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STARS AND BEYOND
Lesson 1 - Page 4

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BRIGHTNESS

The second way stars are classified is by brightness, or absolute magnitude. Absolute magnitude depends on the energy output of a star. Brighter stars release more energy. A problem with this classification is that a very bright star that is far away looks less bright than a dim star that is close by (relative brightness). This issue is fixed by mathematically comparing the brightness of stars as if they were all the same distance from Earth. The chart below shows some examples of stars and their absolute magnitudes. Note that the lower number indicate brighter stars. How much brighter is Spica than our Sun?

 

Star

Absolute Magnitude

Brightness compared to the Sun

Proxima Centauri

15.45

1/17700

Barnardís Star

13.24

1/2310

Sun

4.83

1

Sirius

1.45

22.5

Arcturus

-0.31

114

Spica

-3.55

2250

 

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