Celestia Forums

What are the criteria used to determine the spectral type/subtype of a star? E.g. where would you draw the dividing line between, say, F8 and F9?

Spectral type is determined by obtaining the star's spectrum and comparing it to the spectra of stars which are defined to of a particular classification. The procedure is not necessarily unambiguous. The spectral classification for our Sun is controversial, for example.


http://www.ulo.ucl.ac.uk/~diploma/labor ... S_star.pdf
seems to give a reasonable summary, including homework

selden wrote:The spectral classification for our Sun is controversial, for example.

Really?

Although it's generally considered to be G2V, I've seen at least one article mentioning that some people disagree. Of course, I can't find it now.

Oh, you mean the "Green Sun" theory?

d.m.f.

I don't know about any "green sun" theory. What I read was that some people think the Sun should be classified as G3 or maybe even G4.

And if it was based upon temperature it should be classified as a G1 or G0

spectral types are defined like this , from hottest to coldest :

w, o0, o1, o2, o3, o4, o5, o6, o7, o8, o9, b0, b1, ... b9, a0 ... m9, r, n, s, l, t, y ...

see https://thesciencearchives.miraheze.org/wiki/Spectral_Classification

In my opinion the main types of stars are O, B, A, F, G, K, M, and N.

The old Draper system had O, B, A, C, D, E, F, G, H, I, K, L, M, N, P (planetary nebulae), and Q (other, now for Neutron Stars and Novae). Imagine if Celestia was based on that.

Sorry, but this article is a nigh-absolute-copy of Wikipedia!

I know, but I'm just trying to create a more reliable alternative.

However, I do feel like abandoning that project soon.

6 months later and only now you reply..