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We present and discuss the $HST$ Faint Object Spectrograph observations of star 2, one of the two companions of SN~1987A. Our analysis reveals that star 2 is a B1III star, whose reddening corresponds to $E(B-V)=0.19\pm0.01$. Star 2 has an effective temperature of $T_{eff}=23000\pm1000~K$ and a luminosity of $logL/L_\odot=4.43\pm0.08$. Also, star 2 appears to rotate with an equatorial velocity of $v~sin(i)=275\pm50~km~s^{-1}$, and is presently undergoing mass loss at a rate of $log \dot{M} = -6.8\pm0.3~M_\odot~yr^{-1}$. Judging from its position in the HR diagram and its present parameters, star 2 had an original mass of about $13~M_\odot$ and was born less than $13~Myr$ ago, which makes star 2 coeval to the SN~1987A progenitor Sk-69$^\circ$202.
