jay@rochester.UUCP (Jay Weber) (03/17/85)
A short time ago someone posted an abbreviated version of the Yale Catalog of Stars. I'm enthusiastic about playing with the data, but I don't understand one of the fields; the description is: ***** Color ***** Sign A1 B-V in UBV System I3 (unit = 0.01 magnitude) Can anyone fill me in on what measure of color this is? Thanks. Jay Weber jay@rochester.arpa ..!seismo!rochester!jay
space@mit-mc (03/18/85)
From: Mike Caplinger <mike@rice.ARPA> B-V is the difference between the magnitude of the star when measured through a "blue" filter (440 nm) and a "visual" filter (yellow-green, 548 nm). The difference can be used to determine the star's temperature, since it defines two points on the blackbody curve, via the equation B - V ~ 7000(1/T - 1/15000) (units of Kelvins) (The 15000K comes from the fact that for a star of spectral class A0V B = V by definition.) Alas, stars are often not blackbodies. - Mike