Set chart mode to star chart. Set the field to 45°. Turn on
the lines marking the constellations. Center the display on
the constellation Ursa Major. One by one, click on the 21
stars that outline Ursa Major. Record the spectral type and
B-V. (For the easternmost star in Ursa Major, η UMa,
these are B3 and −0.19.) B-V is the difference between
the magnitudes of the star in the middle of the visual part
of the spectrum and the blue part of the spectrum. Arrange
the stars according to spectral type from hottest to coolest.
How is B-V related to spectral type? Explain the relationship
between B-V and stellar temperature.
