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
Messier 26 Messier 26 Messier 26, also known as NGC 6694, is an open cluster of stars in the southern constellation of Scutum. It was discovered by Charles Messier on June 20, 1764. This 8th magnitude cluster is a challenge to find with typical binoculars, but can be spotted with an 80mm aperture. It is positioned near the open cluster Messier 11 and is across. About 25 stars are visible in a telescope with a aperture. M26 spans a linear size of 22 light years across with a tidal radius of , and is at a distance of 5,160 light years from