Absolute Magnitude and Luminosity Even the intrinsically faintest star's luminosity is much, much greater than all of the power we generate here on the Earth so a "watt" or a "megawatt" are too tiny a unit of power to use for the stars. Star luminosities are specified in units of solar luminosity---relative to the Sun (so the Sun generates one solar luminosity of power). One solar luminosity is about 4 × 10 26 watts. Magnitudes and Distances for some well-known Stars (from the precise measurements of the Hipparcos mission) Star App.Mag. * Distance(pc) Abs.Mag. * Visual Luminosity(rel. to Sun) ** Sun-26.74 4.84813×10-6 4.83 1 Sirius-1.44 2.6371 1.45 22.5 Arcturus-0.05 11.25-0.31 114 Vega 0.03 7.7561 0.58 50.1 Spica 0.98 80.39-3.55 2250 Barnard's Star 9.54 1.8215 13.24 1/2310 Proxima Centauri 11.01 1.2948 15.45 1/17700 * magnitudes measured using ``V'' filter, see the next section. ** The visual luminosity is the energy output in the ``V'' filter. A total luminosity (``bolometric luminosity'') would encompass the energy in all parts of the electromagnetic spectrum. How do you do that?
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