During a program of spectroscopic monitoring of V838 Mon , we serendipitously discovered that a neighboring 16th-mag star is of type B .
We then carried out a spectroscopic survey of other stars in the vicinity , revealing two more B-type stars , all within 45 ^ { \prime \prime } of V838 Mon .
We have determined the distance to this sparse , young cluster , based on spectral classification and photometric main-sequence fitting of the three B stars .
The distance is found to be 6.2 \pm 1.2 kpc , in excellent agreement with the geometric distance to V838 Mon of 5.9 kpc obtained from Hubble Space Telescope polarimetry of the light echoes .
The cluster ’ s age is less than 25 Myr .

The absolute luminosity of V838 Mon during its outburst , based on our distance measurement , was very similar to that of M31 RV , an object in the bulge of M31 that was also a cool supergiant throughout its eruption in 1988 .
However , there is no young population at the site of M31 RV .

It does not appear possible to form a nova-like cataclysmic binary system within the young age of the V838 Mon cluster , and the lack of a young population surrounding M31 RV suggests that the outburst mechanism does not require a massive progenitor .
These considerations appear to leave stellar-collision or -merger scenarios as one of the remaining viable explanations for the outbursts of V838 Mon and M31 RV .