The Milky Way is about 1.9 million light-years wide and the border has finally been “discovered.”

A new study by British scientists suggests that the Milky Way is about 1.9 million light-years (1 light-year equals 946 billion kilometers), a figure that helps them better estimate the mass of the Milky Way and how many galaxies “dance” with the Milky Way, Science News reported Wednesday.

Astronomers have long known that the brightest part of the Milky Way is a pancake-like disk of stars in which the sun is located, about 120,000 light-years wide, and outside the disk of stars is a disk of gas. A huge dark matter halo envelops the two discs and extends far beyond them. But because the halo doesn’t glow, it’s hard for scientists to measure the diameter of the Milky Way.

Now, Durham University astrophysicist Alice Dyson and colleagues have used galaxies near the Milky Way to find the boundaries of the Milky Way. Their latest research shows that the Milky Way is 1.9 million light-years in diameter and no more than 400,000 light-years in error.

To find the boundaries of the Milky Way, Dyson’s team used computers to simulate how giant galaxies, such as the Milky Way, formed, in particular, and their recent large galaxy, Andromeda, appeared side by side. The results show edified small galaxies located near the edge of the great galaxy’s halo.

Using observations from existing telescopes, Dyson’s team found that small galaxies near the Milky Way had experienced the same rate decline. They say this happened about 950,000 light-years from the center of the Milky Way, which should be the boundary of the Milky Way. As a result, they concluded that the Milky Way is about 1.9 million light-years wide. And, although most of the Milky Way’s mass is made up of dark matter, simulations suggest that there may also be stars on the edge of the Milky Way.

They hope to further precision the position of the milky edge by discovering more small nearby galaxies in the future. Mike Colchin, an astrophysicist at the University of Texas at Austin who wasn’t involved in the study, said astronomers could also look for stars at the edge of the Milky Way, which may be very dim in these distant places, but should be found in the future.

Rosemary Wise, an astronomer at Johns Hopkins University, was also not involved in the latest study, but said the latest measurements could also help astronomers clarify other natures of the Milky Way. For example, the larger the Milky Way, the heavier its “weight” will be, and the more galaxies it “dances” with it. Scientists have so far found about 60 “dance partners” in the Milky Way, and more should be found in the future.