A heliologist is someone who studies the sun. They may also be called solar astronomers or solar physicist.
A heliologist studies the Sun.
A heliologist is a person who studies the sun, and solar activities. Heliologists are similar to astronomers except that their primary focus on one the sun and the effects of the sun on the atmosphere.
Heliologist
A person who is involved in the astronomical study of sun is called a Heliologist
The sun, moon, stars, planets, and other celestial bodies collectively, would be the objects of study for astronomers. They would also be of interest to cosmologists and astrophysicists; there would also be specialists within these disciplines - for example the sun specifically would be of interest to a solar physicist or heliophysicist (or heliologist), planets would be the domain of a planetary scientist or planetary physicist, and so forth.