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Name: Janette L Gubala
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Question:
How bright do stars shine?



Replies:
The amount of light a star emits depends on how much nuclear fuel is being consumed and on whether any of the emitted light can escape the surface of the star. The light a star emits during its lifetime will change. When a star exhausts its nuclear fuel, it can expand and become a red giant, or it can collapse and become a black hole. There is lots known about stars and the life they evolve through.

Samuel P Bowen


The brightness of stars as seen from the Earth is called "apparent visual magnitude"; it is designated 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


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