Science & Technologie - Aeronautique - Avions du futur : L'Aeroscraft ML 866, un dirigeable de luxe

Le dirigeable joue l'éternel retour : économique, spacieux et capable d'emporter d'énormes charges, il présente de bons atouts. Mais il a aussi quelques défauts : il est lent, difficile à manœuvrer (surtout par grand vent) et il est vraiment très encombrant. L'idée reste cependant toujours valable, notamment pour des transports de fret et pour des missions de surveillance. L'entreprise Aeros, spécialiste du domaine, a présenté un projet pour une sorte de yacht aérien de luxe, l'Aeroscraft ML 866. Son avenir est incertain mais il illustre la persistance de l'idée d'utiliser des « aéronefs » plus légers que l'air. 

© Aeros

Science & Technologie - Aeronautique - Avions du futur : le retour de l'hélice grâce à l'open rotor ?

Le concept de « rotor ouvert » (open rotor) est à l'étude chez plusieurs motoristes, comme Snecma (du groupe Safran). L'idée n'est pas nouvelle puisqu'elle a été testée, sous le nom de UDF (pour unducted fan), dans les années 1980... et abandonnée. Mais la voilà de nouveau sur les rails, avec l'espoir d'une réduction de la consommation de 25 %.

Comme dans un réacteur double flux actuel, la partie centrale est une turbine qui assure une poussée avec un flux d'air chaud et accéléré. Autour, une « soufflante », entraînée par cette même turbine, fonctionne un peu comme une hélice. Elle produit un flux annulaire autour du flux chaud. Le principe de l'open rotor est d'ôter le carénage du réacteur et d'installer une soufflante prenant la forme de deux propulseurs à pales contrarotatives (tournant en sens inverse). 

© Snecma

Science & Technology - Astronomy picture of the day : M45: The Pleiades Star Cluster

2019 September 1
M45: The Pleiades Star Cluster 
Image Credit & Copyright: Marco Lorenzi (Glittering Lights)

Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured exposure took over 12 hours and covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.

Science & Technology - Astronomy picture of the day : Spitzer's Orion

2019 August 31
Spitzer's Orion 
Image Credit: NASA, JPL-Caltech

Explanation: Few cosmic vistas excite the imagination like the Orion Nebula, an immense stellar nursery some 1,500 light-years away. Spanning about 40 light-years across the region, this infrared image from the Spitzer Space Telescope was constructed from data intended to monitor the brightness of the nebula's young stars, many still surrounded by dusty, planet-forming disks. Orion's young stars are only about 1 million years old, compared to the Sun's age of 4.6 billion years. The region's hottest stars are found in the Trapezium Cluster, the brightest cluster near picture center. Launched into orbit around the Sun on August 25, 2003 Spitzer's liquid helium coolant ran out in May 2009. The infrared space telescope continues to operate though, its mission scheduled to end on January 30, 2020. Recorded in 2010, this false color view is from two channels that still remain sensitive to infrared light at Spitzer's warmer operating temperatures.

Science & Technology - Astronomy picture of the day : NGC 7129 and NGC 7142

2019 August 30
NGC 7129 and NGC 7142 
Image Credit & Copyright: Steve Cannistra (StarryWonders)

Explanation: This wide-field telescopic image looks toward the constellation Cepheus and an intriguing visual pairing of dusty reflection nebula NGC 7129 (right) and open star cluster NGC 7142. The two appear separated by only half a degree on the sky, but they actually lie at quite different distances. In the foreground, dusty nebula NGC 7129 is about 3,000 light-years distant, while open cluster NGC 7142 is likely over 6,000 light-years away. In fact, pervasive and clumpy foreground dust clouds in this region redden the light from NGC 7142, complicating astronomical explorations of the cluster. Still, NGC 7142 is thought to be an older open star cluster, while the bright stars embedded in NGC 7129 are perhaps a few million years young. The telltale reddish crescent shapes around NGC 7129 are associated with energetic jets streaming away from newborn stars.

Science & Technology - Astronomy picture of the day : M27: Not a Comet

2019 August 29
M27: Not a Comet 
Image Credit & Copyright: Bob Franke

Explanation: While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it's not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This impressive color composite highlights details within the well-studied central region and fainter, seldom imaged features in the nebula's outer halo. It incorporates broad and narrowband images recorded using filters sensitive to emission from hydrogen and oxygen atoms.

Science & Technology - Astronomy picture of the day : Messier 61 Close Up

2019 August 28
Messier 61 Close Up 
Image Credit: NASA, ESA, Hubble, ESO, Amateur Data; Processing & Copyright: Robert Gendler & Roberto Colombari

Explanation: Image data from the Hubble Space Telescope, the European Southern Observatory, and small telescopes on planet Earth are combined in this magnificent portrait of face-on spiral galaxy Messier 61 (M61). A mere 55 million light-years away in the Virgo Cluster of Galaxies, M61 is also known as NGC 4303. It's considered to be an example of a barred spiral galaxy similar to our own Milky Way. Like other spiral galaxies, M61 also features sweeping spiral arms, cosmic dust lanes, pinkish star forming regions, and young blue star clusters. The bright galactic core is offset to the left in this 50 thousand light-year wide close-up.

Ciência & Tecnologia - Saude/Medecina : canábis, bom para a saude ?

Investigadores da Universidade de Western Ontário, no Canadá, realizaram um estudo com vista a perceber os diferentes efeitos psicológicos que a canábis provoca nos consumidores. Publicado este mês na revista Scientific Reports, o estudo representa um grande avanço na compreensão dos efeitos da droga no cérebro humano.

A pergunta de partida para a investigação era há muito uma grande dúvida dos cientistas e da população em geral: qual o motivo de algumas pessoas terem emoções positivas como reação ao consumo de canábis e outras demonstrarem emoções negativas.

Segundo Steven Laviolette, um dos autores do estudo, a premissa levou os investigadores para um campo ainda pouco explorado. “Sabemos muito sobre os efeitos a longo e a curto prazo, mas há muito pouco conhecimento sobre as áreas específicas do cérebro que são responsáveis pelo controlo desses efeitos”.

E a resposta pode ter a ver com as diferentes partes do cérebro, em particular, qual das partes é mais sensível ao tetraidrocanabinol (THC), substância psicoativa libertada pela canábis. Em algumas pessoas, a parte do cérebro mais sensível é a frontal e, nesse caso, provoca sentimentos de conforto, tranquilidade e felicidade. Se a parte mais sensível à substância for a região posterior do cérebro, a droga fará a pessoa sentir medo e alguma paranoia infundada.

Esta investigação foi realizada em ratos de laboratório, mas os cientistas acreditam estar muito mais perto da verdade sobre os efeitos da canábis nos seres humanos. O próximo passo passará sobretudo pela experiência relatada por aqueles que consomem.

Visão - Portugal

Science & Technology - Astronomy picture of the day : Dark Dust and Colorful Clouds near Antares

2019 August 27
Dark Dust and Colorful Clouds near Antares 
Image Credit: David McGarvey

Explanation: Why is the sky near Antares and Rho Ophiuchi so dusty yet colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. Backlit dust clouds block starlight and so appear dark. Antares, a red supergiant and one of the brighter stars in the night sky, lights up the yellow-red clouds on the lower left of the featured image. Rho Ophiuchi lies at the center of the blue nebula near the top. The distant globular cluster M4 is visible to the right of Antares. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum.

Music - Live - Video : George Gershwin - Robert Alda, Joan Leslie, Alexis Smith : "Rhapsody in Blue"

"Rhapsody in blue"