A possible way to correct the pronoun references in the passage is:
"When astronomers study neutrinos, they defy all of the laws of physics."
A pronoun is a word used to substitute a noun or a noun phrase. A pronoun should clearly and unmistakably refer to a certain noun or noun phrase in the sentence to avoid ambiguity or uncertainty. That is what pronoun reference means. The word that is substituted or referred back to is called antecedent.
In the sentence we are analyzing here, the pronoun "it" does not have a clear antecedent. The nouns present in the previous clause are plural, but "it" is a singular pronoun.
To correct the pronoun reference, we can change "it" for "they", which is a plural pronoun and can be used to refer to "astronauts" in the first clause.
Therefore, we would have: "When astronomers study neutrinos, they defy all of the laws of physics."
