Science & Technology - Astronomy picture of the day : Meteors, Comet, and Big Dipper over La Palma

2019 April 23
Meteors, Comet, and Big Dipper over La Palma Image Credit & Copyright: Vincent Duparc

Explanation: Meteor showers are caused by streams of solid particles, dust size and larger, moving as a group through space. In most cases, the orbits of these meteor streams can be identified with dust expelled from a comet. When the Earth passes through a stream, the particles leave brilliant trails through the night sky as they disintegrate in Earth's atmosphere. The meteor paths are all parallel to each other, but, like train tracks, the effect of perspective causes them to appear to originate from a radiant point in the distance. The featured image composite was taken during January's Quadrantid meteor shower from La Palma, one of Spain's Canary Islands, off the northwest coast of Africa. The Quadrantids radiant is visible just below the handle of the Big Dipper. A careful eye will also discern the faint green coma of Comet Wirtanen. Tonight is the peak of the modest Lyrid meteor shower, with several meteors per hour visible from dark locations with clear skies.

Music live video - Pavarotti & Bono : "Ave Maria"

"Ave Maria"

Science & Techology : "Magnets and marbles" (video)

"Magnets and marbles"

Science & Technology - Astronomy picture of the day : Spiral Aurora over Icelandic Divide

2019 April 21
Spiral Aurora over Icelandic Divide Image Credit & Copyright: Juan Carlos Casado (TWAN, StarryEarth)

Explanation: Admire the beauty but fear the beast. The beauty is the aurora overhead, here taking the form of great green spiral, seen between picturesque clouds with the bright Moon to the side and stars in the background. The beast is the wave of charged particles that creates the aurora but might, one day, impair civilization. In 1859, following notable auroras seen all across the globe, a pulse of charged particles from a coronal mass ejection (CME) associated with a solar flare impacted Earth's magnetosphere so forcefully that they created the Carrington Event. A relatively direct path between the Sun and the Earth might have been cleared by a preceding CME. What is sure is that the Carrington Event compressed the Earth's magnetic field so violently that currents were created in telegraph wires so great that many wires sparked and gave telegraph operators shocks. Were a Carrington-class event to impact the Earth today, speculation holds that damage might occur to global power grids and electronics on a scale never yet experienced. The featured aurora was imaged in 2016 over Thingvallavatn Lake in Iceland, a lake that partly fills a fault that divides Earth's large Eurasian and North American tectonic plates.

Science & Technology - Astronomy picture of the day : Falcon Heavy Launch Close Up

2019 April 20
Falcon Heavy Launch Close Up Image Credit: SpaceX

Explanation: Twenty seven Merlin rocket engines are firing in this close-up of the launch of a Falcon Heavy rocket. Derived from three Falcon 9 first stage rockets with nine Merlin rocket engines each, the Falcon Heavy left NASA's Kennedy Space Center launch pad 39A on April 11. This second launch of a Falcon Heavy rocket carried the Arabsat 6A communications satellite to space. In February of 2018, the first Falcon Heavy launch carried Starman and a Tesla Roadster. Designed to be reusable, both booster stages and the central core returned safely to planet Earth, the boosters to Cape Canaveral Air Force Station landing zones. The core stage landed off shore on autonomous spaceport drone ship Of Course I Still Love You.

Music live video - Samuel Barber : "Agnus Dei"

"Agnus Dei"

Science & Technology - Astronomy picture of the day : Milky Way in Northern Spring

2019 April 19
Milky Way in Northern Spring 
Image Credit & Copyright: Taha Ghouchkanlu (TWAN)

Explanation: A postcard from planet Earth, this springtime night skyscape looks over Alandan lake in the Alborz mountains. Taken after local midnight on April 17, the central Milky Way is rising over the region's southeast horizon. Its luminous track of stars and nebulae along the plane of our galaxy are reflected in the mirror-like lake. The brightest celestial beacon mingled with the diffuse galactic starlight is Jupiter. Slightly dimmer, Saturn is below and left just above the mountains. As spring brought leaves to the trees and the galactic center to the northern night the photographer found it also gave frogs their voices, heard like a melody across the calm water.

Santé et médecine - Un coeur imprimé en 3D à partir de cellules humaines

Une équipe de chercheurs est parvenue à mettre au point un prototype de coeur imprimé en 3D, à partir de cellules humaines. Un bel espoir pour le traitement des maladies cardiovasculaires, cause principale de décès dans les pays industrialisés, et notamment pour les greffes cardiaques.

Si la greffe de coeur est aujourd’hui de plus en plus souvent pratiquée, les risques de rejets du greffon restent une préoccupation majeure, en plus du manque de donneurs. Cette prouesse réalisée par une équipe de chercheurs israélienne de l’université de Tel-Aviv et publiée le 15 avril dernier dans la revue Advanced Science, représente donc une « avancée majeure » dans ce domaine : ils sont en effet parvenus à mettre au point un prototype de coeur imprimé en 3D à partir de cellules prélevées sur le tissu du patient malade. 

« Nous imprimons un coeur entier qui est complètement biocompatible avec le patient et ne provoquera pas de réponse immunitaire » explique ainsi le Professeur Tal Dvir, l’un des chercheurs. Mais pour l’instant, le coeur imprimé reste minuscule, « de la taille d’un coeur de lapin », 20 mm de hauteur pour 14 mm de diamètre, et ne peut pas encore battre comme un vrai coeur. Ils devraient être dans un premier temps greffés sur des animaux.

Passeport Santé

Science & Technologie - Le monde des requins - Le requin corail : un air grincheux

Contrairement à ce que laisse entendre son nom scientifique (Triaenodon obesus), le requin corail est très élancé et mesure en général jusqu'à 1,6 mètre de long. Il affiche constamment un petit air grincheux. On l'appelle également requin à ailerons (ou pointes) blanches car le bout de ses deux nageoires dorsales, la grande et la petite), ainsi que de sa queue, est blanc. Il a la particularité de pouvoir respirer même en restant immobile, alors que la majorité des requins de sa famille (les Carcharhinidés) sont obligés de se déplacer constamment. Il passe donc ses journées à se prélasser sans bouger sur le fond des récifs où il habite et chasse la nuit.

L'UICN le considère comme quasi-menacé, car il est une cible de la pêche.

© inconnu CCO

Science & Technology - Astronomy picture of the day : The Leo Trio

2019 April 18
The Leo Trio Image Credit & Copyright: Markus Bauer

Explanation: This group is popular in the northern spring. Famous as the Leo Triplet, the three magnificent galaxies gather in one field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top). All three are large spiral galaxies but they tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628, also known as the Hamburger Galaxy, is temptingly seen edge-on, with obscuring dust lanes cutting across its puffy galactic plane. The disks of M66 and M65 are both inclined enough to show off their spiral structure. Gravitational interactions between galaxies in the group have left telltale signs, including the tidal tails and warped, inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous view of the region spans almost two degrees (four full moons) on the sky. The field covers about a million light-years at the trio's estimated distance of 30 million light-years. Of course the spiky foreground stars lie within our own Milky Way.