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The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes), all retained by Earth's gravity.
A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules. The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases. [2]
This type of atmosphere loss may be common to all planets orbiting Sun-like stars closer than around 0.1 AU. [54] In addition to hydrogen, carbon, and oxygen, HD 209458 b is thought to have water vapor in its atmosphere. [55] [56] [57] Sodium and water vapour has also been observed in the atmosphere of HD 189733 b, [58] [59] another hot gas ...
Single stars of known mass and composition follow predictable tracks across this chart over the course of their evolution. Hence, knowing a star's mass and metallicity allows its age to be estimated. Stars of similar types are also found grouped together in specific regions of the chart, including main-sequence, red giant, and white dwarf stars.
Class S stars have excess amounts of zirconium and other elements produced by the s-process, and have more similar carbon and oxygen abundances to class M or carbon stars. Like carbon stars, nearly all known class S stars are asymptotic-giant-branch stars. The spectral type is formed by the letter S and a number between zero and ten.
For the very hottest gas giants, with temperatures above 1400 K (2100 °F, 1100 °C) or cooler planets with lower gravity than Jupiter, the silicate and iron cloud decks are predicted to lie high up in the atmosphere. The predicted Bond albedo of a class V planet around a Sun-like star is 0.55, due to reflection by the cloud decks.
A primary atmosphere is an atmosphere of a planet that forms by accretion of gaseous matter from the accretion disc of the planet's sun. Planets such as Jupiter and Saturn have primary atmospheres. Primary atmospheres are very thick compared to secondary atmospheres like the one found on Earth .
The outermost part of the stellar atmosphere, or upper stellar atmosphere, is the corona, a tenuous plasma which has a temperature above one million Kelvin. [6] While all stars on the main sequence feature transition regions and coronae, not all evolved stars do so. It seems that only some giants, and very few supergiants, possess coronae.