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We firstly examine the critical model assumptions for massive stars, in particular regarding mixing, mass loss and metallicity. The comparisons of models and observations for main sequence stars reveal some interesting problems, such as the lack of O-stars close to the zero-age sequence, the so-called helium and mass discrepancies. We emphasize that this last discrepancy was probably due to the unsafe atmosphere modelling used by spectroscopists. The comparisons for supergiants enlighten a number of most interesting problems: the He and CNO abundances in blue supergiants, the distribution of supergiants in the HR diagram and above all the variations of the blue to red number ratios with metallicity. Then, we examine the properties and chemistry of WR stars and the observations and interpretations concerning the great changes of WR numbers in galaxies of different metallicites. Finally, we emphasize the main WR filiations. [ABSTRACT FROM AUTHOR]

Among the longest known eclipse durations and binary periods is that of the star ϵ Aurigae, which exhibits 2-year long eclipses every 27.1 years. Oddly, the nature of the secondary in the system continues to elude ready identification. In 1965, Huang proposed a massive disk as the eclipsing body, and study of the 1984 eclipse led Lissauer and Backman to suggest an embedded B star binary in the disk to maintain it. A collaboration of observers allows me to present recent optical photometry and spectroscopy, near-IR spectroscopy and Spitzer space telescope IRS and MIPS observations of ϵ Aurigae as it approaches its next eclipse. These data argue for current detectability of the embedded binary, and precession of the disk axis, suggesting a radical change is possible for the next mid-eclipse brightening. An international monitoring campaign for the 2009-2011 is being organized, and participation invited via website http://www.du.edu/~rstencel/epsaur.htm. [ABSTRACT FROM PUBLISHER]

Very recently, a number of obscured massive open clusters have been identified in the Milky Way. A very significant fraction of them lie either close to the base of the Scutum Arm or towards Galactic longitude of 350°. We are studying these clusters and their neighbourhoods, finding very good evidence for a major starburst region close to the near tip of the Galactic Long Bar. [ABSTRACT FROM PUBLISHER]