Betelgeuse is an old red supergiant that has been blowing chunks of itself out into space in successive waves for eons. The star itself would cover our own star system out to the Jovian orbit, and outer shells of water, dust, and energy that used to be the star spread far out beyond our own Neptune or Pluto. It’s a large and dangerous system to fly through, but the Branan didn’t have to fly though most of it when they began their first colonization program. Their homeworld was one of six small planets orbiting the gas giant closest to Betelgeuse, and that gas giant continually plowed a reasonably safe course through the star’s outer shells where its planets and moons could live in general peace. So their first “interplanetary” colonization efforts were actually very short hops to other planets orbiting that very same gas giant. They were dangerous enough to start with, especially in a system like Betelgeuse, but they gave the Branan a taste for interplanetary colonization that would forever drive them in search of new frontiers.