TWO RHYMING RIDDLES

1)
I hang around the stars,
Though I'm found behind bars;
Without me, there's no serenity,
Yet I live in the midst of misery.
With thieves and villains I consort,
In prison you will find me;
But in court I will never be,         
Unless there are two or three.

2)
They are dark,
And always on the run;
Without the sun,
There would be none.

Answers:

1. Letter S 
2. Shadows