ASTRONOMY - M94: A Double Ring Galaxy

 2023 June 7

M94: A Double Ring Galaxy
Image Credit & Copyright: Brian Brennan

Explanation: Most galaxies don't have any rings of stars and gas -- why does M94 have two? First, spiral galaxy M94 has an inner ring of newly formed stars surrounding its nucleus, giving it not only an unusual appearance but also a strong interior glow. A leading origin hypothesis holds that an elongated knot of stars known as a bar rotates in M94 and has generated a burst of star formation in this inner ring. Observations have also revealed another ring, an outer ring, one that is more faint, different in color, not closed, and relatively complex. What caused this outer ring is currently unknown. M94, pictured here, spans about 45,000 light years in total, lies about 15 million light years away, and can be seen with a small telescope toward the constellation of the Hunting Dogs (Canes Venatici).

AERONAUTIQUE - Avions de légende - Le Canadair CL 415 - un bombardier d'eau à la capacité impressionnante

Le Canadair CL-415 est un avion bombardier d’eau fabriqué par la firme canadienne Bombardier Aéronautique. Spécialisé dans la lutte contre les incendies, il est utilisé par de nombreux pays, dont la France où il est affublé du surnom de « Pélican ». Cet avion réputé pour sa fiabilité possède deux réservoirs qui peuvent emmagasiner un peu plus de 6.000 litres d’eau.

© Claudio, CC by-nc 2.0

GEMMOLOGIE - La magnifique topaze

Espèce minérale de formule Al2SiO4(F,OH)2, la topaze peut contenir des traces de fer, de chrome, de magnésium et de titane. Lorsqu'on expose longtemps cette pierre fine à la lumière solaire, elle peut changer de couleur. Couleurs : incolore à blanc, bleu, verdâtre, brun jaune, orange, rose, rougeâtre, violet, brun.

© Rob Lavinsky, Wikimedia Commons, CC by-sa 3.0

ASTRONOMY - Star Eats Planet

 2023 June 6

Star Eats Planet
Illustrative Video Credit: K. Miller & R. Hurt (Caltech, IPAC)

Explanation: It’s the end of a world as we know it. Specifically, the Sun-like star ZTF SLRN-2020 was seen eating one of its own planets. Although many a planet eventually dies by spiraling into their central star, the 2020 event, involving a Jupiter-like planet, was the first time it was seen directly. The star ZTF SLRN-2020 lies about 12,000 light years from the Sun toward the constellation of the Eagle (Aquila). In the featured animated illustration of the incident, the gas planet's atmosphere is first pictured being stripped away as it skims along the outskirts of the attracting star. Some of the planet's gas is absorbed into the star's atmosphere, while other gas is expelled into space. By the video's end, the planet is completely engulfed and falls into the star's center, causing the star's outer atmosphere to briefly expand, heat up, and brighten. One day, about eight billion years from now, planet Earth may spiral into our Sun.

ASTRONOMY - In the Center of the Trifid Nebula

 2023 June 5

In the Center of the Trifid Nebula
Image Credit & Copyright: Martin Pugh

Explanation: What's happening at the center of the Trifid Nebula? Three prominent dust lanes that give the Trifid its name all come together. Mountains of opaque dust appear near the bottom, while other dark filaments of dust are visible threaded throughout the nebula. A single massive star visible near the center causes much of the Trifid's glow. The Trifid, cataloged as M20, is only about 300,000 years old, making it among the youngest emission nebulas known. The star forming nebula lies about 9,000 light years away toward the constellation of the Archer (Sagittarius). The region pictured here spans about 20 light years.

ART FRACTAL - Fractales symétriques envoûtantes

Sur cette fractale, deux formes géométriques jumelles ressemblant à des dragons, l'un jaune et l'autre rouge, se font dos. En grossissant des détails de leurs contours, on peut quasiment reproduire la figure d'origine. Les deux pseudo-dragons sont englobés dans une bulle psychédélique verte. 

© Futura

ASTRONOMY - Charon: Moon of Pluto

 2023 June 3

Charon: Moon of Pluto
Image Credit: NASA, Johns Hopkins Univ./APL, Southwest Research Institute, U.S. Naval Observatory

Explanation: A darkened and mysterious north polar region known to some as Mordor Macula caps this premier high-resolution view. The portrait of Charon, Pluto's largest moon, was captured by New Horizons near the spacecraft's closest approach on July 14, 2015. The combined blue, red, and infrared data was processed to enhance colors and follow variations in Charon's surface properties with a resolution of about 2.9 kilometers (1.8 miles). A stunning image of Charon's Pluto-facing hemisphere, it also features a clear view of an apparently moon-girdling belt of fractures and canyons that seems to separate smooth southern plains from varied northern terrain. Charon is 1,214 kilometers (754 miles) across. That's about 1/10th the size of planet Earth but a whopping 1/2 the diameter of Pluto itself, and makes it the largest satellite relative to its parent body in the Solar System. Still, the moon appears as a small bump at about the 1 o'clock position on Pluto's disk in the grainy, negative,telescopic picture inset at upper left. That view was used by James Christy and Robert Harrington at the U.S. Naval Observatory in Flagstaff to discover Charon in June of

ASTRONOMY - Messier 101

 2023 June 2

Messier 101
Image Credit: NASA, ESA, CFHT, NOAO;
Acknowledgement - K.Kuntz (GSFC), F.Bresolin (U.Hawaii), J.Trauger (JPL), J.Mould (NOAO), Y.-H.Chu (U. Illinois)

Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way. M101 was also one of the original spiral nebulae observed by Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. Assembled from 51 exposures recorded by the Hubble Space Telescope in the 20th and 21st centuries, with additional data from ground based telescopes, this mosaic spans about 40,000 light-years across the central region of M101 in one of the highest definition spiral galaxy portraits ever released from Hubble. The sharp image shows stunning features of the galaxy's face-on disk of stars and dust along with background galaxies, some visible right through M101 itself. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.

CLIMAT - Une invasion impressionnante de méduses sur les plages de la côte Atlantique

Des centaines de milliers de méduses se sont échouées entre le week-end dernier et ce mercredi sur la côte Atlantique. Du Finistère jusqu'aux Landes, quasiment aucune côte de l'arc atlantique n'a échappé à l'invasion des méduses ces derniers jours. En cause, de multiples facteurs.

Le phénomène est courant au mois de mai et juin, mais cette année, la quantité de méduses présentes est exceptionnelle, aux dires des habitants comme des spécialistes du littoral.

En ce début de semaine, Châtelaillon-Plage, la Rochelle, Royan, Pornic, Pornichet, Quiberon et Lorient sont les communes de la côte Atlantique les plus concernées par cette invasion.

L'arrivée massive de méduses sur le littoral et ses plages peut s'expliquer par ces trois facteurs :une hausse rapide des températures de l'eau : sur la côte Atlantique, l'eau s'est réchauffée de 3 à 4 °C en moyenne en l'espace de trois semaines. La température atteint désormais 16 °C au nord de la côte Atlantique, et 18 à 19 °C au sud-ouest. La hausse des températures est la principale cause de prolifération des méduses.

les courants marins : les méduses se laissent porter par les courants en surface, d'autant plus lorsqu'ils sont chauds.

des facteurs environnementaux : la surpêche supprime le nombre de prédateurs potentiels des méduses. Là où les poissons disparaissent, les méduses prolifèrent, de même que la pollution maritime, surtout d'origine agricole, leur est favorable.

FuturaSciences

ASTRONOMY - Simulation: A Disk Galaxy Forms

 2023 May 31

Simulation: A Disk Galaxy Forms
Video Credit: TNG Collaboration, MPCDF, FAS Harvard U.; Music: World's Sunrise (YouTube: Jimena Contreras)

Explanation: How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Specifically, this featured video from the IllustrisTNG collaboration tracks gas from the early universe (redshift 12) until today (redshift 0). As the simulation begins, ambient gas falls into and accumulates in a region of relatively high gravity. After a few billion years, a well-defined center materializes from a strange and fascinating cosmic dance. Gas blobs -- some representing small satellite galaxies -- continue to fall into and become absorbed by the rotating galaxy as the present epoch is reached and the video ends. For the Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years.