The Cepheids are stars 5-20 times as massive as the sun with dim to bright periodic pulsations. In the early 1900’s, the period-luminosity relationship of Cepheids was first reported by Henrietta Leavitt at the Harvard Observatory. See http://outreach.atnf.csiro.au/
Helium Heat Engine Mechanism
In 1917, Eddington proposed the mechanism for the Cepheid pulsation was a heat engine using helium as the working fluid. See thumbnail (TN) showing the dim and bright images from the Cepheid’s cycle. But Zhevakin in 1953 identified doubly ionized helium as the valve for the engine. See http://en.wikipedia.org/
The problem with the Cepheid mechanism is that ionized helium is not opaque, at least not to red light. The TN shows the dim part of the cycle to be clear and distinct with a faint red halo while the bright part is red-spotted and fuzzy. Neutral or ionized helium atoms should produce clear and distinct images for both dim and bright parts of the cycle. Only the lumpiness of the mass ejected from a Cepheid explosion could make the bright image spotted and fuzzy. In this regard, the Cepheids find similarity with the explosions of Supernova where the redshift of light emission is proportional to the mass ejected. See http://www.scienceblog.com/
Proposed Cepheid Mechanism
The proposed mechanism of Cepheid pulsation is similar to the explosion of Supernovae, except Cepheid explosions are smaller in magnitude and periodic. The visible (VIS) light in the TN is not produced by the Cepheid radiation heating the ejected mass, but rather by QED induced radiation in submicron cosmic dust particles (DPs) that accompany the ejected mass. Ibid. But unlike the Supernovae, the mass ejected from the Cepheid is returned by gravitational attraction, except for a small fraction of DPs that produce the faint red halo in the dim image of the TN. In contrast, the fuzziness in the bright image is caused by lumpiness of the mass ejected from the Cepheid. Infrared (IR) radiation is also produced by QED induced UV radiation in larger micron sized DP. By this theory, the dim part of the Cepheid cycle is clear and distinct because the DPs have mostly been returned to the star surface by gravity. IR from thermal radiation by heating DPs with UV to produce the 40-500 K temperatures necessary to explain the excess in IR is not necessary because QED induced emission creates the IR from DPs without an increase in temperature.
QED Induced Redshift in Cosmic Dust
QED induced radiation produces VIS and IR photons by the redshift of UV radiation from the Cepheid. Upon the absorption of UV photons at wavelength L by the DPs, QED creates photons of wavelength Lo = 2nD, where n is the refractive index and D the diameter of the DP. E.g, the red photons of wavelength Lo = 0.675 microns in the TN are created from UV at L = 0.25 microns absorbed in DPs having D = 0.25 micron and n = 1.35. The red photon is created in the DP by redhshifting the UV photon to Z = (Lo-L)/L = 1.7. In larger DPs having D > 1 micron, the UV is induced by QED to create IR photons with Lo > 1 micron at Z >3. All QED induced VIS and IR radiation is produced in DPs without an increase in temperature.
Similarity of DPs in Cepheids with Supernova Explosions
The mass ejected from Cepheids is similar to that from Supernova explosions. See Deasy and Butler, "Evidence for mass loss from IRAS observations of classical Cepheids," See http://www.nature.com/
Cepheids in Distance Measurements
The Baade-Wesselink method is used to determine the distance of a Cepheid by measuring the radial velocity of the star surface from the Doppler shift of spectral lines. See http://www.eso.org/
The Doppler shift of spectral lines as a method to determine the surface velocity of a Cepheid has misled astronomers for some time. In Astronomy: A Physical Perspective, by Kutner (1987), the inward radial surface velocity of the star surface is shown out of phase with the outward moving star radius. If the spectral lines are interpreted by QED induced redshift in DPs that are proportional to mass emission, both the radial surface velocity and the star radius would only then correctly be in phase with each other.
In general, the negation of Doppler shift velocities by cosmic DPs has concerned astronomers since Hubble. See http://www.scienceblog.com/
1. Cepheid pulsation cycles by UV heating are not caused by opaqueness of ionized helium. Fuzzy bright spotted images can only be caused by DPs.
2. Ejected mass in periodic explosions is the more likely Cepheid mechanism and is consistent with the one and only Supernova explosions. Gravitational attraction tends to return ejected mass to the Cepheid.
3. The Cepheid period-luminosity relationship is invalidated by DPs.