A Solar Filament Erupts - Astronomy picture of the day - 2018 September 16

A Solar Filament Erupts 
Image Credit: NASA's GSFC, SDO AIA Team

Explanation: What's happened to our Sun? Nothing very unusual -- it just threw a filament. Toward the middle of 2012, a long standing solar filament suddenly erupted into space producing an energetic Coronal Mass Ejection (CME). The filament had been held up for days by the Sun's ever changing magnetic field and the timing of the eruption was unexpected. Watched closely by the Sun-orbiting Solar Dynamics Observatory, the resulting explosion shotelectrons and ions into the Solar System, some of which arrived at Earth three days later and impacted Earth's magnetosphere, causing visible aurorae. Loops of plasma surrounding an active region can be seen above the erupting filament in the featured ultraviolet image. Although the Sun is now in a relatively inactive state of its 11-year cycle, unexpected holes have opened in the Sun's corona allowing an excess of charged particles to stream into space. As before, these charged particles are creating auroras.

Mont Blanc, Meteor, and Milky Way - Astronomy picture of the day - 2018 September 15

Mont Blanc, Meteor, and Milky Way 
Image Credit & Copyright: Adrien Mauduit

Explanation: Snowy Mont Blanc is near the center of this atmospheric night skyscape. But high, thin clouds fogged the skies at the photographer's location, looking south toward Europe's highest peak from the southern Swiss Alps. Still, the 13 second exposure finds the faint star fields and dark rifts of the Milky Way above the famous white mountain. Bloated by the mist, bright planet Saturn and Antares (right), alpha star of Scorpius, shine through the clouds to flank the galaxy's central bulge. The high-altitude scene is from the rewarding night of August 12/13, so it also includes the green trail of a Perseid meteor shooting along the galactic plane.

Ice Halos at Yellowknife - Astronomy picture of the day - 2018 September 14

Ice Halos at Yellowknife 
Image Credit & Copyright: Stephen Bedingfield

Explanation: You've probably seen a circle around the Sun before. More common than rainbows, ice halos, like a 22 degree circular halo for example, can be easy to spot, especially if you can shade your eyes from direct sunlight. Still it's rare to see such a diverse range of ice halos, including sundogs, tangent, infralateral, and Parry arcs, all found in this snapshot from planet Earth. The picture was quickly taken in the late morning of September 4 from Yellowknife, Northwest Territories, Canada. The beautiful patterns are generated as sunlight (or moonlight) is reflected and refracted in six-sided water ice crystals in Earth's atmosphere. Of course, atmospheric ice halos in the skies ofother worlds are likely to be different.

Real Time Perseid - Astronomy picture of the day - 2018 September 13

Real Time Perseid 
Video Credit & Copyright: Till Credner, AlltheSky.com

Explanation: Bright meteors and dark night skies made this year's Perseid meteor shower a great time for a weekend campout. And while packing away their equipment, skygazers at a campsite in the mountains of southern Germany found at least one more reason to linger under the stars, witnessing this brief but colorful flash with their own eyes. Presented as a 50 frame gif, the two second long video was captured during the morning twilight of August 12. In real time it shows the development of the typical green train of a bright Perseid meteor. A much fainter Perseid is just visible farther to the right. Plowing through Earth's atmosphere at 60 kilometers per second, Perseids are fast enough to excite the characteristic green emission of atomic oxygen at altitudes of 100 kilometers or so.

Lunations - Astronmy picture of the day - 2018 September 12

Lunations 
Video Credit: Data: Lunar Reconnaissance Orbiter ; Animation: NASA's Scientific Visualization Studio;
Music: The Blue Danube (Johann Strauss II)

Explanation: Our Moon's appearance changes nightly. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The featured video animates images taken by NASA's Moon-orbiting Lunar Reconnaissance Orbiter to show all 12 lunations that appear this year, 2018. A single lunation describes one full cycle of our Moon, including all of its phases. A full lunation takes about 29.5 days, just under a month (moon-th). As each lunation progresses, sunlight reflects from the Moon at different angles, and so illuminates different features differently. During all of this, of course, the Moon always keeps the same face toward the Earth. What is less apparent night-to-night is that the Moon's apparent size changes slightly, and that a slight wobble called a libration occurs as the Moon progresses along its elliptical orbit.

Non, cette étude n’a pas conclu qu’un verre d’alcool, c’est trop ! - Santé/médecine

À la fin du mois d’août, une recherche faisait le tour du monde avec des manchettes on ne peut plus éloquentes : un seul verre d’alcool par jour, c’est déjà dangereux pour la santé. En fait, l'étude ne dit pas tout à fait ça.

Les conclusions générales de cette méta-analyse n’étonnent pas : la consommation excessive d’alcool accroît bel et bien le risque de nombreux problèmes, allant de la haute pression sanguine jusqu’au cancer du foie en passant par des pertes de mémoire (on répertorie 23 « troubles de santé » au total).

Le problème réside dans l’attention qui a été accordée à l’affirmation « un seul verre par jour, c’est trop ». Une affirmation qui n’est pas le résultat d’exagérations des médias : c’est ce qu’on peut lire dans le communiqué de presse (« il n’existe pas de niveau sécuritaire d’alcool ») et dans la recherche elle-même.

Verdict :

Bien qu’il ne soit pas faux de dire que « le niveau de consommation qui minimise les pertes de santé est de zéro », la différence d’impact entre zéro verre et un verre est tellement minime qu’elle ne mérite pas de devenir le message central d’une méta-analyse de cette ampleur. Les chercheurs ont dégagé bien davantage de données sur les impacts de la consommation excessive d’alcool.

Science-Presse

Milky Way over Troll's Tongue - Astronomy picture of the day - 2018 September 11

Milky Way over Troll's Tongue 
Image Credit & Copyright: Ruslan Merzlyakov (RMS Photography)

Explanation: You have to take a long hike to see the Troll's Tongue -- ten hours over rocky terrain. And in this case, it took three trips to capture the landform below a clear night sky. Trolltunga itself is a picturesque rock protrusionextending about 700 meters over mountainous cliffs near Lake Ringedalsvatnet in Norway. The overhang is made of billion-year-old Precambrian bedrock that was carved out by glaciers during an ice-age about 10,000 years ago. Thefeatured picture is a composite of two exposures, a 15-second image of the foreground Earth followed 40 minutes later by an 87-second exposure of the background sky. Thousands of discernable stars dot the backdrop starscape in addition to billions of unresolved stars in the nearly vertical band of our Milky Way Galaxy.

Along the Western Veil - Astronomy picture of the day - 2018 September 6

Along the Western Veil 
Image Credit & Copyright: Data - Steve Milne & Barry Wilson, Processing - Steve Milne

Explanation: Delicate in appearance, these filaments of shocked, glowing gas, are draped across planet Earth's sky toward the constellation of Cygnus. They form the western part of the Veil Nebula. The Veil Nebula itself is a largesupernova remnant, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Blasted out in the cataclysmic event, the interstellar shock wave plows through space sweeping up and exciting interstellar material. The glowing filaments are really more like long ripples in a sheet seen almost edge on, remarkably well separated into atomic hydrogen (red) and oxygen (blue-green) gas. Also known as the Cygnus Loop, the Veil Nebula now spans nearly 3 degrees or about 6 times the diameter of the full Moon. While that translates to over 70 light-years at its estimated distance of 1,500 light-years, this telescopic two panel mosaic image of the western portion spans about half that distance. Brighter parts of the western Veil are recognized as separate nebulae, including The Witch's Broom (NGC 6960) along the top of this view andPickering's Triangle (NGC 6979) below and left.

NGC 3682: Sideways Spiral Galaxy - Astronomy picture of the day - 2018 September 5

NGC 3682: Sideways Spiral Galaxy 
Image Credit & Copyright: Data: Paul Gardner, Great Basin Observatory; Processing: Rogelio Bernal Andreo (DeepSkyColors.com)

Explanation: What do spiral galaxies look like sideways? Featured is a sharp telescopic view of a magnificent edge-on spiral galaxy NGC 3628, a puffy galactic disk divided by dark dust lanes. Of course, this deep galactic portraitputs some astronomers in mind of its popular moniker, The Hamburger Galaxy. The tantalizing island universe is about 100,000 light-years across and 35 million light-years away in the northern springtime constellation Leo. NGC 3628shares its neighborhood in the local Universe with two other large spirals M65 and M66 in a grouping otherwise known as the Leo Triplet. Gravitational interactions with its cosmic neighbors are likely responsible for the extended flare and warp of this spiral's disk.

Franz Schubert - "Sérénade" - Video - Music

"Sérénade"