9 - SCIENCE - JoanMira
La Science sous toutes ses formes/Science in all its forms
Nombre total de pages vues
29/03/2025
ASTRONOMY - Stereo Helene
2025 March 29
Image Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA; Stereo Image by Roberto Beltramini
Explanation: Get out your red/blue glasses and float next to Helene, small, icy moon of Saturn. Appropriately named, Helene is a Trojan moon, so called because it orbits at a Lagrange point. A Lagrange point is a gravitationally stable position near two massive bodies, in this case Saturn and larger moon Dione. In fact, irregularly shaped ( about 36 by 32 by 30 kilometers) Helene orbits at Dione's leading Lagrange point while brotherly ice moon Polydeuces follows at Dione's trailing Lagrange point. The sharp stereo anaglyph was constructed from two Cassini images captured during a close flyby in 2011. It shows part of the Saturn-facing hemisphere of Helene mottled with craters and gully-like features.
28/03/2025
ASTRONOMY - Lunar Dust and Duct Tape
2025 March 28
Image Credit: Apollo 17, NASA
Explanation: Why is the Moon so dusty? On Earth, rocks are weathered by wind and water, creating soil and sand. On the Moon, eons of constant micrometeorite bombardment have blasted away at the rocky surface creating a layer of powdery lunar soil or regolith. For the Apollo astronauts and their equipment, the pervasive, fine, gritty dust was definitely a problem. On the lunar surface in December 1972, Apollo 17 astronauts Harrison Schmitt and Eugene Cernan needed to repair one of their rover's fenders in an effort to keep the rooster tails of dust away from themselves and their gear. This picture reveals the wheel and fender of their dust covered rover along with the ingenious application of spare maps, clamps, and a grey strip of "duct tape".
27/03/2025
Pic de Pucheran : le tambour de la fôret à crête rouge
SANTE/MEDECINE La magnétoencéphalographie (MEG) pour lire le cerveau
LA TERRE VUE DU CIEL - Image satellite des montagnes de Bogda en Chine
ASTRONOMY - Messier 81
2025 March 27
Image Credit & Copyright: Lorand Fenyes
Explanation: One of the brightest galaxies in planet Earth's sky is similar in size to our Milky Way Galaxy: big, beautiful Messier 81. Also known as NGC 3031 or Bode's galaxy for its 18th century discoverer, this grand spiral can be found toward the northern constellation of Ursa Major, the Great Bear. The sharp, detailed telescopic view reveals M81's bright yellow nucleus, blue spiral arms, pinkish starforming regions, and sweeping cosmic dust lanes. But some dust lanes actually run through the galactic disk (left of center), contrary to other prominent spiral features. The errant dust lanes may be the lingering result of a close encounter between M81 and the nearby galaxy M82 lurking outside of this frame. Scrutiny of variable stars in M81 has yielded a well-determined distance for an external galaxy -- 11.8 million light-years.
26/03/2025
LA TERRE VUE DU CIEL - L’île de Kyūshū au Japon
ASTRONOMY - Star Formation in the Pacman Nebula
2025 March 26
Image Credit & Copyright: Juan Montilla (AAE)
Explanation: You'd think the Pacman Nebula would be eating stars, but actually it is forming them. Within the nebula, a cluster's young, massive stars are powering the pervasive nebular glow. The eye-catching shapes looming in the featured portrait of NGC 281 are sculpted dusty columns and dense Bok globules seen in silhouette, eroded by intense, energetic winds and radiation from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. Playfully called the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation Cassiopeia. This sharp composite image was made through narrow-band filters in Spain in mid 2024. It combines emissions from the nebula's hydrogen and oxygen atoms to synthesize red, green, and blue colors. The scene spans well over 80 light-years at the estimated distance of NGC 281.
25/03/2025
ASTRONOMY - A Blue Banded Blood Moon
2025 March 25
Image Credit & Copyright: Zixiong Jin
Explanation: What causes a blue band to cross the Moon during a lunar eclipse? The blue band is real but usually quite hard to see. The featured HDR image of last week's lunar eclipse, however -- taken from Norman, Oklahoma (USA) -- has been digitally processed to exaggerate the colors. The gray color on the upper right of the top lunar image is the Moon's natural color, directly illuminated by sunlight. The lower parts of the Moon on all three images are not directly lit by the Sun since it is being eclipsed -- it is in the Earth's shadow. It is faintly lit, though, by sunlight that has passed deep through Earth's atmosphere. This part of the Moon is red -- and called a blood Moon -- for the same reason that Earth's sunsets are red: because air scatters away more blue light than red. The unusual purple-blue band visible on the upper right of the top and middle images is different -- its color is augmented by sunlight that has passed high through Earth's atmosphere, where red light is better absorbed by ozone than blue.
LA TERRE VUE DU CIEL - Dunes dans le désert de Namibie
Hautes dunes dans le désert de Namibie. © Nasa
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2021 May 11 Lightning and Orion Beyond Uluru Image Credit & Copyright: Park Liu Explanation: What's happening behind Uluru? A Un...
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2025 January 14 North Star: Polaris and Surrounding Dust Image Credit & Copyright: Davide Coverta Explanation: Why is Polaris called ...