Question

The motion that is used to change the position of the observer in the most common parallax measurements of distances to relatively nearby stars is the

A) motion of the Sun around the galactic center.
B) change in latitude of the observation point on Earth.
C) motion of Earth in its orbit around the Sun.
D) rotation of Earth on its axis.

Answer 1

The motion of Earth in its orbit around the Sun is used for parallax measurements to calculate distances to nearby stars, with this effect known as stellar parallax.

Step-by-step explanation:

The motion used to change the position of the observer in the most common parallax measurements of distances to relatively nearby stars is the motion of Earth in its orbit around the Sun. This motion causes an apparent shift in the position of a nearby star compared to distant stars, an effect known as stellar parallax. Astronomers use this shift to calculate the distances to stars by defining parallax as one-half the angle that a star appears to shift when observed from opposite sides of Earth's orbit. The units of measurement used for stellar distances based on parallax include the light-year and the parsec, with 1 parsec equating to a parallax of 1 arcsecond or 3.26 light-years.