The association between galaxies is a phenomenon frequently occurring in the universe. Systems called Polar Ring Galaxies (PRGs) can be built for certain interactions. These structures consist of a galaxy known as a host and a ring of gas and stars surrounding a plane nearly perpendicular to its main axis. This research has contributed to the creation of a first library of N-body simulations, to study the parameters required to construct PRGs. A library of this kind is continuously expanding with new simulations based on these first findings. The inherent secular processes of isolated galaxies cannot give rise to this PRG geometry. Such systems are (i) created by galaxy interactions or (ii) by the introduction of cold gas from interstellar filaments within a galaxy. The most popular mechanisms are thought to be (i), and we are interested in this project, particularly where gas from one galaxy to another is introduced, without the need for a fusion. For formation of interaction, orbits with particular geometries are required in order to attach matter to form a polar ring. We review various mass ratios, inclinations and orbital energies in our society. The database which will be developed with the simulation results will contribute to future research on the interaction between galaxies, especially polar rings.

With the development of high resolution sensors in remote sensing satellites, the shadow phenomena has appeared clearly in satellite image. The shadow is a separated feature in the satellite image, some time it may be considered as a problem due to the loss of ray information at the shaded region, other may be considered as a criteria to the height of the body which has a shadow. The length of shadow depends on the height of the body, location on the earth surface, and the sun location in sky at the imaging time. The sun location is varying every hour during the day and every day during year. These varying is calculated by complex astronomic equations. In this article, we simplified these calculations to just on equation depend on one parameter, and examine this equation by field measurements. The suggested equation is sumsine equation with an enough accuracy to be used in civil, ecological, gardens designing near the high buildings, or architectural purposes. The equation can be used to estimate the building height from the shadow length in the satellite image, as will as it may used to estimate shadow length from the known body height on the earth.