Astronomers have arrived at what they believe to be the most accurate measure yet of the mass of the Milky Way: about 4.8 x 1011 times the mass of the sun, or “solar masses,” to use a standard unit of mass in astronomy.

This comes to about 9.5 x 1041 kilograms — that is, 95 followed by 40 zeros. The number, of course, is inexact, as obviously no direct measure of all the billions of stars and other objects in the Milky Way could be taken.

But in a paper to be published in The Astrophysical Journal, scientists used methods of measurement that involve complex mathematical and statistical techniques called hierarchical Bayesian analysis, as well as direct measurements of the velocity of globular clusters, the tightly packed spherical groups of 10,000 to 100,000 old stars that move through the galaxy.

Just as the mass of the sun can be calculated by measuring its gravitational pull on Earth, the mass of the Milky Way can be calculated by measuring its gravitational pull on the globular clusters.