ASTRONOMY - The Eagle Nebula with X-ray Hot Stars

 2023 July 25

The Eagle Nebula with X-ray Hot Stars
Image Credit: X-ray: Chandra: NASA/CXC/SAO, XMM: ESA/XMM-Newton; IR: JWST: NASA/ESA/CSA/STScI, Spitzer: NASA/JPL/CalTech; Visible: Hubble: NASA/ESA/STScI, ESO; Image Processing: L. Frattare, J. Major, N. Wolk, and K. Arcand

Explanation: What do the famous Eagle Nebula star pillars look like in X-ray light? To find out, NASA's orbiting Chandra X-ray Observatory peered in and through these interstellar mountains of star formation. It was found that in M16 the dust pillars themselves do not emit many X-rays, but a lot of small-but-bright X-ray sources became evident. These sources are shown as bright dots on the featured image which is a composite of exposures from Chandra (X-rays), XMM (X-rays), JWST (infrared), Spitzer (infrared), Hubble (visible), and the VLT (visible). What stars produce these X-rays remains a topic of research, but some are hypothesized to be hot, recently-formed, low-mass stars, while others are thought to be hot, older, high-mass stars. These X-ray hot stars are scattered around the frame -- the previously identified Evaporating Gaseous Globules (EGGS) seen in visible light are not currently hot enough to emit X-rays.

ASTRONOMY - The Antikythera Mechanism

 2023 July 23

The Antikythera Mechanism
Image Credit & License: Marsyas, Wikipedia

Explanation: It does what? No one knew that 2,000 years ago, the technology existed to build such a device. The Antikythera mechanism, pictured, is now widely regarded as the first computer. Found at the bottom of the sea aboard a decaying Greek ship, its complexity prompted decades of study, and even today some of its functions likely remain unknown. X-ray images of the device, however, have confirmed that a main function of its numerous clock-like wheels and gears is to create a portable, hand-cranked, Earth-centered, orrery of the sky, predicting future star and planet locations as well as lunar and solar eclipses. The corroded core of the Antikythera mechanism's largest gear is featured, spanning about 13 centimeters, while the entire mechanism was 33 centimeters high, making it similar in size to a large book. Recently, modern computer modeling of missing components is allowing for the creation of a more complete replica of this surprising ancient machine.

GEMMOLOGIE - La fluorine

La fluorine, ou fluorite, est composée de fluorure de calcium (CaF2). Elle possède également des traces de différents ions, ce qui explique ses multiples couleurs. Elle est souvent utilisée en astronomie afin de limiter les phénomènes d'aberration chromatique sur les lentilles et les objectifs. Couleurs : incolore, vert, rose, violet, bleu, etc. 

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

ART FRACTAL - Inquiétante image fractale sur fond rouge

Six petits bonshommes blancs se dirigent avec empressement vers le tapis rouge. Où vont-ils ? Le fond rouge monochrome sur lequel se dessinent des sortes de fissures blanche et verte en forme de flocons de neige ne semble pas très rassurant... 

© Futura

ASTRONOMY - Apollo 11: Armstrong's Lunar Selfie

 2023 July 22

Apollo 11: Armstrong's Lunar Selfie
Image Credit: NASA, Apollo 11, Neil Armstrong; Processing: Michael Ranger

Explanation: A photograph of Buzz Aldrin standing on the Moon taken by Neil Armstrong, was digitally reversed to create this lunar selfie. Captured in July 1969 following the Apollo 11 moon landing, Armstrong's original photograph recorded not only the magnificent desolation of an unfamiliar world, but Armstrong himself reflected in Aldrin's curved visor. In the unwrapped image, the spherical distortion of the reflection in Aldrin's helmet has been reversed. The transformed view features Armstrong himself from Aldrin's perspective. Since Armstrong took the original picture, today the image represents a fifty-four year old lunar selfie. Aldrin's visor reflection in the original image appears here on the left. Bright (but distorted) planet Earth hangs in the lunar sky above Armstrong's figure, toward the upper right. A foil-wrapped leg of the Eagle lander and Aldrin's long shadow stretching across the lunar surface are prominently visible. In 2024 NASA's Artemis II mission will return humans to the Moon.

ASTRONOMY - Meteor and Milky Way over the Alps

 2023 July 16

Meteor and Milky Way over the Alps
Image Credit & Copyright: Nicholas Roemmelt (Venture Photography)

Explanation: Now this was a view with a thrill. From Mount Tschirgant in the Alps, you can see not only nearby towns and distant Tyrolean peaks, but also, weather permitting, stars, nebulas, and the band of the Milky Way Galaxy. What made the arduous climb worthwhile this night, though, was another peak -- the peak of the 2018 Perseids Meteor Shower. As hoped, dispersing clouds allowed a picturesque sky-gazing session that included many faint meteors, all while a carefully positioned camera took a series of exposures. Suddenly, a thrilling meteor -- bright and colorful -- slashed down right next to the nearly vertical band of the Milky Way. As luck would have it, the camera caught it too. Therefore, a new image in the series was quickly taken with one of the sky-gazers posing on the nearby peak. Later, all of the images were digitally combined.

ASTRONOMY - Webb's Rho Ophiuchi

 2023 July 13

Webb's Rho Ophiuchi
Image Credit: NASA, ESA, CSA, STScI, Klaus Pontoppidan (STScI), Processing: Alyssa Pagan (STScI)

Explanation: A mere 390 light-years away, Sun-like stars and future planetary systems are forming in the Rho Ophiuchi molecular cloud complex, the closest star-forming region to our fair planet. The James Webb Space Telescope's NIRCam peered into the nearby natal chaos to capture this infrared image at an inspiring scale. The spectacular cosmic snapshot was released to celebrate the successful first year of Webb's exploration of the Universe. The frame spans less than a light-year across the Rho Ophiuchi region and contains about 50 young stars. Brighter stars clearly sport Webb's characteristic pattern of diffraction spikes. Huge jets of shocked molecular hydrogen blasting from newborn stars are red in the image, with the large, yellowish dusty cavity carved out by the energetic young star near its center. Near some stars in the stunning image are shadows cast by their protoplanetary disks.

ASTRONOMY - Stars, Dust and Nebula in NGC 6559

 2023 July 10

Stars, Dust and Nebula in NGC 6559
Image Credit & Copyright: Adam Block, Telescope Live

Explanation: When stars form, pandemonium reigns. A textbook case is the star forming region NGC 6559. Visible in the featured image are red glowing emission nebulas of hydrogen, blue reflection nebulas of dust, dark absorption nebulas of dust, and the stars that formed from them. The first massive stars formed from the dense gas will emit energetic light and winds that erode, fragment, and sculpt their birthplace. And then they explode. The resulting morass can be as beautiful as it is complex. After tens of millions of years, the dust boils away, the gas gets swept away, and all that is left is a bare open cluster of stars.

METEOROLOGIE - Phénomène extraordinaire : le nuage en forme de champignon atomique

Avez-vous déjà eu l'impression qu'une explosion nucléaire était en train de se produire dans le ciel ? Lors de plus fortes dégradations orageuses, il arrive parfois qu'un nuage en forme de champignon atomique surgisse dans le ciel.

Il s'agit d'un type particulier de nuage d'orage, le Cumulonimbus capillatus incus. Le cumulonimbus est en fait un terme général qui désigne tout nuage d'orage, mais il en existe plusieurs espèces avec des conséquences différentes. Les orages les plus impressionnants en forme de champignon atomique font souvent la Une des actualités des médias locaux. Il arrive même qu'ils créent des moments de panique parmi la population, tant leur forme peut être inquiétante.

Qu'est ce qui donne à un simple cumulonimbus une allure aussi apocalyptique ? C'est en réalité l'enclume très étendue qui donne cette impression de catastrophe nucléaire. L'enclume (incus en latin) est le sommet du nuage d'orage, qui s'étire horizontalement sur 20 à 50 kilomètres lorsqu'il arrive au niveau de la tropopause. Le nuage ne peut plus continuer de monter en altitude, son sommet s'écrase alors contre la tropopause et forme une sorte de couvercle.

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ASTRONOMY - Doomed Star Eta Carinae

 2023 July 9

Doomed Star Eta Carinae
Image Credit & Copyright: NASA, ESA, Hubble; Processing & License: Judy Schmidt

Explanation: Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 170 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This featured image brings out details in the unusual nebula that surrounds this rogue star. Diffraction spikes, caused by the telescope, are visible as bright multi-colored streaks emanating from Eta Carinae's center. Two distinct lobes of the Homunculus Nebula encompass the hot central region, while some strange radial streaks are visible in red extending toward the image right. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks, however, remain unexplained.