Expert: Philip Stahl - 1/23/2010

Question
Mr. Stahl

Thank you for clarifying the previous question regarding the sun.  I never understood the buzz about 2012 until I read about he sunspots and the 11-year cycle, which culminates in 2012.  (I am REALLY learning a lot).

My current question is specific to the HR diagram.  For example, my understanding of the HR diagram is as follows:

The HR diagram is composed of four main groupings with specific characteristics (i.e., the four main groups (A through D), which consist of the main sequence, giants, super giants, and white dwarfs.  

I am aware of how each has some correlation to temperature, luminosity, and magnitudes.  However, what is confusing is that after reading numerous articles I don't know how to bring it all together (i.e., the parallax and formulas).  

Answer
Hello,

Unfortunately, your needs here require a comprehensive approach and more detail than can be reasonably allocated in a question response. Also, I simply lack the time to deliver what's required.

What I suggest is to try and get hold of one or two basic books which cover your issues well:

1) Astronomy Made Simple - by Kevin B. Marvel

2) Astronomy for the Utterl Confused - by Terry Jay Jones and Jeanne K. Hanson.

The last has an especially good basic section (III) on introductory astrophysics, and the H-R diagram is covered in Part IV, along with parallax, star compositions and colors etc.

Hope this helps!