Why different sort order with unicode?

Why different sort order with unicode?

I have this query:
select ' ' C union
select '*' C union
select '-' C
order by C
And the result is space, asterisk and dash, but if I have unicode
characters like this:
select N' ' C union
select N'*' C union
select N'-' C
order by C
I get space, dash, asterisk. Can anyone explain why?
Thanks!