Science & Technologie - Avions du futur : La double bulle D8 du MIT

Le D8 « double bulle » du Massachusetts Institute of Technology (MIT) propose une cabine large, pour 180 passagers sur ce projet. Les matériaux composites allègent la cellule et les réacteurs, disposés au-dessus de la cellule (ce qui réduit le bruit), sont à double flux mais avec un flux central (chaud, car sortant de la turbine) très étroit, tandis que le flux périphérique (issu du grand ventilateur frontal) est plus large. 

© Nasa, MIT, Aurora Flight Sciences

Science & Technology - Astronomy picture of the day : Spiral Galaxy M96 from Hubble

2019 June 12
Spiral Galaxy M96 from Hubble 
Image Credit: NASA, ESA, Hubble; Processing & Copyright: Leo Shatz

Explanation: Dust lanes seem to swirl around the core of Messier 96 in this colorful, detailed portrait of the center of a beautiful island universe. Of course M96 is a spiral galaxy, and counting the faint arms extending beyond the brighter central region, it spans 100 thousand light-years or so, making it about the size of our own Milky Way. M96, also known as NGC 3368, is known to be about 35 million light-years distant and a dominant member of the Leo I galaxy group. The featured image was taken by the Hubble Space Telescope. The reason for M96's asymmetry is unclear -- it could have arisen from gravitational interactions with other Leo I group galaxies, but the lack of an intra-group diffuse glow seems to indicate few recent interactions. Galaxies far in the background can be found by examining the edges of the picture.

Science & Technology - Astronomy picture of the day : Our Galaxy's Magnetic Center

2019 June 19
Our Galaxy's Magnetic Center 
Image Credit: NASA, SOFIA, Hubble

Explanation: What's the magnetic field like in the center of our Milky Way Galaxy? To help find out, NASA's SOFIA -- an observatory flying in a modified 747 -- imaged the central region with an instrument known as HAWC+.HAWC+ maps magnetism by observing polarized infrared light emitted by elongated dust grains rotating in alignment with the local magnetic field. Now at our Milky Way's center is a supermassive black hole with a hobby of absorbing gas from stars it has recently destroyed. Our galaxy's black hole, though, is relatively quiet compared to the absorption rate of the central black holes in active galaxies. The featured image gives a clue as to why -- a surrounding magnetic field may either channel gas into the black hole -- which lights up its exterior, or forces gas into an accretion-disk holding pattern, causing it to be less active -- at least temporarily. Inspection of the featured image -- appearing perhaps like a surreal mashup of impasto art and gravitational astrophysics -- brings out this telling clue by detailing the magnetic field in and around a dusty ring surrounding Sagittarius A*, the black hole in our Milky Way's center.

Science & Technologie - Avions du futur : Lockheed Martin et son moyen-courrier biréacteur économe

Un concept de Lockheed Martin pour un avion moyen courrier biréacteur à faible consommation. Les réacteurs sont à très large ouverture avec un flux d'air central très étroit. On note surtout la voilure extravagante, plus précisément rhomboédrique. 

© Nasa, Lockheed Martin

Science & tchnology - Astronomy picture of the day : Strawberry Moon over the Temple of Poseidon

2019 June 18
Strawberry Moon over the Temple of Poseidon Image Credit & Copyright: Elias Chasiotis

Explanation: Did you see the full moon last night? If not, tonight's nearly full moon should be almost as good. Because full moons are opposite the Sun, they are visible in the sky when the Sun is not -- which should be nearly all night long tonight, clouds permitting. One nickname for June's full moon is the Strawberry Moon, named for when wild strawberries start to ripen in parts of Earth's northern hemisphere. Different cultures around the globe give this full moondifferent names, though, including Honey Moon and Rose Moon. In the foreground of this featured image, taken yesterday in Cape Sounion, Greece, is the 2,400 year-old Temple of Poseidon. Next month will the 50th anniversary of the time humans first landed on the Moon.

Science & Technology - Astronomy picture of the day : Milky Way over Pyramid of the Feathered Serpent

2019 June 17
Milky Way over Pyramid of the Feathered Serpent 
Image Credit & Copyright: Robert Fedez

Explanation: To see the feathered serpent descend the Mayan pyramid requires exquisite timing. You must visit El Castillo -- in Mexico's Yucatán Peninsula -- near an equinox. Then, during the late afternoon if the sky is clear, the pyramid's own shadows create triangles that merge into the famous illusion of the slithering viper. Also known as the Temple of Kukulkan, the impressive step-pyramid stands 30 meters tall and 55 meters wide at the base. Built up as a series of square terraces by the pre-Columbian civilization between the 9th and 12th century, the structure can be used as a calendar and is noted for astronomical alignments. To see the central band of our Milky Way Galaxy descend overhead the Mayan pyramid, however, requires less exquisite timing. Even the ancient Mayans might have been impressed, though, to know that the exact positions of the Milky Way, Saturn (left) and Jupiter (right) in the featured image give it a time stamp more specific than equinox -- in fact 2019 April 7 at 5 am.

Science & Technology - Astronomy picture of the day : Unusual Mountain Ahuna Mons on Asteroid Ceres

2019 June 16
Unusual Mountain Ahuna Mons on Asteroid Ceres 
Image Credit: Dawn Mission, NASA, JPL-Caltech, UCLA, MPS/DLR/IDA

Explanation: What created this unusual mountain? There is a new theory. Ahuna Mons is the largest mountain on the largest known asteroid in our Solar System, Ceres, which orbits our Sun in the main asteroid belt between Mars and Jupiter. Ahuna Mons, though, is like nothing that humanity has ever seen before. For one thing, its slopes are garnished not with old craters but young vertical streaks. The new hypothesis, based on numerous gravity measurements, holds that a bubble of mud rose from deep within the dwarf planet and pushed through the icy surface at a weak point rich in reflective salt -- and then froze. The bright streaks are thought to be similar to other recently surfaced material such as visible in Ceres' famous bright spots. The featured double-height digital image was constructed from surface maps taken of Ceres in 2016 by the robotic Dawn mission. Successfully completing its mission in 2018, Dawn continues to orbit Ceres even though it has exhausted the fuel needed to keep its antennas pointed toward Earth.

Science & Technology - Astronomy picture of the day : NGC 4676: The Mighty Mice

2019 June 14
NGC 4676: The Mighty Mice 
Image Credit & Copyright: Bruce Waddington

Explanation: These two mighty galaxies are pulling each other apart. Known as The Mice because they have such long tails, each large spiral galaxy has actually passed through the other. Their long tails are drawn out by strong gravitational tides rather than collisions of their individual stars. Because the distances are so large, the cosmic interaction takes place in slow motion -- over hundreds of millions of years. They will probably collide again and again over the next billion years until they coalesce to form a single galaxy. NGC 4676 lies about 300 million light-years away toward the constellation of Bernice's Hair (Coma Berenices) and are likely members of the Coma Cluster of Galaxies. Not often imaged in small telescopes, this wide field of view catches the faint tidal tails several hundred thousand light-years long.

Science & Technology - Astronomy picture of the day : The Colors and Magnitudes of M13

2019 June 13
The Colors and Magnitudes of M13 
Image Credit & Copyright: Tolga Gumusayak, Robert Vanderbei

Explanation: M13 is modestly recognized as the Great Globular Star Cluster in Hercules. A ball of stars numbering in the hundreds of thousands crowded into a region 150 light years across, it lies some 25,000 light-years away. The sharp, color picture of M13 at upper left is familiar to many telescopic imagers. Still, M13's Color vs Magnitude Diagram in the panel below and right, made from the same image data, can offer a more telling view. Also known as aHertzsprung Russell (HR) diagram it plots the apparent brightness of individual cluster stars against color index. The color index is determined for each star by subtracting its brightness (in magnitudes) measured through a red filter from its brightness measured with a blue filter (B-R). Blue stars are hot and red stars are cool so that astronomical color index ranging from bluer to redder follows the relative stellar temperature scale from left (hot) to right (cool). In M13's HR diagram, the stars clearly fall into distinct groups. The broad swath extending diagonally from the bottom right is the cluster's main sequence. A sharp turn toward the upper right hand corner follows the red giant branch while the blue giants are found grouped in the upper left. Formed at the same time, at first M13's stars were all located along the main sequence by mass, lower mass stars at the lower right. Over time higher mass stars have evolved off the main sequence into red, then blue giants and beyond. In fact, the position of the turn-off from the main sequence to the red giant branch indicates the cluster's age at about 12 billion years.

Science & Technology - Astronomy picture of the day : Spiral Galaxy M96 from Hubble

2019 June 12
Spiral Galaxy M96 from Hubble 
Image Credit: NASA, ESA, Hubble; Processing & Copyright: Leo Shatz

Explanation: Dust lanes seem to swirl around the core of Messier 96 in this colorful, detailed portrait of the center of a beautiful island universe. Of course M96 is a spiral galaxy, and counting the faint arms extending beyond the brighter central region, it spans 100 thousand light-years or so, making it about the size of our own Milky Way. M96, also known as NGC 3368, is known to be about 35 million light-years distant and a dominant member of the Leo I galaxy group. The featured image was taken by the Hubble Space Telescope. The reason for M96's asymmetry is unclear -- it could have arisen from gravitational interactions with other Leo I group galaxies, but the lack of an intra-group diffuse glow seems to indicate few recent interactions. Galaxies far in the background can be found by examining the edges of the picture.