I want to create a space simulation, but I'm facing some difficulties when I try to create a realistic sun.

Currently, I've a simple ***Point Light*** inside a sphere. But for some reasons, no matter the intensity and the attenuation radius of this light, the other objects in the scene (the planets, for instance) aren't lit any more if their centre are separated by more than 1.5 kilometres approximatively.

![Lit planet](https://i.stack.imgur.com/PUAbS.png)
![Unlit planet](https://i.stack.imgur.com/ATr3X.png)
*(Top) Lit planet, 1.4 km away from the sun.*  

*(Bottom) Unlit planet, 1.5 km away from the sun.*

Do you know what can cause this phenomenon? Is there a way to bypass it? If not, how can I create a realistic sun light in a large space simulation?