BIOMES - Canada

Au Canada, il y a aussi des forêts tempérées

FuturaSciences

ASTRONOMY - NGC 6888: The Crescent Nebula

 2024 November 12

NGC 6888: The Crescent Nebula
Image Credit & Copyright: Team ARO

Explanation: How was the Crescent Nebula created? Looking like an emerging space cocoon, the Crescent Nebula, visible in the center of the featured image, was created by the brightest star in its center. A leading progenitor hypothesis has the Crescent Nebula beginning to form about 250,000 years ago. At that time, the massive central star had evolved to become a Wolf-Rayet star (WR 136), shedding its outer envelope in a strong stellar wind, ejecting the equivalent of our Sun's mass every 10,000 years. This wind impacted surrounding gas left over from a previous phase, compacting it into a series of complex shells, and lighting it up. The Crescent Nebula, also known as NGC 6888, lies about 4,700 light-years away in the constellation of Cygnus. Star WR 136 will probably undergo a supernova explosion sometime in the next million years.

BIOMES - Le Pantanal

Le Pantanal, la plus grande prairie humide de la Planète

FuturaSciences

ASTRONOMY - The Unusual Tails of Comet Tsuchinshan-Atlas

 2024 November 11

The Unusual Tails of Comet Tsuchinshan-Atlas
Image Credit & Copyright: Bray Falls

Explanation: What created an unusual dark streak in Comet Tsuchinshan-Atlas's tail? Some images of the bright comet during mid-October not only caught its impressively long tail and its thin anti-tail, but a rather unexpected feature: a dark streak in the long tail. The reason for the dark streak is currently unclear and a topic of some debate. Possible reasons include a plume of dark dust, different parts of the bright tail being unusually superposed, and a shadow of a dense part of the coma on smaller dust particles. The streak is visible in the featured image taken on October 14 from Texas, USA. To help future analyses, if you have taken a good image of the comet that clearly shows this dark streak, please send it in to APOD. Comet Tsuchinshan–ATLAS has now faded considerably and is returning to the outer Solar System.

BIOMES - Le Deadvlei

Le Deadvlei, un marais mort au cœur du désert.

FuturaSciences

ASTRONOMY - Valles Marineris: The Grand Canyon of Mars

 

2024 November 10

Valles Marineris: The Grand Canyon of Mars
Image Credit: NASA, USGS, Viking Project

Explanation: The largest canyon in the Solar System cuts a wide swath across the face of Mars. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep. By comparison, the Earth's Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep. The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled. Several geologic processes have been identified in the canyon. The featured mosaic was created from over 100 images of Mars taken by Viking Orbiters in the 1970s. 

BIOMES - La mangrove

La mangrove, c’est ce paysage étonnant s’il en est où l’on voit des arbres littéralement sortir de l’eau avec leurs racines, ici, mises à jour par la marée, montrant une rage de vivre qui fait chaud au cœur. Ce biome des régions tropicales est fait de marais maritimes. Il est l’un des écosystèmes les plus productifs en biomasse de notre planète. Et il procure de nombreuses ressources aux populations locales. Mais, un peu partout dans le monde, la mangrove connait aujourd’hui une dégradation rapide. Elle aurait déjà perdu 25 % de son étendue naturelle. 

© Patjosse, Pixabay, DP

ASTRONOMY - Neptune at Night

 2024 November 9

Neptune at Night
Image Credit & Copyright: Voyager 2, NASA

Explanation: Ice giant Neptune is faint in Earth's night sky. Some 30 times farther from the Sun than our fair planet, telescopes are needed to catch a glimpse of the dim and distant world. This dramatic view of Neptune's night just isn't possible for telescopes in the vicinity of planet Earth though. Peering out from the inner Solar System they can only bring Neptune's day side into view. In fact this night side image with Neptune's slender crescent next to the crescent of its large moon Triton was captured by Voyager 2. Launched from planet Earth in 1977 the Voyager 2 spacecraft made a close fly by of the Solar System's outermost planet in 1989, looking back on Neptune as the robotic spacecraft continued its voyage to interstellar space.

BIOMES - La toundra sous la menace du réchauffement climatique

La toundra - ici, celle du Groenland, quelques touches de verdure et de chaleur au milieu de la froideur glacée des icebergs - s'épanouit essentiellement sous le climat froid qui règne autour des pôles. Quelques arbres comme le bouleau, des arbustes, mais surtout, des pelouses, des lichens et des mousses. Et des fleurs. Près de 200 espèces qui ont appris à résister au froid. Côté faune, uniquement des animaux adaptés aux conditions de vie difficiles : le harfang des neiges ou le tétras, de grands ruminants comme le renne ou encore des carnivores que sont l'ours blanc, le loup ou le renard polaire.

La toundra, puits de carbone naturel, est en train de perdre cette propriété sous l'effet du réchauffement climatique.

© Hannes Grobe, Wikimedia Commons, CC 2.5

ASTRONOMY - Helping Hand in Cassiopeia

 2024 November 8

Helping Hand in Cassiopeia
Image Credit & Copyright: Francesco Radici

Explanation: Drifting near the plane of our Milky Way galaxy these dusty molecular clouds seem to extend a helping hand on a cosmic scale. Part of a local complex of star-forming interstellar clouds they include LDN 1358, 1357, and 1355 from American astronomer Beverly Lynds' 1962 Catalog of Dark Nebulae. Presenting a challenging target for astro-imagers, the obscuring dark nebulae are nearly 3,000 light-years away, toward rich starfields in the northern constellation Cassiopeia. At that distance, this deep, telescopic field of view would span about 80 light-years.