Assertion: universe's expansion | /r/HasProperty | detected in the star's brightness
Facets:
value: for over four years
type: TEMPORAL
value: to measure its roundness
type: PURPOSE
Source sentences:
text: Laurent Gizon from the Max Planck Institute for Solar System Research and the University of Göttingen and his colleagues used the star's oscillations, or periodic expansions and contractions that can be detected in the star's brightness, continuously for over four years to measure its roundness.