Posted by Art on November 14, 1997 at 08:24:49:
In Reply to: Help! posted by Lana on November 13, 1997 at 02:17:00:
: Can you please clarify what a color index is because I don't
: understand what the book is saying.
: Thanks!
: Lana
Color index is a quick way of measuring the surface temperature of stars. You measure the apparent magnitude of the star through two or three color filters, for example, blue (B) and visual(V) filters.
If the star is hot, it will be bright in the blue so the blue magnitude will come out small. (Bright star means small magnitude)
A color index is a number like B - V.
For a blue star (hot) B - V will be negative; for a red star (cool) it will be positive. (See table 10-1).
Astronomers would be able to convert the color intex to surface temperature of the star.
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