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43. The local interstellar medium

Creator:
Blitz, Leo
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
space research, mollecular clouds, and interstellar medium
Language:
Czech
Description:
The structure of the local interstellar medium is reviewed with emphasis on the new observations of the cold neutral component. The properties of the high latitude molecular clouds are discussed as well as their relationship to the “infrared cirrus” and atomic gas. The molecular clouds are shown to the preferentially along the loops and filaments of local HI gas, but a detailed examination shows the CO and HI peaks are offset from one another. An expansion velocity of 7 km is derived for one of the shells suggesting an expansion energy of - 8 X 10^47 ergs. which is somewhat smaller than that expected for a supernova explosion. If the pressure in the clumps of the high latitude clouds is in equilibrium with the surrounding gas, the pressure in the shells is 10^4-10^5 cm^-3 K, an order of magnitude higher than what is generally argued to exist in the interstellar medium.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

44. The role of resonances in planetary rings

Creator:
Borderies, N.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
space research, planetary rings, and resonances
Language:
Czech
Description:
The new observations of planetary rings, including those acquired during the encounters of Voyager with Jupiter, Saturn and Uranus and the discovery of incomplete rings around Neptune, reveal the great importance of resonances in determining the dynamics and the shape of planetary rings. Several types of resonances play a part in planetary rings. Current questions of interest are related to the nonlinear theory of density waves, the confinement of the Uranian rings, and the arcs of rings around Neptune.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

45. The spiral-vortex structure of flat galaxies (prediction, theory, laboratoy and numerical experiments, observations)

Creator:
Afanasiev, V. L., P. V., Fridman, A. M., Ivchenko, I. N., Makov, Tu. N., Morozov, A. G., Nezlin, M. V., Pasha, I. I., Polyschenko, V. L., Rylov, A. Yu., Snezhkin, E. N., Torgashin, Yu. V., Trubnikov, A. S., and Zasov, A. V.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
space research, flat galaxies, and spiral-vortex structures
Language:
Czech
Description:
Recent observations show a dip on the rotation curve for most of spiral galaxies,Theoretically, it implies that spiral density waves must be induced by shear instabilities,Calculations prove that the observed amount of gas In galactic disks (10% for the Galaxy) is sufficient to develop the hydrodynamical Instability in gas subsystems. As surface density perturbations of shallow water and galactic gas disks are described by the same equations, experiments with shallow water rotating slmilar to galactic disks have been made, In stationary stages of rotation stationary spiral pattems occur. The number of arms depends on the profile of rotation curve, in agreement with theoretical results, Different rotation parameters lead to different structures: the circular mode, one-, two-, ... , eight-armed spirals. Branching of the spirals is observed when rotation parameters change,which suggests that the spiral branching in several galaxies comes from their non-stationary rotation. Anticyclonic vortices are observed between the arms, Azimuthal averaging of the surface density, gives a good fit for the galaxy: minlmum of before the molecular ring, for realistic profiles of shallow water rotation the spirals are trailing, But they happen to lead for opposite directions of rotation of inner and outer regions, It may explain the leading spirals in galaxies whose spin is opposite either to that oft.blose companions or to the vector of orbital momentum of the pairs. Numerical computations confirm the theoretical and experimental results.They also show a formation like a "molecular ring". Preliminary observational data agree with these results.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

46. Unusual motion of Amor

Creator:
Ziołkowski, K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
space research, minor planet Amor, and motion of asteroids
Language:
Czech
Description:
Rrecise analysis of the orbit of minor planet (1221) Amor, based on all observations made In 1932-1980, shows that in 1956 there was an unexplained event in the motion of the asteroid. Possible interpretations of that fact as well as peculiarities in the long-term motion of Amor in 1650-2170 are discussed. The ephemeris of Amor for 1988 is presented.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

47. Variability in the stellar wind of 68 Cygni - not ‘shells‘ or ‘puffs‘, but streams

Creator:
Prinja, Raman K. and Howarth, Ian D.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
space research, stellar wind, and streams
Language:
Czech
Description:
Results are presented from a study of variability in the stellar wind of G8 Cygni [07.5 III((f))], based on 33 lUE high resolution spectra taken over ~ 7 days. Significant changes are evident in the Si IV resonance line profiles on timescales as short as ~ 1 hour, cliaracterised by broad absorption enhancements at relatively low velocity (0.5 to 0.7 of the terminal velocity, υ∞) which evolve into high velocity discrete absorption components (at > 0.8 over a period of ~ 1 day. The recurrence timescale for the appearance of the broad features is ~ 15-20 hours. Three well monitored consecutive sequenccs of progressive opacity enhancements are described. Their properties are parameterised and incorporated into a self-consistent phenomenological model where the opacity enhancements and ‘underlying’ wind sure radiatively coupled. The model results show that the absorption enhancements do not propagate from the photosphere in any simple way, and are not due to spherically symmetric phenomena. We conclude that the discrete absorption variability in G8 Cyg is not due to ‘shells’ or ‘puffs’ of matter, but instcaid arise from material passing through perturbations in the flow, which may be illustrated in terms of spirally wound-up streams.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public