Progenitor Star
Some details are emerging on the nature of the star that experienced the outburst. Based on an incorrect interpretation of the light echo the eruption generated, the distance of the star was first estimated to be 1,900 to 2,900 light years. Combined with the apparent magnitude measured from pre-eruption photographs, it was thought to be an underluminous F-type dwarf not much unlike our Sun, which posed a considerable enigma.
More accurate measurements gave a much larger distance, 20,000 light years (6 kpc). It appears that the star is considerably more massive and luminous than the Sun. The star probably has a mass of from 5 to 10 times solar, and a luminosity of from 550 to 5,000 times solar. The star may have originally had a radius roughly 5 times solar and temperature of 4,700–30,000 K. Munari et al. (2005) suggest that the progenitor star is in fact a very massive supergiant with a mass of about 65 times solar. They also conclude that the system may be only about 4 million years old.
The spectrum of V838 Monocerotis reveals a companion, a hot blue B-type main sequence star probably not much different from the progenitor star. It is also possible that the progenitor was slightly less massive than the companion and only just entering the main sequence.
Based on the photometric parallax of the companion, Munari et al. get a greater distance, 36,000 light years (10 kpc).
Read more about this topic: V838 Monocerotis
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