Outside forces: gravity, solar wind, something (unknown, not visible particles) are hitting it.Could simply be "outgassing" something. 
 Like a rocket, it moves off in the opposite direction.

 
26 posted on 
03/14/2019 3:09:31 PM PDT by 
ETL
(Obama-Hillary, REAL Russia collusion! Uranium-One Deal, Missile Defense, Iran Deal, Nukes: Click ETL)