The ESRB released their full ratings description for No Man’s Sky today, revealing that it earned a Teen rating on PlayStation 4 and PC due to Fantasy Violence.
In the summary, the ESRB highlights the fact that you can use gun-like weapons to attack alien creatures, and battles include lots of lasers and explosions:
This is a space-exploration adventure game in which players assume the role of a planetary explorer on a quest to reach the center of the universe. From a first-person perspective, players travel between planetary systems to explore alien worlds for resources, upgrade equipment, and discover unique life forms. As players pilot spacecrafts to different planets, they can engage in space combat against enemy ships and space pirates; combat is accompanied by laser fire and large explosions. While on the planet surface, players can use a variety of gun-like weapons and melee attacks to defeat both aggressive and non-aggressive alien creatures. Ground battles can be frenetic at times with frequent laser blasts, screen-shaking effects, and large explosions.