Non-Human Signal Sources are a special type of signal source that can be found in areas of Thargoid activity, Upon finding and entering a NHSS there is a chance you will get one of three outcomes:
If you get option 2, the Thargoid Interceptor will emit an EMP pulse when it arrives and it will be immediately hostile
A NHSS can only be seen while in supercruise. Since they will often appear in bulk, to easily scan them all drop onto the Nav Beacon and scan it. Once you jump into supercruise all NHSS will be unveiled.
NHSS are dynamic and will appear and disappear over time, lasting anywhere up to 30 minutes each.
In some rare cases (Threat 5-8 only) you will have an empty instance with only damaged ships, in these instances there is a chance you may find a Thargoid Probe or a Thargoid Sensor.
See this investigation into NHSS spawn rates and possible instances: NHSS Spawn Analysis
The Anti-Xeno Initiative recommends Asterope in the Pleiades Nebula as one of the best Thargoid hunting systems in the game.
Depending on the Threat Level of the NHSS you will find different types of Interceptors or more Scouts. Understanding this is key to finding the Thargoids you’re after for solo attempts.
At some times in the past, NHSS Threat 0 and 2 have appeared, which spawn Thargoid Probes. These currently cannot be found in-game.
If a NHSS has a Salvage icon next to it in the navigation panel, you will ALWAYS get a solo Interceptor based of the list above. For example, here is a guaranteed Basilisk signal source. Additionally, this instance is slightly different, as it only includes small debris and no green cloud.
Note: The small canister symbol on the left.
The FSS can also be used to identify the contents of a NHSS instance, read more here.