Strong evidence for the existence of planetary systems in the process of formation around other stars comes from:
A) detection of very regular pulses of radio energy from some stars.
B) spectroscopic evidence of large quantities of molecules such as ammonia and methane, which can exist only in planetary atmospheres.
C) direct photography of actual planets near other stars.
D) periodic wobbling of the positions and spectral line displacements of several nearby stars.

Question

Quizplus · Accepted Answer

The periodic wobbling of the positions and spectral line displacements of several nearby stars is the result of the gravitational tug of planets orbiting them. This is known as the radial velocity method and is one of the primary ways astronomers detect exoplanets. It provides strong evidence for the existence of planetary systems around other stars.

Strong Evidence for the Existence of Planetary Systems in the Process