Almost everything has its ambient sounds. Right down to point at the Galactic core vs pointing at the rim
I assume it is the ship picking up the natural emanations of the stellar object and converting it to sound, just as it does with lasers and such.
Just as real planets can be recorded
Ammonia worlds with Ammonia-Carbon based life have a rapid but faint
thumpa-thumpa-thumpa that makes it feel alive.
Gas Giants have a rolling dull roar of the storms below.
Ice worlds feel cold
Inhabited worlds have faint radio transmissions as do outposts, varying on the type of outpost, unsanctioned outposts sound the best
Even stars of different classes sound different.
I plan to catelogue them all one day, but my most recent attempt I had left my mic on and it recorded me typing as the same time darn it.
You want to try park up in a place by a planet so that it is 90 degrees from a line from core to rim where you can shut down the ship, go to the debug camera and face the core and listen, then face the rim, listen, then tyr the planet.