The solar system isn't like a sidewalk, where the curb marks a distinct edge. There are a number of plausible candidates for the "edge" of the solar system.
One would be the orbit of the outermost planet, Neptune. Or should Pluto be included? Or perhaps one of the other minor planets even further out, such as Eris or Makemake?
Maybe the Kuiper Belt marks the "edge" of the solar system. You might suggest the Oort Cloud, the source of many long-period comets, as the "edge".
Many scientists believe that the true edge of the solar system is the point at which the solar wind from the Sun fades into the general background of interstellar gas; this is called the "heliopause".
Limb
The crust.
the outer edge of the cytoplasm is the cell membrane.
If you apply force to the outer edge of the door, this gives you the most leverage.
The cell membrane
region occupied by the electrons
Teeth are the part of a body that is also the edge of a saw.
The outer edge of a circle is called the circumference.
The out edge of a cup is called the 'Rim'.
brim
nebula
circumference
A straight line from the center of a circle to the outer edge is called a radius.
The edge of a river basin is called the watershed.
It is called its bounds. In the case of 2 dimensional objects, it is part of the perimeter.
the outer edge of the cytoplasm is the cell membrane.
The outer edge means the furthest most point from the center. The outer edge is usually the end of the object before the dropping off point.
Tread Width. The tread width is the distance between the outer edge and the inner edge of the tread
It is called its bounds. In the case of 2 dimensional objects, it is part of the perimeter.