They wrote it incorrectly not just once, like a typo, but several times!
The size of the remnant implied that the blast wave from the supernova had expanded at nearly 20 million miles per hour over the nearly 1,000 years since the explosion occurred.
I wonder if whoever wrote this is also writing on the subject of "global warming"?
Yep, our science reporting is in good hands!
Nowhere does the article say that the supernova took place 1000 years ago.
It says that the ring of gas traveled x distance in the 1000 years since the explosion occurred, which is correct, because what we're observing IS where the gas ring was 1000 years after the explosion. The fact that we're observing it 7000 years after the event doesn't change that.