I have an astronomy question?!?

Question

How does knowing the period of variability of a Cepheid Variable star allow us to determine its absolute magnitude?

Also

How could one use the apparanet magnitude of a star to correctly determine the Period-Luminosity relation?

I have been struggling with this....please help!

Answer 1

I think you might be asking the wrong question. The period/Luminosity relation isn't something you determine, it's just the observation that period is related to absolute magnitude.
Delta Cephei, the closest Cepheid variable is close enough to do a parallax distance measurement, so it was a good one to calibrate the scale with. Henrietta Leavitt took measurements of a bunch of cepheids in the Small Magelennic cloud, which would all be about the same distance from us to get the relationship between their periods and luminosities. More accurate parralax measurements of other cepheids along with better knowledge of stellar evolution and the mechanism behind the variable luminosities have allowed us to fine tune the scale.
So, you use the period to find the absolute magnitude of the star, and then use the absolute magnitude ratio to the apparent magnitude to calculate it's distance.

Answer 2

Dear Tina, this is modular simullation astronomy math and for this question the best solution is to contact NASA's astronomy Base in Albuqerkie, New Mexico - I think that I'm type name of City correct). Best Regards and veradisca! Neven.

Answer 3

I agree with the author Nomadd

Answer 4

Try here

http://en.wikipedia.org/wiki/Cepheid

Answer 5

Better yet, try here http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_cepheids.html