<p>The continuum spectrum could be described as &quot;blue&quot; as it is skewed towards shorter wavelengths.  There is an excess of blue light compared to red.</p>
<p>You can see this in the way that the continuum part of this spectrum curves up towards the left and down towards the right.</p>

CC BY-SA 4.0
2021-09-23T21:29:16.803Z
2021-09-23T21:29:16.803Z
James K
<p>The textbook <a href="https://icourse.club/uploads/files/2595aa50f227b3c89fdccd2dfd42e86c3ef069e7.pdf" rel="nofollow noreferrer">Astrophysics in a Nutshell</a>, talks about the &quot;blue continuum spectrum&quot; in relation to the spectrum of an AGN:
<a href="https://i.sstatic.net/XNKd8.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/XNKd8.png" alt="enter image description here" /></a></p>
<p>I know that a <a href="https://astronomy.swin.edu.au/cosmos/s/Spectral+Continuum" rel="nofollow noreferrer">continuum spectrum</a> is caused by the interaction of a large number of atoms, ions or molecules spreading out the discrete emission lines of an object.</p>
<p>What is the meaning of the reference to the <strong>blue</strong> 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.</p>

CC BY-SA 4.0
2021-09-24T09:50:52.613Z
Note that the black body spectrum is not the spread of emission lines. At least not if standard dictionary is used.
Alchimista
<spectra><active-galaxy>
Meaning of "blue continuum spectrum"?
Jim421616
# Meaning of "blue continuum spectrum"?

(Asked by: username_0 on 2021-09-23)

The textbook [Astrophysics in a Nutshell](https://icourse.club/uploads/files/2595aa50f227b3c89fdccd2dfd42e86c3ef069e7.pdf), talks about the "blue continuum spectrum" in relation to the spectrum of an AGN:
[![enter image description here](https://i.sstatic.net/XNKd8.png)](https://i.sstatic.net/XNKd8.png)

I know that a [continuum spectrum](https://astronomy.swin.edu.au/cosmos/s/Spectral+Continuum) 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.

**Tags:** spectra, active-galaxy
> **Comments:**
> **username_1**: Note that the black body spectrum is not the spread of emission lines. At least not if standard dictionary is used.  

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## 1 answers

### Answer by username_2 on 2021-09-23. Score: 2 | Accepted answer

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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