# Ages of starts from CMD

by randa177
Tags: ages, starts
 P: 91 why is getting the age from CMD more accurate than getting it from photometry?
 P: 91 I mean ages of start clusters!
 P: 91 Why no one answered my question? Does it make sense? Why are we requiring color magnitude diagrams to get ages.. Why are they the best?
HW Helper
P: 8,962

## Ages of starts from CMD

CMD isn't a very common abbreviation, most people would say HR diagram.
Do you mean - how to get the age of stars from a color magnitude (ie Hertzsprung–Russell) diagram?
P: 91
 Quote by mgb_phys CMD isn't a very common abbreviation, most people would say HR diagram. Do you mean - how to get the age of stars from a color magnitude (ie Hertzsprung–Russell) diagram?
Actually I am reading papers about large magelanic cloud, and it always mentions that getting the age using CMD (H-R diagram) is more accurate than using photometry. why CMDs give the only truly accurate ages for star clusters?
 HW Helper Sci Advisor P: 8,962 Not sure I understand the question. You use photometry to get the color index of the star. Then plotted on the HR diagram gives you the age (or at least the evolutionary state of the star) for an accurate age you would also need to know metalicity and mass.
P: 91
 Quote by mgb_phys Not sure I understand the question. You use photometry to get the color index of the star. Then plotted on the HR diagram gives you the age (or at least the evolutionary state of the star) for an accurate age you would also need to know metalicity and mass.
Yes, that's right, but that uses the photometry of each star in the cluster, not the color/magnitude of the whole cluster, because the magnitude and integrated colors for a cluster as a whole doesn't give very accurate information... Oh, wait I think i've just answered my original question!!! .... i got confused too now!
 P: 91 Hi, I just wanted to let you know that I was right about the reason CMD (HR diagram)give most accurate ages for stellar clusters. But can anyone let me know HOW we get the ages from CMDs (H-R diagrams)?

 Related Discussions Calculus 48 Earth 7 Earth 27 Biology, Chemistry & Other Homework 2 General Discussion 2