Assertion: nebula's distance | /r/HasProperty | estimated
Facets:
value: by measuring its doppler shift
type: MANNER
value: because of the expansion of the universe
type: CAUSE
Source sentences:
text: Images taken several years apart reveal the slow expansion of the nebula, and by comparing this angular expansion with its spectroscopically determined expansion velocity, the nebula's distance can be estimated.
text: The distances to star clusters can be estimated by using a Hertzsprung–Russell diagram or colour–colour diagram to calibrate the absolute magnitudes of the stars, for example fitting the main sequence or identifying features such as a horizontal branch, and hence their distance from Earth.
text: Because of the expansion of the universe, the distance to a remote object with a known emission spectrum can be estimated by measuring its Doppler shift (or redshift); on average, more-distant objects recede with greater velocity than those nearby, and so have a higher redshift.
text: Images taken several years apart reveal the slow expansion of the nebula, and by comparing this angular expansion with its spectroscopically-determined expansion velocity, the nebula's distance can be estimated.