ASTRONOMY - A SAR Arc from New Zealand

 2024 January 3

A SAR Arc from New Zealand
Image Credit & Copyright: Tristian McDonald; Text: Tiffany Lewis (Michigan Tech U.)

Explanation: What is that unusual red halo surrounding this aurora? It is a Stable Auroral Red (SAR) arc. SAR arcs are rare and have only been acknowledged and studied since 1954. The featured wide-angle photograph, capturing nearly an entire SAR arc surrounding more common green and red aurora, was taken earlier this month from Poolburn, New Zealand, during an especially energetic geomagnetic storm. Why SAR arcs form remains a topic of research, but is likely related to Earth's protective magnetic field, a field created by molten iron flowing deep inside the Earth. This magnetic field usually redirects incoming charged particles from the Sun's wind toward the Earth's poles. However, it also traps a ring of ions closer to the equator, where they can gain energy from the magnetosphere during high solar activity. The energetic electrons in this ion ring can collide with and excite oxygen higher in Earth's ionosphere than typical auroras, causing the oxygen to glow red. Ongoing research has uncovered evidence that a red SAR arc can even transform into a purple and green STEVE.

ASTRONOMY - Rocket Transits Rippling Moon

 2024 January 2

Rocket Transits Rippling Moon
Image Credit & Copyright: Steven Madow

Explanation: Can a rocket make the Moon ripple? No, but it can make a background moon appear wavy. The rocket, in this case, was a SpaceX Falcon Heavy that blasted off from NASA's Kennedy Space Center last week. In the featured launch picture, the rocket's exhaust plume glows beyond its projection onto the distant, rising, and nearly full moon. Oddly, the Moon's lower edge shows unusual drip-like ripples. The Moon itself, far in the distance, was really unchanged. The physical cause of these apparent ripples was pockets of relatively hot or rarefied air deflecting moonlight less strongly than pockets of relatively cool or compressed air: refraction. Although the shot was planned, the timing of the launch had to be just right for the rocket to be transiting the Moon during this single exposure.

ASTRONOMY - NGC 1232: A Grand Design Spiral Galaxy

 2024 January 1

NGC 1232: A Grand Design Spiral Galaxy
Image Credit: FORS, 8.2-meter VLT Antu, ESO

Explanation: Galaxies are fascinating not only for what is visible, but for what is invisible. Grand spiral galaxy NGC 1232, captured in detail by one of the Very Large Telescopes, is a good example. The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms revolving about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate the dynamics of the inner galaxy. Leading theories indicate that even greater amounts of matter are invisible, in a form we don't yet know. This pervasive dark matter is postulated, in part, to explain the motions of the visible matter in the outer regions of galaxies.

ASTRONOMIE - Photo - La lune dans les ailes

"La Lune dans les ailes" 

"J'avais remarqué la possibilité de faire une photo sympa moulin et lune. Parti le bon soir, avec une bonne météo et de la patience.

Ce moulin se trouve a terdeghem 59"

Pierre Derycke

BIOMIMETISME - Innovations inspirées par la Nature - Des robots spatiaux équipés de patte de gecko

Comment font les geckos pour escalader des surfaces totalement lisses sans tomber ? Le dessous de leurs pattes est tapissé de milliers de replis eux-mêmes recouverts de petits poils. Ces lamelles adhésives ne sécrètent pas de mucus ou autres substances biologiques, leur capacité adhésive tient seulement dans l'apparition des forces de van der Waals entre les poils des pattes et la surface sur laquelle le gecko marche. Elles sont suffisamment fortes pour que le petit reptile puisse marcher au plafond.

Cette prouesse a inspiré les ingénieurs en aérospatial pour créer des systèmes d'adhérence sèche qui pourraient équiper des robots officiant dans le vide spatial où les ventouses sont inefficaces. Un matériau conçu à partir des pattes de gecko a été testé avec succès en 2017 par des chercheurs de l'université de Standford.

© Brian Gratwicke, Wikimedia Commons, CC by-sa 2.0 Générique

FuturaSciences

ASTRONOMY - Illustris: A Simulation of the Universe

 2023 December 31

Illustris: A Simulation of the Universe
Video Credit: Illustris Collaboration, NASA, PRACE, XSEDE, MIT, Harvard CfA;
Music: The Poisoned Princess (Media Right Productions)

Explanation: How did we get here? Click play, sit back, and watch. A computer simulation of the evolution of the universe provides insight into how galaxies formed and perspectives into humanity's place in the universe. The Illustris project exhausted 20 million CPU hours in 2014 following 12 billion resolution elements spanning a cube 35 million light years on a side as it evolved over 13 billion years. The simulation tracks matter into the formation of a wide variety of galaxy types. As the virtual universe evolves, some of the matter expanding with the universe soon gravitationally condenses to form filaments, galaxies, and clusters of galaxies. The featured video takes the perspective of a virtual camera circling part of this changing universe, first showing the evolution of dark matter, then hydrogen gas coded by temperature (0:45), then heavy elements such as helium and carbon (1:30), and then back to dark matter (2:07). On the lower left the time since the Big Bang is listed, while on the lower right the type of matter being shown is listed. Explosions (0:50) depict galaxy-center supermassive black holes expelling bubbles of hot gas. Interesting discrepancies between Illustris and the real universe have been studied, including why the simulation produced an overabundance of old stars.

MUSIC - Johann Sebastian Bach - Air on g string

"Air on g string"

ASTRONOMY - The Last Full Moon

 2023 December 30

The Last Full Moon
Image Credit & Copyright: Giacomo Venturin

Explanation: Known to some in the northern hemisphere as December's Cold Moon or the Long Night Moon, the last full moon of 2023 is rising in this surreal mountain and skyscape. The Daliesque scene was captured in a single exposure with a camera and long telephoto lens near Monte Grappa, Italy. The full moon is not melting, though. Its stretched and distorted appearance near the horizon is caused as refraction along the line of sight changes and creates shifting images or mirages of the bright lunar disk. The changes in atmospheric refraction correspond to atmospheric layers with sharply different temperatures and densities. Other effects of atmospheric refraction produced by the long sight-line to this full moon rising include the thin red rim seen faintly on the distorted lower edge of the Moon and a thin green rim along the top.

MUSIC - Friar Alessandro - Adeste fideles

"Adeste fideles"

ASTRONOMY - The Same Color Illusion

 2023 December 18

The Same Color Illusion
Image Credit: Edward H. Adelson, Wikipedia

Explanation: Are squares A and B the same color? They are! To verify this, either run your cursor over the image or click here to see them connected. The featured illusion, an example of the same color illusion, illustrates that purely human perceptions in science may be ambiguous or inaccurate, even such a seemingly direct perception as relative color. Similar illusions exist on the sky, such as the size of the Moon near the horizon, or the apparent shapes of astronomical objects. The advent of automated, reproducible measuring devices such as CCDs have made science in general and astronomy in particular less prone to, but not free of, human-biased illusions.