# How accurately can the distance of a star be measured?

With the launch of the GAIA mission some years ago, a new precedent was set in mankind's ability to map our universe. However, how accurate are the distances created by this? From ESA's website, I found:

In the final Gaia catalogue, expected in the early 2020s, brighter objects (3-13 magnitude) will have positions measured to a precision of 5 microarcseconds, parallaxes to 6.7 microarcseconds, and proper motions to 3.5 microarcseconds per year

If we take the value 6.7, and put that into the equation: d=1/p, we get d=1/0.0000067=150,000 parsecs. This is immensely accurate given that most sources tell me that the most accurate is around 1000 parsecs (accurate to 0.001 arcseconds). Are my calculations correct, or did I use a wrong value somewhere?

• Are you asking if ESA made a mistake? Jun 9 '18 at 18:21
• I'm asking if I'm calculating it correctly Jun 9 '18 at 18:41
• O, I see. I will change my answer accordingly. Jun 9 '18 at 20:05

• Correct. 1500 parsec corresponds to 670 micro arcsec and the precision of 6.7 micro arcsec gives 1 % precision of the distance, so $\pm$ 15 parsec. Jun 9 '18 at 21:35