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Amine Belkhir
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Amine Belkhir

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LL Orionis: When Cosmic Winds Collide
Image Credit: Hubble Heritage Team (AURA / STScI), C. R. O'Dell(Vanderbilt U.), +NASA
http://apod.nasa.gov/apod/ap160522.html

What created this great arc in space? This arcing, graceful structure is actually a bow shock about half a light-year across, created as the wind from young star LL Orionis collides with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the lower right hand edge of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. The complex stellar nursery in Orion shows a myriad of similar fluid shapes associated with star formation, including the bow shock surrounding a faint star at the upper right. Part of a mosaic covering the Great Nebula in Orion, this composite color image was recorded in 1995 by the Hubble Space Telescope.
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Amine Belkhir

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A Blazing Fireball between the Orion Nebula and Rigel
Image Credit & Copyright: Ivo Scheggia
http://apod.nasa.gov/apod/ap151116.html

What's happening to that meteor? A few days ago, a bright fireball was photographed from the Alps mountain range in Switzerland as it blazed across the sky. The fireball, likely from the Taurids meteor shower, was notable not only for how bright it was, but for the rare orange light it created that lingered for several minutes. Initially, the orange glow made it seem like the meteor trail was on fire. However, the orange glow, known as a persistent train, originated neither from fire nor sunlight-reflecting smoke. Rather, the persistent train's glow emanated from atoms in the Earth's atmosphere in the path of the meteor -- atoms that had an electron knocked away and emit light during reacquisition. Persistent trains often drift, so that the long 3-minute exposure actually captured the initial wind-blown displacement of these bright former ions. The featured image was acquired when trying to image the famous Orion Nebula, visible on the upper left. The bright blue star Rigel, part of the constellation of Orion, is visible to the right. This week the fireball-rich Taurids meteor shower continues to be active even though it has passed its peak, while the more active Leonids meteor shower is just peaking.
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Amine Belkhir

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#science #halloween2015 #radiopulsar  
Un astéroïde va froler la Terre le jour d'Halloween.

Un gros astéroïde de 470 mètres de diamètre passera relativement près de la #Terre le 31 octobre, jour d'Halloween. Rassurez-vous : son passage ne présente pas de danger selon la #Nasa.

Cet objet, baptisé 2015 TB145, devrait être le corps céleste connu le plus grand à s'approcher de notre planète et ce jusqu'en 2027, a indiqué l'agence spatiale américaine.

Si l'estimation faite de sa taille est exacte, cet astéroïde est 28 fois plus massif que le météore de Chelyabinsk qui a pénétré l'atmosphère au-dessus de la Russie en février 2013, précise le site spécialisé "Earth and Sky".

L'astéroïde 2015 TB145 croisera la Terre à une distance d'environ 500 000 km, soit 1,3 fois la distance séparant notre planète de la Lune. D'ailleurs, il passera à seulement 466 000 km de cette dernière.

Cet objet ne sera probablement pas visible à l'oeil nu mais les astronomes amateurs pourront le voir avec des télescopes. Il passera au plus près de la Terre à 15h14 GMT (17h14 en France) le 31 octobre.
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Cette balade temporelle revisite les faits marquants de l'année 2013 et s'attarde sur les événements scientifiques, technologiques et environnementaux. Suivez le guide et retrouvez ces images...
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Des citations sur le thème paix.
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Flamant rose : une carte virtuelle à envoyer à vos amis.
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The Rise and Fall of Supernova 2015F
Video Credit & Copyright: Changsu Choi & Myungshin Im (Seoul National University)
http://apod.nasa.gov/apod/ap160209.html

Sit back and watch a star explode. The actual supernova occurred back when dinosaurs roamed the Earth, but images of the spectacular event began arriving last year. Supernova 2015F was discovered in nearby spiral galaxy NGC 2442 by Berto Monard in 2015 March and was unusually bright -- enough to be seen with only a small telescope. The pattern of brightness variation indicated a Type Ia supernova -- a type of stellar explosion that results when an Earth-size white dwarf gains so much mass that its core crosses the threshold of nuclear fusion, possibly caused by a lower mass white-dwarf companion spiraling into it. Finding and tracking Type Ia supernovae are particularly important because their intrinsic brightness can be calibrated, making their apparent brightness a good measure of their distance -- and hence useful toward calibrating the distance scale of the entire universe. The featured video tracked the stellar disruption from before explosion images arrived, as it brightened, and for several months as the fission-powered supernova glow faded. The remnants of SN2015F are now too dim to see without a large telescope. Just yesterday, however, the night sky lit up once again, this time with an even brighter supernova in an even closer galaxy: Centaurus A.
2016 February 9
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Massive Stars in NGC 6357
Image Credit & Copyright: CHART32 Team, Processing - Johannes Schedler
http://apod.nasa.gov/apod/ap160205.html

Massive stars lie within NGC 6357, an expansive emission nebula complex some 6,500 light-years away toward the tail of the constellation Scorpius. In fact, positioned near center in this ground-based close-up of NGC 6357, star cluster Pismis 24 includes some of the most massive stars known in the galaxy, stars with nearly 100 times the mass of the Sun. The nebula's bright central region also contains dusty pillars of molecular gas, likely hiding massive protostars from the prying eyes of optical instruments. Intricate shapes in the nebula are carved as interstellar winds and energetic radiation from the young and newly forming massive stars clear out the natal gas and dust and power the nebular glow. Enhancing the nebula's cavernous appearance, narrowband image data was included in this composite color image in a Hubble palette scheme. Emission from sulfur, hydrogen, and oxygen atoms is shown in red green and blue hues. The alluring telescopic view spans about 50 light-years at the estimated distance of NGC 6357.
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Le Sahara, plus grand désert de sable du monde, couvre 9 000 000 km² (l’équivalent des États-Unis) répartis sur 11 pays. © Photo Yann Arthus-Bertrand - Tous droits réservés...
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Nice lines +Amine Belkhir 
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Au cours des deux derniers siècles, la région du lac Itasy s'est convertie à la riziculture inondée, une culture intensive contrôlée par de grands propriétaires fonciers. Le passage de la...
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Martin Pêcheur d'Europe : une carte virtuelle à envoyer à vos amis.
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Ara bleu : une carte virtuelle à envoyer à vos amis.
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