Not a Supergiant?

[osser]

How can this be? It's much bigger than Rigel. Am I missing something?
Bug?

 

[DLewth]

I'm sure somebody will come along to correct me but AFAIK, "Supergiant" is a measure of how bright a star is, as well as how big it is. It's all very rule-of-thumb and unscientific but if this star isn't that luminous, it might not count as one (depending on who you ask).

Yeah, I know. [wacko]

 

[osser]

Fair enough! Here's the Galaxy map Shot showing the star type

 

[DLewth]

I just checked the dictionary: "Supergiant: A star that is larger, brighter, and more massive than a giant star."

Well, that helps.

Spoiler

 

[Pirin]

Class IV stars are classified as sub-giants so technically this is correct. It seems that giant/sub-giant classification is more related to the stage of the star evolution than to its size.

 

[Jackie Silver]

The luminosity class is assigned by looking at whether lines in the star's spectrum are broadened out by pressure so it's not a measure of absolute size.