The European Souther Observatory used Scholz's star's radial velocity using Doppler shift which is a way of detecting the speed of light spectrums in relation to the rest of space. With this method, scientist Valentin Ivanov determined that Scholz's star did, in fact, pass by our Solar System and that it is moving away from it at an extraordinary speed at about 55 miles a second. Scholz's star is considered a rogue star since it is moving through space without and gravitational hold in one location. However, some questions still remain. Why did it fly by our Solar System? What caused it to form this trajectory? Where did it originate from?
Source:
http://iopscience.iop.org/2041-8205/800/1/L17
http://www.universetoday.com/119038/a-star-passed-through-the-solar-system-just-70000-years-ago/
http://www.bbc.com/news/science-environment-31519875
http://www.space.com/28611-star-flew-through-solar-system.html
http://www.iflscience.com/space/star-passed-less-light-year-earth