Eric E. Mamajek, Scott A. Barenfeld, Valentin D. Ivanov, Alexei Y. Kniazev, Petri Väisänen, Yuri Beletsky, Henri M. J. Boffin. THE CLOSEST KNOWN FLYBY OF A STAR TO THE SOLAR SYSTEM. The Astrophysical Journal, 2015; 800 (1): L17 DOI: 10.1088/2041-8205/800/1/L17 The Science Daily article discusses the observation (with 98% probability) that analysis of the trajectory of Scholz's star (a tiny nearby star with 8% the mass of the sun) passed within 0.8 lightyears of the sun 70000 years ago. This relates to the concept of Oort cloud perturbations by external bodies causing Oort cloud objects to change trajectory and orbit much closer to the sun. Sort of a looong period comet shower. From our point of view anyway. The reasoning goes, it appears possible to have happened previously with more dramatic results, since Scholz's star apparently was too far away to impact the inner Oort cloud. (my version of the article's comments).