Normally you require PS Plus in order to play PS4 video games online. Hello Games is being kinder to gamers as PS Plus is not required to play No Man’s Sky.
A Sony rep told Game Informer:
PS Plus won’t be a requirement to play online, however you will need to connected to the internet for your discoveries to register with the universal atlas
The chances of seeing other online players are very slim anyway. There are 18 quintillion (a real number) planets in the game so everyone is likely to be full spread out.