Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star?
A) All stars put out most of their light in the visible range of the spectrum.
B) In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.
C) Most stars do not put out the light in other ranges of the spectrum.
D) They are identical for most stars.
E) Astronomers are lazy.
Answer: B