Which of the following is one of the facts that must be known in order to determine the distance to a star by parallax?
A) The star's spectral type
B) The star's apparent magnitude
C) The wavelength at which the star's spectrum is most intense
D) The distance between the Sun and Earth

Question

Quizplus · Accepted Answer

In order to determine the distance to a star by parallax, we need to know the baseline distance between the Earth and the Sun. This is because we measure the apparent shift of the star against the background of more distant stars over a six-month period as Earth moves from one side of its orbit to the other. Knowing this baseline distance, we can then use trigonometry to calculate the distance to the star. The other options (A, B, and C) are useful for determining other properties of the star, but not necessary for determining its distance by parallax.

Which of the Following Is One of the Facts That