Question

Parallax is

a) the apparent motion of an object due to the motion of the observer.
b) the distance between two foci of an ellipse.
c) the small circle that the planets slid along in Ptolemys geocentric universe
d) the circular orbits used in Copernicus heliocentric universe.
e) half the length of the shortest diameter of an ellipse.

Answer 1

Parallax is the apparent shift in the direction of an object due to the motion of the observer. In astronomy, stellar parallax refers to the shift in the apparent direction of a star due to Earth's orbital motion. Astronomers define parallax as one-half the angle that a star shifts when seen from opposite sides of Earth's orbit.

Step-by-step explanation:

Parallax is the apparent shift in the direction of an object as a result of the motion of the observer. In the context of astronomy, stellar parallax refers to the shift in the apparent direction of a star due to Earth's orbital motion. Astronomers define parallax as one-half the angle that a star shifts when seen from opposite sides of Earth's orbit. The smaller the parallax, the more distant the object being measured must be.