"Roda viva"
2016-04-16
Astronomy picture of the day - 2016 April 16 - Heliopause Electrostatic Rapid Transit System
Illustration Credit: NASA, Marshall Space Flight Center
Explanation: Want to take a fast trip to the edge of the Solar System? Consider a ride on a Heliopause Electrostatic Rapid Transit System (HERTS). The concept is currently being tested and it might take only 10 to 15 years to make the trip of over 100 Astronomical Units (15 billion kilometers). That's fast compared to the 35 years it took Voyager 1, presently humanity's most distant spacecraft, to approach the heliopause or outer boundary of the influence of the solar wind. HERTS would use an advanced electric solar sail that works by extending multiple, 20 kilometer or so long, 1 millimeter thin, positively charged wires from a rotating spacecraft. The electrostatic force generated repels fast moving solar wind protons to create thrust. Compared to a reflective solar light sail, another propellantless deep space propulsion system, the electric solar wind sail could continue to accelerate at greater distances from the Sun, still developing thrust as it cruised toward the outer planets.
Fotos - Passeando por Toulouse - "Rue Bouquinières" - 10-04-2015
"Rue Bouquinières"
Toulouse, 10-04-2015
JoanMira
2016-04-15
Fotos - Lisboa antiga - Rua dos Caminhos de Ferro - 1953
-A22607-Rua%2Bdos%2BC.%2BFerro-Correios%2Be%2BFontan%C3%A1rio-1953-.jpg)
Rua dos Caminhos de Ferro (antiga Rua Cais dos soldados) com a sua estação de Correio a funcionar.
1953
Fernando Martinez Pozal
Astronomy picture of the day - 2016 April 15 - Mercury and Crescent Moon Set
Image Credit & Copyright: Miguel Claro (TWAN, Dark Sky Alqueva)
Explanation: Innermost planet Mercury and a thin crescent Moon are never found far from the Sun in planet Earth's skies. Taken near dusk on April 8, this colorful evening skyscape shows them both setting toward the western horizon just after the Sun. The broad Tagus River and city lights of Lisbon, Portugal run through the foreground under the serene twilight sky. Near perigee or closest approach to Earth, the Moon's bright, slender crescent represents about 3 percent of the lunar disk in sunlight. Of course as seen from the Moon, a nearly full Earth would light up the lunar night, and that strong perigee earthshine makes the rest of the lunar disk visible in this scene. Bright Mercury stays well above the western horizon at sunset for northern skywatchers in the coming days. The fleeting planet reaches maximum elongation, or angular distance from the Sun, on April 18. But Mercury will swing back toward the Sun and actually cross the solar disk on May 9, the first transit of Mercury since November 8, 2006.
2016-04-14
Fotos - Passeando por Mondim de Basto - 03-10-2011
"Mondim de Basto"
Mondim de Basto, 03-10-2011
JoanMira
Inscription à :
Commentaires (Atom)