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 Ήλιος : The Sun

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ΔημοσίευσηΘέμα: Ήλιος : The Sun   12.10.09 13:48

October 13, 2008

The Sun is now in the quietest phase of its 11-year activity cycle, the solar minimum - in fact, it has been unusually quiet this year - with over 200 days so far with no observed sunspots.
The solar wind has also dropped to its lowest levels in 50 years.
Scientists are unsure of the significance of this unusual calm, but are continually monitoring our closest star with an array of telescopes and satellites.

Seen below are some recent images of the Sun in more active times.



A sweeping prominence, a huge cloud of relatively cool dense plasma is seen suspended in the Sun's hot, thin corona.
At times, promineces can erupt, escaping the Sun's atmosphere. Emission in this spectral line shows the upper chromosphere at a temperature of about 60,000 degrees K (over 100,000 degrees F). Every feature in the image traces magnetic field structure. The hottest areas appear almost white, while the darker red areas indicate cooler temperatures. (Courtesy of SOHO/EIT consortium)



Detailed closeup of magnetic structures on the Sun's surface, seen in the H-alpha wavelength on August 22, 2003. (Swedish 1-m Solar Telescope (SST) operated by the Royal Swedish Academy of Sciences, Oddbjorn Engvold, Jun Elin Wiik, Luc Rouppe van der Voort) #



NASA's STEREO satellite captured the first images ever of a collision between a solar "hurricane", called a coronal mass ejection (CME), and a comet on April 4, 2007. The collision caused the complete detachment of the comet's plasma tail. Comets are icy leftovers from the solar system's formation billions of years ago. They usually hang out in the cold, distant regions of the solar system, but occasionally a gravitational tug from a planet, another comet, or even a nearby star sends them into the inner solar system. Once there, the sun's heat and radiation vaporizes gas and dust from the comet, forming its tail. Comets typically have two tails, one made of dust and a fainter one made of electrically conducting gas, called plasma. (NASA/STEREO) #



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ΔημοσίευσηΘέμα: Απ: Ήλιος : The Sun   12.10.09 14:02



The total solar eclipse of February 16, 1980 was photographed from Palem, India, by a research team from the High Altitude Observatory of the National Center for Atmospheric Research. The photograph of the solar corona was taken with a camera system developed by Gordon A. Newkirk, Jr. This specialized instrument photographs the corona in red light, 6400 A -- through a radially graded filter that suppresses the bright inner corona in order to show the much fainter streamers of the outer corona in the same photograph. (Rhodes College, Memphis, Tennessee / High Altitude Observatory (HAO), University Corporation for Atmospheric Research (UCAR)) #



Image of an active solar region taken on July 24, 2002 near the eastern limb of the Sun. The image highlights the three-dimensional nature of the photosphere when seen at these large angles. The structures in the dark sunspots in the upper central area of the image show distinct elevation above the dark "floor" of the sunspot. The height of the structures has been estimated by Dr. Bruce Lites of the High Altitude Observatory to be between 200 and 450 km. The smallest resolvable features in the image are about 70 km in size. There are also numerous bright "faculae" visible on the edges of granules that face towards the observer. (Prof. Goran Scharmer/Dr. Mats G. Löfdahl/Institute for Solar Physics of the Royal Swedish Academy of Sciences) #



A view of a sunspot and granules on the Sun's surface, seen in the H-alpha wavelength on August 4, 2003. (Swedish 1-m Solar Telescope (SST) operated by the Royal Swedish Academy of Sciences, Göran Scharmer and Kai Langhans, ISP) #



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ΔημοσίευσηΘέμα: Απ: Ήλιος : The Sun   12.10.09 14:31



An animation of the sun, seen by NASA's Extreme ultraviolet Imaging Telescope (EIT) over the course of 6 days, starting June 27, 2005. (Courtesy of SOHO/EIT consortium) #



Hinode (formerly known as Solar-B) successfully captured a massive solar flare on 13 December 2006. It was one of the largest flares occurring in that period of solar activity minimum. (JAXA/NASA/PPARC) #



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ΔημοσίευσηΘέμα: Απ: Ήλιος : The Sun   12.10.09 14:34



The image shows the corona for a moderately active Sun, with some (red) hot active regions in both hemispheres, surrounded by the (blue/green) cooler plasma of the quiet-Sun corona. Notice also the north polar-crown filament, the trans-equatorial loops, and the coronal hole in the south-east (lower-right) corner of the image and the smaller one over the north pole. This image shows the solar corona in a false-color, 3-layer composite: the blue, green, and red channels show the 171Å, 195Å, and 284Å wavelengths, respectively (most sensitive to emission from 1, 1.5, and 2 million degree gases). (TRACE Project, Stanford-Lockheed Institute for Space Research, NASA) #



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Ήλιος : The Sun
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