Stellar dynamics
The stellar deals with the apparent and absolute motion of stars in various star clusters and other star systems, in order to deduce their formation and further development.
This branch of astronomy has to contend with many difficulties, including the vast distances, the smallness of the measured effects, the effect of systematic errors and the mutual influence of hundreds to millions of heavy masses.
Measurement methods
The underlying measurement methods are astrometric nature (especially high-precision meridian circles and passages instruments), further astrophotography ( today CCD sensors ) with appropriate evaluation devices (mono-and stereocomparators ), as well as special since the 1990s astrometry.
The primary measurement results are so-called proper motions of stars in two components ( right ascension, declination ) on the celestial sphere; they are usually in the range of a few 0.01 " per year, at very nearby stars also 1-10 ". Multiplied by the distance ( s.jährliche parallax) results in the linear movement - typically some 10 km / s The third component takes the radial velocity ( in view direction) added.
Motion analysis of star clusters and galaxies
In particular, the stellar dynamics studied by precise spatial movements analysis, such as star clusters and galaxies form, how they evolve and disappear. It uses this long-standing series of measurements by means of astrometry, photographic plates and satellite scanning, the changes result in the stellar motions. The theoretical model form the Newtonian axioms and the general theory of relativity.
Special methods have been developed for the study of stellar associations and streams. Such groups of stars are formed together and move approximately parallel by our galaxy, including the nearby Bear group of about 50 stars that pass around in our solar system. Such analyzes, however, are to be adjusted for two delicate factors: the Sonnenapex ( movement toward the constellation Hercules ) and the locally different rotation around the Milky Way center ( approximately 200-250 km / s), which in turn depends on the exact mass distribution (see also astronomical speed measurement).
Computer simulations
With the growing use of mainframes and supercomputers partly also very extensive simulations of motion in stellar systems were possible that a so-called " experimental " stellar created. Various models are calculated and compared with observational data. Thus, the mutual influence of the heavenly bodies - that until recently unsolvable many-body problem - be treated mathematically.