The Earth-Sun L4 Lagrange point is not a physical object with a size, like a planet. It's a point in space, a location defined by the gravitational balance between the Earth, the Sun, and the object placed at that point.

Therefore, it doesn't have a size. However, the region around L4, known as the L4 region, can be thought of as a region of gravitational stability, where objects can remain for extended periods without being pulled away by the Sun or Earth.

The size of the L4 region is influenced by factors like the mass of the Sun, Earth, and the object at the L4 point. It's not a well-defined boundary and is often described in terms of Hill's sphere, a region where the object's gravitational influence is dominant over the larger bodies.

For the Earth-Sun system, the L4 region is quite large, spanning millions of kilometers.

It's important to remember that the L4 region is not empty. It contains dust, asteroids, and other celestial objects that are influenced by the Sun and Earth's gravity.