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.

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.