The cepheid mass discrepancy problem has no solution in the standard model of stars. Recent findings by the ESO confirm that the standard model of stellar evolution is wrong, thereby calling the use of cepheids as standard candles into question.
ESO press release reports:
Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20–30% less than predictions from the theory of the evolution of stars. This embarrassing discrepancy has been known since the 1960s.
The observers carefully measured the brightness variations of this rare object, known as OGLE-LMC-CEP0227 , as the two stars orbited and passed in front of one another. They also used HARPS and other spectrographs to measure the motions of the stars towards and away from the Earth — both the orbital motion of both stars and the in-and-out motion of the surface of the Cepheid as it swelled and contracted.
This very complete and detailed data allowed the observers to determine the orbital motion, sizes and masses of the two stars with very high accuracy — far surpassing what had been done before for a Cepheid. The mass of the Cepheid is now known to about 1% and agrees exactly with predictions from the theory of stellar pulsation. However, the larger mass predicted by stellar evolution theory was shown to be significantly in error.
Astronomer Mel Acheson comments:
That the result confirms the stellar pulsation theory necessitates that it falsifies the stellar evolution theory. If astronomers were philosophically honest, they would declare the theory nullified in accordance with Karl Popper’s 1959 proposal of falsification as a criterion to distinguish a scientific theory from a pseudoscientific one. Falsification was to be a “convention” that required scientists to agree not to adjust a theory to accommodate test results but, when falsified, to start over with searches for alternative theories. Falsification is not a property of a theory that justifies acquiescence in orthodoxy but a convention that enables opportunities for discovery of new theories and the overthrow of conceptual monopolies.