You have more problems than completely misusing switch.
You never GET a value for the number of stars/planets. You issue a prompt, but you ignore the user's response.
And your HTML is completely invalid.
You have your <style> in the <body> and your <input> in the <head>. Utterly backwards.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.