pulsation theory was proposed by??

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The pulsation theory was first proposed as a possible explanation as early as 1879, was applied to Cepheids in 1914, and was further developed by Arthur Eddington in 1917–18.

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Pulsation theory was developed by Arthur Eddington
In which .This theory state that after big bang the space and universe is expanding..but after it it get attract with one another due to excess gravity.....and again big bang happen .......this is also called cycling theory ...or cyclic model

Answer

Pulsation Theory

The theory of pulsation was proposed by Arthur Eddington, a British astrophysicist, in the early 20th century. It is a concept that attempts to explain the variations in brightness observed in certain types of stars, known as variable stars. These stars undergo periodic changes in their luminosity, which can span from minutes to years. Pulsation theory aims to understand the underlying physical mechanisms that cause these fluctuations.

Understanding Variable Stars

Variable stars are categorized into different types based on their brightness variations. One of the most well-known types is the Cepheid variable stars. These stars exhibit a regular pulsation pattern, with a period directly related to their intrinsic luminosity. This relationship, known as the period-luminosity relation, allows astronomers to use Cepheids as standard candles to measure cosmic distances.

Pulsation Mechanism

According to the pulsation theory, the variations in brightness of variable stars are caused by periodic expansion and contraction of their outer layers. This pulsation is driven by the interplay between the star's internal energy generation and its gravitational structure. The energy generated in the star's core is transported outward, causing the outer layers to expand. As these layers expand, they cool and become less opaque, allowing radiation to escape more easily. Consequently, the star's luminosity decreases.

On the other hand, when the outer layers contract, they become hotter and more opaque, trapping radiation within the star. This results in an increase in luminosity. The cycle of expansion and contraction repeats, leading to the observed periodic variations in brightness.

Importance and Applications

The pulsation theory has significant implications in astrophysics. By studying the pulsation patterns of variable stars, astronomers can determine fundamental parameters such as the star's mass, radius, and temperature. Additionally, the period-luminosity relation of Cepheids allows for the measurement of cosmic distances, which is crucial for studying the scale and expansion of the universe.

Furthermore, pulsation theory helps in understanding stellar evolution. By analyzing the pulsation properties of stars at different stages of their lives, scientists can gain insights into the internal processes and structural changes that occur during stellar evolution.

Conclusion

In summary, the pulsation theory proposed by Arthur Eddington provides a framework for explaining the variations in brightness observed in variable stars. By considering the interplay between internal energy generation and gravitational structure, the theory elucidates the mechanism behind the periodic expansion and contraction of these stars' outer layers. This theory not only aids in understanding the properties and evolution of stars but also enables the measurement of cosmic distances and the exploration of the universe's scale and expansion.

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