In short: what mass is appropriate for absolute magnitude $M_V \sim -7$?

Some context: I'm processing the observational data (supernova light curve) and curve fitting gives me about $0.4M_\bigodot$ for ejecta mass. However, possible progenitor candidate has $M_V \sim -7$, which, I suppose, points to quite a large star. My background in astronomy is not so good (I was mostly doing theoretical physics, namely nonlinear optics and GR before I got to supernovae), so I'm doubting correctness of either my estimates or progenitor candidate parameters.

  • $\begingroup$ @AtmosphericPrisonEscape M_V is a magnitude in V band not visual one. $\endgroup$
    – Tajimura
    Mar 8, 2018 at 18:02
  • $\begingroup$ The apparent magnitude of the sun ins -26. The absolute magnitude is 4.83 (visual) or 4.75 (bolometric) Absolute mag of -7 is more than 10000 times brighter than the sun. $\endgroup$
    – James K
    Mar 8, 2018 at 19:00
  • $\begingroup$ @JamesK that's exactly what I'm talking about. Judging by the magnitude of the candidate, progenitor should be quite a massive star. But, on the other hand, Sutherland's and Arnett's models for light curves are proven to give reliable estimates on parameters, and in my case those models point to a low-mass star. $\endgroup$
    – Tajimura
    Mar 8, 2018 at 19:04
  • $\begingroup$ As a guide, Betelgeuse is about ab M -6 and about 11 times the mass of the sun. By comparison a roughly stellar mass red giant like Aldebaran has an ab M of -0.6. But during late stages of a star's life there can be some big changes in brightness (eta Carinae) so the mass/magnitude relation may not be simple. $\endgroup$
    – James K
    Mar 8, 2018 at 19:13
  • $\begingroup$ @JamesK Right, my mistake. $\endgroup$ Mar 8, 2018 at 23:24

1 Answer 1


A star with absolute magnitude of -7 is big and powerful, It would be among the most powerful stars in the galaxy.

The star would be near the end of its life, so comparing with other aging stars:

Aldebaran is slightly more massive than the sun. It is a red giant (or orange giant according to some sources) It has an absolute magnitude of about -0.6. Aldebaran is too small to undergo a supernova.

Betelgeuse is much bigger. Estimates of its mass put it at about 11 solar masses, but it could be bigger. It has a magnitude of about -6 (it is variable and there is some uncertainty on its distance).

Eta Carinae is one of the most powerful stars in this part of the galaxy. It is also variable, but has an absolute magnitude of -8—-9, and mass of 100-200 suns

AG Carinae is a LBV with a mass of 50 suns and a minimum absolute magnitude of about -8, but becoming much brighter during outbursts. (as bright as -11)

So an evolved star with a magnitude of -7 could be supposed to be between the LBV stars and Betelgeuse, with a mass of around 15-20 suns. Stars do get very unstable this late in life, and there could be a great deal of uncertainty.

Others here know more about supernovae mechanics, and may be able to explain any discrepancy between the supposed stellar mass, and the mass of the ejecta.


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