Ask A Scientist© Astronomy Archive

Question:  How bright do stars  shine?
janette l gubala

Answer:  The brightness of stars as seen from the Earth is called "apparent
visual magnitude"; it is designinated by "m subscript v" and is a
logarithmic scale like the Richter scale used for earthquakes.
The brightest star seen from the Earth's northern hemisphere is
Sirius, the Dog Star with a _m subscript v_ of -1.5 (the stellar
magnitude scale is one in which a negative number is brighter than
a positive number).
The absolute visual magnitude, designated by "M subscript v", gives
the true brightness:
Deneb (alpha Cygnus) has Mv = -6.9, and
Rigel (beta Orion) is almost as bright with Mv = -6.8.
On the absolute scale, Sirius is only Mv = +1.4; it *appears* to be
the brightest because of its nearby distance, only 2.65 parsecs.
hawley