Astronomy Problem: How to Find Apparent and Absolute Magnitude of a Cepheid

[Ivan91]

I didnt find an astronomy subforum on the Homework section so I decided to post here.

If I have the period of a cepheid (2.5 for instance), how to find apparent and absolute magnitude ?

 

[NobodySpecial]

Apparent magnitude you have to measure - the absolute magnitude you get from the period see:
http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_cepheids.html

 

[Ivan91]

Ok, thanks. One more question.
What are some differences between active and normal galaxies ?

 

[davenn]

Ok, thanks. One more question.
What are some differences between active and normal galaxies ?

did you try googling... active galaxies ?

the first hit is a wikipedia link explaining the difference :)

Dave

 

[pmacias]

To find the apparent magnitude of a cepheid, you will need to measure its brightness as seen from Earth. This can be done by using a photometer or a telescope with a CCD camera. Once you have the measured apparent magnitude, you can use the following formula to calculate the absolute magnitude:

M = m - 5log(d/10)

Where M is the absolute magnitude, m is the apparent magnitude, and d is the distance to the cepheid in parsecs.

To find the distance to the cepheid, you can use the period-luminosity relationship for cepheids. This relationship states that the period of a cepheid is directly related to its luminosity. By comparing the period of the cepheid to known values on a period-luminosity diagram, you can determine its luminosity and therefore its distance.

Once you have the distance to the cepheid, you can plug it into the formula to calculate the absolute magnitude. This will give you the intrinsic brightness of the cepheid, independent of its distance from Earth.

To find the apparent magnitude, you can simply measure the brightness of the cepheid using a photometer or telescope and compare it to a standard star of known apparent magnitude. This will give you the apparent magnitude of the cepheid as seen from Earth.

In summary, to find the apparent and absolute magnitude of a cepheid, you will need to measure its brightness, determine its distance using the period-luminosity relationship, and use the distance to calculate the absolute magnitude. This information can then be used to study the properties and evolution of cepheids and their host galaxies.