ASTRONOMY - Comet C/2025 R2 (SWAN)

2025 September 18

Comet C/2025 R2 (SWAN)
Image Credit & Copyright: Team Ciel Austral

Explanation: A new visitor from the outer Solar System, comet C/2025 R2 (SWAN) also known as SWAN25B was only discovered late last week, on September 11. That's just day before the comet reached perihelion, its closest approach to the Sun. First spotted by Vladimir Bezugly in images from the SWAN instrument on the sun-staring SOHO spacecraft, the comet was surprisingly bright but understandably difficult to see against the Sun's glare. Still close to the Sun on the sky, the greenish coma and tail of C/2025 R2 (SWAN) are captured in this telescopic snapshot from September 17. Spica, alpha star of the constellation Virgo, shines just beyond the upper left edge of the frame while the comet is about 6.5 light-minutes from planet Earth. Near the western horizon after sunset and slightly easier to see in binoculars from the southern hemisphere, this comet SWAN will pass near Zubenelgenubi, alpha star of Libra, on October 2. C/2025 R2 (SWAN) is scheduled to make its closest approach to our fair planet around October 20. 

ASTRONOMY - Nebulas and Clusters in Sagittarius

 2025 September 17

Nebulas and Clusters in Sagittarius
Image Credit & Copyright: J. De Winter, C. Humbert, C. Robert & V. Sabet; Text: Ogetay Kayali (MTU)

Explanation: Can you spot famous celestial objects in this image? 18th-century astronomer Charles Messier cataloged only two of them: the bright Lagoon Nebula (M8) at the bottom, and the colorful Trifid Nebula (M20) at the upper right. The one on the left that resembles a cat's paw is NGC 6559, and it is much fainter than the other two. Even harder to spot are the thin blue filaments on the left, from supernova remnant (SNR G007.5-01.7). Their glow comes from small amounts of glowing oxygen atoms that are so faint that it took over 17 hours of exposure with just one blue color to bring up. Framing this scene of stellar birth and death are two star clusters: the open cluster M21 just above Trifid, and the globular cluster NGC 6544 at lower left.

ASTRONOMY - New Comet SWAN25B over Mexico

 2025 September 16

New Comet SWAN25B over Mexico
Image Credit & Copyright: Daniel Korona

Explanation: A newly discovered comet is already visible with binoculars. The comet, C/2025 R2 (SWAN) and nicknamed SWAN25B, is brightening significantly as it emerges from the Sun's direction and might soon become visible on your smartphone -- if not your eyes. Although the brightnesses of comets are notoriously hard to predict, many comets appear brighter as they approach the Earth, with SWAN25B reaching only a quarter of the Earth-Sun distance near October 19. Nighttime skygazers will also be watching for a SWAN25B-spawned meteor shower around October 5 when our Earth passes through the plane of the comet's orbit. The unexpectedly bright comet was discovered by an amateur astronomer in images of the SWAN instrument on NASA's SOHO satellite. The comet is currently best observed in southern skies but is slowly moving north. The featured image was captured at sunset three days ago just above the western horizon in Zacatecas, Mexico.

ASTRONOMY - Earth During a Powerful Solar Storm

2025 september 15

Earth During a Powerful Solar Storm
Video Credit: NASA's SVS, SWRC, CCMC, SWMF; T. Bridgeman et al.

Explanation: Can our Sun become dangerous? Yes, sometimes. Every few years our Sun ejects a scary-large bubble of hot gas into the Solar System. Every hundred years or so, when the timing, location, and magnetic field connections are just right, such a Coronal Mass Ejection (CME) will hit the Earth. When this happens, the Earth not only experiences dramatic auroras, but its magnetic field gets quickly pushed back and compressed, which causes electric grids to surge. Some of these surges could be dangerous, affecting satellites and knocking out power grids -- which can take months to fix. Just such a storm -- called the Carrington Event -- occurred in 1859 and caused telegraph wires to spark. A similar CME passed near the Earth in 2012, and the featured animated video shows a computer model of what might have happened if it had been a direct hit. In this model, the Earth's magnetopause becomes so compressed that it went inside the orbit of geosynchronous communication satellites.

LES BELLES INVENTIONS DE LEONARD DE VINCI - Un des pionniers du parachute

Il est difficile de dire si Léonard de Vinci est bien le premier à avoir inventé le parachute mais il est certainement un des pionniers de ce concept du point de vue scientifique.

Le dessin en arrière-plan est extrait du Codex Atlanticus, un recueil de dessins et de notes de Léonard de Vinci conservé à la bibliothèque Ambrosienne de Milan. Le dessin a probablement été réalisé entre 1485 et 1502.

© Nevit Dilmen, CC by-sa 3.0

ASTRONOMY - Planets of the Solar System: Tilts and Spins

 2025 September 14

Planets of the Solar System: Tilts and Spins
Video Credit: NASA, Animation: James O'Donoghue (U. Reading)

Explanation: How does your favorite planet spin? Does it spin rapidly around a nearly vertical axis, or horizontally, or backwards? The featured video animates NASA images of all eight planets in our Solar System to show them spinning side-by-side for an easy comparison. In the time-lapse video, a day on Earth -- one Earth rotation -- takes just a few seconds. Jupiter rotates the fastest, while Venus spins not only the slowest (can you see it?), but backwards. The inner rocky planets across the top underwent dramatic spin-altering collisions during the early days of the Solar System. Why planets spin and tilt as they do remains a topic of research with much insight gained from modern computer modeling and the recent discovery and analysis of hundreds of exoplanets: planets orbiting other stars.

ASTRONOMY - Star Trails over One-Mile Radio Telescope

 2025 September 13

Star Trails over One-Mile Radio Telescope
Image Credit & Copyright: Joao Yordanov Serralheiro

Explanation: The steerable 60 foot diameter dish antenna of the One-Mile Telescope at Mullard Radio Astronomy Observatory, Cambridge, UK, is pointing skyward in this evocative night-skyscape. To capture the dramatic scene, consecutive 30 second exposures were recorded over a period of 90 minutes. Combined, the exposures reveal a background of gracefully arcing star trails that reflect planet Earth's daily rotation on its axis. The North Celestial Pole, the extension of Earth's axis of rotation into space, points near Polaris, the North Star. That's the bright star that creates the short trail near the center of the concentric arcs. But the historic One-Mile Telescope array also relied on planet Earth's rotation to operate. Exploring the universe at radio wavelengths, it was the first radio telescope to use Earth-rotation aperture synthesis. That technique uses the rotation of the Earth to change the relative orientation of the telescope array and celestial radio sources to create radio maps of the sky at a resolution better than that of the human eye.

ASTRONOMY - Lunar Eclipse in Two Hemispheres

 2025 September 12

Lunar Eclipse in Two Hemispheres
Image Credit & Copyright: North - Zhouyue Zhu, South - Lucy Yunxi Hu

Explanation: September's total lunar eclipse is tracked across night skies from both the northern and southern hemispheres of planet Earth in these two dramatic timelapse series. In the northern hemisphere sequence (top panel) the Moon’s trail arcs from the upper left to the lower right. It passes below bright planet Saturn, seen under mostly clear skies from the international campus of Zhejiang University in China at about 30 degrees north latitude. In contrast, the southern hemisphere view from Lake Griffin, Canberra, Australia at 35 degrees south latitude, records the Moon’s trail from the upper right to the lower left. Multiple lightning flashes from thunderstorms near the horizon appear reflected in the lake. Both sequences were photographed with 16mm wide-angle lenses and both cover the entire eclipse, with the darkened red Moon totally immersed in Earth's umbral shadow near center. But the different orientations of the Moon’s path across the sky reveal the perspective shifts caused by the views from northern vs. southern latitudes.

SANTé/MEDECINE - Remèdes de Grand-mère - Dépuratif du foie

À jeun, dès votre réveil, avalez 1 cuillère à soupe d'huile d'olive "première pression à froid". Pour faciliter l'ingestion de l'huile d'olive, ajoutez quelques gouttes de jus de citron pressé dans la cuillère. 

Sachez que les mauvais aliments pour le foie sont ceux qui ont une haute teneur en graisse, les sauces grasses, les fritures, les pâtisseries et l'alcool. 

Les bons aliments pour le foie sont les artichauts et les pissenlits qui ont le pouvoir de désintoxiquer un foie irrité. Et si vous cherchez les "légumes-miracles" pour le foie, tournez-vous vers les carottes, le cresson, toutes les salades (même cuites), les tomates et les olives. Certains fruits ont aussi des bienfaits sur le foie comme les agrumes, le raisin sec et les pommes.

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ASTRONOMY - The Umbra of Earth

2025 September 11

The Umbra of Earth
Image Credit & Copyright: Wang Letian (Eyes at Night)

Explanation: The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. And on the night of September 7/8 the Full Moon passed near the center of Earth's umbral cone, entertaining eclipse watchers around much of our fair planet, including parts of Antarctica, Australia, Asia, Europe, and Africa. Recorded from Zhangjiakou City, China, this timelapse composite image uses successive pictures from the total lunar eclipse, progressing left to right, to reveal the curved cross-section of the umbral shadow sliding across the Moon. Sunlight scattered by the atmosphere into Earth's umbra causes the lunar surface to appear reddened during totality. But close to the umbra's edge, the limb of the eclipsed Moon shows a distinct blue hue. The blue eclipsed moonlight originates as rays of sunlight pass through layers high in the upper stratosphere, colored by ozone that scatters red light and transmits blue. In the total phase of this leisurely lunar eclipse, the Moon was completely within the Earth's umbra for about 83 minutes.