Cepheid Stars & the Hubble Parameter: What is Their Role?

[UMich1344]

What is the role of Cepheid stars in determining the Hubble parameter?

 

[mgb_phys]

Cepheids change in brightness, the period depends on the absolute magnitude.
By measuring the period you know how bright the star really is, you can measure how bright it appears and so find the distance.

 

[tacman]

Cepheid stars play a crucial role in determining the Hubble parameter, which is a measure of the rate at which the universe is expanding. These stars are a particular type of variable star that pulsates in a very regular pattern, with a period of brightness that is directly related to its intrinsic luminosity. This makes them extremely useful for measuring distances in the universe.

By observing the pulsation period of Cepheid stars in distant galaxies, astronomers can determine their intrinsic luminosity and use this information to calculate the distance to the galaxy. This is known as the period-luminosity relationship and was first discovered by American astronomer Henrietta Swan Leavitt in 1908. This relationship allows us to measure the distances to galaxies much further away than was previously possible.

The Hubble parameter is calculated by measuring the redshift of light from distant galaxies, which is a result of the expanding universe stretching the light as it travels. By combining this redshift data with the distance measurements obtained from Cepheid stars, astronomers can determine the rate of expansion of the universe.

In summary, Cepheid stars are essential in determining the Hubble parameter because their regular pulsations allow us to accurately measure distances to galaxies, which is crucial for calculating the rate of expansion of the universe. Without the use of Cepheid stars, our understanding of the universe and its evolution would be significantly limited.