Final answer:
The evidence for how planets in our solar system formed includes the observation of circumstellar disks around other stars, which are analogous to our own solar nebula, the birthplace of our planetary system.
Step-by-step explanation:
One piece of evidence that can help astronomers sort out how the planets in our solar system formed is finding circumstellar disks of material around nearby stars. These disks are significant as they are the sites where planets can form, affirming the theory that the planets of our solar system likely originated from a similar protoplanetary disk known as the solar nebula. Our solar system's planets share certain properties, such as similar orbits and chemical compositions, suggesting a common origin. Observations of circumstellar disks around other stars also provide clues about the stages of planetary formation and the dynamics within these disks, such as the presence of protoplanets and resonances shaped by developing planets.