ASTRONOMY - A Map of the Observable Universe

 2023 July 5

A Map of the Observable Universe
Image Credit & Copyright: B. Ménard & N. Shtarkman; Data: SDSS, Planck, JHU, Sloan, NASA, ESA

Explanation: What if you could see out to the edge of the observable universe? You would see galaxies, galaxies, galaxies, and then, well, quasars, which are the bright centers of distant galaxies. To expand understanding of the very largest scales that humanity can see, a map of the galaxies and quasars found by the Sloan Digital Sky Survey from 2000 to 2020 -- out to near the edge of the observable universe -- has been composed. Featured here, one wedge from this survey encompasses about 200,000 galaxies and quasars out beyond a look-back time of 12 billion years and cosmological redshift 5. Almost every dot in the nearby lower part of the illustration represents a galaxy, with redness indicating increasing redshift and distance. Similarly, almost every dot on the upper part represents a distant quasar, with blue-shaded dots being closer than red. Clearly shown among many discoveries, gravity between galaxies has caused the nearby universe to condense and become increasingly more filamentary than the distant universe.

ASTRONOMY - Aurora over Icelandic Waterfall

 2023 July 4

Aurora over Icelandic Waterfall
Image Credit & Copyright: Cari Letelier

Explanation: It seemed like the sky exploded. The original idea was to photograph an aurora over a waterfall. After waiting for hours under opaque clouds, though, hope was running out. Others left. Then, unexpectedly, the clouds moved away. Suddenly, particles from a large solar magnetic storm were visible impacting the Earth's upper atmosphere with full effect. The night sky filled with colors and motion in a thrilling auroral display. Struggling to steady the camera from high Earthly winds, the 34 exposures that compose the featured image were taken. The resulting featured composite image shows the photogenic Godafoss (Goðafoss) waterfall in northern Iceland in front of a very active aurora in late February. The solar surface explosion that expelled the energetic particles occurred a few days before. Our Sun is showing an impressive amount of surface activity as it approaches solar maximum, indicating that more impressive auroras are likely to appear in Earth's northern and southern sky over the next few years.

PHOTOGRAPHIE - Le monde explosif d'Alain Sailer - Explosion d'une crème glacée au ralenti

Cette délicieuse crème glacée garnie de noix est frappée par une petite bille d'un roulement à bille en acier. La bille a été propulsée par un canon à air haute pression (10 bars). L'énergie totale de la bille d'acier est d'environ 100 joules. 

© Alan Sailer

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.