Are Cepheid variable stars main sequence stars?

Because of these properties, one can determine a distance to a Cepheid variable by measuring its period and its apparent brightness. Cepheid variables are not main sequence stars. Rather, they are stars that are in the helium burning stage of their lives.

Read more

Consequently, what important discoveries were made early in this century using rr lyrae variables?

What important discoveries were made early in the 20th centure by using RR Lyrae variables? 2) By measuring the direction and distance of each cluster, he was able to determine their 3D distribution in space. Thus, Globular Clusters map out a truly gigantic and roughly spherical volume of space about 20kpc across. What makes a star a Cepheid? A Cepheid variable (/?s?fi??d, ?si?fi??d/) is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.

What is the main factor that determines the evolution of a star?

The primary factor determining how a star evolves is its mass as it reaches the main sequence. The following is a brief outline tracing the evolution of a low-mass and a high-mass star. Stars are born out of the gravitational collapse of cool, dense molecular clouds. One may also ask what are the most important factors determining which nuclear reactions take place in a star and how fast they take place? The higher temperatures mean that the nuclear reactions occur at a much greater rate in massive stars. They thus use up their fuel much quicker than lower mass stars. This is analogous to the situation with many chemical reactions, the higher the temperature the faster the reaction rate.

What is the main factor driving the evolution of a star and why?

The primary factor driving stellar evolution is the star's mass. Stars form from the gravitational collapse of cool, dense molecular clouds. What did Harlow Shapley believe? Heber Curtis Harlow Shapley believed that everything in the universe was located within our own galaxy. He thought that the Galaxy was quite large ? 300,000 light-years in diameter ? and that the sun was not at the center.