Fact 1: Nuclear reactions in stars causes stars to produce light.

Fact 2: June Summer Triangle Three bright stars light up the summer sky.

Given the two facts above, answer the question "Nuclear reactions in stars cause them to brighten up what?" with the following options: 
- the morning grass
 - the elemental waves
 - an object
 - the summer sky
 - hydrogen and oxygen
 - Change colors
 - the evening tide
 - an electron lens


 

    the summer sky     