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
Kos (unit) Kos (unit) The kos (Sanskrit: कोस), also spelled Kosh, Krosh, krosha and Koss, is an ancient Indian subcontinental "Arthashastra standard unit" of distance, since at least 4 BCE. A kos is about 3.00 km or 1.91 miles. The ""Arthashastra: Chapter XX. Measurement of space and time"", authored in 4th century BCE by Chanakya (Vishnugupta Kauṭilya), sets this standard breakup of Indian units of length: Kos may also refer to roughly 1.8 km (1 mile) or 3.2 km (2 miles). "Arthashastra Standard unit" of Kos or krosh is equal to 3075 metres in SI units and 1.91 miles in Imperial units.