ASTRONOMY - Cygnus Without Stars

 2020 November 30

Cygnus Without Stars
Image Credit & Copyright: Bowen James Cameron

Explanation: The sky is filled with faintly glowing gas, though it can take a sensitive camera and telescope to see it. For example, this twelve-degree-wide view of the northern part of the constellation Cygnus reveals a complex array of cosmic clouds of gas along the plane of our Milky Way galaxy. The featured mosaic of telescopic images was recorded through two filters: an H-alpha filter that transmits only visible red light from glowing hydrogen atoms, and a blue filter that transmits primarily light emitted by the slight amount of energized oxygen. Therefore, in this 18-hour exposure image, blue areas are hotter than red. Further digital processing has removed the myriad of point-like Milky Way stars from the scene. Recognizable bright nebulas include NGC 7000 (North America Nebula), and IC 5070 (Pelican Nebula) on the left with IC 1318 (Butterfly Nebula) and NGC 6888 (Crescent Nebula) on the right -- but others can be found throughout the wide field.

Astronomy - Verona Rupes: Tallest Known Cliff in the Solar System

 2020 November 29

Verona Rupes: Tallest Known Cliff in the Solar System
Image Credit: Voyager 2, NASA

Explanation: Could you survive a jump off the tallest cliff in the Solar System? Quite possibly. Verona Rupes on Uranus' moon Miranda is estimated to be 20 kilometers deep -- ten times the depth of the Earth's Grand Canyon. Given Miranda's low gravity, it would take about 12 minutes for a thrill-seeking adventurer to fall from the top, reaching the bottom at the speed of a racecar -- about 200 kilometers per hour. Even so, the fall might be survivable given proper airbag protection. The featured image of Verona Rupes was captured by the passing Voyager 2 robotic spacecraft in 1986. How the giant cliff was created remains unknown, but is possibly related to a large impact or tectonic surface motion.

Astronomy - NGC 6822: Barnard's Galaxy

 2020 November 28

NGC 6822: Barnard's Galaxy
Image Credit & Copyright: Data - Martin Pugh, Processing - Mark Hanson

Explanation: Grand spiral galaxies often seem to get all the glory, flaunting their young, bright, blue star clusters in beautiful, symmetric spiral arms. But small galaxies form stars too, like nearby NGC 6822, also known as Barnard's Galaxy. Beyond the rich starfields in the constellation Sagittarius, NGC 6822 is a mere 1.5 million light-years away, a member of our Local Group of galaxies. A dwarf irregular galaxy similar to the Small Magellanic Cloud, NGC 6822 is about 7,000 light-years across. Brighter foreground stars in our Milky Way have a spiky appearance. Behind them, Barnard's Galaxy is seen to be filled with young blue stars and mottled with the telltale pinkish hydrogen glow of star forming regions in this deep color composite image.

Astronomy - Chang'e 5 Mission Launch

 2020 November 27

Chang'e 5 Mission Launch
Image Credit & Copyright: Jeff Dai (TWAN)

Explanation: This Long March-5 rocket blasted off from the Wenchang launch site in southernmost Hainan province on Tuesday November 24, at 4:30 am Beijing Time, carrying China's Chang'e-5 mission to the Moon. The lunar landing mission is named for the ancient Chinese goddess of the moon. Its goal is to collect about 2 kilograms (4.4 pounds) of lunar material from the surface and return it to planet Earth, the first robotic sample return mission to the Moon since the Soviet Union's Luna 24 mission in 1976. The complex Chang'e-5 mission landing target is in the Oceanus Procellarum (Ocean of Storms). The smooth volcanic plain was also visited by the Apollo 12 mission in 1969. Chang'e-5's lander is solar-powered and scheduled to operate on the lunar surface during its location's lunar daylight, which will last about two Earth weeks, beginning around November 27. A capsule with the lunar sample on board would return to Earth in mid-December.

Astronomy - The Helix Nebula from CFHT

2020 November 24

The Helix Nebula from CFHT
Image Credit & Copyright: CFHT, Coelum, MegaCam, J.-C. Cuillandre (CFHT) & G. A. Anselmi (Coelum)

Explanation: Will our Sun look like this one day? The Helix Nebula 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 outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. 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 Helix Nebula, given a technical designation of NGC 7293, lies about 700 light-years away towards the constellation of the Water Bearer (Aquarius) and spans about 2.5 light-years. The featured picture was taken with the Canada-France-Hawaii Telescope (CFHT) located atop a dormant volcano in Hawaii, USA. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin. 

Batteries : faut-il les vider intégralement pour qu'elles durent plus longtemps ?

Il existe de nombreuses idées pour faire durer les batteries le plus longtemps possible. Mais la croyance selon laquelle il faudrait vider entièrement une batterie pour la préserver n'est plus vraie pour les dispositifs actuels.

Tenace, cette injonction n'en est pas moins dépassée aujourd'hui. Dans les anciennes batteries nickel-cadmium ou nickel-hydrure métallique, des réactions secondaires provoquaient la formation d'alliages parasites qui détournaient petit à petit les espèces chimiques nécessaires au bon fonctionnement d'une batterie et dégradaient ses performances.

Pour y remédier, il convenait donc d'opérer régulièrement une décharge profonde afin de dissoudre les matériaux indésirables.

Cependant, dans les batteries lithium-ions, les plus courantes aujourd'hui, ces réactions parasites n'ont plus cours. La façon dont une batterie est chargée ou déchargée n'a donc plus aucun effet sur son vieillissement.

Science & Vie

Astronomy - A Jupiter Vista from Juno

 2020 November 23

A Jupiter Vista from Juno
Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill;

Explanation: Why do colorful cloud bands encircle Jupiter? Jupiter's top atmospheric layer is divided into light zones and dark belts that go all the way around the giant planet. It is high horizontal winds -- in excess of 300 kilometers per hour -- that cause the zones to spread out planet-wide. What causes these strong winds remains a topic of research. Replenished by upwelling gas, zonal bands are thought to include relatively opaque clouds of ammonia and water that block light from lower and darker atmospheric levels. One light-colored zone is shown in great detail in the featured vista taken by the robotic Juno spacecraft in 2017. Jupiter's atmosphere is mostly clear and colorless hydrogen and helium, gases that are not thought to contribute to the gold and brown colors. What compounds create these colors is another active topic of research -- but is hypothesized to involve small amounts of sunlight-altered sulfur and carbon. Many discoveries have been made from Juno's data, including that water composes an unexpectedly high 0.25 percent of upper-level cloud molecules near Jupiter's equator, a finding important not only for understanding Jovian currents but for the history of water in the entire Solar System.

Astronomy - Dark Molecular Cloud Barnard 68

 2020 November 22

Dark Molecular Cloud Barnard 68
Image Credit: FORS Team, 8.2-meter VLT Antu, ESO

Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured here. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.

Astronomy - Global Map: Mars at Opposition

 2020 November 20

Global Map: Mars at Opposition
Image Credit & Copyright: F. Colas / J.L. Dauvergne / G. Dovillaire / T. Legault /
G. Blanchard / B. Gaillard / D. Baratoux / A, Klotz / S2P / IMCCE / OMP / Imagine Optic

Explanation: This may be the best global Mars map made with a telescope based on planet Earth. The image data were captured by a team of observers over six long nights at the Pic du Midi mountaintop observatory between October 8 and November 1, when the fourth rock from the Sun had not wandered far from its 2020 opposition and its biggest and brightest appearance in Earth's night sky. The large telescope used, 1 meter in diameter with a 17 meter focal length, was also used in support of NASA's Apollo lunar landing missions. After about 30 hours of processing, the data were combined to produced this remarkably sharp projected view of the martian surface extending to about 45 degrees northern latitude. The image data have also been mapped onto a rotating sphere and rotating stereo, views. Fans of Mars can easily pick out their favorite markings on the Red Planet by eyeing a labeled version of this global map of Mars.

Astronomy - The Tarantula Zone

 2020 November 13

The Tarantula Zone
Image Credit & Copyright: Ignacio Diaz Bobillo

Explanation: The Tarantula Nebula, also known as 30 Doradus, is more than a thousand light-years in diameter, a giant star forming region within nearby satellite galaxy the Large Magellanic Cloud. About 180 thousand light-years away, it's the largest, most violent star forming region known in the whole Local Group of galaxies. The cosmic arachnid sprawls across the top of this spectacular view, composed with narrowband filter data centered on emission from ionized hydrogen and oxygen atoms. Within the Tarantula (NGC 2070), intense radiation, stellar winds and supernova shocks from the central young cluster of massive stars, cataloged as R136, energize the nebular glow and shape the spidery filaments. Around the Tarantula are other star forming regions with young star clusters, filaments, and blown-out bubble-shaped clouds. In fact, the frame includes the site of the closest supernova in modern times, SN 1987A, right of center. The rich field of view spans about 2 degrees or 4 full moons, in the southern constellation Dorado. But were the Tarantula Nebula closer, say 1,500 light-years distant like the local star forming Orion Nebula, it would take up half the sky.

Astronomy - Comet ATLAS and Orion's Belt

 2020 November 12

Comet ATLAS and Orion's Belt
Image Credit & Copyright: Charles Bracken

Explanation: With its closest approach to planet Earth scheduled for November 14, this Comet ATLAS (C/2020 M3) was discovered just this summer, another comet found by the NASA funded Asteroid Terrestrial-impact Last Alert System. It won't get as bright as Comet NEOWISE but it can still be spotted using binoculars, as it currently sweeps through the familiar constellation of Orion. This telephoto field from November 8, blends exposures registered on the comet with exposures registered on Orion's stars. It creates an effectively deep skyview that shows colors and details you can't quite see though, even in binoculars. The comet's telltale greenish coma is toward the upper left, above Orion's three belt stars lined-up across the frame below center. You'll also probably spot the Orion Nebula, and famous Horsehead Nebula in the stunning field of view. Of course one of Orion's belt stars is nearly 2,000 light-years away. On November 14, this comet ATLAS will fly a mere 2.9 light-minutes from Earth.

Astronomy - Colors of the moon

 2020 November 11

Colors of the Moon
Image Credit & Copyright: Marcella Giulia Pace

Explanation: What color is the Moon? It depends on the night. Outside of the Earth's atmosphere, the dark Moon, which shines by reflected sunlight, appears a magnificently brown-tinged gray. Viewed from inside the Earth's atmosphere, though, the moon can appear quite different. The featured image highlights a collection of apparent colors of the full moon documented by one astrophotographer over 10 years from different locations across Italy. A red or yellow colored moon usually indicates a moon seen near the horizon. There, some of the blue light has been scattered away by a long path through the Earth's atmosphere, sometimes laden with fine dust. A blue-colored moon is more rare and can indicate a moon seen through an atmosphere carrying larger dust particles. What created the purple moon is unclear -- it may be a combination of several effects. The last image captures the total lunar eclipse of 2018 July -- where the moon, in Earth's shadow, appeared a faint red -- due to light refracted through air around the Earth. The next full moon will occur at the end of this month (moon-th) and is known in some cultures as the Beaver Moon.

Astronomie - The Central Soul Nebula Without Stars

 2020 November 10

The Central Soul Nebula Without Stars
Image Credit & Copyright: Jason Guenzel

Explanation: This cosmic close-up looks deep inside the Soul Nebula. The dark and brooding dust clouds near the top, outlined by bright ridges of glowing gas, are cataloged as IC 1871. About 25 light-years across, the telescopic field of view spans only a small part of the much larger Heart and Soul nebulae. At an estimated distance of 6,500 light-years the star-forming complex lies within the Perseus spiral arm of our Milky Way Galaxy, seen in planet Earth's skies toward the constellation Cassiopeia. An example of triggered star formation, the dense star-forming clouds in the Soul Nebula are themselves sculpted by the intense winds and radiation of the region's massive young stars. In the featured image, stars have been digitally removed to highlight the commotion in the gas and dust.

Adstronomy - In Green Company: Aurora over Norway

 2020 November 9

In Green Company: Aurora over Norway
Image Credit & Copyright: Max Rive

Explanation: Raise your arms if you see an aurora. With those instructions, two nights went by with, well, clouds -- mostly. On the third night of returning to same peaks, though, the sky not only cleared up but lit up with a spectacular auroral display. Arms went high in the air, patience and experience paid off, and the creative featured image was captured as a composite from three separate exposures. The setting is a summit of the Austnesfjorden fjord close to the town of Svolvear on the Lofoten islands in northern Norway. The time was early 2014. Although our Sun has just passed the solar minimum of its 11-year cycle, surface activity should pick up over the next few years with the promise of triggering more spectacular auroras on Earth.

 2020 November 8

Martian Moon Phobos from Mars Express
Image Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA; Acknowledgement: Peter Masek

Explanation: Why is Phobos so dark? Phobos, the largest and innermost of two Martian moons, is the darkest moon in the entire Solar System. Its unusual orbit and color indicate that it may be a captured asteroid composed of a mixture of ice and dark rock. The featured picture of Phobos near the limb of Mars was captured in 2010 by the robot spacecraft Mars Express currently orbiting Mars. Phobos is a heavily cratered and barren moon, with its largest crater located on the far side. From images like this, Phobos has been determined to be covered by perhaps a meter of loose dust. Phobos orbits so close to Mars that from some places it would appear to rise and set twice a day, but from other places it would not be visible at all. Phobos' orbit around Mars is continually decaying -- it will likely break up with pieces crashing to the Martian surface in about 50 million years.

Astronomy - Moon over ISS

 2020 November 6

Moon over ISS
Image Credit & Copyright: Derek Demeter (Emil Buehler Planetarium)

Explanation: Completing one orbit of our fair planet in 90 minutes the International Space Station can easily be spotted by eye as a very bright star moving through the night sky. Have you seen it? The next time you do, you will have recognized the location of over 20 years of continuous human presence in space. In fact, the Expedition 1 crew to the ISS docked with the orbital outpost some 400 kilometers above the Earth on November 2, 2000. No telescope is required to spot the ISS flashing through the night. But this telescopic field of view does reveal remarkable details of the space station captured as it transited the waning gibbous moon on November 3, just one day after the space age milestone. The well-timed telescopic snapshot also contains the location of another inspirational human achievement. About 400,000 kilometers away, the Apollo 11 landing site on the dark, smooth lunar Sea of Tranquility is to the right of the ISS silhouette.

Astronomy - North of Orion's Belt

 2020 November 5

North of Orion's Belt
Image Credit & Copyright: Terry Hancock (Grand Mesa Observatory)

Explanation: Bright stars, interstellar clouds of dust and glowing nebulae fill this cosmic scene, a skyscape just north of Orion's belt. Close to the plane of our Milky Way Galaxy, the wide field view spans just under 5 degrees or about 10 full moons on the sky. Striking bluish M78, a reflection nebula, is at the lower right. M78's tint is due to dust preferentially reflecting the blue light of hot, young stars. In colorful contrast, the red swath of glowing hydrogen gas streaming through the center is part of the region's faint but extensive emission nebula known as Barnard's Loop. At upper left, a dark dust cloud forms a prominent silhouette cataloged as LDN 1622. While M78 and the complex Barnard's Loop are some 1,500 light-years away, LDN 1622 is likely to be much closer, only about 500 light-years distant from our fair planet Earth.

Astronomy - Fifty Gravitational Wave Events Illustrated

 2020 November 4

Fifty Gravitational Wave Events Illustrated
Image Credit: LIGO Virgo Collaborations, Frank Elavsky, Aaron Geller, Northwestern U.

Explanation: Over fifty gravitational wave events have now been detected. These events mark the distant, violent collisions of two black holes, a black hole and a neutron star, or two neutron stars. Most of the 50 events were detected in 2019 by the LIGO gravitational wave detectors in the USA and the VIRGO detector in Europe. In the featured illustration summarizing the masses of the first 50 events, blue dots indicate higher-mass black holes while orange dots denote lower-mass neutron stars. Astrophysicists are currently uncertain, though, about the nature of events marked in white involving masses that appear to be in the middle -- between two and five solar masses. The night sky in optical light is dominated by nearby and bright planets and stars that have been known since the dawn of humanity. In contrast, the sky in gravitational waves is dominated by distant and dark black holes that have only been known about for less than five years. This contrast is enlightening -- understanding the gravitational wave sky is already reshaping humanity's knowledge not only of star birth and death across the universe, but properties of the universe itself.

Astronomy picture of the day - Tagging Bennu: The Movie

 2020 November 3

Tagging Bennu: The Movie
Video Credit: OSIRIS-REx, NASA's GSFC, U. Arizona, Lockheed Martin

Explanation: This is what it looks like to punch an asteroid. Last month, NASA's robotic spacecraft OSIRIS-REx descended toward, thumped into, and then quickly moved away from the small near-Earth asteroid 101955 Bennu. The featured video depicts the Touch-And-Go (TAG) sampling event over a three-hour period. As the movie begins, the automated probe approaches the 500-meter, diamond-shaped, space rock as it rotates noticeably below. About 20 seconds into the video, Nightingale comes into view -- a touchdown area chosen to be relatively flat and devoid of large boulders that could damage the spaceship. At 34 seconds, the shadow of OSIRIS-REx's sampling arm suddenly comes into view, while very soon thereafter rocks and gravel fly from the arm's abrupt hard impact. The wily spacecraft was able to capture and successfully stow some of Bennu's ejecta for return to Earth for a detailed analysis. This long return is scheduled to start in 2021 March with arrival back on Earth in 2023 September. If the return sample does successfully reach Earth, it will be scrutinized for organic compounds that might have seeded a young Earth, rare or unusual elements and minerals, and clues about the early history of our Solar System.

Astronomy picture of the day - Half Sun with Prominence

 2020 November 2

Half Sun with Prominence
Image Credit & Copyright: Rainee Colacurcio

Explanation: What's happening to the Sun? Clearly, the Sun's lower half is hidden behind a thick cloud. Averaging over the entire Earth, clouds block the Sun about 2/3rds of the time, although much less over many land locations. On the Sun's upper right is a prominence of magnetically levitating hot gas. The prominence might seem small but it could easily envelop our Earth and persist for over a month. The featured image is a combination of two exposures, one optimizing the cloud and prominence, and the other optimizing the Sun's texture. Both were taken about an hour apart with the same camera and from the same location in Lynnwood, Washington, USA. The shaggy texture derives from the Sun's chromosphere, an atmospheric layer that stands out in the specifically exposed color. The uniformity of the texture shows the surface to be relatively calm, indicative of a Sun just past the solar minimum in its 11-year cycle. In the years ahead, the Sun will progress toward a more active epoch where sunspots, prominences, and ultimately auroras on Earth will be more common: solar maximum.

Astronomy picture of the day - In the Center of the Trifid Nebula

 2020 November 1

In the Center of the Trifid Nebula
Image Credit: Subaru Telescope (NAOJ), Hubble Space Telescope, Martin Pugh; Processing: Robert Gendler

Explanation: What's happening at the center of the Trifid Nebula? Three prominent dust lanes that give the Trifid its name all come together. Mountains of opaque dust appear near the bottom, while other dark filaments of dust are visible threaded throughout the nebula. A single massive star visible near the center causes much of the Trifid's glow. The Trifid, cataloged as M20, is only about 300,000 years old, making it among the youngest emission nebulas known. The star forming nebula lies about 9,000 light years away toward the constellation of the Archer (Sagittarius). The region pictured here spans about 10 light years. The featured image is a composite with luminance taken from an image by the 8.2-m ground-based Subaru Telescope, detail provided by the 2.4-m orbiting Hubble Space Telescope, color data provided by Martin Pugh and image assembly and processing provided by Robert Gendler.

Belezas de Braga - Jardim de Santa Bárbara

 

Envolvendo a fonte com a estátua da santa que dá nome ao lugar, o Jardim de Santa Bárbara é situado no centro histórico de Braga e abriga variedades de flores e vegetação bem cuidadas.

O ambiente, assim, é agradável, um dos melhores lugares turísticos de Braga para tomar sol e tirar fotos.

Junto aos muros da ala medieval do Paço Episcopal Bracarense, o jardim ganha vida até de noite, com iluminação que deixa o cenário de flores e muralha medieval ainda mais bonito.

Un avion promet de réduire la pollution des voyages d'affaires

 

La forme ovoïde du Celera 500L permet de diviser la consommation de carburant par 8 et les émissions carbone de 80% par rapport à un avion similaire. Il devrait rentrer en service en 2025.

L'un des problèmes des avions est leur consommation de carburant. Afin de la réduire, la société américaine Otto Aviation a misé sur l'aérodynamisme. La forme ovoïde de son avion d'affaire Celera 500L permet de diviser cette consommation par huit et ses émissions en carbone de 80% par rapport à un avion similaire !

Science & Vie