AERONAUTIQUE - La reaversée de la Manche en flyboard

 

ASTRONOMY - Video: Flash on Jupiter

 2021 September 17

Video: Flash on Jupiter
Video Credit & Copyright: T. Humbert, S. Barré, A. Desmougin & D. Walliang (Société Lorraine d'Astronomie), Astroqueyras

Explanation: There has been a flash on Jupiter. A few days ago, several groups monitoring our Solar System's largest planet noticed a two-second long burst of light. Such flashes have been seen before, with the most famous being a series of impactor strikes in 1994. Then, fragments of Comet Shoemaker-Levy 9 struck Jupiter leaving dark patches that lasted for months. Since then, at least seven impacts have been recorded on Jupiter -- usually discovered by amateur astronomers. In the featured video, variations in the Earth's atmosphere cause Jupiter's image to shimmer when, suddenly, a bright flash appears just left of center. Io and its shadow are visible on the right. What hit Jupiter will likely never be known, but considering what we do know of the nearby Solar System, it was likely a piece of rocky and ice -- perhaps the size of a bus -- that broke off long-ago from a passing comet or asteroid.

ASTRONOMY - Firefly Milky Way over Russia

 2021 September 6

Firefly Milky Way over Russia
Image Credit & Copyright: Anton Komlev

Explanation: It started with a pine tree. The idea was to photograph a statuesque pine in front of the central band of our Milky Way Galaxy. And the plan, carried out two months ago, was successful -- they both appear prominently. But the resulting 3-frame panorama captured much more. Colorful stars, for example, dot the distant background, with bright Altair visible on the upper left. The planet Saturn, a bit closer, was captured just over the horizon on the far left. Just beyond the Earth's atmosphere, seen in the upper right, an Earth-orbiting satellite was caught leaving a streak during the 25-second exposure. The Earth's atmosphere itself was surprisingly visible -- as green airglow across the image top. Finally, just by chance, there was a firefly. Do you see it? Near the image bottom, the firefly blinked in yellow several times as it fluttered before the rolling hills above Milogradovka River in Primorsky Krai, Russia.

POURQUOI - Pourquoi rêve-t-on ?

Il s'agit de quelque chose de nécessaire à la vie. Il semblerait que sans cela nous mourons. Nous avons donc besoin de le faire afin que notre cerveau effectue sa "maintenance quotidienne".

Lorsque l'on dort, il nous arrive de rêver. Certains se voient en train de chevaucher des licornes, d'autre volent. Il y en a même qui se prennent pour des flamants roses. Bref, ils sont parfois étranges et il nous est bien difficile de les interpréter lorsque l'on se réveille. Mais au fait, pourquoi rêve-t-on ?

En fait, il nous faut commencer par le début et comprendre le sommeil. Ce dernier a une fonction réparatrice et récupératrice. Il possède trois phases, qui forment un cycle : le sommeil lent léger, le sommeil lent lourd et enfin le sommeil paradoxal (période de rêves).

Chaque cycle dure environ 1 h 30 à 2 h, donc nous rêvons plusieurs fois dans la nuit. Selon le moment où l'on se réveille, on peut s'en rappeler ou non (un phénomène que nous vous détaillons dans cet article). On peut comparer notre cerveau à un ordinateur dans ce cas, le rêve ayant une fonction de défragmentation. En d'autres termes, on peut dire qu'au cours du rêve, nos souvenirs se mettent en place. Chez les bébés, il sert à mettre en place la mémoire. D'ailleurs, plus on vieillit, moins on rêve.

Il est encore peu connu, mais sa fonction principale est de réorganiser les souvenirs et connaissances que nous avons accumulés dans la journée. Il peut aussi évoquer des malaises que l'on a dans la vie, tout comme nos bonheurs quotidiens. Ils sont l'expression la plus claire de ce que nous sommes.

ASTRONOMY - A Falcon 9 Nebula

 2021 September 4

A Falcon 9 Nebula
Image Credit & Copyright: Dennis Huff

Explanation: Not the Hubble Space Telescope's latest view of a distant galactic nebula, this illuminated cloud of gas and dust dazzled early morning spacecoast skygazers on August 29. The snapshot was taken at 3:17am from Space View Park in Titusville, Florida. That's about 3 minutes after the launch of a SpaceX Falcon 9 rocket on the CRS-23 mission to resupply the International Space Station. It captures drifting plumes and exhaust from the separated first and second stage of the rocket rising through still dark skies. The lower bright dot is the second stage continuing on to low Earth orbit. The upper one is the rocket's first stage performing a boostback burn. Of course the first stage booster returned to make the first landing on the latest autonomous drone ship to arrive in the Atlantic, A Short Fall of Gravitas.

AERONAUTIQUE - M4 Bison

"M4 Bison"

ASTRONOMY - M51: The Whirlpool Galaxy

 2021 September 2

M51: The Whirlpool Galaxy
Image Credit & Copyright: Josep Drudis

Explanation: Find the Big Dipper and follow the handle away from the dipper's bowl until you get to the last bright star. Then, just slide your telescope a little south and west and you'll come upon this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (top), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the eye, deep images like this one reveal its striking colors and galactic tidal debris.

ASTRONOMY - Dancing Ghosts: Curved Jets from Active Galaxies

2021 September 1

Dancing Ghosts: Curved Jets from Active Galaxies
Image Credit: Jayanne English & Ray Norris, EMU-ASKAP, DES; Text: Jayanne English (U. Manitoba)

Explanation: Why would galaxies emit jets that look like ghosts? And furthermore, why do they appear to be dancing? The curled and fluffy jets from the supermassive black holes at the centers of two host galaxies (top center and lower left) are unlike anything seen before. They were found by astronomers using the Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope when creating maps tracing the evolution of galaxies. Images preceding this Evolutionary Map of the Universe survey only showed amorphous blobs. Eventually, comparisons of relative amounts of energy emitted revealed the glowing elongated structures were created by electrons streaming around magnetic field lines. Overlaying the radio data on an optical view of the sky (Dark Energy Survey) confirmed that the electron streams originated from the centers of active galaxies. Usually such Active Galactic Nuclei (AGN) produce straight jets. A leading hypothesis for the geometric origin of these unusually graceful shapes involves the flow of large-scale intergalactic winds. 

ASTRONOMY - A Blue Hour Full Moon

 2021 August 26

A Blue Hour Full Moon
Image Credit & Copyright: Giorgia Hofer

Explanation: Nature photographers and other fans of planet Earth always look forward to the blue hour. That's the transition in twilight, just before sunrise or after sunset, when the Sun is below the horizon but land and sky are still suffused with a beautiful blue light. After sunset on August 21, this blue hour snapshot captured the nearly full Moon as it rose opposite the Sun, above the rugged Italian Alps from Cortina d'Ampezzo, Italy. Sharing bluish hues with the sky, the rocky pyramid of Monte Antelao, also known as the King of the Dolomites, is the region's prominent alpine peak. The moonlight is yellow, but even so this full Moon was known to some as a seasonal Blue Moon. That's because by one definition the third full Moon of a season with four full moons in it is called a Blue Moon. Recognizing a season as the time between a solstice and an equinox, this season's fourth full Moon will be rising in the blue hour of September 20, just before September's equinox.

MINERAUX - Le sélénite, une pierre de lune

Considéré comme une variété de gypse, le sélénite permet de voir « l'éclat de la Lune ». Son nom provient d'ailleurs de selentis, qui signifie « pierre de Lune » en grec. La région de Bologne, en Italie, est connue pour en contenir beaucoup. Elle fut d'ailleurs utilisée pour construire les premières fortifications de la ville, aujourd'hui disparue.

Couleur : incolore à rougeâtre.

© mockbird, Flickr, CC by-sa 2.0