<p>Neutron stars and black holes do not have assigned spectral types since they do not have a measurable optical/IR spectrum - which is the basis for assigning a spectral type.</p>

<p>There are many classifications for systems containing black holes and neutron stars. They are not related to the letter-based spectral types of "normal" stars or white dwarfs, but more to do with their X-ray, radio or inferred physical properties (e.g low- or high-mass X-ray binary systems).</p>

CC BY-SA 3.0
2017-07-25T20:04:15.043Z
2017-07-25T20:04:15.043Z
ProfRob
<p>We have OBAFGKM to denote the strength of hydrogen lines.</p>

<p>Apparently we added S, N, C, and the W classes when we learned of new kinds of stars.</p>

<p>We use T, L, and Y to denote brown dwarfs.</p>

<p>The D classes refer to electron-degenerate stars (white dwarfs).</p>

<p>I've looked around quite a bit and I haven't seen anything regarding neutron stars and black holes. Does this mean there's no common symbol or abbreviation? What do they use in star catalogs? (I've never found a catalog with stars of all degeneracies in it.)</p>

<star><classification><notation>
What abbreviations, letters, or symbols do we use to denote highly degenerate stars?
MackTuesday
# What abbreviations, letters, or symbols do we use to denote highly degenerate stars?

(Asked by: username_0 on 2017-07-25)

We have OBAFGKM to denote the strength of hydrogen lines.

Apparently we added S, N, C, and the W classes when we learned of new kinds of stars.

We use T, L, and Y to denote brown dwarfs.

The D classes refer to electron-degenerate stars (white dwarfs).

I've looked around quite a bit and I haven't seen anything regarding neutron stars and black holes. Does this mean there's no common symbol or abbreviation? What do they use in star catalogs? (I've never found a catalog with stars of all degeneracies in it.)

**Tags:** star, classification, notation

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## 1 answers

### Answer by username_1 on 2017-07-25. Score: 4 | Accepted answer

Neutron stars and black holes do not have assigned spectral types since they do not have a measurable optical/IR spectrum - which is the basis for assigning a spectral type.

There are many classifications for systems containing black holes and neutron stars. They are not related to the letter-based spectral types of "normal" stars or white dwarfs, but more to do with their X-ray, radio or inferred physical properties (e.g low- or high-mass X-ray binary systems).


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