Need help understanding use of cepheid variables

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In summary, the distance to stars and galaxies can be determined using Cepheid variable stars by using the period of their contraction/expansion to calculate their absolute brightness and using the inverse square law to determine their distance. This method relies on using nearby Cepheid variables as standards, but more distant Cepheid stars can also be used to estimate distances to other galaxies.
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gsonnet911
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Can someone please explain how the distance to stars/galaxies can be determined using Cepheid variable stars? I know that you can find the distance to the cepheid using the period of its contraction/expansion but how is this used?
Im in high school so please use layman's terms :)
 
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The period gives the absolute brightness of the star. Observation gives the apparent brightness. Using the inverse square law, the distance can then be calculated.

This approach is based on using nearby Cepheid variables as standards, since their distances can be obtained directly, using parallax.
 
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  • #3
how does this help in finding the distance to non-cepheid stars whose distance away is too great to be measured using the parallax method?
 
  • #4
The more distant cepheid stars are primarily used to estimate distances to other galaxies. They are of not much help in estimating distances within our galaxy.
 
  • #5


Cepheid variable stars are a specific type of star that pulsates, meaning they expand and contract at regular intervals. This pulsation is directly related to the brightness of the star, so by measuring the pulsation period (the time it takes for the star to go through one cycle of expansion and contraction), we can determine its intrinsic brightness.

Now, because we know the intrinsic brightness of the star, we can compare it to its observed brightness from Earth. By doing this, we can calculate the distance to the star using a simple formula: distance = (intrinsic brightness / observed brightness)^1/2.

This method works because the further away a star is, the fainter it appears to us on Earth. So by comparing the intrinsic and observed brightness, we can determine how far away the star is.

Cepheid variable stars are especially useful for determining distances to distant galaxies. This is because they have a known relationship between their pulsation period and intrinsic brightness, and they are bright enough to be observed in distant galaxies. By studying the Cepheid variable stars in a galaxy and measuring their pulsation periods, we can calculate the distance to that galaxy.

In summary, the use of Cepheid variable stars allows us to determine the distance to stars and galaxies by measuring their pulsation periods and comparing their intrinsic and observed brightness. I hope this helps clarify the concept for you!
 

1. What are cepheid variables?

Cepheid variables are a type of pulsating star with a regular and predictable change in brightness. They are named after the first discovered star of this type, Delta Cephei.

2. How are cepheid variables used in scientific research?

Cepheid variables are used as standard candles, meaning that their brightness is directly related to their true luminosity. This makes them useful for measuring distances to other galaxies and determining the expansion rate of the universe.

3. What causes the brightness variation in cepheid variables?

The brightness variation in cepheid variables is caused by periodic changes in their size and temperature. As they expand and contract, their brightness also changes.

4. Can cepheid variables be used to measure distances within our own galaxy?

Yes, cepheid variables can be used to measure distances within our own galaxy, but they are most commonly used to measure distances to other galaxies that are too far away for other methods to be effective.

5. Are there different types of cepheid variables?

Yes, there are two main types of cepheid variables: classical and type II. Classical cepheids are more massive and have longer periods of brightness variation, while type II cepheids are less massive and have shorter periods.

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