Need help understanding use of cepheid variables

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Discussion Overview

The discussion centers on the method of determining distances to stars and galaxies using Cepheid variable stars. Participants explore the relationship between the period of Cepheid variables and their brightness, as well as the implications for measuring distances in both local and distant astronomical contexts.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant asks for an explanation of how the distance to stars and galaxies can be determined using Cepheid variable stars, specifically requesting a layman's terms approach.
  • Another participant explains that the period of a Cepheid variable provides its absolute brightness, and that the apparent brightness observed can be used with the inverse square law to calculate distance.
  • A participant questions how this method applies to non-Cepheid stars that are too distant for parallax measurements.
  • It is noted that more distant Cepheid stars are primarily used for estimating distances to other galaxies, while they are less useful for measuring distances within the Milky Way.

Areas of Agreement / Disagreement

Participants express different perspectives on the utility of Cepheid variables for measuring distances, particularly concerning their application to non-Cepheid stars and within the Milky Way versus other galaxies. The discussion does not reach a consensus on these points.

Contextual Notes

The discussion does not address specific limitations or assumptions regarding the methods described, nor does it clarify the extent of applicability for Cepheid variables in various contexts.

Who May Find This Useful

Individuals interested in astronomy, particularly those seeking to understand distance measurement techniques in astrophysics, may find this discussion relevant.

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.
 
Last edited:
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?
 
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.
 

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