PRATIQUE - Empêcher l'eau bouillante de déborder

 

ASTRONOMY - The Aurora Tree

 2021 February 28

The Aurora Tree
Image Credit & Copyright: Alyn Wallace

Explanation: Yes, but can your tree do this? Pictured is a visual coincidence between the dark branches of a nearby tree and bright glow of a distant aurora. The beauty of the aurora -- combined with how it seemed to mimic a tree right nearby -- mesmerized the photographer to such a degree that he momentarily forgot to take pictures. When viewed at the right angle, it seemed that this tree had aurora for leaves. Fortunately, before the aurora morphed into a different overall shape, he came to his senses and capture the awe-inspiring momentary coincidence. Typically triggered by solar explosions, aurora are caused by high energy electrons impacting the Earth's atmosphere around 150 kilometers up. The unusual Earth-sky collaboration was witnessed in March of 2017 in Iceland.

DESCOBERTAS CIÊNCIA - A pilha voltaica

Em 1779, o cientista italiano Alessandro Volta (1745 - 1827) apresenta a pilha voltaica, o primeiro gerador estático de energia elétrica a ser criado.

Descobertas posteriores, como a decomposição elétrica (eletrólise) da água em oxigénio e hidrogénio e o isolamento de elementos químicos como o sódio, o potássio, o cálcio, o boro, o bário, o estrôncio e o magnésio, deu origem, nos nossos dias, a diversos tipos de baterias recarregáveis.

Se não fosse essa invenção, dificilmente teríamos hoje aparelhos portáteis como os tablets e os smartphones que podem funcionar sem estarem ligados a uma tomada elétrica.

ASTRONOMIE - Un cratère géant rempli de glasse immortalisé sur Mars

Un cratère géant rempli de glasse immortalisé sur Mars

ASTRONOMY - Mars Perseverance Sol 3

 2021 February 26

Mars Perseverance Sol 3
Image Credit: NASA, JPL-Caltech, MSSS, ASU

Explanation: Stitched together on planet Earth, 142 separate images make up this 360 degree panorama from the floor of Jezero Crater on Mars. The high-resolution color images were taken by the Perseverance rover's zoomable Mastcam-Z during mission sol 3, also known as February 21, 2021. In the foreground of Mastcam-Z's view is the car-sized rover's deck. Broad light-colored patches in the martian soil just beyond it were scoured by descent stage rocket engines during the rover's dramatic arrival on February 18. The rim of 45 kilometer-wide Jezero Crater rises in the distance. In the coming sols, Perseverance will explore the ancient lake-delta system in the crater, hunting for signs of past microscopic life and collecting samples for potential future return to planet Earth.

ASTRONOMY - A Venus flyby

 2021 February 25

A Venus Flyby
Image Credit: NASA, JHUAPL, Naval Research Lab, Guillermo Stenborg and Brendan Gallagher

Explanation: On a mission to explore the inner heliosphere and solar corona, on July 11, 2020 the Wide-field Imager on board NASA's Parker Solar Probe captured this stunning view of the nightside of Venus at distance of about 12,400 kilometers (7,693 miles). The spacecraft was making the third of seven gravity-assist flybys of the inner planet. The gravity-asssist flybys are designed to use the approach to Venus to help the probe alter its orbit to ultimately come within 6 million kilometers (4 million miles) of the solar surface in late 2025. A surprising image, the side-looking camera seems to peer through the clouds to show a dark feature near the center known as Aphrodite Terra, the largest highland region on the Venusian surface. The bright rim at the edge of the planet is nightglow likely emitted by excited oxygen atoms recombining into molecules in the upper reaches of the atmosphere. Bright streaks and blemishes throughout the image are likely due to energetic charged particles, and dust near the camera reflecting sunlight. Skygazers from planet Earth probably recognize the familiar stars of Orion's belt and sword at lower right.

ASTRONOMY - Spiral Galaxy M66 from Hubble

 2021 February 24

Spiral Galaxy M66 from Hubble
Image Credit: NASA, ESA, Hubble, Janice Lee; Processing & Copyright: Leo Shatz; Text: Karen Masters

Explanation: It’s always nice to get a new view of an old friend. This stunning Hubble Space Telescope image of nearby spiral galaxy M66 is just that. A spiral galaxy with a small central bar, M66 is a member of the Leo Galaxy Triplet, a group of three galaxies about 30 million light years from us. The Leo Triplet is a popular target for relatively small telescopes, in part because M66 and its galactic companions M65 and NGC 3628 all appear separated by about the angular width of a full moon. The featured image of M66 was taken by Hubble to help investigate the connection between star formation and molecular gas clouds. Clearly visible are bright blue stars, pink ionized hydrogen clouds -- sprinkled all along the outer spiral arms, and dark dust lanes in which more star formation could be hiding.

ASTRONOMY - Video: Perseverance Landing on Mars

 2021 February 23

Video: Perseverance Landing on Mars
Video Credit: NASA/JPL-Caltech, Mars 2020 Mission Team

Explanation: What would it look like to land on Mars? To better monitor the instruments involved in the Entry, Decent, and Landing of the Perseverance Rover on Mars last week, cameras with video capability were included that have now returned their images. The featured 3.5-minute composite video begins with the opening of a huge parachute that dramatically slows the speeding spacecraft as it enters the Martian atmosphere. Next the heat shield is seen separating and falls ahead. As Perseverance descends, Mars looms large and its surface becomes increasingly detailed. At just past 2-minutes into the video, the parachute is released and Perseverance begins to land with dust-scattering rockets. Soon the Sky Crane takes over and puts Perseverance down softly, then quickly jetting away. The robotic Perseverance rover will now begin exploring ancient Jezero Crater, including a search for signs that life once existed on Earth's neighboring planet.

ASTRONOMY - Moon Rising Between Starships

 2021 February 22

Moon Rising Between Starships
Image Credit & Copyright: John Kraus

Explanation: What's that on either side of the Moon? Starships. Specifically, they are launch-and-return reusable rockets being developed by SpaceX to lift cargo and eventually humans from the Earth's surface into space. The two rockets pictured are SN9 (Serial Number 9) and SN10 which were captured near their Boca Chica, Texas launchpad last month posing below January's full Wolf Moon. The Starships house liquid-methane engines inside rugged stainless-steel shells. SN9 was test-launched earlier this month and did well with the exception of one internal rocket that failed to relight during powered descent. SN10 continues to undergo ground tests and may be test-launched later this month.

ASTRONOMY - NGC 2244: A Star Cluster in the Rosette Nebula

 2021 February 21

NGC 2244: A Star Cluster in the Rosette Nebula
Image Credit & Copyright: Don Goldman

Explanation: In the heart of the Rosette Nebula lies a bright open cluster of stars that lights up the nebula. The stars of NGC 2244 formed from the surrounding gas only a few million years ago. The featured image taken in January using multiple exposures and very specific colors of Sulfur (shaded red), Hydrogen (green), and Oxygen (blue), captures the central region in tremendous detail. A hot wind of particles streams away from the cluster stars and contributes to an already complex menagerie of gas and dust filaments while slowly evacuating the cluster center. The Rosette Nebula's center measures about 50 light-years across, lies about 5,200 light-years away, and is visible with binoculars towards the constellation of the Unicorn (Monoceros).