Recent planning for Constellation-X has driven the exploration of grazing incidence telescopes with focal lengths of 50 m or greater. Formation flying, wherein separate optic and detector spacecraft travel in formation, is one approach to implementing such long focal lengths. This approach eliminates the telescope tube that is an integral part of

We present new intermediate-band Strömgren photometry based on more than 300 u, v, b, y images of the Galactic globular cluster ω Cen. Optical data were supplemented with new multiband near-infrared (NIR) photometry (350 J, H, Ks images). The final optical-NIR catalog covers a region of more than 20 × 20 arcmin squared across the cluster center. We

We use spectra of the double-lensed quasars HE0047–1756 and SDSS1155+6346 to study their unresolved structure through the impact of microlensing. There is no significant evidence of microlensing in the emission line profiles except for the Lyα line of SDSS1155+6346, which shows strong differences in the shapes for images A and B. However, the

Non-axisymmetric features (such as bars and spirals) as well as general triaxialities (such as those of the bulge and halo) drive the dynamical and secular evolution of disk galaxies by exerting gravitational torques which redistribute mass and angular momentum. While most (> 70 %) spirals are barred in the local Universe, early studies of the HDF

We present an analysis of the orientation measurements of the Bronze Age Temple of Pella, took by the authors on the field in winter 2011. The site, famous for its huge ancient Roman ruins, had revealed on its lower acropolis the remains of a large sacred building, constructed in the 19th century BC during the Middle Bronze Age, that was

The next generation of solar observatories aim to understand the magnetism of the solar chromosphere. Therefore, it is crucial to understand the polarimetric signatures of chromospheric spectral lines. For this purpose, we here examine the suitability of the three Fraunhofer Mg I b1, b2, and b4 lines at 5183.6, 5172.7, and 5167.3 Å, respectively