakan Özsaraç

Explanation: Why is Venus so different from Earth? To help find out, Japan launched the robotic Akatsuki spacecraft which entered orbit around Venus late in 2015 after an unplanned five-year adventure around the inner Solar System. Even though Akatsuki was past its original planned lifetime, the spacecraft and instruments were operating so well that much of its original mission was reinstated. Also known as the Venus Climate Orbiter, Akatsuki's instruments investigated unknowns about Earth's sister planet, including whether volcanoes are still active, whether lightning occurs in the dense atmosphere, and why wind speeds greatly exceed the planet's rotation speed. In the featured image taken by Akatsuki's UVI camera, the day-side of Venus is seen shown with planet-scale V-shaped cloud pattern. The image displays three ultraviolet colors and indicates a dip in the relative abundance of sulfur dioxide shown in faint blue. Analyses of Akatsuki images and data has shown, among other discoveries, that Venus has equatorial jet similar to Earth's jet stream.

PHOTOGRAPHIE - Le monde explosif d'Alan Sailer - Au ralenti : de la pâte à modeler qui explose

Une pâte à modeler Play-Doh explose sous l'impact d'une balle de plomb très rapide qui se déplace à environ 200 mètres par seconde. Tirée à partir d'un fusil à plomb, la balle a une énergie totale d'environ 10 joules.

© Alan Sailer

ASTRONOMY - The Belt of Venus over Mount Everest

 2023 June 26

The Belt of Venus over Mount Everest
Image Credit & Copyright: Soumyadeep Mukherjee

Explanation: You've surely seen it, but you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly dark and off-color. Called the Belt of Venus, this transitional band between the dark eclipsed sky and the bright day sky can be seen most prominently in the direction opposite the Sun. Straight above, blue sky is normal sunlight reflecting off the atmosphere, while near the horizon the clear sky can appear more orange or red. In the Belt of Venus, the atmosphere reflects more light from the setting (or rising) Sun and so appears more red. Featured here, the Belt of Venus was photographed over several Himalayan mountains including, second from the right, Mount Everest, the tallest mountain on Earth. Although usually not mentioned, the belt is frequently caught by accident in other photographs.

PHOTOGRAPHIE - Le monde explosif d'Alan Sailer - Une bille de paintball qui explose au ralenti

Une bille de peinture du jeu paintball qui explose sous l'impact d'une balle de plomb très rapide qui se déplace à environ 200 mètres par seconde. Tirée à partir d'un fusil à plomb, la balle a une énergie totale d'environ 10 joules.

FuturaSciences

ASTRONOMY - Messier 24: Sagittarius Star Cloud

 2023 June 28

Messier 24: Sagittarius Star Cloud
Image Credit & Copyright: Emmanuel Astronomono

Explanation: Unlike most entries in Charles Messier's famous catalog of deep sky objects, M24 is not a bright galaxy, star cluster, or nebula. It's a gap in nearby, obscuring interstellar dust clouds that allows a view of the distant stars in the Sagittarius spiral arm of our Milky Way galaxy. Direct your gaze through this gap with binoculars or small telescope and you are looking through a window over 300 light-years wide at stars some 10,000 light-years or more from Earth. Sometimes called the Small Sagittarius Star Cloud, M24's luminous stars fill this gorgeous starscape. Covering over 3 degrees or the width of 6 full moons in the constellation Sagittarius, the telescopic field of view includes dark markings B92 and B93 near center, along with other clouds of dust and glowing nebulae toward the center of the Milky Way.

PHOTOGRAPHIE - le monde explosif d'Alan Sailer

Cette photo montre ce qui se passe quand on tire avec une carabine à air comprimé un plomb à travers un globe de verre rempli de gélatine rouge. La vitesse du plomb, de 4,5 mm, est d'environ 200 mètres / seconde.

© Alan Sailer

FuturaSciences

ASTRONOMY - Lightning on Jupiter

 2023 June 25

Lightning on Jupiter
Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill

Explanation: Does lightning occur only on Earth? No. Spacecraft in our Solar System have detected lightning on other planets, including Mars, Jupiter and Saturn, and lightning is likely on Venus, Uranus, and Neptune. Lightning is a sudden rush of electrically charged particles from one location to another. On Earth, drafts of colliding ice and water droplets usually create lightning-generating charge separation, but what happens on Jupiter? Images and data from NASA's Jupiter-orbiting Juno spacecraft bolster previous speculation that Jovian lightning is also created in clouds containing water and ice. In the featured Juno photograph, an optical flash was captured in a large cloud vortex near Jupiter's north pole. During the next few months, Juno will perform several close sweeps over Jupiter's night side, likely allowing the robotic probe to capture more data and images of Jovian lightning.

ASTRONOMY - Sublime carte postale de Mars

Il explore la planète Mars depuis plus de dix ans maintenant. Et le rover Curiosity vient encore de nous en renvoyer des images à couper le souffle. Une spectaculaire carte postale de la Planète rouge.

Le résultat final est saisissant. Le rover qui apparaît au bas de l'image se situe dans les contreforts du mont Sharp. Celui-ci s'élève à 5 kilomètres de hauteur, dans le cratère Gale. C'est le cratère que Curiosity explore depuis son atterrissage en 2012. Au loin au-delà de ses traces se trouve Marker Band Valley, une zone sinueuse dans le « région sulfatée » dans laquelle le rover a découvert des signes inattendus d'un ancien lac. Plus près du rover -- au centre de la carte postale -- se trouvent deux collines, Bolívar et Deepdale, que Curiosity a parcourues tout en explorant Paraitepuy Pass.

FuturaSciences

GEMMOLOGIE - La topaze, un silicate

 

La topaze fait partie des nésosubsilicates tout comme l'andalousite, le disthène et le sillimanite. Elle a longtemps été confondue avec l'olivine jaune. Son nom est d'ailleurs tiré de l'île de Topazios qui était un gisement d'olivine de la mer Rouge. La topaze peut changer de teinte par procédé artificiel. Couleurs : variées. © DidierDescouens, 

Wikimedia Commons, CC by-sa 3.0

FuturaSciences

ASTRONOMY - 3D Ingenuity

 2023 June 24

3D Ingenuity
Image Credit: NASA, JPL-Caltech, MSSS, ASU

Explanation: The multicolor, stereo imaging Mastcam-Z on the Perseverance rover zoomed in to capture this 3D close-up (get out your red/blue glasses) of the Mars Ingenuity helicopter on mission sol 45. That's Earth-date 2021 April 5. Casting a shadow on the Martian surface, Ingenuity is standing alone on its four landing legs next to the rover's wheel tracks. The experimental helicopter's solar panel, charging batteries that keep it warm through the cold Martian nights and power its flight, sits just above Ingenuity's two 1.2 meter (4 foot) long counter-rotating blades. Thirteen sols later, on April 19, Ingenuity became the first aircraft to perform powered, controlled flight on another planet. It has since gone on to complete more than 50 flights through the thin atmosphere of Mars.