Editing Double star (section)

==Distinction between binary stars and other double stars==
Confirmation of a visual double star as a binary star can be achieved by observing the relative motion of the components. If the motion is part of an [[orbit]], or if the stars have similar [[radial velocities]] or the difference in their [[proper motion]]s is small compared to their common proper motion, the pair is probably physical. When observed over a short period of time, the components of both optical doubles and long-period visual binaries will appear to be moving in straight lines; for this reason, it can be difficult to distinguish between these two possibilities.<ref name=Heintz1718>{{cite book | last=Heintz | first=W. D. | year=1978 | pages=[https://archive.org/details/DoubleStars/page/17 17–18] | title=Double Stars | publisher=[[D. Reidel]] Publishing Company | location=Dordrecht | isbn=90-277-0885-1 | url=https://archive.org/details/DoubleStars/page/17 }}</ref>