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- Stellar_pulsations abstract "Stellar pulsations are caused by expansions and contractions in the outer layers as a star seeks to maintain equilibrium. These fluctuations in stellar radius causes corresponding changes in the luminosity of the star. Astronomers are able to deduce this mechanism by measuring the spectrum and observing the Doppler effect. Many intrinsic variable stars that pulsate with large amplitudes, such as the classical Cepheids, RR Lyrae stars and large-amplitude Delta Scuti stars show regular light curves. (By regular one means that Fourier analysis shows amplitudes that are constant in time.)This regular behavior is in contrast with the variability of stars that lie parallel to and to the high-luminosity/low-temperature side of the classicalvariable stars in the Hertzsprung-Russell diagram. These giant stars are observed to undergo pulsations ranging from weak irregularity, when one can still define an average cycling time or period, (as in most RV Tauri and Semiregular variables) to the near absence ofrepetitiveness in the Irregular variables. The W Virginis variables are at the interface; the short period ones are regular and the longer period ones show first relatively regular alternations in the pulsationscycles, followed by the onset of mild irregularity as in the RV Tauri stars into which they gradually morph as their periods get longer. Stellar evolution and pulsation theories suggest that these irregular stars have a much higher luminosity to mass (L/M) ratios.A third category of variable stars are the non-radial pulsators which typically have much smaller pulsationamplitudes. With relative fluctuations in brightness from ~10% down the observable limit, non-radial pulsation is very common among stars.Here we address the mathematical and physical reasons for the difference between the regular and irregular large amplitude stars. Intuitively, a prerequisite for irregular variability is that the star be able to changeits amplitude on the time scale of a period. In other words, the coupling between pulsation and heat flow must be sufficiently large to allow such changes. This coupling is measured by the relative linear growth- or decay rate of the amplitude of a given normal mode in one pulsation cycle (period). For the regular variables (Cepheids, RR Lyrae, etc.) numerical stellar modeling and linear stability analysis show that is at most of the order of a couple of percent for the relevant, excited pulsation modes. On the other hand, the sametype of analysis shows that for the high L/M models is considerably larger (30% or higher).".
- Stellar_pulsations wikiPageID "25613797".
- Stellar_pulsations wikiPageRevisionID "604193232".
- Stellar_pulsations coi "September 2010".
- Stellar_pulsations essayLike "September 2010".
- Stellar_pulsations hasPhotoCollection Stellar_pulsations.
- Stellar_pulsations synthesis "September 2010".
- Stellar_pulsations subject Category:Astrophysics.
- Stellar_pulsations subject Category:Variable_stars.
- Stellar_pulsations type CelestialBody109239740.
- Stellar_pulsations type NaturalObject100019128.
- Stellar_pulsations type Object100002684.
- Stellar_pulsations type PhysicalEntity100001930.
- Stellar_pulsations type Star109444100.
- Stellar_pulsations type VariableStar109469152.
- Stellar_pulsations type VariableStars.
- Stellar_pulsations type Whole100003553.
- Stellar_pulsations comment "Stellar pulsations are caused by expansions and contractions in the outer layers as a star seeks to maintain equilibrium. These fluctuations in stellar radius causes corresponding changes in the luminosity of the star. Astronomers are able to deduce this mechanism by measuring the spectrum and observing the Doppler effect.".
- Stellar_pulsations label "Estrella variable pulsante".
- Stellar_pulsations label "Pulsationsveränderlicher Stern".
- Stellar_pulsations label "Stella variabile pulsante".
- Stellar_pulsations label "Stellar pulsations".
- Stellar_pulsations label "脈動変光星".
- Stellar_pulsations sameAs Pulsationsveränderlicher_Stern.
- Stellar_pulsations sameAs Παλλόμενοι_μεταβλητοί_αστέρες.
- Stellar_pulsations sameAs Estrella_variable_pulsante.
- Stellar_pulsations sameAs Izar_aldagarri_pultsante.
- Stellar_pulsations sameAs Stella_variabile_pulsante.
- Stellar_pulsations sameAs 脈動変光星.
- Stellar_pulsations sameAs m.09v63cr.
- Stellar_pulsations sameAs Q353834.
- Stellar_pulsations sameAs Q353834.
- Stellar_pulsations sameAs Stellar_pulsations.
- Stellar_pulsations wasDerivedFrom Stellar_pulsations?oldid=604193232.
- Stellar_pulsations isPrimaryTopicOf Stellar_pulsations.