Classes of material systems:
- Meteor associations,
- Satellite systems,
- Planetary structures,
i.e. meteors, moons and stars surrounded by a family of planets. - DOUBLE AND MULTIPLE STARS:
I. Close systems:
a) eclipsing,
b) spectroscopic.
II. Visual systems:
a) gravitational
P) optical.
III. Pairs and groups of stars with a common motion;