a person who studies planets is a planetologist.
Astronomer
An astronomer.
astronomist
You call someone that studies metal a metallurgist.
A physicist.
Someone who studies the planet would be called a Geologist. Someone who studies Space would be called an astronaimist. Both work together to gather information about earth.
There is no special name for someone who studies Hebrew.
florist
An Anthropologist.
Microbiologists
Brocollogist
A Zoologist