A Long Snaking Filament on the Sun

Explanation: Earlier this month, the Sun exhibited one of the longer filaments on record. Visible as the bright curving streak around the image center, the snaking filament's full extent was estimated to be over half of the Sun's radius -- more than 350,000 kilometers long. A filament is composed of hot gas held aloft by the Sun's magnetic field, so that viewed from the side it would appear as a raised prominence. A different, smaller prominence is simultaneously visible at the Sun's edge. The featured image is in false-color and color-inverted to highlight not only the filament but the Sun's carpet chromosphere. The bright dot on the upper right is actually a dark sunspot about the size of the Earth. Solar filaments typically last from hours to days, eventually collapsing to return hot plasma back to the Sun. Sometimes, though, they explode and expel particles into the Solar System, some of which trigger auroras on Earth. The pictured filament appeared in early September and continued to hold steady for about a week.

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Why isn't it better known? The Great Lacerta Nebula can be seen towards the constellation of the lizard. The emission nebula is difficult to see with a wide-field binoculars because it is so small, but also difficult to see with a large telescope because it is so large. The Sharpless 126 can be viewed and appreciated with a long duration camera exposure. There was a combined exposure of 10 hours over five different colors and six nights at the IC Astronomy Observatory in Spain. The hydrogen gas in the Great Lacerta Nebula is red because it is excited by light from a bright blue star. The stars are a long way from us.