Last month, I began a discussion of how stars are classified by their brightness and color, or more technically, by their luminosity and spectroscopic classification. I spent most of that column on ...

Take a look up at a dark night sky, and you'll find it illuminated by hundreds or even thousands of individual twinkling points of light. While they might seem, to an untrained eye, to all be the same ...

Stellar spectral classification utilizes seven main classes (O, B, A, F, G, K, M), ordered by decreasing surface temperature, with each class further subdivided into numerical subclasses (0-9) ...

Early stellar spectral classifications followed an alphabetical system based on hydrogen line strength, initially lacking a consistent temperature-based organization. Angelo Secchi's 1866 ...