**Classes of material systems:**
![](https://images.ecency.com/DQmVkr2zcFj4aUpWk82SrT5UuvtDP4WcfeccBGWq34BUTXn/b3410849_9ecf_4dcf_928f_cabe4f5ea7c6.jpeg)



  1. Meteor associations,
  2. Satellite systems,
  3. Planetary structures,
 i.e. meteors, moons and stars surrounded by a family of planets.
 4. 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;