``Say it with equations''
A blackbody radiator glows brightest (is most intense) at a wavelength (in meters)
. 
is related to the temperature (in Kelvins) by
Wien's Law:
Let's work out some examples. I just said that objects at a finite temperature emit light,
but that seems to be a lie. The tabletop is hotter than absolute zero, but it is not
glowing. What's up? Use Wien's law.
Temperature of tabletop is 
K. Figure out wavelength at which it is
brightest.
meters. This equals
10 microns. It is more than ten times longer than the longest wavelength that
the human eye is sensitive to. It is in the infrared part of the spectrum.
Now let's try the Sun.
Longrightarrow Spectrum of Sun. It looks like a blackbody in the sense of a steep
rise and a slow decline with wavelength. There is a peak at about 475 nanometers
= 
meters.
Let's use Wien's Law, 
K
Real hot! This gives us our first idea of what the temperatures of stars are like.
Now think about the color of Vega, and think about what that tells
you about the star.