star classification - SERP Analysis

https://en.wikipedia.org/wiki/Stellar_classification

https://www.britannica.com/science/stellar-classification

https://lco.global/spacebook/stars/types-stars/

https://science.nasa.gov/universe/stars/types/

https://www.astroleague.org/stellar-classifications/

https://lweb.cfa.harvard.edu/~pberlind/atlas/htmls/note.html

http://www.star.ucl.ac.uk/~pac/spectral_classification.html

http://hyperphysics.phy-astr.gsu.edu/hbase/Starlog/staspe.html

https://www.ebsco.com/research-starters/astronomy-and-astrophysics/stellar-classification

https://astrobackyard.com/types-of-stars/