In every visitable system, with the exception of the retired King of the Zone, Venturi, Neurona, and Co-op, there is at least one sun. Often there are multiple suns. Mitrilion alone has five separate suns! In Zergilin, two suns orbit around their mutual center of gravity.
In AstroFlux, suns have a strong and often sudden, unexpected gravitational pull. The sun causes large amounts of constant damage on contact, destroying unwary nearby ships. It is important to keep an eye on the system map, or steer way clear of yellow dots on the radar/minimap.
Activating shields just before colliding with a Sun reduces any damage (except for Death Lines) to 1, allowing you to rocket out the other side at incredible speeds. This technique is also used to collect loot left behind when people collide.