Part I. In Example 1, you learned that Arcturus, the brightest star in the Bootes, gives off more red light than green. Arcturus’s thermal radiation curve peaks at about 6430 Angstroms, in the red part of the electromagnetic spectrum. What is its average temperature?
Arcturus’s peak wavelength is 6430 Angstroms. Convert this length to meters (1 meter = 1010 Angstroms).
6430 Angstroms (1 meter / 1010 Angstroms) = 6.43 x 10-7 meters.
Plug this length into the peak wavelength equation:
λpeakT = 2.897 x 10-3 m K.
to get:
(6.43 x 10-7 m)T = 2.897 x 10-3 m K.
Now, solve for T:
T = (2.897 x 10 -3 m K) / (6.43 x 10-7 m)
Using a calculator, T = 4,500 K.
In Practice 3, you will find the Sun’s temperature. How does Arcturus’s temperature compare to the Sun’s? What could this tell you about Arcturus?