Answer:
"If you enjoy learning about stars, visit a planetarium."
Step-by-step explanation:
The first letter of every starting sentence needs to be capitalized, therefore, that is the first punctuation error.
Second, "If you enjoy learning about stars," is a dependent clause, which means it cannot stand on its own. "Visit a planetarium" is an independent clause, which means it can stand on its own. This is a complex sentence, therefore, a comma should go right after the dependent clause.
Lastly, the period. A period is a way to end a statement. It may not seem crucial, but it is when it comes to fixing grammatical errors.
I hope you found this answer helpful, let me know if you have any questions.
~Jinachi~