This illustration shows how the precision stellar distance measurements from NASA's Hubble Space Telescope have been extended 10 times farther into our Milky Way galaxy than possible previously. This greatly extends the volume of space accessible to refining the cosmic yardstick needed for measuring the size of the universe. This most solid type of measurement is based on trigonometric parallax, which is commonly used by surveyors. Because the stars are vastly farther away than a surveyor's sightline, Hubble must measure extremely small angles on the sky.
Illustration Credit: NASA, ESA, and A. Feild (STScI);
Science Credit: NASA, ESA, A. Riess (JHU/STScI), S. Casertano (STScI/JHU), J. Anderson and J. MacKenty (STScI), and A. Filippenko (University of California, Berkeley)