How to Classify Stars
Determine the star's colour., Put a number after the letter to show precise temperature.
Step-by-Step Guide
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Step 1: Determine the star's colour.
Colour serves as a rough guide to temperature.
Currently, there are ten colours, each with an associated temperature range.
O class stars are blue/UV.
B class are blue-white, A class white, F yellow-white, G yellow, K orange and M red.
The other three classes are infrared.
L class appear very deep red in visual light.
Their spectra show alkali metals and metal hydrides.
T class are cooler than L class.
Their spectra show methane.
Y class are the coolest of all, and apply only to brown dwarves.
Their spectra are different to T and L class, but there is no definite definition. -
Step 2: Put a number after the letter to show precise temperature.
Within each colour, there are ten temperature bands, 0-9, with 0 being hottest.
Thus, A0 is hotter than A5, which is hotter than A9, which is hotter than F0 (as an example)
Detailed Guide
Colour serves as a rough guide to temperature.
Currently, there are ten colours, each with an associated temperature range.
O class stars are blue/UV.
B class are blue-white, A class white, F yellow-white, G yellow, K orange and M red.
The other three classes are infrared.
L class appear very deep red in visual light.
Their spectra show alkali metals and metal hydrides.
T class are cooler than L class.
Their spectra show methane.
Y class are the coolest of all, and apply only to brown dwarves.
Their spectra are different to T and L class, but there is no definite definition.
Within each colour, there are ten temperature bands, 0-9, with 0 being hottest.
Thus, A0 is hotter than A5, which is hotter than A9, which is hotter than F0 (as an example)
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