Leaving a planet setting course for the system's Space Station, I noticed the following icon showing up on my HUD:

Click image for entire screenshot
Being the responsible Starman I am, I immediately set a course for it, only to realize minutes later there was no indication of distance, and I could be doing this for hours on end without actually getting anywhere. Space is a large space, after all.
My initial thought was that it represented a stronghold, since it looks like a typical symbol for a gate or donjon, but AFAIK there is no such thing in No Man's spaaaace. Its red colour might suggest it's part of a mission branch, but it's not anywhere in my log.
Does anyone know what this icon means?
One Reddit post suggests "the rectangles are discovered buildings that you may need to go to for various reasons", but I've never seen this red one before, and buildings are usually on planets, not towards the edge of a solar system—but that could just be a bug.
They are also all over the place on the Wiki, and present in a lot of the older screenshots posted online. Are they perhaps obsolete icons?
This post also doesn't help, because as far as I'm aware this is not the spaceship icon.