In a report published in the December 8^th issue of the journal Science, scientists from China, the United States, and Germany wrote that they have for the first time measured up the distance between the Sun and the Perseus, the nearest spiral arm of the Milky Way. Dr. XU Ye, the lead author from the Department of Astronomy, a part of the Nanjing University, and his collaborators calculate out the distance between the Sun and the Perseus arm as 1.95 kiloparsecs, or about 6360 light years, with a possible error less than 2.1%. 

Using the Very Long Baseline Array at the US National Radio Astronomy Observatory, Dr. XU and his collaborators observed a massive star-forming region W3OH in the Perseus arm of the Milky Way, from which the distance between the Sun and the arm is measured. Scientists believe that one can map out the structures of spiral arms on the Milky Way, using observing equipment like the Very Long Baseline Array.