We present the integrated 411 ks Chandra ACIS-S exposure of the Antennae galaxies (NGC 4038/39). Besides a rich population of point-like sources, this spectacular image reveals a spatially and spectrally complex hot diffuse gaseous component. For the first time we detect intense line emission from Fe, Ne, Mg and Si in The Antennae, and obtain a detailed picture of spatially varied metal abundan...

A representative sample of unevolved early B-type stars in nearby OB associations and the field is analysed to unprecedented precision using NLTE techniques. The resulting chemical composition is found to be more metal-rich and much more homogeneous than indicated by previous work. A rms scatter of ∼10% in abundances is found for the six stars (and confirmed by six evolved stars), the same as r...

The chromosphere is the site of weak emission lines characterizing the flash spectrum observed for a few seconds during a total eclipse. This layer of the solar atmosphere is known to possess an opaque Hα emission and a great number of spicules, which can extend well above the photosphere. A stunning variety of hydrogen emission lines have been observed in this region. The production of these l...

We study the morphology of dark lanes and filaments in the dust-rich galaxy NGC 253 using an unsharp-masked B-band optical photograph. Dust features are classified as ‘arcs’, which have heights and scale radius of about 100 to 300 pc, connecting two or more dark clouds, and ‘loops’ and ‘bubbles’, which are developed forms of arcs, expanding into the disk-halo interface. These have diameters of ...

I review some recent advances in methods to diagnose polarized radiation with which we may hope to explore the magnetism of the solar chromosphere and corona. These methods are based on the remarkable signatures that the radiatively induced quantum coherences produce in the emergent spectral line polarization and on the joint action of the Hanle and Zeeman effects. Some applications to spicules...

At present, the heliosphere is embedded in a warm low density interstellar cloud that belongs to a cloud system flowing through the local standard of rest with a velocity near ∼18 km s. The velocity structure of the nearest interstellar material (ISM), combined with theoretical models of the local interstellar cloud (LIC), suggest that the Sun passes through cloudlets on timescales of ≤ 10–10 y...

Short-lived nuclides, now extinct in the solar system, are expected to be present in interstellar matter (ISM). Grains of ISM origin were recently discovered in the inner solar system and at Earth orbit and may accrete onto Earth after ablation in the atmosphere. A favorable matrix for detection of such extrater-restrial material is presented by deep-sea sediments with very low sedimentation ra...