If Polaris were to go supernova today, no one currently on Earth ever know it happened because it would take 434 light years to reach the Earth
Explanation:
The Polaris or the North Star that we can see at the North Pole of the Earth in the night historically dates back to 434 years in the past. If the Polaris becomes a supernova or if it dies now, it will take 434 years in the future from now to know about it.
This is simply because ‘one light year is the distance traveled by light in one year’. Hence currently, one cannot know about what happened to the Polaris supernova even if it happens now.