What is the H-R Diagram Method for Determining the Age of a Star Cluster?

In summary, by finding the main sequence turnoff point and looking at the lifetimes of specific classes of stars in the H-R diagram on pages 326-327 of the textbook "The Cosmic Perspective," the age of the star cluster can be determined. This method is useful for finding the age of other star clusters as well. Information on the classes of stars (O, B, A, F, G, K, M) and their general lifetimes can be found in the textbook.
  • #1
bobo1455
33
0
Here's the question:

The following figure is the H-R diagram of a star cluster. Use this diagram to determine the age of the cluster.

wvW1FyO.png


The answers are multiple choice:

(A) 600 thousand years
(B) 6 million years
(C) 60 million years
(D) 600 million years
(E) 6 billion years

Here's my attempt:

I know that to determine the age of the cluster, we need to start by determining where in the graph the stars start changing from main sequence. And at that point, we find on the horizontal axis one of the following: OBAFGKM

And then the letter has 10 sub-groups, so I believe the classification to be G2 or G1. This is the part I'm stuck on, if it is G1 or G2 (or pretty much any sub-group of G in general), how do I get the age?

I read in my textbook that G1 is about the age of the Sun, but all of the multiple choice answers are 6-something and I don't understand how to get that, or at least something close to that.

I determined the answer to be 10^10, which is 10 billion, I believe. But it's really off and completely wrong.

Thanks in advance.
 
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  • #2
AST201 UTM? :D

The best way to figure out this question is to look at the diagrams + text on p.326-27 and compare the cluster to the examples given. Finding the Main sequence turnoff point and reading up on the 'general' lifetimes of specific classes of stars given on these two pages as well will go a long way in helping to determine the most appropriate answer. GLHF
 
  • #3
yeah, I figured it out. You go to UTM too?
 
  • #4
yeah lol
 
  • #5
:cry:
Hey you guys, 100 people have already looked at this thread in the hope to either be able to help or to learn something. And all you can utter is OBAFGKM, AST201 UTM? GLHF !​

And the only stuff left on the public part of the site is the 2009intro and the syllabus. But I could just about dig up a book The Cosmic Perspective, 5th edition, by Bennet, Donahue, Schneider and Voit which might have a p326-327 with diagrams+text. Right ? Or am I barking up the wrong UTM ?

BvU
 
  • #6
We're talking about University of Toronto Mississauga lol

BvU are you attending UTM too? this is hilarious
 
  • #7
BvU is in GMT+1 and it's bedtime there. You guys amuse yourself, Ok, but try to make this thread somewhat more informative for others, pls!
 
  • #8
Well I don't want to just give the answer away

I've already given so much information
 
  • #9
:tongue:
 
  • #10
BvU, You seem confused that the information mentioned exists only in the specifically mentioned source, but it just so happens to be be highly relevant in this situation and to the OP.

The idea of finding the main sequence turnoff point and reading up on the 'general' lifetimes of specific classes of stars (O,B,A,F,G,K & M) is extremely helpful towards solving this problem.

Please consider the broader implications of an answer rather then just focusing on specifics.
 

1. What is an H-R diagram and how is it used to study star clusters?

An H-R (Hertzsprung-Russell) diagram is a graph that plots the luminosity (brightness) of stars against their surface temperature. It is a useful tool for studying star clusters because it allows scientists to see the different stages of stellar evolution and compare the characteristics of stars within a cluster.

2. What is the main purpose of studying H-R diagrams of star clusters?

The main purpose of studying H-R diagrams of star clusters is to understand the physical properties and evolutionary processes of stars within a cluster. This can provide insights into the formation and development of the cluster itself, as well as the larger scale processes of star formation and evolution.

3. What can we learn from the distribution of stars on an H-R diagram?

The distribution of stars on an H-R diagram can tell us about the age and chemical composition of a star cluster. Younger clusters tend to have more massive, hotter and brighter stars, while older clusters have smaller, cooler and fainter stars. The chemical composition of stars can also be determined by their position on the H-R diagram, as different elements affect the surface temperature and luminosity of stars.

4. How does the H-R diagram help us classify stars within a cluster?

The H-R diagram allows us to classify stars based on their spectral type, which is determined by their surface temperature. This classification can help us understand the physical properties and evolutionary stage of a star. For example, red giants are classified as low-temperature, high-luminosity stars, while main sequence stars are classified as medium-temperature, medium-luminosity stars.

5. What is the relationship between a star's mass and its position on the H-R diagram?

The position of a star on the H-R diagram is directly related to its mass. More massive stars are hotter and more luminous, and therefore appear higher on the diagram. Less massive stars are cooler and less luminous, and appear lower on the diagram. This relationship is known as the mass-luminosity relationship and is an important aspect of stellar evolution and the study of star clusters.

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