<p>OK, I see what you want.</p>

<p>What I did was take the revised Hipparcos catalogue and select all stars closer than 50pc. At this distance there should be a <em>complete</em> sample of the types of stars you were interested in. I can plot an absolute magnitude versus colour diagram for these 7096 stars (see below) and use this to select giants and OB main sequence stars.</p>

<p>I do this by using data from chapter 2 of <a href="http://ads.harvard.edu/books/hsaa/toc.html" rel="nofollow noreferrer">Zombeck (1992)</a>, I define O and B main sequence stars to have $B-V&lt;0$ and $M_V&lt;5$ (to exclude hot white dwarfs). Evolved giants are selected (a bit arbitrarily) to lie significantly above the main sequence.</p>

<p><a href="https://i.sstatic.net/MbmNu.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/MbmNu.png" alt="Stars closer than 50pc"></a></p>

<p>Then I can plot a frequency histogram of the B-V values of those stars and label them with spectral types, again according to tables in Zombeck (1992).
The result is seen below.</p>

<p><a href="https://i.sstatic.net/MsMqy.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/MsMqy.png" alt="Distribution of &quot;giant stars&quot;"></a></p>

<p>Of these 235 stars: None are O stars, 29 are B stars, about 120 are G giants, about 80 are K giants and only 2-3 are M giants</p>

CC BY-SA 3.0
2016-10-03T02:25:53.950Z
I think I'm misunderstanding something. I thought that Red Gian and Supergiants were the dominant, but your answer seems to indicate Yellow Giants are the dominant and there are barely any Reds...
Durakken
CC BY-SA 3.0
2016-10-03T06:36:56.633Z
@Durakken It is what it is. Of course if you were interested in a magnitude limited sample, rather than a volume limited sample, the answer might be different. Perhaps I have misinterpreted what you meant bt "stars in a given area"?
ProfRob
CC BY-SA 3.0
2016-10-03T06:39:10.493Z
@Durakken Also, all of the giants are redder than the Sun.
ProfRob
CC BY-SA 3.0
2016-10-03T12:29:00.527Z
i think the issue is that I'm thinking that there are a class for each spectral type, when it now seems that all spectral types are wrapped up in the terms/classes Red Giant, Red Supergiant, and Yellow Hypergiants which are special specific instances... So my question isn't right to what i needed to know, but your answer helped with what i really did.
Durakken
CC BY-SA 3.0
2016-10-03T12:41:53.160Z
@Durakken There are no "hypergiants" or "supergiants" in the sample above. These are rare (but luminous).
ProfRob
CC BY-SA 3.0
2016-10-03T13:47:21.867Z
Astounding answer!
Fattie
CC BY-SA 3.0
2016-10-03T14:04:31.117Z
@Durakken When I find a moment I will add the answer for a magnitude limited sample.
ProfRob
CC BY-SA 3.0
2016-10-04T10:48:02.793Z
Should I be amused that the numbers of types of stars in your answer does not add up to 235? but 232, or am I missing something?
Durakken
CC BY-SA 3.0
2016-10-04T10:58:06.133Z
@Durakken "about 120 are G giants, about 80 are K giants". Why do you think the numbers should add up exactly?
ProfRob
CC BY-SA 3.0
2016-10-04T11:09:25.320Z
Why wouldn't they add up?
Durakken
CC BY-SA 3.0
2016-10-04T12:00:17.060Z
@Durakken Because I don;t know exactly where the boundary is and have not provide spurious 3 significant figure accuracy.
ProfRob
CC BY-SA 3.0
2016-10-04T12:07:36.503Z
Ahh I see. I figured it was something like that.
Durakken
CC BY-SA 3.0
2016-10-02T21:32:09.847Z
2016-10-02T21:32:09.847Z
ProfRob
<p>I'm looking for the distribution of spectral types in the "giant" star category. This category is defined as basically B and O main sequence stars and any star that is larger than main sequences outside of it.</p>

<p>My first thought was that the M, K, G, F, and A type distribution were the same as they are in the main sequence but then I realized M has to be dropped, and then i'm not quite sure how K, G, F, and A types evolve and usually only Red Giants are mentioned and I couldn't find numbers for the giants so I'm stuck. </p>

<p>To be clear, I want to know the percentage of giant stars that are in each of the spectral types. So if there are 1000 stars in a given area and 100 giant stars in that areas I only want to know the percentage of each spectral type of the stars in that 100.</p>

CC BY-SA 3.0
2016-10-02T20:06:49.890Z
I can't work out what it is you want to know, or what you've done to find an answer.
ProfRob
CC BY-SA 3.0
2016-10-02T20:20:46.167Z
@RobJeffries Does that new added last paragraph help?
Durakken
CC BY-SA 3.0
2016-10-02T20:44:09.443Z
So essentially you want to know the temperature distribution of giants, where your definition of giant includes main sequence OB stars.
ProfRob
<star>
Distribution of spectral types of "giant" stars
Durakken
# Distribution of spectral types of "giant" stars

(Asked by: username_0 on 2016-10-02)

I'm looking for the distribution of spectral types in the "giant" star category. This category is defined as basically B and O main sequence stars and any star that is larger than main sequences outside of it.

My first thought was that the M, K, G, F, and A type distribution were the same as they are in the main sequence but then I realized M has to be dropped, and then i'm not quite sure how K, G, F, and A types evolve and usually only Red Giants are mentioned and I couldn't find numbers for the giants so I'm stuck.

To be clear, I want to know the percentage of giant stars that are in each of the spectral types. So if there are 1000 stars in a given area and 100 giant stars in that areas I only want to know the percentage of each spectral type of the stars in that 100.

**Tags:** star

> **Comments:**
> **username_1**: I can't work out what it is you want to know, or what you've done to find an answer.  
> **username_0**: @RobJeffries Does that new added last paragraph help?  
> **username_1**: So essentially you want to know the temperature distribution of giants, where your definition of giant includes main sequence OB stars.  

---

## 1 answers

### Answer by username_1 on 2016-10-02. Score: 3

OK, I see what you want.

What I did was take the revised Hipparcos catalogue and select all stars closer than 50pc. At this distance there should be a *complete* sample of the types of stars you were interested in. I can plot an absolute magnitude versus colour diagram for these 7096 stars (see below) and use this to select giants and OB main sequence stars.

I do this by using data from chapter 2 of [Zombeck (1992)](http://ads.harvard.edu/books/hsaa/toc.html), I define O and B main sequence stars to have $B-V<0$ and $M\_V<5$ (to exclude hot white dwarfs). Evolved giants are selected (a bit arbitrarily) to lie significantly above the main sequence.

[![Stars closer than 50pc](https://i.sstatic.net/MbmNu.png)](https://i.sstatic.net/MbmNu.png)

Then I can plot a frequency histogram of the B-V values of those stars and label them with spectral types, again according to tables in Zombeck (1992).
The result is seen below.

[![Distribution of ](https://i.sstatic.net/MsMqy.png)](https://i.sstatic.net/MsMqy.png)

Of these 235 stars: None are O stars, 29 are B stars, about 120 are G giants, about 80 are K giants and only 2-3 are M giants

> **Comments:**
> **username_0**: I think I'm misunderstanding something. I thought that Red Gian and Supergiants were the dominant, but your answer seems to indicate Yellow Giants are the dominant and there are barely any Reds...  
> **username_1**: @username_0 It is what it is. Of course if you were interested in a magnitude limited sample, rather than a volume limited sample, the answer might be different. Perhaps I have misinterpreted what you meant bt "stars in a given area"?  
> **username_1**: @username_0 Also, all of the giants are redder than the Sun.  
> **username_0**: i think the issue is that I'm thinking that there are a class for each spectral type, when it now seems that all spectral types are wrapped up in the terms/classes Red Giant, Red Supergiant, and Yellow Hypergiants which are special specific instances... So my question isn't right to what i needed to know, but your answer helped with what i really did.  
> **username_1**: @username_0 There are no "hypergiants" or "supergiants" in the sample above. These are rare (but luminous).  
> **username_2**: Astounding answer!  
> **username_1**: @username_0 When I find a moment I will add the answer for a magnitude limited sample.  
> **username_0**: Should I be amused that the numbers of types of stars in your answer does not add up to 235? but 232, or am I missing something?  
> **username_1**: @username_0 "about 120 are G giants, about 80 are K giants". Why do you think the numbers should add up exactly?  
> **username_0**: Why wouldn't they add up?  
> **username_1**: @username_0 Because I don;t know exactly where the boundary is and have not provide spurious 3 significant figure accuracy.  
> **username_0**: Ahh I see. I figured it was something like that.  

---

