Final answer:
To distinguish between population I and II stars, one must consider their chemical composition, age, and orbital motion. Population II stars are older, with fewer heavy elements and eccentric orbits, while population I stars can be young or old, have more heavy elements, and are concentrated in spiral arms.
Step-by-step explanation:
To determine whether an individual star seen with a telescope is a member of population I or population II, one would need to observe the star's characteristics, such as its chemical composition, age, and orbital motion. Population II stars are generally older, with typical ages of 11 to 13 billion years, and contain fewer heavy elements.
They do not correlate with the location of the spiral arms and are found throughout the galaxy, including in the disk and the halo, often on eccentric elliptical orbits. Examples include stars in globular clusters. In contrast, population I stars are found in the disk and particularly concentrated in the spiral arms. They follow nearly circular orbits around the galactic center, contain more heavy elements, and can range from very young to as old as 10 billion years, like the Sun.