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The Sun's atmosphere is composed of five layers: the photosphere, the chromosphere, the transition region, the corona, and the heliosphere. The coolest layer of the Sun is a temperature minimum region extending to about 500 km above the photosphere, and has a temperature of about 4,100 K. [77]
At any one time, the Sun's surface is covered by about 4 million granules. Below the photosphere is a layer of " supergranules " up to 30,000 kilometres (19,000 mi) in diameter with lifespans of up to 24 hours.
The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun.It takes the shape of a vast, tailed bubble-like region of space.In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium.
The red color of the chromosphere could be seen during the solar eclipse of August 11, 1999.. The density of the Sun's chromosphere decreases exponentially with distance from the center of the Sun by a factor of roughly 10 million, from about 2 × 10 −4 kg/m 3 at the chromosphere's inner boundary to under 1.6 × 10 −11 kg/m 3 at the outer boundary. [7]
The Sun is composed primarily of the chemical elements hydrogen and helium; they account for 74.9% and 23.8%, respectively, of the mass of the Sun in the photosphere.All heavier elements, colloquially called metals in stellar astronomy, account for less than 2% of the mass, with oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%) being the most abundant.
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Below, gravity tends to dominate the shape of most features, so that the Sun may often be described in terms of layers and horizontal features (like sunspots); above, dynamic forces dominate the shape of most features, so that the transition region itself is not a well-defined layer at a particular altitude.
A corona (pl.: coronas or coronae) is the outermost layer of a star's atmosphere. It is a hot but relatively dim region of plasma populated by intermittent coronal structures known as solar prominences or filaments. The Sun's corona lies above the chromosphere and extends millions of kilometres into outer