When you look at the night sky, you're actually looking back in time. The star Sirius is about 8.6 light-years away, so you're seeing it as it was 8.6 years ago. Some of the stars we see might have already died, but we won't know for years!
It's All Historical
Every star you see in the night sky is in the past. Some are hundreds of light-years away, some thousands. The most distant stars we can see are millions of years old by the time their light reaches us.