Tags: Star.
BI 253 is an O-type main sequence star in the Large Magellanic Cloud with one of the earliest spectra known. It is classified as spectral type O2V(f*) and was cited in the article introducing the O2 star type and is a primary standard of the type. The star is classified as a runaway star with relative motion detected spectrographically in excess of 100 km/s (225000 mph).