Elongated Filament (February 25, 2005)
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This ultraviolet image of the Sun shows a very long filament slanting up
roughly at a 45 degree angle across much of the Sun, underneath a long and
narrow coronal hole (22 Feb. 2005). Filaments are twisting masses of cooler
("only" 10,000 - 100,000 degrees Kelvin) gas contained by magnetic fields
above the Sun's surface in the midst of the much hotter (~ 1,500,000 K) corona.
And just to keep the terms straight, filaments are called prominences if
observed on the Sun's limb or edge. Sometimes filaments erupt, though they
can remain stable for weeks at a time. This particular filament was already
there 28 days ago (one solar rotation earlier), as were the two coronal holes.
While filaments are fairly common, this one is longer than most that we
have seen. It will be interesting to see how they appear as the Sun's
rotation brings them over the edge of the Sun beginning around Feb. 25.
The filament is particularly well visible in this H-alpha image obtained
at the Kanzelhoehe Solar Observatory.
The video shows the filament virtually unchanged for almost two days earlier in the week. The close observer will detect (around 10:00 UT on Feb. 22) a small coronal mass ejection as it blasts out into space from the lighter, upper active region on the right edge of the Sun.
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