Can you use the radius/scale of an instanced static mesh instance in the material editor?

I’ve been having issues trying to use the radius or scale of an instanced static mesh instance in a material. Both object radius and object scale get the size of the whole instanced static mesh component, is there a way to get the scale or radius of the individual instance? I’ve included an image of the material if that helps, it’s approximating the temperature of the star based on the radius of the instance, or rather it is meant to.

No. You can on the other hand extract the information about world position of an instance, but only for pixel shader not vertex shader (so for base color, not world displacement). Additional you can try to do something out of WorldAlignedTexture.

As mentioned, per instance information is only available in vertex shader calls. For example for World Position Offset.
Deathrey mentions in this thread that you can pass information from vertex shader to pixel shader by using custom UVs. I think this should also work with Object Scale.