How can astronomers measure the period of a planet's orbit?
A)by measuring the time between peaks in the star's velocity curve
B)by measuring the time between repeated transits
C)by timing the cycle of small changes in a stars position on the sky
D)all of the above

Question

Quizplus · Accepted Answer

Astronomers can measure the period of a planet's orbit by using all of these methods.

A) The time between peaks in the star's velocity curve can be used to determine the planet's orbital period through the radial velocity method. As the planet orbits the star, it causes the star to move slightly towards and away from us, causing a Doppler shift in the star's spectrum. By measuring the time between peaks in the star's velocity curve, astronomers can determine the planet's orbital period.

B) The time between repeated transits can be used to determine the planet's orbital period through the transit method. As the planet passes in front of its star, it causes a slight dip in the star's brightness. By measuring the time between repeated transits, astronomers can determine the planet's orbital period.

C) Timing the cycle of small changes in a star's position on the sky can be used to determine the planet's orbital period through the astrometry method. As the planet orbits the star, it causes the star to move slightly back and forth in its position on the sky. By measuring the time it takes for the star to complete a full cycle of these small changes in position, astronomers can determine the planet's orbital period.

How Can Astronomers Measure the Period of a Planet's Orbit