There has never been any credible, reproducible evidence of the existence of
aliens. Mainstream researchers refer to people who study them as "wing nuts".
Bioluminologist .
He is called 'unemployed' and 'seeking other opportunities', since there are no aliens available to study.
A physicist and a pathologist. There is no single term for someone that does both. A pathologist may specifically study the effects of gravity on vaccines
An astronomer
Someone who studies the planet Mars is called an areologist.
You call someone that studies metal a metallurgist.
A physicist.
Lonely. Xenophilic, perhaps.
a person who studies planets is a planetologist.
There is no special name for someone who studies Hebrew.
An Anthropologist.
malacologist
euclidist
Gemologists
psychologist
A numismatist.
A Zoologist