Bolometric
Luminosity
The total energy radiated by an object at all wavelengths,
usually given in joules per second (identical to watts).
Luminosity is generally understood as a measurement of brightness. Each
discipline, however, defines the term differently, depending on what is being
measured.
Image
of galaxy NGC 4945 showing the
huge luminosity of the central few star clusters, suggesting there are 10 to
100 supergiant stars in each of these, packed into regions just a few parsecs across.
In astronomy, luminosity measures
the total amount of energy emitted by a star or other astronomical object in joules per second, which are watts. A watt
is one unit of power, and so just as a light
bulb is
measured in watts, so too is the Sun, the
latter having a total power output of 3.846×1026 W. It is
this number which constitutes the basic metric used in astronomy and is known
as 1 solar
luminosity.Radiant power, however, is not the only way to conceptualize brightness, so
other metrics are also used. The most common is apparent magnitude, which is the perceived brightness of an object from an observer on Earth at visible wavelengths.
Source: wikipedia, NASA
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