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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.
The photosphere denotes those solar or stellar surface layers from which optical radiation escapes. These stellar outer layers can be modeled by different computer programs. Often, calculated models are used, together with other programs, to calculate synthetic spectra for stars. For example, in varying the assumed abundance of a chemical ...
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 photosphere, which is the atmosphere's lowest and coolest layer, is normally its only visible part. [1] Light escaping from the surface of the star stems from this region and passes through the higher layers. The Sun's photosphere has a temperature in the 5,770–5,780 K (5,500–5,510 °C; 9,930–9,940 °F) range.
Between the photosphere and the corona, the thin region through which the temperature increases is known as the transition region. It ranges from only tens to hundreds of kilometers thick. Energy cannot be transferred from the cooler photosphere to the corona by conventional heat transfer as this would violate the second law of thermodynamics.
The spectrum of sunlight has approximately the spectrum of a black-body radiating at 5,772 K (9,930 °F), [12] interspersed with atomic absorption lines from the tenuous layers above the photosphere. The photosphere has a particle density of ~10 23 m −3 (about 0.37% of the particle number per volume of Earth's atmosphere at sea level). The ...
Faculae are slightly brighter areas that form around sunspot groups as the flow of energy to the photosphere is re-established and both the normal flow and the sunspot-blocked energy elevate the radiating 'surface' temperature. Scientists began speculating on possible relationships between sunspots and solar luminosity in the 17th century.
The heart wall is made up of three layers: the inner endocardium, middle myocardium and outer epicardium. These are surrounded by a double-membraned sac called the pericardium. The innermost layer of the heart is called the endocardium. It is made up of a lining of simple squamous epithelium and covers heart chambers