A solar probe was a type of probe capable of being fired into a sun for the purpose of scientific research.
In 2371, Tolian Soran, an El-Aurian scientist, utilized a solar probe outfitted with trilithium to destroy the Amargosa star. He later attempted to perform the same action on the Veridian star, but was stopped by Jean-Luc Picard and the crew of the USS Enterprise. (Star Trek Generations)