<p>I am working with data from the NASA Exoplanet Archive. From my understanding, stars are assigned spectral types (O, B, A, F, G, K, M) based primarily on stellar temperature. <a href="https://pages.uoregon.edu/imamura/122/lecture-4/mk.html" rel="nofollow noreferrer">ref</a></p>
<p>However, I’ve noticed some mismatches when comparing the stellar temperatures in the data to their assigned spectral types. For instance, a star with a temperature of 4874 K, which I would expect to be classified as a K-type star, but in the dataset, it is listed as a G-type star.</p>
<p>Am I misunderstanding how the classification correlates with stellar temperatures? Is there another factor in the classification process that I might be missing.</p>
<p>Any clarification on this would be greatly appreciated!</p>

CC BY-SA 4.0
2024-10-08T13:35:47.263Z
Stars are assigned (MK) spectral types by looking at their spectra. To be specific, by looking at their spectra in the spectral classification wavelength band - basically blue and green light. You are right that this strongly correlates with temperature. Surface gravity and metallicity can play a role.
ProfRob
CC BY-SA 4.0
2024-10-08T15:37:47.233Z
okay that makes sense. so ill be unable to get correct class with only temp and other data. i need the spectral band too?
CovetTachi
CC BY-SA 4.0
2024-10-08T16:03:15.907Z
Well you can *estimate* what the spectral class is if you have a temperature (there are no estimated temperatures that are accurate to 4 significant figures). But you have to be aware that this estimate might be in error if the star is (a) not a main sequence star or (b) has an unusual composition. If you know that the star is not on the main sequence, but is say a giant, then you should use a SpT-Teff relationship that is appropriate for giants. Note that "K-type" is not really a spectral classification. It should be something like K2V or K5III or similar.
ProfRob
<star><spectra><spectral-type>
How Stellar Spectral Types are assigned
CovetTachi
# How Stellar Spectral Types are assigned

(Asked by: username_0 on 2024-10-08)

I am working with data from the NASA Exoplanet Archive. From my understanding, stars are assigned spectral types (O, B, A, F, G, K, M) based primarily on stellar temperature. [ref](https://pages.uoregon.edu/imamura/122/lecture-4/mk.html)

However, I’ve noticed some mismatches when comparing the stellar temperatures in the data to their assigned spectral types. For instance, a star with a temperature of 4874 K, which I would expect to be classified as a K-type star, but in the dataset, it is listed as a G-type star.

Am I misunderstanding how the classification correlates with stellar temperatures? Is there another factor in the classification process that I might be missing.

Any clarification on this would be greatly appreciated!

**Tags:** star, spectra, spectral-type
> **Comments:**
> **username_1**: Stars are assigned (MK) spectral types by looking at their spectra. To be specific, by looking at their spectra in the spectral classification wavelength band - basically blue and green light. You are right that this strongly correlates with temperature. Surface gravity and metallicity can play a role.  
> **username_0**: okay that makes sense. so ill be unable to get correct class with only temp and other data. i need the spectral band too?  
> **username_1**: Well you can *estimate* what the spectral class is if you have a temperature (there are no estimated temperatures that are accurate to 4 significant figures). But you have to be aware that this estimate might be in error if the star is (a) not a main sequence star or (b) has an unusual composition. If you know that the star is not on the main sequence, but is say a giant, then you should use a SpT-Teff relationship that is appropriate for giants. Note that "K-type" is not really a spectral classification. It should be something like K2V or K5III or similar.  

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