Why do all stars and galaxies in the sky of any planet describe ellipses with the same semi-major axis for a given planet?

The reason for this is the annual aberration of the light of the stars, caused by the relative movement of the star and the observer. Aberration is due to the finite speed of light.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.