Science & Technology - Astronomy picture of the day : Northern Summer on Titan

2020 June 20
Northern Summer on TitanImage Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: Today's solstice brings summer to planet Earth's northern hemisphere. But the northern summer solstice arrived for ringed planet Saturn over three years ago on May 24, 2017. Orbiting the gas giant, Saturn's moon Titan experiences the Saturnian seasons that are about 7 Earth-years long. Larger than inner planet Mercury, Titan was captured in this Cassini spacecraft image about two weeks after its northern summer began. The near-infrared view finds bright methane clouds drifting through Titan's dense, hazy atmosphere as seen from a distance of about 507,000 kilometers. Below the clouds, dark hydrocarbon lakes sprawl near its fully illuminated north pole.

Science & Technologie - La Terre vue du ciel : L’île de Kyūshū au Japon

L'île de Kyūshū est la parfaite illustration de la complexité de l'œkoumène du Japon qui se trouve à l'intersection de quatre plaques tectoniques : le Pacifique, la mer des Philippines, l'Amérique du Nord, et l'Eurasie. Kyūshū se situe sur une zone de subduction où une plaque tectonique plonge sous une autre, donnant naissance à une topographie mêlant montagnes, plaines, volcans actifs (mont Unzen) et éteints (mont Tara).

Sur cette image satellite dont les couleurs ont été simulées, l'eau est bleue, la végétation verte et les zones urbaines sont en blanc et dégradé de bleu-gris. On peut ainsi se rendre compte de l'intrication complexe entre les zones habitées et montagneuses.

Science & Technology - Astronomy pictures of the day : The Veins of Heaven

2020 June 19
The Veins of Heaven
Image Credit & Copyright: Ruslan Merzlyakov (RMS Photography)

Explanation: Transfusing sunlight through a darkened sky, this beautiful display of noctilucent clouds was captured earlier this week, reflected in calm waters from Nykobing Mors, Denmark. From the edge of space, about 80 kilometers above Earth's surface, the icy clouds themselves still reflect sunlight, though the Sun is below the horizon as seen from the ground. Usually spotted at high latitudes in summer months the night shining clouds have made an early appearance this year as northern nights grow short. Also known as polar mesopheric clouds they are understood to form as water vapor driven into the cold upper atmosphere condenses on the fine dust particles supplied by disintegrating meteors or volcanic ash. NASA's AIM mission provides daily projections of noctilucent clouds as seen from space.

Science & Technologie - Informatique : Un internet quantique inviolable

À l'université de technologie de Delft, une équipe de scientifiques conduite par Stephanie Wehner est en train de créer un réseau reliant quatre villes au Pays-Bas, uniquement via la technologie quantique.

Cette technologie repose sur un phénomène particulier appelé «intrication quantique». La particularité de ce phénomène est que les données intriquées ne peuvent pas être lues sans que leurs contenus ne soient compromis –une sécurité parfaite, en somme.

Science & Technology - Astronomy picture of the day : Magnetic Streamlines of the Milky Way

2020 June 17
Magnetic Streamlines of the Milky Way
Image Credit: ESA, Planck; Text: Joan Schmelz (USRA)

Explanation: What role do magnetic fields play in interstellar physics? Analyses of observations by ESA's Planck satellite of emission by small magnetically-aligned dust grains reveal previously unknown magnetic field structures in our Milky Way Galaxy -- as shown by the curvy lines in the featured full-sky image. The dark red shows the plane of the Milky Way, where the concentration of dust is the highest. The huge arches above the plane are likely remnants of past explosive events from our Galaxy's core, conceptually similar to magnetic loop-like structures seen in our Sun's atmosphere. The curvy streamlines align with interstellar filaments of neutral hydrogen gas and provide tantalizing evidence that magnetic fields may supplement gravity in not only in shaping the interstellar medium, but in forming stars. How magnetism affected our Galaxy's evolution will likely remain a topic of research for years to come.

Science & Technology - Astronomy picture of the day : A Ring of Fire Sunrise Solar Eclipse: :

2020 June 16
A Ring of Fire Sunrise Solar Eclipse
Video Credit: Colin Legg & Geoff Sims; Music: Peter Nanasi

Explanation: What's rising above the horizon behind those clouds? It's the Sun. Most sunrises don't look like this, though, because most sunrises don't include the Moon. In the early morning of 2013 May 10, however, from Western Australia, the Moon was between the Earth and the rising Sun. At times, it would be hard for the uninformed to understand what was happening. In an annular eclipse, the Moon is too far from the Earth to block the entire Sun, and at most leaves a ring of fire where sunlight pours out around every edge of the Moon. The featured time-lapse video also recorded the eclipse through the high refraction of the Earth's atmosphere just above the horizon, making the unusual rising Sun and Moon appear also flattened. As the video continues on, the Sun continues to rise, and the Sun and Moon begin to separate. This weekend, a new annular solar eclipse will occur, visible from central Africa, the Arabian Peninsula, and a narrow band across Asia, with much of Earth's Eastern hemisphere being able to see a partial solar eclipse.

Science & Technology - Astronomy picture of the day : The Milky Way over Snow-Capped Himalayas

2020 May 26

Image Credit & Copyright: Tomas Havel

Explanation: What’s higher than the Himalayas? Although the Himalayan Mountains are the tallest on planet Earth, they don't measure up to the Milky Way. Visible above the snow-capped mountains in the featured image is the arcing central band of our home galaxy. The bright spot just above the central plane is the planet Jupiter, while the brightest orange spot on the upper right is the star Antares. The astrophotographer braved below-zero temperatures at nearly 4,000-meters altitude to take the photographs that compose this image. The featured picture is a composite of eight exposures taken with same camera and from the same location over three hours, just after sunset, in 2019 April, from near Bimtang Lake in Nepal. Over much of planet Earth, the planets Mercury (faint) and Venus (bright) will be visible this week after sunset.

Science & Technologie - Astronomie : Région de la nébuleuse du Cône

Région de la nébuleuse du Cône

26-05-2020

Jérôme Ridelle

Science & Technology - Astronomy picture of the day : South of Carina

2020 May 22

South of Carina
Image Credit & Copyright: Ignacio Diaz Bobillo

Explanation: With natal dust clouds in silhouette against glowing atomic gas, this colorful and chaotic vista lies within one of the largest star forming regions in the Milky Way galaxy, the Great Carina Nebula. The telescopic close-up frames a field of view about 80 light-years across, a little south and east of Eta Carinae, the nebula's most energetic and enigmatic star. Captured under suburban skies improved during national restrictions, a composite of narrowband image data was used to create the final image. In it, characteristic emission from the nebula's ionized sulfur, hydrogen, and oxygen atoms is mapped to red, green, and blue hues, a color palette also popular in Hubble Space Telescope images. The celestial landscape of bright ridges of emission bordered by cool, obscuring dust lies about 7,500 light-years away toward the southern constellation Carina.

Science & Technologie - Le monde vu du ciel : Dunes dans le désert de Namibie

Le mot « désert » est dérivé du latin desertum et désigne un lieu vaste et inculte, abandonné, livré à la solitude. Cela concerne autant les forêts inoccupées par l'Homme que les espaces secs. Au Moyen Âge, le terme avait une connotation religieuse, associé aux retraites, ermitages, par opposition au monde.