<p>The most well known use of Greek letters is in the names of stars created by Johann Bayer in 1603 for his star atlas <em>Uranometria</em>.</p>
<p>Bayer gave each star in his atlas a two-part name.  The first part is a greek letter, the second part is the constellation that the star is in (in the Latin genetive form). Generally the brightest star in each constellation is designated &quot;Alpha&quot;, the second brightest is Beta and so on.</p>
<p>So Alpha Centauri is the brightest star in the constellation of the Centaur.</p>

CC BY-SA 4.0
2021-08-17T07:38:38.383Z
2021-08-17T07:38:38.383Z
James K
<p>There is no general way to answer where Greek letters are used.</p>
<p>There is the Bayer naming convention for (some of) the brightest stars where he named them in each constellation, giving <span class="math-container">$\alpha$</span> to the brightest, <span class="math-container">$\beta$</span> to the 2nd brightest and so on - but this naming usually stops even before <span class="math-container">$\omega$</span> is reached, covering just the brightest few per constellation (and even the ordering is not always strictly by brightness).</p>
<p>In other areas as generally in physics or science in general, Greek letters are used as symbols for certain properties in equations. There do exist conventions like <span class="math-container">$\varrho$</span> being used for density, <span class="math-container">$\alpha$</span> for kinematic viscosity, etc - but these definitions are not a given nor are they unique. Their meaning has to be established in every context anew; used is what fits the context. Important is only that every reader can know what is meant with each symbol in a given context - thus be consistent throughout your paper or book with their usage.</p>

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2021-08-17T10:24:05.980Z
2021-08-18T03:56:38.850Z
2021-08-18T03:56:38.850Z
planetmaker
<p>We see letters such as <span class="math-container">$\epsilon$</span> or <span class="math-container">$\alpha$</span> or <span class="math-container">$\beta$</span> or <span class="math-container">$\eta$</span> etc... (possibly all Greek letters)</p>
<p>Can Somebody state the use of all Greek letters in astronomy?</p>

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2021-08-17T07:38:07.463Z
it would be better if somebody mentions some names of good reference books to learn this topic....
Hi-Tech
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2021-08-17T07:42:49.333Z
Hello @Hi-Tech  This is a question and answer site, please take the [tour]  You ask a question and get answers. Requests for resources are not so useful. You are expected to do your own research first, and then ask a specific question.
James K
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2021-08-17T07:43:57.280Z
@Hi-Tech Go through these questions: https://astronomy.stackexchange.com/questions/19362/variable-types-of-stars/19364#19364 ... https://astronomy.stackexchange.com/questions/43654/nomenclature-of-interstellar-objects-and-stars/43681#43681 .. https://astronomy.stackexchange.com/questions/36182/a-question-about-star-names-e-g-cw-tauri-dz-bootis-iq-lupi-eu-eridani/36186#36186 ... https://astronomy.stackexchange.com/questions/39583/what-exactly-are-h30%ce%b1-and-he30%ce%b1-images-alma
Nilay Ghosh
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2021-08-17T07:56:40.000Z
Regarding your first comment, you can visit [IAU](https://www.iau.org/public/themes/naming/).
Nilay Ghosh
CC BY-SA 4.0
2021-08-17T09:50:36.483Z
I’m voting to close this question because it is too broad. The list of all possible uses of Greek letters in astronomy could be very long and in some cases not objective: anyone can choose to call an astrophysics quantity with whatever letter they like. Naming conventions are often not well established and listing the Greek variable names used by any author in any paper ever published is an unreasonable task. Try focusing the question. Maybe you are only interested in celestial objects names?
Prallax
CC BY-SA 4.0
2021-08-17T22:38:49.490Z
@JamesK "[Requests for resources are not so useful](https://astronomy.stackexchange.com/questions/45339/what-is-use-of-greek-letters-in-astronomy#comment99093_45339)" Has this been established as a consensus view anywhere? Should we then close all [52 questions tagged resource-request](https://astronomy.stackexchange.com/questions/tagged/resource-request)?
uhoh
<star><observational-astronomy><night-sky><constellations>
What is use of Greek Letters in Astronomy?
Hi-Tech
# What is use of Greek Letters in Astronomy?

(Asked by: username_0 on 2021-08-17)

We see letters such as $\epsilon$ or $\alpha$ or $\beta$ or $\eta$ etc... (possibly all Greek letters)

Can Somebody state the use of all Greek letters in astronomy?

**Tags:** star, observational-astronomy, night-sky, constellations

> **Comments:**
> **username_0**: it would be better if somebody mentions some names of good reference books to learn this topic....  
> **username_1**: Hello @username_0  This is a question and answer site, please take the [tour]  You ask a question and get answers. Requests for resources are not so useful. You are expected to do your own research first, and then ask a specific question.  
> **username_2**: @username_0 Go through these questions: https://astronomy.stackexchange.com/questions/19362/variable-types-of-stars/19364#19364 ... https://astronomy.stackexchange.com/questions/43654/nomenclature-of-interstellar-objects-and-stars/43681#43681 .. https://astronomy.stackexchange.com/questions/36182/a-question-about-star-names-e-g-cw-tauri-dz-bootis-iq-lupi-eu-eridani/36186#36186 ... https://astronomy.stackexchange.com/questions/39583/what-exactly-are-h30%ce%b1-and-he30%ce%b1-images-alma  
> **username_2**: Regarding your first comment, you can visit [IAU](https://www.iau.org/public/themes/naming/).  
> **username_3**: I’m voting to close this question because it is too broad. The list of all possible uses of Greek letters in astronomy could be very long and in some cases not objective: anyone can choose to call an astrophysics quantity with whatever letter they like. Naming conventions are often not well established and listing the Greek variable names used by any author in any paper ever published is an unreasonable task. Try focusing the question. Maybe you are only interested in celestial objects names?  
> **username_4**: @JamesK "[Requests for resources are not so useful](https://astronomy.stackexchange.com/questions/45339/what-is-use-of-greek-letters-in-astronomy#comment99093_45339)" Has this been established as a consensus view anywhere? Should we then close all [52 questions tagged resource-request](https://astronomy.stackexchange.com/questions/tagged/resource-request)?  

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## 2 answers

### Answer by username_1 on 2021-08-17. Score: 2 | Accepted answer

The most well known use of Greek letters is in the names of stars created by Johann Bayer in 1603 for his star atlas *Uranometria*.

Bayer gave each star in his atlas a two-part name. The first part is a greek letter, the second part is the constellation that the star is in (in the Latin genetive form). Generally the brightest star in each constellation is designated "Alpha", the second brightest is Beta and so on.

So Alpha Centauri is the brightest star in the constellation of the Centaur.


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### Answer by username_5 on 2021-08-17. Score: 1

There is no general way to answer where Greek letters are used.

There is the Bayer naming convention for (some of) the brightest stars where he named them in each constellation, giving $\alpha$ to the brightest, $\beta$ to the 2nd brightest and so on - but this naming usually stops even before $\omega$ is reached, covering just the brightest few per constellation (and even the ordering is not always strictly by brightness).

In other areas as generally in physics or science in general, Greek letters are used as symbols for certain properties in equations. There do exist conventions like $\varrho$ being used for density, $\alpha$ for kinematic viscosity, etc - but these definitions are not a given nor are they unique. Their meaning has to be established in every context anew; used is what fits the context. Important is only that every reader can know what is meant with each symbol in a given context - thus be consistent throughout your paper or book with their usage.


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