SANTé/MEDECINE - Marcher c'est réduire les risques de cancer (1/4)

Et si votre balade quotidienne devenait une arme secrète contre le cancer ? Une étude américaine livre un chiffre surprenant, mais tout à fait accessible.

Vous pensiez qu'il fallait transpirer des heures en salle pour rester en bonne santé ? Détrompez-vous, ce n'est pas forcément le cas. Selon une étude relayée par Le Journal des Femmes, une activité douce, à la portée de toutes et tous, pourrait bien faire baisser significativement les risques de développer certains cancers. Et il ne s'agit pas de suivre un programme sportif intensif, mais d'un geste simple du quotidien : marcher. Mais alors, combien de pas par jour faut-il faire pour se prémunir au mieux du cancer ?

Grazia

(à suivre)

ASTRONOMY - A Helix Nebula Deep Field

 2025 July 29

A Helix Nebula Deep Field
Image Credit & Copyright: George Chatzifrantzis

Explanation: Is the Helix Nebula looking at you? No, not in any biological sense, but it does look quite like an eye. The Helix Nebula is so named because it also appears that you are looking down the axis of a helix. In actuality, it is now understood to have a surprisingly complex geometry, including radial filaments and extended outer loops. The Helix Nebula (aka NGC 7293) is one of brightest and closest examples of a planetary nebula, a gas cloud created at the end of the life of a Sun-like star. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The featured picture, taken in red, green, and blue but highlighted by light emitted primarily by hydrogen was created from 12 hours of exposure through a personal telescope located in Greece. A close-up of the inner edge of the Helix Nebula shows complex gas knots the origin of which are still being researched.

ASTRONOMY - Collision at Asteroid Dimorphos

2025 july 28

Collision at Asteroid Dimorphos

Video Credit: ASI NASA, Johns Hopkins APL, DART, LICIACube, LUKE, IOP

Explanation: Why was this collision so strange? In 2022, to develop Earth-saving technology, NASA deliberately crashed the DART spacecraft into the asteroid moonlet Dimorphos. The hope was that this collision would alter the trajectory of Dimorphos around its parent asteroid Didymos and so demonstrate that similar collisions could, in theory, save the Earth from being hit by (other) hazardous asteroids. But analyses of new results show that the effects of the collision are different than expected -- and we are trying to understand why. Featured here is the time lapse video taken by the ejected LICIACube camera LUKE showing about 250 seconds of the expanding debris field of Dimorphos after the collision, with un-impacted Didymos passing in the foreground. In 2026, Europe's Hera mission will reach the asteroids and release three spacecraft to better study the matter.

ASTRONOMY - Lightning over the Volcano of Water

2025 July 27

Lightning over the Volcano of Water
Image Credit: Sergio Montúfar (Pinceladas Nocturnas)

Explanation: Have you ever watched a lightning storm in awe? You're not alone. Details of what causes lightning are still being researched, but it is known that inside some clouds, internal updrafts cause collisions between ice and snow that slowly separate charges between cloud tops and bottoms. The rapid electrical discharges that are lightning soon result. Lightning usually takes a jagged course, rapidly heating a thin column of air to about three times the surface temperature of the Sun. The resulting shock wave starts supersonically and decays into the loud sound known as thunder. On average, around the world, about 6,000 lightning bolts occur between clouds and the Earth every minute. Pictured in July 2019 in a two-image composite, lightning stems from communication antennas near the top of Volcán de Agua (Volcano of Water) in Guatemala. 

MUSIQUE - Jean-Sébastien Bach - Canon de Pachelbel

"Pachelbel's canon"

ASTRONOMY - Globular Cluster Omega Centauri

 2025 July 26

Globular Cluster Omega Centauri
Image Credit & Copyright: Data acquisition - SkyFlux Team, Processing - Leo Shatz

Explanation: Globular star cluster Omega Centauri packs about 10 million stars much older than the Sun into a volume some 150 light-years in diameter. Also known as NGC 5139, at a distance of 15,000 light-years it's the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. With a yellowish hue, Omega Centauri's red giant stars are easy to pick out in this sharp telescopic view. A two-decade-long exploration of the dense star cluster with the Hubble Space Telescope has revealed evidence for a massive black hole near the center of Omega Centauri.

SANTé/MEDECINE - Les bénéfices de la marche pour le corps

Une révolution douce pour la santé

Si l’on en croit le spécialiste Dr. Manan Vora, la marche quotidienne représente l’un des exercices les plus simples mais aussi les plus efficaces pour améliorer durablement sa santé. Installé à Mumbai, cet orthopédiste et expert en médecine du sport partage régulièrement ses conseils à ses 450 000 abonnés sur Instagram. Récemment, il a détaillé dans une vidéo comment chaque minute passée à marcher transforme notre organisme, cumulant des effets bénéfiques étonnants au fil du temps.

L’effet immédiat de la marche sur le corps

Dès la première minute, le corps réagit : la circulation sanguine s’active, apportant un surplus d’oxygène et de nutriments essentiels vers muscles et organes. Passés cinq minutes, le moral s’améliore nettement grâce à l’afflux d’endorphines – ces fameuses «hormones du bonheur » –, offrant une sensation rapide de bien-être.

À dix minutes, le niveau de cortisol, hormone du stress, commence à chuter, permettant ainsi d’alléger rapidement les tensions accumulées. Quinze minutes suffisent pour que la marche contribue à réguler le glucose sanguin : un atout indéniable dans la gestion du diabète ou la prévention des pics glycémiques après les repas.

Les bénéfices qui s’accumulent avec la durée

Mais l’intérêt ne s’arrête pas là. Selon le Dr Vora, trente minutes de marche enclenchent un processus de combustion des graisses : c’est ici que le corps «commence à puiser dans ses réserves ». Une donnée précieuse pour celles et ceux qui cherchent à perdre du poids ou à améliorer leur composition corporelle. D’ailleurs, une étude menée en 2017 confirmait déjà que marcher modérément renforçait les effets d’un régime hypocalorique sur la perte de masse grasse et l’amélioration des marqueurs de risque cardiovasculaire.

En poursuivant jusqu’à quarante-cinq minutes, il devient possible d’apaiser l’esprit et d’interrompre les ruminations mentales : marcher longtemps calme littéralement le cerveau. Enfin, atteindre soixante minutes offre un dernier cadeau – non négligeable : un pic de dopamine, neurotransmetteur associé au plaisir et à la motivation.

Voici ce que retient le Dr Vora pour résumer ces bienfaits croissants :

・Dès quelques pas, circulation et humeur sont stimulées.

・À partir de 10-15 minutes, gestion du stress et du sucre s’améliore.

・Au-delà d’une demi-heure, perte de poids et équilibre mental deviennent tangibles.

ActusanteNet

ASTRONOMY - Twelve Years of Kappa Cygnids

 2025 July 25

Twelve Years of Kappa Cygnids
Image Credit & Copyright: Petr Horálek, Josef Kujal, Tomáš Slovinský; Acknowledgement: Mahdi Zamani

Explanation: Meteors from the Kappa Cygnid meteor shower are captured in this time-lapse composite skyscape. The minor meteor shower, with a radiant not far from its eponymous star Kappa Cygni, peaks in mid-August, almost at the same time as the much better-known and better-observed Perseid meteor shower. But, seen to have a peak rate of only about 3 meteors per hour, Kappa Cygnids are vastly outnumbered by the more popular, prolific Perseid shower's meteors that emanate from the heroic constellation Perseus. To capture dozens of Kappa Cygnids, this long term astro-imaging project compiled meteors in exposures selected from over 51 August nights during the years 2012 through 2024. Most of the exposures with identified Kappa Cygnid meteors were made in August 2021, a high point of the shower's known 7-year activity cycle. All twelve years worth of Kappa Cygnids are registered against a base sea and night skyscape of the Milky Way above Elafonisi Beach, Crete, Greece, also recorded in August of 2021.

ASTRONOMY - Titan Shadow Transit

 2025 July 24

Titan Shadow Transit
Image Credit & Copyright: Volodymyr Andrienko

Explanation: Every 15 years or so, Saturn's rings are tilted edge-on to our line of sight. As the bright, beautiful ring system grows narrower and fainter it becomes increasingly difficult to see for denizens of planet Earth. But it does provide the opportunity to watch transits of Saturn's moons and their dark shadows across the ringed gas giant's still bright disk. Of course Saturn's largest moon Titan is the easiest to spot in transit. In this telescopic snapshot from July 18, Titan itself is at the upper left, casting a round dark shadow on Saturn's banded cloudtops above the narrow rings. In fact Titan's transit season is in full swing now with shadow transits every 16 days corresponding to the moon's orbital period. Its final shadow transit will be on October 6, though Titan's pale disk will continue to cross in front of Saturn as seen from telescopes on planet Earth every 16 days through January 25, 2026.

ASTRONOMY - Fireball over Cape San Blas

2025 July 23

Fireball over Cape San Blas
Image Credit & Copyright: Jason Rice

Explanation: Have you ever seen a fireball? In astronomy, a fireball is a very bright meteor -- one at least as bright as Venus and possibly brighter than even a full Moon. Fireballs are rare -- if you see one you are likely to remember it for your whole life. Physically, a fireball is a small rock that originated from an asteroid or comet that typically leaves a fading smoke trail of gas and dust as it shoots through the Earth's atmosphere. It is unlikely that any single large ground strike occurred -- much of the rock likely vaporized as it broke up into many small pieces. The featured picture was captured last week from a deadwood beach in Cape San Blas, Florida, USA.