"Despite residing in it, it’s hard for us to know exactly how big the Milky Way is. But new research has found that our galaxy is bigger than previously thought. Using a large survey of stars instead of just models (as previous researchers did), astronomers have now determined the disk of our galaxy to be 200,000 light-years across — twice as large as was believed a decade ago."
http://www.astronomy.com/news/2018/06/supersize-me
https://www.aanda.org/articles/aa/abs/2018/04/aa32880-18/aa32880-18.html
http://www.astronomy.com/news/2018/06/supersize-me
https://www.aanda.org/articles/aa/abs/2018/04/aa32880-18/aa32880-18.html