Formation of Hydrogen Emission Lines in the Magnetospheres of Young Stars

Astronomy Letters - The formation of hydrogen emission lines in the magnetospheres of young stars is considered. The magnetosphere is assumed to be formed by a dipolar magnetic field whose axis is...     

Light Scattering and Extinction in M 82

Published low-resolution measurements of colour and polarisation over the face of M82 are discussed to separate the contribution of starlight and scattered light. We show that in all places of the middle and outer halo the scattered light comes predominantly from a central source of very high ultraviolett excess, the contribution of the disc is negligble there. The projected distributions of H_α-light and scattered continuum are of considerable similarity. Major extinction occurs in the southern half of the main body and of the inner halo; the northern half of the bright body, and the northern halo, are free of extinction, excluding some regions near the minor axis. The light of the central source is reddened only before it is scattered in the halo. The variation of the true degree of polarisation (after correction for starlight) is interpreted in terms of the variation of the mean scattering angle. From this, conclusions can be drawn concerning the location of the dust and the geometry of the illumination. The high brightness of the scattered light near the minor axis is caused axis is caused by a bright illuminating beam there, strengthened in some places by comparatively low scattering angles (45°) and a higher (projected) density of the scattering material. The stellar populations seen in M82 are different in the northern and in the southern halfs of the galaxy. The main body and the region of the northern “halo” consist of an old population of normal metal content (pop. I); the colours of the southern parts – which are partly considerably influenced by extinction – can be due to either metal poor F-stars (pop. II) or to young B-stars. To solve the latter ambiguity and at the same time the question in what direction the plane of the galaxy is tilted, good spectra of the faint southern parts of M82 outside the minor axis are needed.     

Method for Validation of the Onboard Attitude Control System Software of the <Emphasis Type="Italic">Auriga</Emphasis> Earth Remote Sensing Small Spacecraft

The paper considers a digital modeling complex for the attitude control system of the Auriga Earth remote sensing small spacecraft. Mathematical models of measuring and executive devices are described. The results of spacecraft orbital attitude tests are presented.     

Technologies of measurements of the sea level

We analyze the contemporary methods and means of measurements of the sea level and inland waters, describe a CTD-meter designed at the Marine Hydrophysical Institute of the Ukrainian National of Science for the determination of the sea level, formulate the requirements to the perfect meter of the water level, and demonstrate that an electronic sounding stick based on the distributed Walsh thermoprofilometers can play the role of a device of this kind.