Question

Which of the following is an advantage of using parallax rather than the Doppler effect to determine star distance?

Answer 1

Doppler shift is a velocity dependent effect, not a position dependent effect, so it doesn't tell you where the star is, only how fast it's moving.

Answer 2

The next nearest neighbor to the Sun beyond the Alpha Centauri system is called Barnard's Star. Its parallax is 0.55´´, so it lies at a distance of 1.8 pc, or 6.0 light years. The farther into space astronomers look, the greater the volume of space they observe and more stars they find. About 30 stars are known to lie within 4 pc of Earth. Figure 17.2 is a map of our nearest galactic neighbors.