Hi there! 
I found this PG too: Best way to recreate the star from the image - Questions - Babylon.js (babylonjs.com), but it’s more for point stars, not a big sphere stars.
I agree that the sun helper looks like a good starting point, maybe you can also play with the Glow Layer Making Meshes Glow | Babylon.js Documentation (babylonjs.com).
Anyways, I think @PatrickRyan will have more useful ideas than me 