| Piú viste - The Sun: just a star, like many others... |
The Sun-UvcseitG_c.jpgOur "restless" Sun... (12)54 visitenessun commento
|
|
Earth&Sun-001-magfieldG_b.jpgMagnetic Fields... (2)54 visitenessun commento
|
|
The_Sun_and_Mercury.jpgThe Sun and Mercury54 visiteEnjoying the transit of Mercury from Dallas, Texas, astronomer Phil Jones recorded this detailed image of the Sun. Along with a silhouette of the innermost Planet, a network of cells and dark filaments can be seen against a bright solar disk with spicules and prominences along the Sun's edge. The composited image was taken through a telescope equiped with an H-alpha filter that narrowly transmits only the red light from Hydrogen atoms. Such images emphasize the Solar Chromosphere, the region of the Sun's atmosphere immediately above its Photosphere or normally visible surface. Left of center, the tiny disk of Mercury seems to be imitating a small sunspot that looks a little too round. But in H-alpha pictures, sunspot regions are usually dominated by bright splotches (called plages) on the Solar Chromosphere.
|
|
Green-Sun.jpgGreen flash from Italy54 visiteCaption originale, da "NASA - Picture of the Day" del 29 Gennaio 2007:"How could the Sun turn green? Difficult to observe, the momentary green flash above the rising or setting Sun has been documented as a phenomenon caused by the atmospheric bending or refraction of sunlight.
Like a weak prism, the Earth's atmosphere breaks white sunlight into colors, bending red colors slightly and green and blue colors through increasingly larger angles.
When the sky is (VERY) clear, a green flash just above the Sun's edge can sometimes be seen for a second or so, when the sun is close to a distant horizon. Still, from a site atop Mt. Autore (altitude 1.850 mt) in Italy, astrophotographer Danilo Pivato captured this dramatic green flash movie. The time between frames varies from over one minute in the beginning to about one second as the flash becomes visible".
|
|
The_Sun_from_SOHO_-_Coronal_Mass_Ejection.jpgCoronal Mass Ejection54 visiteCaption NASA originale:"What's happening to our Sun? Another Coronal Mass Ejection (CME)!
The Sun-orbiting SOHO spacecraft has imaged many erupting filaments lifting off the active solar surface and blasting enormous bubbles of magnetic plasma into space. Direct light from the sun is blocked in the inner part of the above image, taken in 2002, and replaced by a simultaneous image of the Sun in ultraviolet light.
The field of view extends over 2 MKM from the Solar Surface. While hints of these explosive events, called Coronal Mass Ejections or CMEs, were discovered by spacecraft in the early 70s, this dramatic image is part of a detailed record of this CME's development from the presently operating SOHO spacecraft.
Near the minimum of the Solar Activity Cycle CMEs occur about once a week, but near solar maximum rates of two or more per day are typical. Strong CMEs may profoundly influence space weather. Those directed toward our Planet can have serious effects".
|
|
Sunspot~0.jpgAn Active Sunspot Viewed Sideways54 visiteCaption NASA:"Why are there dark spots on the Sun? Although noted for thousands of years, sunspots have been known for decades to be regions of the Sun that are slightly depressed and cooled by the Sun's complex and changing Magnetic Field.
High resolution pictures like the above image from Japan's new Sun-watching Hinode satellite, however, are helping to increase modern understanding. In the center of the above image is a sunspot, but not seen in the usual orientation - this sunspot is seen sideways.
Of particular interest is erupting glowing gas that shows how the Sun's Magnetic Field comes right out of the spot center, but curves markedly around the spot edges. Better understanding of how the Sun ejects particles into space may result in more accurate predictions of solar storms that affect satellites, astronauts and even power grids on Earth".
|
|
The_Sun-PIA09331.jpgThe South Pole of the Sun54 visiteThis image is a composite of left and right eye color image pairs taken by the SECCHI Extreme UltraViolet Imager (EUVI) mounted on the STEREO-B and STEREO-A Spacecraft.
STEREO-B is located behind the Earth, and follows the Earth in orbit around the Sun, This location enables us to view the Sun from the position of a virtual left eye in space.
STEREO-A is located ahead of the Earth, and leads the Earth in orbit around the Sun, This location enables us to view the Sun from the position of a virtual right eye in space.
The EUVI imager is sensitive to wavelengths of light in the extreme ultraviolet portion of the spectrum.
EUVI bands at wavelengths of 304, 171 and 195 Angstroms have been mapped to the red blue and green visible portion of the spectrum and processed to emphasize the three-dimensional structure of the solar material.MareKromium
|
|
The_Sun-PIA09332.jpgLeft Limb of North Pole of the Sun (March 20, 2007)54 visitenessun commentoMareKromium
|
|
The_Sun-PIA09324.jpgCloser View of the Equatorial Region of the Sun (March 24, 2007)54 visitenessun commentoMareKromium
|
|
The_Sun.jpgNever too close, never too far...54 visiteCaption NASA:"When is the Sun most distant from Earth? It happened again just this past weekend.
A common misconception is that the Sun is most distant during the Winter, when it's the coldest. In truth, however, the seasonal temperatures are more greatly influenced by the number of daylight hours and how high the Sun rises.
For example, during Northern Winter, the tilt of the Earth causes the Sun to be above the horizon for a shorter time and remain lower in the sky than in Northern Summer. The picture compares the relative size of the Sun during Earth's closest approach in January (Northern Winter) on the left, and in July (Northern Summer) on the right. The angular size of the Sun is noticeably smaller during July, when it is farther away. If the Earth's orbit was perfectly circular, the Sun would always appear to be the same size.
These two solar images were taken from Spain during 2006, but the same effect can be seen in any year from any Earth-bound location".MareKromium
|
|
Solar-Cycle.jpgA "Full Solar Cycle", from SOHO (extreme UV Light)54 visiteCaption NASA:"Every 11 years, our Sun goes through a Solar Cycle.
A complete Solar Cycle has now been imaged by the Sun-orbiting SOHO Spacecraft, celebrating the 12th anniversary of its launch yesterday (December, 12th, 2007).
A Solar Cycle is caused by the changing Magnetic Field of the Sun, and varies from Solar Maximum, when Sunspot, Coronal Mass Ejection, and Flare phenomena are most frequent, to Solar Minimum, when such activity is relatively infrequent.
Solar Minimums occurred in 1996 and 2007, while the last Solar Maximum occurred in 2001.
Pictured above is a SOHO image of the Sun in extreme ultraviolet light for each year of the last Solar Cycle, with images picked to illustrate the relative activity of the Sun".MareKromium
|
|
Sunspot-10982.jpgSunspot 1098254 visiteDa "NASA - Picture of the Day", del giorno 6 Febbraio 2008:"A new Solar Cycle has begun on our Sun. Over the past year, the Sun's Magnetic Field has reset and now a new 11 year period is beginning.
Pictured above in a specific color of light emitted by Hydrogen is Sunspot 10982, one of the first sunspots of the new Solar Cycle. The two dark lines visible just above and to either side of the bright sunspot are cool filaments held aloft by the Sun's Magnetic Field. Hot and cold regions are shown as regions of relative light and dark, respectively.
A Solar Cycle is caused by the changing Magnetic Field, and varies from Solar Maximum (when sunspots, coronal mass ejections and flare phenomena are most frequent), to Solar Minimum (meaning when such activity is relatively infrequent).
Solar Minima occurred in 1996 and 2007, while the last Solar Maximum occurred in 2001 (...)".MareKromium
|
|
| 143 immagini su 12 pagina(e) |
 |
|
|
|
|
|
|
|
|
11 |
|
