Here's the breakdown:
* Supernova 1987A: The supernova observed in 1987, known as Supernova 1987A, occurred in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way.
* Distance: The Large Magellanic Cloud is about 168,000 light-years away from Earth.
* Light Travel Time: Light travels at a finite speed, roughly 299,792 kilometers per second (186,282 miles per second). This means it takes time for light from distant objects to reach us.
* Observation Delay: Since the Large Magellanic Cloud is 168,000 light-years away, the light from the supernova explosion took 168,000 years to reach Earth. Even though the explosion happened 169,000 years ago, we only observed it in 1987 because that's when the light finally reached our planet.
In simpler terms: We are seeing events in the universe as they were in the past, because the light takes time to travel to us. So, when we observed the Supernova 1987A in 1987, we were actually seeing an event that happened 169,000 years earlier.
