The correct article to use before the word "universe" is "a."
The choice between "a" and "an" depends on the sound that follows the article. "A" is used before words that begin with a consonant sound, while "an" is used before words that begin with a vowel sound.
Although the word "universe" starts with a vowel letter 'u,' it is pronounced with a "y" sound at the beginning, as in "you-niverse." Since the "y" sound is a consonant sound, we use "a" before "universe."
Therefore, the correct form is "a universe."