Possible Clues:

• Big name in satellite radio
• A star not to be taken lightly, as some might say
• Harry Potter's godfather __ Black
• Dogstar
• 13's creation - star seemingly eclipsed?
• XM Radio alternative
• Brightest star in the sky also known as the Dogstar
• The Dog Star, brightest of the fixed stars
• The knight one will see at night with us
• At 19, as 18 said, you cannot be 5