Final answer:
The outermost stars referenced are red and highly luminous, earning them the designation of either 'giant stars' or 'supergiant stars,' with Betelgeuse being a prime example. These celestial bodies are part of the thin, rotating disk of the Milky Way Galaxy, where most star formation occurs.
Step-by-step explanation:
The stars you are referring to, which are red and very luminous, are typically known as giant stars or supergiant stars. These stars include some of the largest in the universe, such as Betelgeuse in the constellation of Orion. Betelgeuse has a staggering diameter that's more than 10 Astronomical Units (AU) or 1.5 billion kilometers, which is substantial enough to span across the inner solar system almost reaching Jupiter. When we speak of stars in the context of the Galaxy, particularly our Milky Way, young stars and the materials that form stars are predominantly found within 100 light-years of the galactic plane in a thin, rotating disk. This disk is about 100,000 light-years in diameter and relatively thin, with a thickness of about 2000 light-years. Our own Sun is located near the inner edge of the Orion Spur, an arm of the Milky Way Galaxy, and is part of the dense collection of stars that form our galaxy.