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Autor/Urheber: Nevit Dilmen, Lizenz: CC-BY-SA-3.0
Tension lines in plastic protractor seen under cross polarized light. When a ray of plane polarised light is passed through a photoelastic material, it gets resolved along the two principal stress directions and each of these components experiences different refractive indices. The difference in the refractive indices leads to a relative phase retardation between the two component waves. The birefringence of the plastic layer shows colored fringes. Also called Photoelasticimetry or photoelasticity. Not seen does not mean No difference. WYSIATI
Autor/Urheber: Sculpture by Franz Stuck, photograph by Rufus46, Lizenz: CC BY-SA 3.0
P icons: Geschichte – symbolisiert durch einen bewaffneten Reiter
Autor/Urheber: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team STScI/AURA), Lizenz: CC BY 3.0
The Whirlpool Galaxy (Spiral Galaxy M51, NGC 5194) is a classic spiral galaxy located in the Canes Venatici constellation.
Out of this whirl: The Whirlpool Galaxy (M51) and companion galaxy
The graceful, winding arms of the majestic spiral galaxy M51 (NGC 5194) appear like a grand spiral staircase sweeping through space. They are actually long lanes of stars and gas laced with dust.
This sharpest-ever image, taken in January 2005 with the Advanced Camera for Surveys aboard the NASA/ESA Hubble Space Telescope, illustrates a spiral galaxy's grand design, from its curving spiral arms, where young stars reside, to its yellowish central core, a home of older stars. The galaxy is nicknamed the Whirlpool because of its swirling structure.
The Whirlpool's most striking feature is its two curving arms, a hallmark of so-called grand-design spiral galaxies. Many spiral galaxies possess numerous, loosely shaped arms that make their spiral structure less pronounced. These arms serve an important purpose in spiral galaxies. They are star-formation factories, compressing hydrogen gas and creating clusters of new stars. In the Whirlpool, the assembly line begins with the dark clouds of gas on the inner edge, then moves to bright pink star-forming regions, and ends with the brilliant blue star clusters along the outer edge.
Some astronomers believe that the Whirlpool's arms are so prominent because of the effects of a close encounter with NGC 5195, the small, yellowish galaxy at the outermost tip of one of the Whirlpool's arms. At first glance, the compact galaxy appears to be tugging on the arm. Hubble's clear view, however, shows that NGC 5195 is passing behind the Whirlpool. The small galaxy has been gliding past the Whirlpool for hundreds of millions of years.
As NGC 5195 drifts by, its gravitational muscle pumps up waves within the Whirlpool's pancake-shaped disk. The waves are like ripples in a pond generated when a rock is thrown in the water. When the waves pass through orbiting gas clouds within the disk, they squeeze the gaseous material along each arm's inner edge. The dark dusty material looks like gathering storm clouds. These dense clouds collapse, creating a wake of star birth, as seen in the bright pink star-forming regions. The largest stars eventually sweep away the dusty cocoons with a torrent of radiation, hurricane-like stellar winds, and shock waves from supernova blasts. Bright blue star clusters emerge from the mayhem, illuminating the Whirlpool's arms like city streetlights.
The Whirlpool is one of astronomy's galactic darlings. Located 31 million light-years away in the constellation Canes Venatici (the Hunting Dogs), the Whirlpool's beautiful face-on view and closeness to Earth allow astronomers to study a classic spiral galaxy's structure and star-forming processes.
Credit:
NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team STScI/AURA)
About the Image
NASA caption Id: heic0506a Type: Observation Release date: 25 April 2005, 06:00 Related releases: heic0506 Size: 11477 x 7965 px
About the Object
Name: Messier 51, Whirlpool Galaxy Type: • Local Universe : Galaxy : Type : Spiral • Galaxies Images/Videos Distance: 25 million light years
Colours & filters
Band Wavelength Telescope Optical B 435 nm Hubble Space Telescope ACS Optical V 555 nm Hubble Space Telescope ACS Optical H-alpha + Nii 658 nm Hubble Space Telescope ACS Infrared I 814 nm Hubble Space Telescope ACS.
Autor/Urheber:
- .משתמש:נעמה מ.P_social_sciences.png:
- derivative work: Vaikunda Raja (talk) 09:44, 17 July 2009 (UTC)
Iconic image for social science.
Scouts gathering for the opening ceremony at Jiingijamborii national jamboree in Rinkaby, Sweden.
Autor/Urheber: MadGeographer, Lizenz: CC BY-SA 3.0
Montage for the Geneva article on Wikipedia
Autor/Urheber: Benh LIEU SONG, Lizenz: CC BY-SA 3.0
Saulnier Watermill, in the Menier chocolate factory, Noisiel, France. Built in 1872, it was the first building in the world with a visible metallic structure and is also characterized by its ceramic tiles patterns. The three years above the entrance correspond respectively to the year the old mill was built (1157), the year the Menier factory was moved to Noisiel (1825) and to the year the Saulnier Mill replaced the old one. The Menier chocolate factory is now headquarters of Nestlé France. This picture is a mosaic of 6 photos (2x3) taken with a Canon EOS 400D+EF 100mm f/2.8 Macro at 100mm, f/8.0, 1/800 sec and ISO 200. Stitching was done with Hugin and Enblend.
Darstellung des Brockens von L. S. Bestehorn aus dem Jahr 1732
