CHARA Array measurements (red ellipses) of the motion of the stripped star (dashed line) that orbits the Be star HR2142 (yellow star) every 81 days. The small black star symbols are the calculated positions of the stripped companion during the time of our observations. The orbit is circular, but appears elliptical because it is tilted with respect to the plane of the sky. The top and right axes show the apparent physical separation in Astronomical Units (AU, the mean Earth–Sun distance) while the bottom and left axes give the angular separation in the angular units of milliarcseconds (mas). For comparison, the full Moon in the sky has an angular diameter of about 2 million milliarcseconds.