ART FRACTAL - Définition

Art et fractales : découverte d’un monde infini

 

Rapide définition de ce qu’est une fractale :

Venant du latin « fractus » (brisé ou irrégulier), une figure fractale est un objet géométrique pouvant s’apparenter à une poupée russe à l’infini. Autrement dit, qu’importe l’endroit où l’on zoome et le niveau de ce rapprochement, on pourra observer le même motif. La forme se reproduit à des échelles différentes, sans fin.

Évidemment, « à l’infini » n’est pas toujours possible, mais l’idée est là. On retrouve ce principe dans la nature ; un exemple assez parlant est le chou romanesco :

Le chou romanesco : une fractale naturelle

On observe bien la répétition du motif d’un splendide vert clair : les excroissances sont formées d’ensembles similaires plus petits, et ainsi de suite. Ce n’est évidemment pas le seul exemple naturel : les poumons et leurs alvéoles peuvent aussi être considérés fractales.

Lartboratoire

ASTRONOMY - Star Formation in the Eagle Nebula

 2022 March 14

Star Formation in the Eagle Nebula
Image Credit: NASA, ESA, Hubble; Processing & Copyright: Ignacio Diaz Bobillo & Diego Gravinese

Explanation: Where do stars form? One place, star forming regions known as "EGGs", are being uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16). Short for evaporating gaseous globules, EGGs are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas and dust -- revealing yet more EGGs and more young stars. This featured picture was created from exposures spanning over 30 hours with the Earth-orbiting Hubble Space Telescope in 2014, and digitally processed with modern software by experienced volunteers in Argentina. Newborn stars will gradually destroy their birth pillars over the next 100,000 years or so -- if a supernova doesn't destroy them first.

ASTRONOMY - A Flower-shaped rock on Mars

 2022 March 9

A Flower-Shaped Rock on Mars
Image Credit: NASA, JPL-Caltech, MSSS

Explanation: It is one of the more unusual rocks yet found on Mars. Smaller than a penny, the rock has several appendages that make it look, to some, like a flower. Although it would be a major discovery if the rock was truly a fossilized ancient Martian flower, there are less spectacular -- and currently preferred -- explanations for its unusual structure. One theory that has emerged is that the rock is a type of concretion created by minerals deposited by water in cracks or divisions in existing rock. These concretions can be compacted together, can be harder and denser than surrounding rock, and can remain even after the surrounding rock erodes away. The flower structure may also be caused by crystal clusters. The small rock, named Blackthorn Salt, has similarities to previously imaged Martian pebbles. The featured image was taken by the Curiosity rover on Mars in late February. Scientists will continue to study data and images taken of this -- and similar -- surprising Martian rocks.

ASTRONOMY - Moon in Inverted Colors

 2022 March 8

Moon in Inverted Colors
Image Credit & Copyright: Dawid Glawdzin

Explanation: Which moon is this? It's Earth's moon -- but in inverted colors. Here, the pixel values corresponding to light and dark areas have been translated in reverse, or inverted, producing a false-color representation reminiscent of a black and white photographic negative. However, this is an inverted color image -- where the muted colors of the moon are real but digitally exaggerated before inversion. Normally bright rays from the large crater Tycho dominate the southern (bottom) features as easily followed dark green lines emanating from the 85-kilometer diameter impact site. Normally dark lunar mare appear light and silvery. The image was acquired in Southend-on-Sea, England, UK. Historically, astronomical images recorded on photographic plates were directly examined on inverted-color negatives because it helped the eye pick out faint details.

ASTRONOMY - A lion in Orion

 2022 March 7

A Lion in Orion
Image Credit & Copyright: Maroun Mahfoud

Explanation: Yes, but can you see the lion? A deep exposure shows the famous dark indentation that looks like a horse's head, visible just left and below center, and known unsurprisingly as the Horsehead Nebula. The Horsehead Nebula (Barnard 33) is part of a vast complex of dark absorbing dust and bright glowing gas. To bring out details of the Horsehead's pasture, an astrophotographer artistically combined light accumulated for over 20 hours in hydrogen (orange), oxygen (blue), and sulfur (green). The resulting spectacular picture captured from Raachine, Lebanon, details an intricate tapestry of gaseous wisps and dust-laden filaments that were created and sculpted over eons by stellar winds and ancient supernovas. The featured composition brings up another pareidolic animal icon -- that of a lion's head -- in the expansive orange colored gas above the horse's head. The Flame Nebula is visible just to the left of the Horsehead. The Horsehead Nebula lies 1,500 light years distant towards the constellation of Orion.

ASTRONOMY - Venus and the Triply Ultraviolet Sun

 022 March 6

Venus and the Triply Ultraviolet Sun
Image Credit: NASA/SDO & the AIA, EVE, and HMI teams; Digital Composition: Peter L. Dove

Explanation: This was a very unusual type of solar eclipse. Typically, it is the Earth's Moon that eclipses the Sun. In 2012, though, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun. Eventually the alignment became perfect and the phase of Venus dropped to zero. The dark spot of Venus crossed our parent star. The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire. Pictured here during the occultation, the Sun was imaged in three colors of ultraviolet light by the Earth-orbiting Solar Dynamics Observatory, with the dark region toward the right corresponding to a coronal hole. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again. The next Venusian transit across the Sun will occur in 2117.

ASTRONOMY - The Multiwavelength crab

 2022 March 4

The Multiwavelength Crab
NASA, ESA, G. Dubner (IAFE, CONICET-University of Buenos Aires) et al.;
A. Loll et al.; T. Temim et al.; F. Seward et al.; VLA/NRAO/AUI/NSF; Chandra/CXC;
Spitzer/JPL-Caltech; XMM-Newton/ESA; Hubble/STScI

Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from massive star's death explosion, witnessed on planet Earth in 1054 AD. This brave new image offers a 21st century view of the Crab Nebula by presenting image data from across the electromagnetic spectrum as wavelengths of visible light. From space, Chandra (X-ray) XMM-Newton (ultraviolet), Hubble (visible), and Spitzer (infrared), data are in purple, blue, green, and yellow hues. From the ground, Very Large Array radio wavelength data is shown in red. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.

Microphotography - Mareck Mis - Air bubbles

 

Air bubbles formed from melted ascorbic acid (vitamin C) crystals

FuturaSciences

ASTRONOMY - Spiral Galaxy NGC 2841

 2022 March 3

Spiral Galaxy NGC 2841
Image Credit & Copyright: Vitali Pelenjow

Explanation: A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This deep view of the gorgeous island universe was captured during 32 clear nights in November, December 2021 and January 2022. It shows off a striking yellow nucleus, galactic disk, and faint outer regions. Dust lanes, small star-forming regions, and young star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions. NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way. X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo around NGC 2841.

AERONAUTIQUE - Avions de légende - Le Canadair CL-415

 

Bombardier d'eau à la capacité impressionante, le Canadair CL-415 est un avion 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

FuturaSciences