This sounds like a philosophical probe. You could say that a scientist is an explorer as (s)he is going in to new, maybe unknown 'territory' and seeing what's there. Our common perception of exploration is that it relates to geography but in more general terms it can include science, art, or anything that enhances our knowledge and understanding of the world, or of the universe.

A scientist studies science and does research in scientific fields. E.g. people trying to develop vaccines are scientists. An explorer travels to places (especially little-known or remote ones) to find out more about them. E.g. someone going up Mount Everest is an explorer. You could have someone who is both a scientist and an explorer.

An expolorer is not always a scientist, altough they both make researches. Scientist has a special education such as postgraduate school, makes dissertation, and write articles for scientific journals. If somebody conduct researches, but don't have scientific aducation and publication on the topic of the dissertation, there is an explorer only.

I believe the synonym for a "scientist" you are looking for would be a "researcher".