Solar Analog - By Similarity To The Sun

By Similarity To The Sun

Defining the three categories by their similarity to the Sun reflects the evolution of astronomical observational techniques. Originally, solar-type was the closest that similarity to the Sun could be defined. Later, more precise measurement techniques and improved observatories allowed for greater precision of key details like temperature, enabling the creation of a solar analog category for stars that were particularly similar to the Sun. Later still, continued improvements in precision allowed for the creation of a solar twin category for near-perfect matches.

Similarity to the Sun allows for checking derived quantities — like temperature, which is derived from the color index — against the Sun, the only star whose temperature is confidently known. For stars which aren't similar to the Sun, this cross-checking can't be done.