I've never heard any solar physicist refer to "Sun". I have heard "the Sun" and ...

I've never heard any solar physicist refer to "Sun". I have heard "the Sun" and "Our Sun".

"The Boss said please take the day off"

"Our Boss is nice"

"Jill is the boss"

"The Sun is bigger than any planet in our solar system"

"Our Sun is 8 light minutes away"

"Sol is the name of our sun"

I've not once heard a solar physicist use "sun" as a name

"Sun is bright" - bad grammar