Artefact in World background

Question

I'm making a space World with shader nodes. Here's a simplified version with only black background and the Sun. The Sun location is set by an object:

This is how the Sun looks:

However, in the opposite direction, there's a small artefact:

How to get rid of the artefact?

Edit. I'm using Eevee.

Answer 1

Allright I figured it out. All I had to do is to clamp that arccosine argument.