Provides background and analysis for a paper that suggests that the sun during its formative stage may have been a much more powerful X-ray source than it is today. The possibility of cataclysmic events influencing the evolution of the inner Solar System; The use of the Rontgensatellit observatory to detect an X-ray outburst from the young star YLW15; The paper by Grosso and others in the May 1, 1997 issue of `Nature.'