Spark image

Temperature and colour

The hottest colour that can be seen from (a) a heated metal (b) a star would be violetish white. True?
A yellowish star would have a different temperature from a yellowish heated bar. Could you explain in detail the difference?

Answer:

The colour that you see depends on the temperature of the object and of course your ability to see that colour. All bodies emit radiation but as they get hotter and hotter the maximum of the energy-temperature curve moves into the ultra violet.


Of course the amount of energy radiated at different wavelengths also depends on the nature of the surface of the body. Stars are considered to be "black bodies". That is they are the most efficient emitter an absorber at this wavelength. Hot metal bars may not be quite black bodies.

Yes a very hot star will be a violet-white colour because all visible wavelengths are being emitted (hence white) but a greater energy in the violet end of the spectrum (see curves)
 
 
 
© Keith Gibbs 2007