Nasa : La Terre vue de l'Espace - "Les dunes en étoile du Grand Erg Oriental, en Algérie" - (Science & Technologie)

Dans le désert du Sahara algérien, le Grand Erg Oriental se caractérise par ses dunes en étoile de forme pyramidale qui sont façonnées par des vents dont l'orientation ne cesse de changer. Ainsi, d'est en été, les vents tournent en ouest une fois l'hiver venu. C'est la combinaison de ces vents changeant avec les spécificités géographiques de cette région et les tempêtes qui la traversent qui façonnent ces dunes en étoile.

Cette image satellite a été obtenue en associant de la lumière proche infrarouge et visible. Le sable est de couleur ocre, les ombres sont noires ou grises. Les zones bleutées représentent des roches évaporites.

© Nasa

Science & Technologie - La Terre vue de l'Espace : Eruption du mont Saint Helens

Photo prise le 8 mars 2005, une semaine après l'éruption de poussière et de vapeur. La dernière éruption depuis ce réveil du mont Saint Helens datait alors de septembre 2004. La végétation est en vert et la neige en bleu.

© Nasa/GSFC/METI/ERSDAC/JAROS et U.S./Japan Aster Science Team

NASA : Iron in the Butterfly Nebula (Science & Technology - Astronomy picture of the day)

2020 July 21
Iron in the Butterfly Nebula
Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt

Explanation: Can stars, like caterpillars, transform themselves into butterflies? No, but in the case of the Butterfly Nebula -- it sure looks like it. Though its wingspan covers over 3 light-years and its estimated surface temperature exceeds 200,000 degrees, C, the dying central star of NGC 6302, the featured planetary nebula, has become exceptionally hot, shining brightly in visible and ultraviolet light but hidden from direct view by a dense torus of dust. This sharp close-up was recorded by the Hubble Space Telescope and is reprocessed here to show off the remarkable details of the complex planetary nebula, highlighting in particular light emitted by iron, shown in red. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius). Planetary nebulas evolve from outer atmospheres of stars like our Sun, but usually fade in about 20,000 years.

Somak Raychaudhury : Eclipse under the Bamboo (Science & Technology - Astronomy picture of the day)

                   Eclipse under the Bamboo
Image Credit & Copyright: Somak Raychaudhury (Inter-University Centre for Astronomy & Astrophysics)

Explanation: Want to watch a solar eclipse safely? Try looking down instead of up, though you might discover you have a plethora of images to choose from. For example, during the June 21st solar eclipse this confusing display appeared under a shady bamboo grove in Pune, India. Small gaps between close knit leaves on the tall plants effectively created a network of randomly placed pinholes. Each one projected a separate image of the eclipsed Sun. The snapshot was taken close to the time of maximum eclipse in Pune when the Moon covered about 60 percent of the Sun's diameter. But an annular eclipse, the Moon in silhouette completely surrounded by a bright solar disk at maximum, could be seen along a narrow path where the Moon's dark shadow crossed central Africa, south Asia, and China.

Tom Masterson : Finding NEOWISE - Science & Technology - Astronomy picture of the day

Finding NEOWISE
Image Credit & Copyright: Tom Masterson

Explanation: If you can see the stars of the Big Dipper, you can find comet NEOWISE in your evening sky tonight. After sunset look for the naked-eye comet below the bowl of the famous celestial kitchen utensil of the north and above your northwestern horizon. You're looking for a fuzzy 'star' with a tail, though probably not so long a tail as in this clear sky snapshot taken from Los Padres National Forest in California on the evening of July 16. Recent photographs of C/2020 F3 (NEOWISE) often show this comet's broad dust tail and fainter but separate ion tail extending farther than the eye can follow. Skygazers around the world have been delighted to find NEOWISE, surprise visitor from the outer Solar System.

Christouf Prod - "Hyper tsunami" - Science & Technologie - Tsunami

Youtube : Océan inconnu - Science & Technologie - Océans - Video

Une médecine ultra personnalisée : Maladies génétiques très rares (Science & Technologie - Santé/Médecine)

En médecine, de nouveaux médicaments contre les maladies génétiques très rares sont en train de voir le jour. L'un des premiers cas est celui de Mila Makovec, une jeune fille souffrant d'une maladie génétique unique, qui a reçu un traitement conçu spécifiquement pour elle.

Remplacer, modifier ou supprimer des gènes n'a jamais été aussi facile. Reste à répondre à une question cruciale: qui paiera pour ces médicaments alors qu'ils n'aident à chaque fois qu'une seule personne et demandent de lourds investissements humains?

Philipp Salzgeber, foto-webcam.eu; Text: Adam Block : Comet NEOWISE over the Swiss Alps (Science & Technology - Astronomy picture of the day)

2020 July 15
Comet NEOWISE over the Swiss Alps
Image Credit & Copyright: Philipp Salzgeber, foto-webcam.eu; Text: Adam Block

Explanation: Comet NEOWISE has been wowing photographers around much of the world during dawn and dusk, at the margins of day and night. For the most northern residents of planet Earth, however, the comet circles the North Star and never sets. The night part of this circular arc is apparent in the featured composite of images assembled from a webcam located at a ski resort in the Swiss Alps. Images were selected at 30-minute intervals throughout the night from July 12th -13th. Comet NEOWISE (C/2020 F3) will continue to become more accessible to northern hemisphere observers as its motion places it higher in the sky each evening after sunset over the next few weeks, as it begins its outbound journey. As with all comets, departure from the inner Solar System comes with inevitable fading. Binoculars are the best way to find and observe the comet visually.

Declan Deval : Comet NEOWISE over Stonehenge (Science & Technology - Astronomy picture of the day)

2020 July 14
Comet NEOWISE over Stonehenge
Image Credit & Copyright: Declan Deval Explanation: Have you ever seen a comet? Tonight -- and likely the next few nights -- should be a good chance. Go outside just at sunset and look to your northwest. The lower your horizon, the better. Binoculars may help, but if your sky is cloudless and dark, all you should need is your unaided eyes and patience. As the Sun sets, the sky will darken, and there will be an unusual faint streak pointing diagonally near the horizon. That is Comet NEOWISE. It is a 5-kilometer-wide evaporating dirty iceberg visiting from -- and returning to -- the outer Solar System. As the Earth turns, the comet will soon set, so you might want to take a picture. In the featured image, Comet C/2020 F3 (NEOWISE) was captured two mornings ago rising over Stonehenge in the UK. Discovered with the NASA satellite NEOWISE toward the end of March, Comet NEOWISE has surprised many by surviving its closest approach to the Sun, brightening dramatically, and developing impressive (blue) ion and (white) dust tails.