Vulcanologie - PACAYA - GUATEMALA

Le Pacaya très beau volcan à 50km au sud de la capitale du Guatemala.

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Astronomy - A COLLISION OF GALAXY CLUSTERS

 2026 May 21

A Collision of Galaxy Clusters
Image Credit: X-ray: NASA/CXC/CfA/C. Watson et al.; Optical: PanSTARRS; Image Processing: NASA/CXC/SAO/N. Wolk and P. Edmonds
Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: This big beautiful spiral shines in X-ray light. It is about 20 times larger than our Galaxy. It belongs to Abell 2029, a galaxy cluster one billion light-years away. (To see only the galaxies, hover your cursor over the image, or follow this link.) Galaxy clusters are the largest structures in the universe that are supported by gravity. Abell 2029 is formed by thousands of galaxies, surrounded by a huge cloud of hot gas and the equivalent of hundreds of trillions times the mass of the Sun in dark matter. The spiral is made of gas, mostly hydrogen and helium, heated to tens of millions of degrees. It was found in a recent study that used data from NASA's Chandra X-ray Observatory to show that Abell 2029 had a collision with a smaller cluster four billion years ago. The collision affected the gravitational field and caused the intracluster gas to slosh, like wine moving in a wine glass, shaping the spiral.

Astronomie - ETOILES FILANTES : PERSEIDE ACCOMPAGNEE D'AURORE BOREALE ET NUAGES NOCTULESCENTS

Perséide surprise dans le ciel de Suède, dans la nuit du 12 au 13 août 2016. Au même moment, à d'autres niveaux dans l'atmosphère terrestre, une aurore verdâtre dansait au-dessus d'une bande de nuages noctulescents (nuages glacés de haute altitude).

© Göran Strand

Astronomy - AURORA SLATHERS UP THE SKY

 2026 May 16

Aurora Slathers Up the Sky
Image Credit: Jack Fischer, Expedition 52, NASA

Explanation: Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth's limb.

Astronomy - R3PanSTARRS : AN ORION COMET

 2026 May 15

R3 PanSTARRS: An Orion Comet
Image Credit & Copyright: Chester Hall-Fernandez

Explanation: Comet R3 PanSTARRS might be best remembered as an Orion comet. A key reason is because Comet C/2025 R3 (PanSTARRS) was near its most spectacular -- in terms of tail visibility -- when passing in front of the iconic constellation. Although rare, other bright comets, too, have ventured across Orion, including Lovejoy in 2015, Hale-Bopp in 1997, and the Great Comet of 1264. Best visible in long duration exposures, the featured image was captured last week from the Craigieburn Mountain Range in New Zealand. Visible in the deep background image are the Orion Nebula, Barnard's Loop, and through R3's tail, the bright star Saiph, the sixth brightest star in the constellation of Orion. Comet R3 PanSTARRS continues to fade as it moves further south, passing into the constellation of the Unicorn (Monoceros) in the next few days.

Astronomy - MESSIER CATALOG AT UNIFORM SCALE

 2026 May 14

Messier Catalog at Uniform Scale
Image Credit: Sylvain Villet
Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: What are some of the most interesting astronomical objects you can see in the night sky? Armed with a good pair of binoculars or a small telescope, if you live in the Northern Hemisphere, you can look for the very popular objects in the Messier Catalog. Most of them, but not all, are also visible from the southern half of the Earth. The featured image shows all 110 objects in the catalog at uniform scale -- the same magnification. Charles Messier created the catalog in the 18th century. He was interested in comets, and his catalog was a list of known comet-like "objects to avoid" in the sky when observing or hunting for comets. The deep sky objects in the catalog include a supernova remnant (the Crab Nebula, M1), other galaxies (such as Andromeda, M31), nebulae (e.g. the Orion Nebula, M42, a star-forming region) and stellar clusters (such as the Pleiades, M45, a bright young open cluster).

Astronomy - NGC188: OLD CLUSTER IN THE NEW GENERAL CATALOG

 2026 May 13

NGC 188: Old Cluster in the New General Catalog
Image Credit & Copyright: Neven Krcmarek

Explanation: The New General Catalog of star clusters and nebulae really isn't so new. In fact, it was published in 1888 - an effort by J. L. E. Dreyer to consolidate the work of astronomers William, Caroline, and John Herschel along with others into a useful single, complete catalog of astronomical discoveries and measurements. Dreyer's work was largely successful and is still important today, as this famous catalog continues to lend its "NGC" to bright clusters, galaxies, and nebulae. Take for example the star cluster known as NGC 188 (item number 188 in the NGC compilation). It lies about 6,000 light-years distant in the northern constellation Cepheus and represents a galactic or open star cluster. With an age of about 7 billion years, NGC 188 is old for an open cluster. Its old, evolved red giant stars have yellowish hues in this colorful, deep sky view. NGC 188 also enjoys the designation Caldwell 1 in a modern compilation of deep sky objects. Located well above the plane of the Milky Way and seen in the direction of planet Earth's north celestial pole, the ancient stellar group is known to some as the Polarissima Cluster.

Astronomie - SPLENDIDES RAPPROCHEMENTS LUNE-VENUS-JUPITER

Du 18 au 20 mai, un beau croissant de lune s'approche de Vénus puis de Jupiter dans le ciel du soir. Un très beau spectacle à admirer à l'œil nu, tout simplement.

Stelvision

Astronomy - THE CUNJUNCTION OF COMET R3 PauSTARRS AND THE ORION NEBULA

 2026 May 12

The Conjunction of Comet R3 PanSTARRS and the Orion Nebula
Image Credit & Copyright: Julien De Winter, Sascha Ebeler
Text: Keighley Rockcliffe (NASA GSFC, UMBC CSST, CRESST II)

Explanation: Today’s composite image features something old, something new, something borrowed, and something blue! Comet R3 PanSTARRS, streaking across the right of the image, likely originated from the Oort Cloud, meaning it is an old Solar System relic from billions of years ago. It’s bright extended ion tail glows blue as the gas escaping the comet’s core is ionized by sunlight. Astronomers are fascinated by comets for all sorts of reasons: comet compositions are untouched time capsules containing the building blocks of Solar System planets; comets may have delivered water to the young Earth; the behavior of cometary tails shed light on solar wind and radiation interactions. The background mosaic, featuring the Orion Nebula (M42), was taken over two nights of observation with the comet captured on the third night. The Orion Nebula is our nearest stellar nursery and, at about 2 million years old, is our something (relatively) new! Now at around 127.5 million kilometers from Earth, we wave goodbye to the borrowed Comet R3 PanSTARRS as it leaves the Solar System.

Vulcanologie - NGAURUHOE (NOUVELLE ZELANDE)

Avec 2,291 mètres d'altitude, sa dernière éruption a eu lieu en 1977. Ce paysage est de toute beauté.

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