Physics - Explore the discovery of planets around other stars. What methods did the astronomers use?

Explore the discovery of planets around other stars. What methods did the astronomers use? What measurements did they take? How did they use Kepler’s third law?

Answer:

Astronomers measure the star’s tiny velocity due to the gravitational force exerted on it by a massive planet. The velocity is calculated by measuring the Doppler shift of the star’s light that results from that motion. The velocity oscillates back and forth as the planets orbit the star, allowing calculation of the planet’s period. From the size of the velocity they can estimate the planet’s distance and mass. By comparing the distances and periods of planets in solar systems with multiple planets and using Kepler’s third law, astronomers can better separate the distances and masses of stars and planets.