Scientists have finally been able to accurately calculate the weight of the Milky Way, overcoming the difficult hurdle of measuring dark matter, the European Space Agency (ESA) announced Thursday. After years of struggling to estimate the size of our galaxy, astronomers with NASA and the ESA used data from the Hubble Space Telescope and the ESA’s Gaia mission to determine the Milky Way weighs about 1.5 trillion solar masses within a radius of 129,000 light years from the center. Because dark matter makes up about 90 percent of the galaxy, estimates of the Milky Way’s weight have differed widely in...