Well, it just so happens that I am an astronomer, and they are able to make such conclusions based off of certain assumptions that don’t hold true in your example. Space is isotropic (the same in all directions) and homogeneous (consistent in composition everywhere), which New York is not. Hope this helps

Proximity to a star, maybe? My assumption was that exoplanets are discovered by monitoring variations in the light we receive from their local stars, caused by their gravitational pulls. Objects in our Oort cloud are too far away from our own sun to make that method of discovery feasible.