The distance to the Orion Nebula Cluster ( ONC ) is estimated using the rotational properties of its low-mass pre main-sequence ( PMS ) stars .
Rotation periods , projected equatorial velocities and distance-dependent radius estimates are used to form an observational \sin i distribution ( where i is the axial inclination ) , which is modelled to obtain the distance estimate .
A distance of 440 \pm 34 , pc is found from a sample of 74 PMS stars with spectral types between G6 and M2 , but this falls to 392 \pm 32 pc when PMS stars with accretion discs are excluded on the basis of their near-infrared excess .
Since the radii of accreting stars are more uncertain and probably systematically underestimated , then this closer distance is preferred .
The quoted uncertainties include statistical errors and uncertainties due to a number of systematic effects including binarity and inclination bias .
This method is geometric and independent of stellar evolution models , though does rely on the assumption of random axial orientations and the Cohen & Kuhi ( 1979 ) effective temperature scale for PMS stars .
The new distance is consistent with , although lower and more precise , than most previous ONC distance estimates .
A closer ONC distance implies smaller luminosities and an increased age based on the positions of PMS stars in the Hertzsprung-Russell diagram .