We present Spitzer IRS observations of a small sample of heavily obscured IRAS sources displaying both the infrared and OH maser emission characteristic of OH/IR stars on the asymptotic giant branch (AGB), but also radio continuum emission typical of ionized planetary nebulae (PNe), the so-called OHPNe. Our observations show that their mid-infrared

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Context: Based on radial velocity measurements, it has been found that the two giant planets detected around the star HD 73526 are in 2:1 resonance. However, as our numerical integration shows, the derived orbital data for this system result in chaotic behavior of the giant planets, which is uncommon among the resonant extrasolar planetary systems

In this article, we hope to illustrate the great qualitative and quantitative strides that star-formation studies have taken in the past few years, by looking at three highlights from our own work using the ESO Very Large Telescope UT1, Antu, and its facility near-infrared camera/spectrograph, ISAAC. In particular, we have chosen examples which

We present a study of the optical spectra of a sample of eight star-forming nuclear rings and the nuclei of their host galaxies. The spectra were obtained with the Intermediate dispersion Spectrograph and Imaging System spectrograph on the William Herschel Telescope and cover a wide range in wavelength, enabling the measurement of several stellar

Large-scale propagating star formation in galaxies is studied as a self-regulatin process. The model connects the energy injection by star formation with the resultin interstellar structures in a differentially rotating disc. The star formation cycl includes the formation of new stars in groups, multisupernova remnants agglomerafin the gas into