The Sun: just a star, like many others...
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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".
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Hungarian Eclypse.jpgMoments of the last Total Eclipse54 visiteCaption NASA originale:"Only in the fleeting darkness of a total solar eclipse is the light of the Solar Corona easily visible from Earth. Normally overwhelmed by the bright solar disk, the expansive corona, the Sun's outer atmosphere, is an alluring sight. But the subtle details and extreme ranges in the corona's brightness discernible to the eye are notoriously difficult to photograph. In this series of images recorded from Siofok, Hungary during the total phase of the August 11, 1999 eclipse, progressively longer exposures (top left to bottom center) have been used to more faithfully capture different regions of the elusive solar corona. The final image (at bottom right) shows light from the solar disk emerging from behind the moon's edge at the end of totality".
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Mercury and the Sun.jpgA "Superior Conjunction" Of Mercury54 visiteCaption originale NASA dal "NASA - Picture of the Day" dell'8-9-1999: "In astronomical parlance, an interior planet is at "Superior Conjunction" when it is located on the opposite side of the Sun from Earth. Mercury, the solar system's innermost planet, zips past this point in its orbit today. In fact, in this picture (taken on September 1999) from a solar coronagraph on board the the space-based SOHO observatory, shows Mercury positioned very close to the Sun as seen from a near Earth vantage point. The coronagraph uses an internal occulting disk to block the intense solar glare which otherwise hides this sight from ground-based observers. The shadow of the occulting disk is at the center with the Sun's size and position indicated by the white circle. Mercury is the bright dot with a horizontal line (a digital artifact), while faint dots scattered throughout the field are stars. Bright regions of the sun's outer atmosphere are also visible".
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Parker_Solar_Probe_trajectory.gifThe Parker Solar Probe's Trajectory92 visiteInteressante.MareKromium
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PerihelionAphelion_cervignon800.jpgPerihelion and Aphelion55 visiteDa "NASA - Picture of the Day" del giorno 3 Luglio 2009:"This year Aphelion, the point in Earth's elliptical orbit when it is farthest from the Sun, occurs tomorrow, July 4th.
Of course, that doesn't affect the seasons on our fair Planet, because those are determined by the tilt of Earth's Axis of Rotation and not Earth's distance from the Sun: so July is still Winter in the South and Summer in Northern Hemisphere. But it does mean that on July 4th the Sun will be at its smallest apparent size. This composite neatly compares two pictures of the Sun taken with the same telescope and camera on the dates of Perihelion (closest approach) and Aphelion in 2008.
The image labels include Earth's distance in kilometers from the Sun on the two dates.
Otherwise difficult to notice, the change in the Sun's apparent diameter between Perihelion and Aphelion is clear. The difference amounts to a little over 3%".MareKromium
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Solar Corona.jpgThe 2006 Total Solar Eclipse: the Solar Corona54 visiteDa "NASA - Picture of the Day", del 7 Aprile 2006:"During a total Solar Eclipse, the Sun's extensive outer atmosphere (or Corona) is an awesome and inspirational sight. The subtle shades and shimmering features of the corona that engage the eye span a brightness range of over 10.000 to 1, making them notoriously difficult to capture in a single picture. But this composite of 33 digital images ranging in exposure time from 1/8000 to 1/5th of second comes very close to revealing the crown of the Sun in all its glory. The telescopic views were recorded from Side, Turkey, during the March 29, 2006, Solar Eclipse, a geocentric celestial event that was widely seen under nearly ideal conditions.
The composite also captures a pinkish prominence extending just beyond the upper edge of the eclipsed Sun".
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Solar Eclipse 2006.jpgFrom Space, from Earth...54 visiteDa "NASA - Picture of the Day" del 31 Marzo 2006:"Neither rain, nor snow, nor dark of night can keep the space-based SOlar Heliospheric Observatory (SOHO) from watching the Sun. In fact, from its vantage point 150 MKM sunward of planet Earth, SOHO's cameras can always monitor the Sun's Outer Atmosphere, or Corona.
But only during a total solar eclipse can earth-based observers see the lovely coronal streamers and structures - such as when the Moon briefly blocks the overwhelmingly bright solar surface.
In this composite view, SOHO's uninterrupted view of the Solar Corona above the Solar Photosphere (center) and Corona far beyond the Sun's disk, are shown in orange hues. The middle, donut-shaped region is the Corona as recorded by the Williams College Eclipse Expedition to Kastelorizo Island, Greece during the March 29th, 2006 total solar eclipse.
Merging ground and space-based views allows astronomers to trace features in the Corona that reach from just above the Sun's surface into the Solar Wind".
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Solar Eclypse 2006-tse2006_ayiomamitis_f.jpgThe "Diamond Ring"54 visiteDa "NASA - Picture of the Day" del 30 Marzo 2006:"The track of totality for the first solar eclipse of 2006 began early yesterday on the East coast of Brazil and ended half a world away at sunset in Western Mongolia. In between, the shadow of the Moon crossed the Atlantic Ocean, Northern Africa, central Asia and so came for a moment to the small Greek island of Kastelorizo in the Eastern Aegean.
Astronomer Anthony Ayiomamitis reports that the islanders and many eclipse-watching visitors were indeed treated to an inspiring display of the beautiful Solar Corona as totality lasted about 3 minutes.
As the total phase of the eclipse ended, he was able to capture this striking "Diamond Ring" image. In it, the first rays of sunlight shining through edge-on lunar valleys create the fleeting appearance of glistening diamonds set in a bright ring around the Moon's silhouette".
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Solar Flare.jpgLoops over the Sun56 visiteCaption originale:"How can gas float above the Sun? Twisted magnetic fields arching from the Solar Surface can trap ionized gas, suspending it in huge looping structures. These majestic plasma arches are seen as prominences above the Solar Limb. In September 1999, this dramatic and detailed image was recorded by the EIT experiment on board the space-based SOHO observatory in the light emitted by ionized Helium. It shows hot plasma escaping into space as a fiery prominence breaks free from magnetic confinement a hundred thousand kilometers above the Sun. These awesome events bear watching as they can affect communications and power systems over 100 MKM away on Planet Earth".
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Solar Flares.jpgSolar Flares58 visiteCaption NASA originale:"On June, 14th, 1999, SOHO observatory recorded this stunning view of an immense prominence erupting from the Sun's southern latitudes. The false-color image was made in the extreme Ultraviolet light produced by ionized Helium atoms in the solar plasma".
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Solar Prominence.jpgSolar "Blow"...66 visiteDa "NASA - Picture of the Day" del 7 Agosto 2006:"Our Sun is still very active. In the year 2000, our Sun went though Solar Maximum, the time in its 11-year cycle where the most sunspots and explosive activities occur. Sunspots, the Solar Cycle, and Solar Prominences are all caused by the Sun's changing magnetic field.
Pictured above is a solar prominence that erupted in 2002, July, throwing electrons and ions out into the Solar System.
The above image was taken in the ultraviolet light emitted by a specific type of Ionized Helium, a common element on the Sun. Particularly hot areas appear in white, while relatively cool areas appear in red. Our Sun should gradually quiet down until Solar Minimum occurs, and the Sun is most quiet. No one can precisely predict when Solar Minimum will occur, although some signs indicate that it has started already".
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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
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