Science & Technology - Astronomy picture of the day : MyCn 18: The Engraved Hourglass Planetary Nebula

2019 September 29
MyCn 18: The Engraved Hourglass Planetary Nebula Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt

Explanation: Do you see the hourglass shape -- or does it see you? If you can picture it, the rings of MyCn 18 trace the outline of an hourglass -- although one with an unusual eye in its center. Either way, the sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this brief, spectacular, closing phase of a Sun-like star's life occurs as its outer layers are ejected - its core becoming a cooling, fadingwhite dwarf. In 1995, astronomers used the Hubble Space Telescope (HST) to make a series of images of planetary nebulae, including the one featured here. Pictured, delicate rings of colorful glowing gas (nitrogen-red, hydrogen-green, and oxygen-blue) outline the tenuous walls of the hourglass. The unprecedented sharpness of the Hubble images has revealed surprising details of the nebula ejection process that are helping to resolve the outstanding mysteries of the complex shapes and symmetries of planetary nebulas like MyCn 18.

Science & Technology - Astronomy picture of the day : An Analemma of the Sun

2019 September 28
An Analemma of the Sun 
Image Credit & Copyright: Gyorgy Soponyai

Explanation: This week the equinox found the Sun near the middle, but not at the crossing point, of an analemma in its annual trek through planet Earth's skies. In this scenic view, that graceful, figure-8-shaped curve was intentionally posed above the iconic Danube River and the capital city of Hungary. Looking south from Budapest's Margaret Bridge it combines digital frames taken at exactly the same time of day (11:44 CET) on dates between 2018 September 24 and 2019 September 15. That puts the metropolitan Pest on the left, regal Buda on the right, and the positions of the Sun on the solstice dates at the top and bottom of the analemma curve. December's near solstice Sun is just hidden behind a dramatic cloud bank.

Science & Technology - Astronomy picture of the day : Da Vinci Rise

2019 September 26
Da Vinci Rise 
Image Credit & Copyright: Likai Lin

Explanation: An old Moon rose this morning, its waning sunlit crescent shining just above the eastern horizon before sunrise. But earthshine, light reflected from a bright planet Earth, lit the shadowed portion of the lunar disk and revealed most of a familiar lunar near side to early morning risers. In fact, a description of earthshine in terms of sunlight reflected by Earth's oceans illuminating the Moon's dark surface was written over 500 years ago by Leonardo da Vinci. One lunation ago this old Moon also rose above the eastern horizon. Its sunlit crescent and da Vinci glow were captured in stacked exposures from the Badain Jilin Desert of Inner Mongolia, China on August 29, 2019. This year marks the 500th anniversary of Leondardo da Vinci's death.

Science & Technology - Astronomy picture of the day : The Pelican Nebula in Gas, Dust, and Stars

2019 September 25
The Pelican Nebula in Gas, Dust, and Stars 
Image Credit & Copyright: Yannick Akar

Explanation: The Pelican Nebula is slowly being transformed. IC 5070, the official designation, is divided from the larger North America Nebula by a molecular cloud filled with dark dust. The Pelican, however, receives much study because it is a particularly active mix of star formation and evolving gas clouds. The featured picture was produced in three specific colors -- light emitted by sulfur, hydrogen, and oxygen -- that can help us to better understand these interactions. The light from young energetic stars is slowly transforming the cold gas to hot gas, with the advancing boundary between the two, known as an ionization front, visible in bright orange on the right. Particularly dense tentaclesof cold gas remain. Millions of years from now this nebula might no longer be known as the Pelican, as the balance and placement of stars and gas will surely leave something that appears completely different.

Science & Technologie - Aeronautique - Avions du futur ? :Hoax : le Boeing 797, un vrai-faux projet d'avion géant

Le concept de Boeing X48 BWB (Blended Wing Body, fuselage porteur) a inspiré des plaisantins qui ont utilisé cette image publiée dans la revue Popular Science pour annoncer, au moment de la présentation de l'Airbus A380, ce « Boeing 797 » qui pourrait embarquer un millier de passagers. Il s'agissait d'un canular (ou hoax) mais la réalité pourrait un jour rattraper la fiction... 

© DR

Science & Technologie - Santé : Comment lire son analyse de sang - Taux du cholestérol sanguin - 1 de 10

Le sang est une véritable mine d'informations sur l'état de santé. L'analyse de sang permet tout à la fois de surveiller une maladie chronique, de vérifier que tout va bien avant une opération ou de rechercher le dysfonctionnement d'un organe.

Seulement, entre l'hémogramme, la vitesse de sédimentation et les autres paramètres, il y a de quoi s'y perdre ! D'autant que les normes peuvent varier entre les laboratoires. "Ce sont des moyennes, explique le Dr Isabelle Bernard, médecin-biologiste. Elles peuvent être légèrement différentes d'un laboratoire à l'autre : tout dépend des techniques utilisées."stérol sanguin

C'est la quantité de graisses (lipoprotéines) circulant dans le sang. La mesure du cholestérol total est suffisante pour un contrôle de base. Pour une analyse plus fine, le biologiste dose les substances qui transportent le cholestérol dans le sang : les HDL (high density lipoproteine) correspondent au "bon" cholestérol, les LDL (low density lipoproteine) au "mauvais". Ce sont les LDL qui se déposent sur les parois des artères et qui sont facteurs de troubles. Le rapport cholestérol total/HDL permet d'évaluer le risque cardio-vasculaire.

Le taux est élevé

Le patient présente un risque de maladie cardio-vasculaire.

Le taux est bas

Une valeur trop faible n'est pas normale non plus. C'est le signe d'un trouble hormonal ou d'une malnutrition.

Valeur normale du cholestérol total : inférieure à 2 g/l.

Santé Magazine - France

Science & Technologie - Astronomie - Équinoxe d'automne

Le terme « équinoxe » vient du latin æquinoctium, qui lie æequs (égal) à nox (nuit), et désigne le moment où la durée du jour est égale à celle de la nuit.

Pour l'équinoxe de septembre, cela se produit le 20 et le 23 du mois selon les années (l'été de l'hémisphère Nord est plus long que celui de l'hémisphère austral).

Schéma explicatif des équinoxes et des saisons sur notre planète. © Wikimedia Commons, DP 

Le début de l'automne dans l'hémisphère Nord

Pour les habitants de l'hémisphère Nord, cette date marque le début de l'automne. Les jours continuent de diminuer jusqu'au solstice d'hiver, le 21 décembre, date de la fin de l'automne. En revanche, dans l'hémisphère Sud, c'est le printemps qui arrive. La longueur des jours augmente jusqu'au solstice d'été, le 21 décembre.

À gauche : la Terre lors des deux solstices. À droite : la Terre lors des deux équinoxes. Pour ceux-ci, on constate que les deux hémisphères sont éclairés de la même façon. Images du satellite Meteosat-9 prises en 2011. © Eumetsat.

L'équinoxe de septembre se produit lorsque, du point de vue de la Terre, nous observons que le Soleil atteint le point (ou nœuds) à l'intersection du plan de l'écliptique où il chemine - le plan de l'orbite des planètes - et de l'équateur céleste (projection dans le ciel de l'équateur terrestre). L'astre du jour passe alors dans la moitié sud de la voûte céleste. Étant donné que notre planète est penchée, l'équateur céleste croise par deux fois le plan de l'écliptique.

Vu du Soleil, lors des deux équinoxes, la Planète bleue apparaît éclairée de façon égale dans ses deux hémisphères.

Music - Slides - Video - Schubert : "Serenade"

"Serenade"

Music - Slides - Video - Ernesto Cortazar : "Remembrance (Autumn song)"

"Remembrance (Autumn song)"

Science & Technology - Astronomy picture of the day : Eye Sky a Dragon

2019 September 22
Eye Sky a Dragon 
Image Credit & Copyright: Anton Komlev

Explanation: What do you see when you look into this sky? In the center, in the dark, do you see a night sky filled with stars? Do you see a sunset to the left? Clouds all around? Do you see the central band of our Milky Way Galaxy running down the middle? Do you see the ruins of an abandoned outpost on a hill? (The outpost is on Askold Island, Russia.) Do you see a photographer with a headlamp contemplating surreal surroundings? (The image is a panorama of 38 images taken last month and compiled into a Little Planet projection.) Do you see a rugged path lined with steps? Or do you see the eye of a dragon?

Science & Technology - Astronomy picture of the day : Atlas at Dawn

2019 September 21
Atlas at Dawn 
Image Credit & Copyright: Michael Seeley

Explanation: This single, 251-second long exposure follows the early flight of an Atlas V rocket on August 8, streaking eastward toward the dawn from Cape Canaveral Air Force Station, planet Earth. The launch of the United Launch Alliance rocket was at 6:13am local time. Sunrise was not until 6:48am, but the rocket's downrange plume at altitude is brightly lit by the Sun still just below the eastern horizon. Waters of the Indian River Lagoon in Palm Shores, Forida reflect subtle colors and warming glow of the otherwise calm, predawn sky. The mighty Atlas rocket carried a military communications satellite into Earth orbit. Of course, this weekend the streaks you see in clear skies before the dawn could be Perseid Meteors.

Science & Technology - Astronomy picture of the day : Saturn at Night

2019 September 20
Saturn at Night 
Image Credit: NASA, JPL-Caltech, Space Science Institute, Mindaugas Macijauskas

Explanation: Still bright in planet Earth's night skies, good telescopic views of Saturn and its beautiful rings often make it a star at star parties. But this stunning view of Saturn's rings and night side just isn't possible from telescopes closer to the Sun than the outer planet. They can only bring Saturn's day into view. In fact, this image of Saturn's slender sunlit crescent with night's shadow cast across its broad and complex ring system was captured by the Cassini spacecraft. A robot spacecraft from planet Earth, Cassini called Saturn orbit home for 13 years before it was directed to dive into the atmosphere of the gas giant on September 15, 2017. This magnificent mosaic is composed of framesrecorded by Cassini's wide-angle camera only two days before its grand final plunge. Saturn's night will not be seen again until another spaceship from Earth calls.

Music - Slides - Pachelbel : "Canon in D Major"

"Canon in D Major"

Ciência & Tecnologia - Electricidade - Video : Energia infinita ou magica ?

Energia infinita ou mágica? - Este vídeo possui uma lâmpada led modificada que pode ser usada em vários truques mágicos. Aqui é apresentado como se estivesse extraindo eletricidade de uma batata. Isso é apenas uma brincadeira.

Ciência Tranquila

Science & Technologie - Aeronautique - Avions du futur : Le projet X48, de Boeing, basé sur une étude de McDonnell Douglas

Avec le projet X48, Boeing reprend une étude sur une aile volante menée par McDonnell Douglas dans les années 1990. Le projet s'est poursuivi sous la forme d'une collaboration avec la Nasa et l'université britannique de Cranfield pour un appareil à fuselage porteur. Après le X48A, resté dans les cartons, deux modèles réduits baptisés X48B ont été construits et testés en vol. Une autre version, le X48C, a été testé en vol également entre 2012 et 2013.

En 2011, Boeing a présenté ce projet à la Nasa dans le cadre de son étude sur les avions de 2025. On voit ici une image d'artiste avec deux types de motorisation. Les moteurs sont installés sur la partie supérieure, ce qui réduit le bruit perçu au sol. 

© Nasa, The Boeing Company

Science & Technologie - Informatique - Cyber-sécurité : Les pires mots de passe

Le nom de votre chat, votre date d’anniversaire, nombreux sont les mots de passe que vous utilisez chaque jour sur vos différents comptes en ligne. Si on a tendance à minimiser leur importance, ils représentent une sécurité indéniable pour nos activités en ligne. GadgetNow, dévoile les pires mots de passe. Attention, à ne surtout pas reproduire chez vous…

Pour un mot de passe, il faut faire preuve d’originalité, et si l’idée de taper des chiffres sur votre clavier vous paraissait bonne, vous n’êtes pas seul à y avoir pensé. 123456 est le premier mot utilisé par les internautes imprudents. Environ 23.2 millions de potentielles victimes, qui s’exposent à l’usurpation d’identité numérique ou le vol, par exemple. Si l’étude est américaine, Avast révélait en avril dernier que 93% des mots de passe français étaient jugés trop faibles. Autres exemples : 123456789, QWERTY, Password, 1111111...

Pour lutter contre ces cyber-attaques, la recette est simple. Un mot de passe efficace, c’est un mot de passe qui se change tous les ans. Il comportera des symboles, des lettres majuscules et minuscules et des chiffres. 16 caractères sont nécessaires pour assurer la sécurité de vos comptes. Certains opteront pour des phrases de passes, ces phrases faites de symboles et qui ont un sens pour l’utilisateur, sans qu’il soit trop évident. On prendra par exemple une parole de chanson pour l’adapter. « F4iscommesij’4v4isprislamer. » On vous laisse deviner l’artiste. Pour les étourdis, de nombreux gestionnaires de mots de passe permettent de les conserver en sécurité, on prendra l’exemple de Keepass. Pour un maximum de sécurité, on n’utilisera pas le même mot de passe pour tous ses comptes.

Journal du Geek

Science & Technology - Astronomy picture of the day : Along the Western Veil

2019 September 19
Along the Western Veil 
Image Credit & Copyright: Min Xie

Explanation: Delicate in appearance, these filaments of shocked, glowing gas, are draped across planet Earth's sky toward the constellation of Cygnus. They form the western part of the Veil Nebula. The Veil Nebula itself is a large supernova remnant, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Blasted out in the cataclysmic event, the interstellar shock wave plows through space sweeping up and exciting interstellar material. The glowing filaments are really more like long ripples in a sheet seen almost edge on, remarkably well separated into atomic hydrogen (red) and oxygen (blue-green) gas. Also known as the Cygnus Loop, the Veil Nebula now spans nearly 3 degrees or about 6 times the diameter of the full Moon. While that translates to over 70 light-years at its estimated distance of 1,500 light-years, this telescopic image of the western portion spans about half that distance. Brighter parts of the western Veil are recognized as separate nebulae, including The Witch's Broom (NGC 6960) along the top of this view and Pickering's Triangle(NGC 6979) below and left.

Science & Technologie - Video - Archéologie : Sur les traces des premiers peintres d’Afrique

Avec ses milliers d’abris décorés, le massif des Matopos, dans le sud-ouest du Zimbabwe, s’impose comme l’un des lieux emblématiques de l’art pariétal dans le monde. Dans ce reportage diffusé avec LeMonde.fr, partez avec une équipe d’archéologues qui tente de remonter l’histoire de ces peintures très énigmatiques.

Science & Technologie - Nucléaire - Déchets : 500 mètres sous la terre, dans le labo de Cigéo à Bure

Au laboratoire souterrain de l’Andra à Bure (Meuse), à  490 mètres sous terre, travaux de recherche sur le stockage des déchets nucléaires de haute activité vie longue (HA/VL) et de moyenne activité vie longue (MA/VL) pour le projet de centre industriel de stockage géologique (Cigéo).

Usine Nouvelle 

Science & Technologie - Aeronautique - Avions du futur : Des moteurs au-dessus de l'avion plutôt que dessous

Pour réduire le bruit des avions perçu au sol, une excellente solution, simple mais efficace, est d'installer les moteurs au-dessus de l'avion. Pourquoi n'y a-t-on pas pensé plus tôt ? Parce que les équipes de maintenance n'aiment pas... L'accès aisé aux moteurs est en effet un gage de sécurité mais aussi d'économie puisqu'il est plus rapide. Les placer sur le fuselage ou les ailes, voire les intégrer dans le corps de l'avion, comme dans les ailes volantes, a toujours fait peur aux avionneurs. Mais si les moteurs du futur sont plus fiables ? © Bauhaus Luftfahrt

Science & Technology - Astronomy picture of the day : Gigantic Jet Lightning over India

2019 September 18
Gigantic Jet Lightning over India 
Image Credit & Copyright: Hung-Hsi Chang

Explanation: Yes, but can your lightning bolt do this? While flying from Munich to Singapore earlier this month, an industrious passenger took images of a passing lightning storm and caught something unexpected: gigantic jet lightning. The jet was captured on a single 3.2-second exposure above Bhadrak, India. Although the gigantic jet appears connected to the airplane's wing, it likely started in a more distant thundercloud, and can be seen extending upwards towards Earth's ionosphere. The nature of gigantic jets and their possible association with other types of Transient Luminous Events (TLEs) such as blue jets and red sprites remains an active topic of research.

Science & Technology - Astronomy picture of the day : Water Vapor Discovered on Distant Exoplanet

2019 September 17
Water Vapor Discovered on Distant Exoplanet 
Illustration Credit: ESA, NASA, Hubble; Artist: M. Kornmesser

Explanation: Where else might life exist? One of humanity's great outstanding questions, locating planets where extrasolar life might survive took a step forward recently with the discovery of a significant amount of water vapor in the atmosphere of distant exoplanet K2-18b. The planet and it parent star, K2-18, lie about 124 light years away toward the constellation of the Lion (Leo). The exoplanet is significantly larger and more massive than our Earth, but orbits in the habitable zone of its home star. K2-18, although more red than our Sun, shines in K2-18b's sky with a brightness similar to the Sun in Earth's sky. The discovery was made in data from three space telescopes: Hubble, Spitzer, and Kepler, by noting the absorption of water-vapor colors when the planet moved in front of the star. The featured illustration imagines exoplanet K2-18b on the right, its parent red dwarf star K2-18 on the left, and an unconfirmed sister planet between them.

Science & Technology - Astronomy picture of the day : A Lunar Corona over Turin

2019 September 16
A Lunar Corona over Turin 
Image Credit & Copyright: Giorgia Hofer (Cortina Astronomical Association)

Explanation: What are those colorful rings around the Moon? A corona. Rings like this will sometimes appear when the Moon is seen through thin clouds. The effect is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently. Lunar Coronae are one of the few quantum mechanical color effects that can be easily seen with the unaided eye. The featured lunar corona was captured around full Moon above Turin, Italy in 2014. Similar coronae that form around the Sun are usually harder to see because of the Sun's great brightness.

Music - Video - Phil Spitalny/Evelyn : "Here Come the Co-Eds"

"Here Come the Co-Eds"

Phil Spitalny fue un músico, crítico musical, compositor y líder de banda estadounidense, habitual en la programación radiofónica de las décadas de 1930 y 1940. Se hizo famoso por formar una orquesta en la que todos sus componentes eran mujeres, algo novedoso en esa época. En esta edición podemos apreciar a la orquesta en su plenitud, teniendo como solista a Evelyn y su Violin Mágico. Las escenas pertenecen a la película "Here Come the Co-Eds", de 1945, protagonizada por el dúo Abbott & Costello.

Music - Wolfgang Amadeus Mozart - "Piano Concerto No. 21 - Andante"

"Piano Concerto No. 21 - Andante"

Science & Technology - Astronomy picture of the day : A Harvest Moon

2019 September 13
A Harvest Moon 
Image Credit & Copyright: Jean-Francois Graffand

Explanation: Famed in festival, story, and song the best known full moon is the Harvest Moon. For northern hemisphere dwellers that's a traditional name of the closest full moon to the September equinox. In most North America time zones this year's Harvest Moon will officially rise on Friday, September 13. In fact the same Harvest Moon will rise on September 14 for much of the planet though. Of course the Moon will look almost full in the surrounding days. Regardless of your time zone the Harvest Moon, like any other full moon, will rise just opposite the setting Sun. Near the horizon, the Moon Illusion might make it appear bigger and brighter to you but this Harvest Moon will be nearlunar apogee. That's the closest point in its orbit, making it the most distant, and so the smallest, full moon of the year. On August 15 a wheat field harvested in south central France made this a harvest moon scene too, the full moon shining on with beautiful iridescent clouds at sunset.

Science & Technology - Astronomy picture of the day : IC 1805: The Heart Nebula

2019 September 11
IC 1805: The Heart Nebula 
Image Credit & Copyright: Bray Falls

Explanation: What energizes the Heart Nebula? First, the large emission nebula dubbed IC 1805 looks, in whole, like a human heart. The nebula glows brightly in red light emitted by its most prominent element: hydrogen. The red glow and the larger shape are all powered by a small group of stars near the nebula's center. In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillarswith their energetic light and winds. The open cluster of stars contains a few bright stars nearly 50 times the mass of our Sun, many dim stars only a fraction of the mass of our Sun, and an absent microquasar that was expelled millions of years ago. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia. Coincidentally, a small meteor was captured in the foreground during imaging and is visible above the dust pillars. At the top right is the companion Fishhead Nebula.

Science & Technology - Astronomy picture of the day : "Pluto in True Color"

2019 September 10
Pluto in True Color 
Image Credit: NASA, JHU APL, SwRI, Alex Parker

Explanation: What color is Pluto, really? It took some effort to figure out. Even given all of the images sent back to Earth when the robotic New Horizons spacecraft sped past Pluto in 2015, processing these multi-spectral frames to approximate what the human eye would see was challenging. The result featured here, released three years after the raw data was acquired by New Horizons, is the highest resolution true color image of Pluto ever taken. Visible in the image is the light-colored, heart-shaped, Tombaugh Regio, with the unexpectedly smooth Sputnik Planitia, made of frozen nitrogen, filling its western lobe. New Horizons found the dwarf-planet to have a surprisingly complex surfacecomposed of many regions having perceptibly different hues. In total, though, Pluto is mostly brown, with much of its muted color originating from small amounts of surface methane energized by ultraviolet light from the Sun.

Science & Technology - Astronomy picture of the day : M31: The Andromeda Galaxy

2019 September 9
M31: The Andromeda Galaxy 
Image Credit & Copyright: Amir H. Abolfath (TWAN)

Explanation: How far can you see? The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy, over two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda. But a bright yellow nucleus, dark winding dust lanes, luminous blue spiral arms, and bright red emission nebulas are recorded in this stunning six-hour telescopic digital mosaic of our closest major galactic neighbor. While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers seriously debated this fundamental concept only 100 years ago. Were these "spiral nebulae" simply outlying gas clouds in our own Milky Way Galaxy or were they "island universes" -- distant galaxies of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations favoring Andromeda being just like our Milky Way Galaxy -- a conclusion making the rest of the universe much more vast than many had ever imagined.

Science & Technology - Astronomy picture of the day : In Wolf's Cave

2019 September 7
In Wolf's Cave Image Credit & Copyright: Charlie Bracken, Mladen Dugec, Max Whitby

Explanation: The mysterious blue reflection nebula found in catalogs as VdB 152 or Ced 201 really is very faint. It lies at the tip of the long dark nebula Barnard 175 in a dusty complex that has also been called Wolf's Cave. At the center of this deep and widefield telescopic view, the cosmic apparitions are nearly 1,400 light-years away along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star giving the the nebula its characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through space is very different from the cloud's velocity. Another dense, obscuring dark nebula, LDN 1221, is easy to spot at the upper right in the frame, while the more colorful planetary nebula Dengel-Hartl 5 is just below center. Faint reddish emission from an ancient supernova remnant can also be traced (lower right to upper left) against the dust-rich complex in Cepheus.

Science & Technology - Astronomy picture of the day : Recycling Cassiopeia A

2019 September 6
Recycling Cassiopeia A 
Image Credit: X-ray - NASA, CXC, SAO; Optical - NASA,STScI

Explanation: Massive stars in our Milky Way Galaxy live spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant would have been first seen in planet Earth's sky about 350 years ago, although it took that light about 11,000 years to reach us. This false-color image, composed of X-ray and optical image data from the Chandra X-ray Observatory and Hubble Space Telescope, shows the still hot filaments and knots in the remnant. It spans about 30 light-years at the estimated distance of Cassiopeia A. High-energy X-ray emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help astronomers explore the recycling of our galaxy's star stuff. Still expanding, the outer blast wave is seen in blue hues. The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core.

Science & Technology - Astronomy picture of the day : The Large Cloud of Magellan

2019 September 5
The Large Cloud of Magellan 
Image Credit & Copyright: Alessandro Cipolat Bares

Explanation: The 16th century Portuguese navigator Ferdinand Magellan and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two fuzzy cloud-like objects easily visible to southern hemisphere skygazers are known as the Clouds of Magellan, now understood to be satellite galaxies of our much larger, spiral Milky Way galaxy. About 160,000 light-years distant in the constellation Dorado, the Large Magellanic Cloud (LMC) is seen here in a remarkably deep, colorful, image. Spanning about 15,000 light-years or so, it is the most massive of the Milky Way's satellite galaxies and is the home of the closest supernova in modern times,SN 1987A. The prominent patch below center is 30 Doradus, also known as the magnificent Tarantula Nebula, a giant star-forming region about 1,000 light-years across.

Science & Technologie - Astronomie - HOJE, AUJOURD'HUI, TODAY : Triangle Lune Jupiter Antarès

Jeudi 5 septembre à la nuit tombante, la Lune, Jupiter et Antarès forment un triangle visible à l’œil nu.

Alors que la journée se termine en ce jeudi 5 septembre, recherchez sur l’horizon sud sud-ouest la Lune au premier quartier. A peu près à la même hauteur mais plus à l’est, la brillante planète Jupiter se repère facilement même avant la nuit. Ces deux astres matérialisent deux des trois sommets d’un triangle céleste remarquable et presque équilatéral.

Pour voir le troisième sommet du triangle, il faut attendre que la nuit s’installe un peu, vers 21h (heure de Paris). Vous distinguerez alors sans peine la brillante étoile orangée Antarès située dans la constellation du Scorpion, plus près de l’horizon. L’ensemble s’observe jusqu’aux environs de 22h30, heure à laquelle Antarès se couche.

Notre satellite, une planète géante gazeuse et une étoile supergéante joliment colorée, voilà un joli trio à observer pour faire sa rentrée astronomique !

Stelvision

Science & Technology - Astronomy picture of the day : The Spider Nebula in Infrared

2019 September 4
The Spider Nebula in Infrared Image Credit: NASA, JPL-Caltech, Spitzer Space Telescope, 2MASS

Explanation: Will the spider ever catch the fly? Not if both are large emission nebulas toward the constellation of the Charioteer (Auriga). The spider-shaped gas cloud on the left is actually an emission nebula labelled IC 417, while the smaller fly-shaped cloud on the right is dubbed NGC 1931 and is both an emission nebula and a reflection nebula. About 10,000 light-years distant, both nebulas harbor young, open star clusters. For scale, the more compact NGC 1931 (Fly) is about 10 light-years across. The featured picture in scientifically-assigned, infrared colors combines images from the Spitzer Space Telescope and the Two Micron All Sky Survey (2MASS). Spitzer is celebrating its 16th year orbiting the Sun near the Earth.

Science & Technology - Astronomy picture of the day : Unusual Signal Suggests Neutron Star Destroyed by Black Hole

2019 September 3
Unusual Signal Suggests Neutron Star Destroyed by Black Hole Illustration Video Credit: NASA, Dana Berry (Skyworks Digital)

Explanation: What created this unusual explosion? Three weeks ago, gravitational wave detectors in the USA and Europe -- the LIGO and Virgo detectors -- detected a burst of gravitational radiation that had the oscillating patternexpected when a black hole destroys a neutron star. One object in event S190814sv was best fit with a mass greater than five times the mass of the Sun -- making it a good candidate for a black hole, while the other object appeared to have a mass less than three times the mass of the Sun -- making it a good candidate for a neutron star. No similar event had been detected with gravitational waves before. Unfortunately, no light was seen from this explosion, light that might have been triggered by the disrupting neutron star. It is theoretically possible that the lower mass object was also a black hole, even though no clear example of a black hole with such a low mass is known. The featured video was created to illustrate a previously suspected black hole - neutron star collision detected in light in 2005, specifically gamma-rays from the burst GRB 050724. The animated video starts with a foreground neutron star orbiting a black hole surrounded by an accretion disk. The black hole's gravity then shreds the neutron star, creating a jet as debris falls into the black hole. S190814sv will continue to be researched, with clues about the nature of the objects involved possibly coming from future detections of similar systems.

Science & Technology - Astronomy picture of the day : The Moon and Jupiter over the Alps

2019 September 2
The Moon and Jupiter over the Alps 
Image Credit & Copyright: Giorgia Hofer (Cortina Astronomical Association)

Explanation: What are those bright lights in the sky ahead? When hiking a high mountain pass in northern Italy three weeks ago, a conjunction between our Moon and the distant planet Jupiter was visible as both rose together in the southwest after sunset. The picturesque mountains in the distance are Tre Cime di Lavaredo (Three Peaks of Lavaredo), a UNESCO World Heritage Site and three of the best known mountain peaks in Italy, the Dolomites, and the entire Alps. In the foreground on the left is Locatelli Hut, a refuge for tired hikers as it is located over an hour from nearest parking lot. The bright sky object on the upper left is Saturn. The entire scene was captured on a single 8-second exposure. Jupiter and Saturn will remain prominent in the western sky after sunset this month, while the Moon, in its monthly orbit around the Earth, will pass near Jupiter again in about four days.

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.