A pair of stars that appear to form a double star but are not actually gravitationally bound is called an optical double.

Here's why:

* Optical illusion: These stars are simply aligned along our line of sight from Earth. They are at vastly different distances, and there's no actual physical connection between them.

* No gravitational influence: Unlike true binary stars, optical doubles don't orbit each other, as they are not affected by each other's gravity.

Think of it like looking at two cars driving along a road. From a distance, they might appear close together, but they are actually quite far apart and traveling independently. Similarly, optical doubles are stars that just happen to be in the same direction in the sky, but they are not a true pair.