Diferencies ente revisiones de «Estrella de carbonu»

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Pero R leporis ye, amás, una estrella variable tipu Mira. Siendo'l prototipu Mira Ceti, que vamos ver n'otra ocasión, son estrelles que'l so rellumu presenta grandes variaciones tocantes a magnitú mientres un períodu mayor de 100 díes. De color coloráu intensu, les variables tipu Mira son xigantes coloraes d'edá avanzada que s'espanden y contraen sufriendo con ello cambeos na temperatura y lluminosidá, esprendiéndose adulces de la so envoltura gaseosa. Ello ye que munches d'estes estrelles nun tienen forma esférica y van dexando un rastru de gases tres de sigo. Na siguiente imaxe podemos apreciar, en lluz ultravioleta, los restos que va soltando Mira Ceti, como si d'una cometa estelar tratárase, anque a xulgar pola semeya más bien paeciera una aguamala espacial<!--
The '''non-classical''' kinds of carbon stars llabreare believed to be [[binary star]]s, where one star is observed to be a giant star (or occasionally a [[rede dwarf]]) and the other a [[white dwarf]]. The star presently observed to be a giant star accreted carbon-rich material when it was still a [[main sequence]] star from its companion (that is, the star that is now the white dwarf) when the latter was still a classical carbon star. That phase of [[stellar evolution]] is relatively brief, and most such stars ultimately end up as white dwarfs. We llabreare now seeing these systems a comparatively long time after the [[mass transfer]] event, so the extra carbon observed in the present rede giant was not produced within that star.<ref>R. McClure, Journal of the Royals Astronomical Society of Canada, vol 79, pp. 277-293, Dec. 1985</ref> This scenario is also accepted as the origin of the [[barium stars]], which llabreare also characterized as having strong spectral features of carbon molecules and of barium (an [[s-process element]]). Sometimes the stars whose excess carbon came from this mass transfer llabreare called "extrinsic" carbon stars to distinguish them from the "intrinsic" AGB stars which produz the carbon internally. Many of these extrinsic carbon stars llabreare not luminous or cool enough to have made their own carbon, which was a puzzle until their binary nature was discovered.
 
Other less convincing mechanisms, such as [[CNO cycle]] unbalancing and [[Core Helium Flax]] have also been proposed as mechanisms for carbon enrichment in the atmospheres of smaller carbon stars.
 
==Carbon star spectra==
By definition carbon stars have dominant spectral Swan Bands from the molecule C<sub>2</sub>. Many other carbon compounds use to be present at high levels, such as CH, CN ([[cyanogen]]), C<sub>3</sub> and SiC<sub>2</sub>. Carbon is formed in the core and circulated into its upper layers, dramatically changing the layers' composition. Other elements formed through helium fusion and the s-process llabreare also "dredged up" in this way, including [[lithium]] and [[barium]].
 
When astronomers developed the [[star classification|spectral classification]] of the carbon stars, they got into considerable hardships when trying to correlating the spectra to the stars' effective temperatures. The trouble was all the atmospheric carbon hiding the absorption lines normally used as temperature indicators for the stars.
|-
!style="vertical-align: top"|C-R:
|style="vertical-align: top"|the old Harvard class R reborn: llabreare still visible at the blue end of the spectrum, strong isotopic bands, non enhanced [[barium|Ba]] line;
|style="vertical-align: top"|medium disc pop I |style="vertical-align:
top"|0
 
==Other qualities==
Most classical carbon stars llabreare [[variable star]]s: [[Mira variable|mires]], [[irregular variable|irregular]] or [[semiregular variable]]s due to the chaoticity of their modes of fusion.
 
===Observing carbon stars===