<p>Globular clusters vary in size quite a bit. They contain from a few hundred thousand to over a million stars. Probably best way to determine size is to measure its extent across the sky by telescope and then calculate that distance in km. One could also model the size by assuming the number of stars, the average size of the stars, and the spacing based on this size.  One could build a globular cluster of 300,000 stars or so and determine the approximate size.</p>

<p>You ask if 120-150 ly is the average diameter of such globular clusters. I'm confused by exactly what you mean but you have sampled a small range of sizes considering globular clusters can be well over 300 ly in diameter. </p>

<p>From Wikipedia, and based on comment from @AtmosphericPrisonEscape, you have "Almost all globular clusters have a half-light radius of less than 10 pc, although there are well-established globular clusters with very large radii (i.e. NGC 2419 (Rh = 18 pc) and Palomar 14 (Rh = 25 pc)).[64]"</p>

CC BY-SA 4.0
2018-05-20T17:18:10.593Z
2018-06-19T17:55:54.227Z
2018-06-19T17:55:54.227Z
Natsfan
<p>I am doing a homework on globular clusters and could not find trustworthy data on the average diameter of a globular cluster. Most clusters I included had a diameter of 120-150 ly.
But is <strong>that</strong> the average diameter of such globular clusters?</p>

CC BY-SA 3.0
2018-01-23T23:32:27.953Z
You probably want to look for the 'half light radius' of clusters. There is not THE diameter of a cluster. There is only a cluster size distribution.
AtmosphericPrisonEscape
CC BY-SA 4.0
2018-06-19T17:58:32.737Z
@adriankroeger I edited my answer, maybe it helps more now if you're still interested.
Natsfan
<globular-clusters>
Globular Cluster diameter
adriankroeger
# Globular Cluster diameter

(Asked by: username_0 on 2018-01-23)

I am doing a homework on globular clusters and could not find trustworthy data on the average diameter of a globular cluster. Most clusters I included had a diameter of 120-150 ly.
But is **that** the average diameter of such globular clusters?

**Tags:** globular-clusters

> **Comments:**
> **username_1**: You probably want to look for the 'half light radius' of clusters. There is not THE diameter of a cluster. There is only a cluster size distribution.  
> **username_2**: @username_0 I edited my answer, maybe it helps more now if you're still interested.  

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## 1 answers

### Answer by username_2 on 2018-05-20. Score: 0 | Accepted answer

Globular clusters vary in size quite a bit. They contain from a few hundred thousand to over a million stars. Probably best way to determine size is to measure its extent across the sky by telescope and then calculate that distance in km. One could also model the size by assuming the number of stars, the average size of the stars, and the spacing based on this size. One could build a globular cluster of 300,000 stars or so and determine the approximate size.

You ask if 120-150 ly is the average diameter of such globular clusters. I'm confused by exactly what you mean but you have sampled a small range of sizes considering globular clusters can be well over 300 ly in diameter.

From Wikipedia, and based on comment from @username_1, you have "Almost all globular clusters have a half-light radius of less than 10 pc, although there are well-established globular clusters with very large radii (i.e. NGC 2419 (Rh = 18 pc) and Palomar 14 (Rh = 25 pc)).[64]"


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