The textbook Astrophysics in a Nutshell, talks about the "blue continuum spectrum" in relation to the spectrum of an AGN: enter image description here

I know that a continuum spectrum is caused by the interaction of a large number of atoms, ions or molecules spreading out the discrete emission lines of an object.

What is the meaning of the reference to the blue continuum spectrum? Is it referring to the blue visible wavelengths, which would be around 4500 Anstroms? But the wording of the caption seems to indicate that the entire spectrum is referred to as a blue continuum spectrum.

  • $\begingroup$ Note that the black body spectrum is not the spread of emission lines. At least not if standard dictionary is used. $\endgroup$
    – Alchimista
    Sep 24, 2021 at 9:50

1 Answer 1


The continuum spectrum could be described as "blue" as it is skewed towards shorter wavelengths. There is an excess of blue light compared to red.

You can see this in the way that the continuum part of this spectrum curves up towards the left and down towards the right.


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