Chapter 7, Problem 1QQ

Choose the best answer to each of the following. Explain your reasoning.

Which detection method or methods measure the gravitational tug of a planet on its star, allowing us to estimate planetary mass? (a) the transit method only (b) the Doppler method only (c) the astrometric and Doppler methods

To determine

The method or methods use to estimate planetary mass.

Answer to Problem 1QQ

Correct option is (c) the astrometric and Doppler methods both allow us to estimate the planetary mass.

Explanation of Solution

Introduction:

Planets are extremely faint; their parent stars are billion times brighter than them they are used to find the information about extrasolar planets. Scientist found indirect methods to find and explore the existence of extrasolar planets.

Astrometry is one of the most sensitive methods to detect information about extrasolar planets. To estimate the planet's mass Astronomers, observe the minuscules motion of stars about the center of mass. The gravitational force of the planet effects the stars.

Doppler method is used to detect the orbital motion of the wobbling stars. In the spectrum of stars absorption line shift towards blue when stars move towards the planet while the spectrum shift towards red if stars move away from the planet. This method helps us to detect the mass of the planet as a more massive planet has a greater gravitational effect on the orbital motion of the stars.

The transit method cannot measure the mass of a single planet but in multiple planetary systems, the gravitational force of one planet over other planet affects the timing of transits.

Conclusion:

Astrometric and Doppler's methods are used to measure the gravitational tug of a planet on a star can help us measure and estimate planetary mass.