"Ao cair do dia"
14-03-2018
JoanMira
2018-03-14
Raquel Taraborelli - "Vasos de gerânios ensolarados" - Pintura impressionista contemporânea
Mort de Stephen Hawking : la communauté scientifique salue "un ambassadeur de la science" - Science et technologie
L’astrophysicien britannique, spécialiste des trous noirs, est mort aujourd'hui à 76 ans. Scientifiques mais aussi responsables scientifiques lui rendent hommage.
« Un être unique, dont on se souviendra avec affection non seulement à Cambridge, mais dans le monde entier », a écrit Stephen Toope, le vice-président de l’université de Cambridge, où Stephen Hawking avait étudié et travaillait, quelques minutes après l’annonce de la mort du physicien, mercredi 14 mars. "Son exceptionnelle contribution au savoir scientifique, aux mathématiques et à la vulgarisation laisse une contribution indélébile", a-t-il ajouté.
Sur Twitter, la NASA a salué "un physicien de renom et un ambassadeur de la science". "Ses découvertes ont ouvert un univers de possibilités que nous et le monde continuons à explorer", a déclaré l’agence spatiale américaine.
"D'où vient l'Univers? Comment et pourquoi a-t-il commencé? Connaîtra-t-il une fin, et si oui, comment?"
Voici ce qu'écrivait Stephen Hawking dans la préface de son livre "Une brève histoire du temps" paru en 1988.
Astronomy picture of the day - 2018 March 14 - Night Sky Highlights: March to May
Illustration Credit & Copyright: Universe2go.com
Explanation: What might you see in the night sky over the next few months? The featured graphic gives a few highlights. Viewed as a clock face centered at the bottom, sky events in March fan out toward the left, April toward the top, and May toward the right. Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center -- although almost everything pictured can be seen without a telescope.Sky highlights this season include a bright Venus in the evening sky during March, the Lyrids meteor shower during April, and Jupiter entering the evening sky during May. As true in every season, the International Space Station (ISS) can be sometimes be found drifting across your sky if you know just when and where to look.
2018-03-13
Astronomy picture of the day - 2018 March 13 - The Complete Galactic Plane: Up and Down
Image Credit & Copyright: Moophz Himself (Maroun Habib)
Explanation: Is it possible to capture the entire plane of our galaxy in a single image? Yes, but not in one exposure -- and it took some planning to do it in two. The top part of the featured image is the night sky above Lebanon, north of the equator, taken in 2017 June. The image was taken at a time when the central band of the Milky Way Galaxy passed directly overhead. The bottom half was similarly captured six months later in latitude-opposite Chile, south ofEarth's equator. Each image therefore captured the night sky in exactly the opposite direction of the other, when fully half the Galactic plane was visible. The southern half was then inverted -- car and all -- and digitally appended to the top half to show the entire central band of our Galaxy, as a circle, in a single image. Many stars and nebulas are visible, with the Large Magellanic Cloud being particularly notable inside the lower half of the complete galactic circle.
2018-03-12
Astronomy picture of the day - 2018 March 12 - Flying over the Earth at Night II
Video Credit: NASA, Gateway to Astronaut Photography; Music: The Low Seas (The 126ers)
Explanation: What would it be like to orbit the Earth? The International Space Station (ISS) does this every 90 minutes, and sometimes the astronauts on board take image sequences that are made into videos. The featured time-lapse video shows many visual spectacles of the dark Earth below. First, as the video begins, green and red auroras are visible on the upper left above white clouds. Soon city lights come into view, and it becomes clear you are flying overNorth America, eventually passing over Florida. In the second sequence you fly over Europe and Africa, eventually passing over the Nile River. Brief flashes of light are lightning in storms. Stars far in the distance can be seen rising through the greenish-gold glow of the Earth's atmosphere.
2018-03-11
Astronomy picture of the day - 2018 March 11 - Dual Particle Beams in Herbig-Haro 24
Image Credit: NASA, ESA, Hubble Heritage (STScI/AURA)/Hubble-Europe Collaboration;
Acknowledgment: D. Padgett (NASA's GSFC), T. Megeath (U. Toledo), B. Reipurth (U. Hawaii)
Explanation: This might look like a double-bladed lightsaber, but these two cosmic jets actually beam outward from a newborn star in a galaxy near you. Constructed from Hubble Space Telescope image data, the stunning scene spans about half a light-year across Herbig-Haro 24 (HH 24), some 1,300 light-years away in the stellar nurseries of the Orion B molecular cloud complex. Hidden from direct view, HH 24's central protostar is surrounded by cold dust and gas flattened into a rotating accretion disk. As material from the disk falls toward the young stellar object it heats up. Opposing jets are blasted out along the system's rotation axis. Cutting through the region's interstellar matter, the narrow, energetic jets produce a series of glowing shock fronts along their path.
2018-03-10
Astronomy picture of the day - 2018 March 10 - Phases of the Moon
Image Credit & Copyright: Jean-Francois Gout, Tom Polakis
Explanation: Look at the Moon every night and its visible sunlit portion gradually changes. In phases progressing from New Moon to Full Moon to New Moon again, a lunar cycle or lunation is completed in about 29.5 days. Top left to bottom right, these frames show the range of lunar phases for 25 consecutive nights beginning on January 18, following an almost complete lunation. They skip the 2 days just after and 2 days before New Moon, when the lunar phase is at best a narrow crescent, close to the Sun and really hard to see. Of course, mostly clear Arizona night skies and a little help from a friend were required to complete this lunar cycle project, imaging in early evening for the first half and late evening and early morning for the second half of the lunation. For extra credit, the cycle was centered on the Full Moon of January 31. That was the second Full Moon in January, when the Moon was near lunar orbit perigee and took on reddish hues during a total lunar eclipse.
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