Elite: Dangerous PvE - Mobius

What do the "glowing" halos around stars in the galaxy map represent? If you colour the map by star type, then disable the various star types, you can often see the glow without the star icon.

I thought it might mean there's something rare in the system, but after investigating a few I've still no idea what it represents...

To answer my own post - it seems like they are nothing more than particularly bright stars...

Planetary nebulae could fit that description, in some cases.