Absolute magnitude from an absolute magnitude in a specific filter band to absolute bolometric magnitude, a bolometric correction is applied. For Solar System bodies that shine in reflected light, a different definition of absolute magnitude (H) is used, based on a standard reference distance of one astronomical unit. In stellar and galactic astronomy, the standard distance is 10 parsecs (about 32.616 light-years, 308.57 petameters or 308.57 trillion kilometres). A star at 10 parsecs has a parallax of 0.1″ (100 milliarcseconds). Galaxies (and other extended objects) are much larger than 10 parsecs, their light is radiated over an extended patch of sky, and
Rocheworld focusing light onto the smaller sail, slowing the craft. Using the light sail system, the spaceship "Prometheus" continued to accelerate for 20 years, traveling 2 light years' distance toward Barnard's Star before going into coast mode and traveling an additional 20 years' time at a constant speed of 0.2 "c", covering the remaining 4 light years (ca. 23 trillion miles; 38 trillion km). Flouwen (the Middle English word for 'flow') are the alien creatures in the book. They are the sole intelligent inhabitants of the planet Eau, which makes up the watery half of Rocheworld. Flouwen are blob-like, happy-go-lucky aliens