We have embarked on a program to directly compare spectroscopic and evolutionary masses with those obtained from a combination of spectroscopic and photometric orbital solutions for O-type binary systems. The ability to directly determine the spectroscopic masses of the individual components of O-type binary systems has been difficult, because of

Although seismic tomography evidence leaves no room for fully layered mantle convection, it is still arguable that over Earth's history convection has efficiently homogenized mantle composition. We first searched for remains of the early differentiation of the planet in the 3.8 Ga rocks from Isua, Greenland. A sensitive indicator is the extinct

The fragile and rare isotope 6Li has a spallative origin. It is rapidly destroyed in solar-type stars while fully preserved in low-mass brown dwarfs and planets. So far, 6Li has been unambigiously detected in only few metal-poor halo and disk stars whereas it has never been observed with a high level of confidence in any metal-rich or even solar

We report the largest mass-loss rate of ~5 % of the solar mass per year, directly observed in any stellar object so far during the recent outburst of the Yellow Hypergiant ρ Cas. In the fall of 2000, the enigmatic cool luminous supergiant dimmed by more than a full visual magnitude, thereby changing its spectral type form early F- to early M-type

We have determined the gravitational torque of a sample of 45 galaxies observed at K band with the 4.2m William Herschel Telescope. The results of this sample, combined with those for a sample of 30 galaxies previously analysed (Buta & Block 2001), show that the gravitational bar torque correlates only weakly with the optical bar type listed in the

We present a study of the grand-design spiral galaxy NGC 5248 (Jogee et al. 2002a,b) based on a combination of multi-wavelength % optical, near-infrared, and CO (J=1--O) observations and hydrodynamical modeling.