If all of the stars ceased to exist today, it would be impossible for us to ever determine this fact. The reason is that they have been sending light our way for 14 billion years and it would take that long again for us to see the last of it. It may have already happened.
Even if our nearest star, the sun, ceased to exist, we would not know for over 8 minutes. The next nearest star to the earth could have ceased to exist 3 years ago and we would not know yet.
This line of reasoning leads us to the inescapable fact that we are always living in the past and we can only approximate an instant called "now" for those things which are very near to us.
So our eyes are a little like a time machine always seeing things in the past. The moon is about 1.29 seconds away, the sun is about 8 1/3 minutes away, and Mars is around 14 minutes distant.
And, of course, we can see all the way back to about 14 billion years by looking at the most distant stars.