In Modified Newtonian Dynamics (MOND), a phenomenological tweak to Newtonian gravity proposed in 1983 by Mordehai Milgrom to replicate the galactic rotation curves attributed with dark matter without using dark matter, there is one experimentally determined physical constant:
a0 = 1.2 x 10-10 ms-2
In MOND, this constant is the characteristic acceleration due to a gravitational field, above which ordinary Newtonian gravity applies and below which an enhanced gravitational field strength leading to flat rotation curves in spiral galaxies is present.
What does this mean in reference to something understandable?
The gravitational field of the Sun alone falls to that strength at a distance of about 1,052 billion km (about 7000 astronomical units (AU). An AU, which is 149.6 million km, is the average distance of the Earth from the Sun.
This is about 1/9th of the light year from the Sun, which is about 175 times the average distance of Pluto from the Sun. Pluto's average distance from the Sun is about 6 billion km).
This is about 58 times more distant from the Sun that the heliosphere, which is a functional definition of where the solar system ends and deep interstellar space begins, that is about 18 billion km (120 astronomical units) from the Sun.
As of February 2018, Voyager 1, the most distant man made object from Earth, was about 21 billion km from Earth, and Voyager 2, the second most distant man made object from Earth is about 17 billion km from Earth. Both were launched 43 years ago in 1977. These probes (which will run about of power around the year 2025), will reach this distance from the Sun about 2000 years from now in around 4000 CE.