The USS Enterprise-D arrived at Praxillus on stardate 44807.5 in order for Doctor Timicin of Kaelon II to conduct a helium fusion experiment to revitalize the star. Praxillus was chosen because it was so similar to the Kaelon sun. It was Timicin's hope that, if successful, the same process could be used to save the Kaelon sun.
Several modified photon torpedoes were launched at the sun that were directed at the stellar core meant to ignited there. At first, the experiment seemed to work and the sun's temperature was rising from 60 million to the desired 220 million Kelvin. Unfortunately, the temperature kept rising, and nuclear fusion in the star's core went out of control and the experiment failed, forcing the Enterprise to leave the system at warp two as Praxillus went nova. (TNG: "Half a Life")