[Request] How was the age of the Cat's Eye Nebula (~1000 years old) calculated when it is ~3300 light years away?
How has light from the formation of that system reached us already?
Posted Mar 27, 2018, 7:22 AM UTC
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If it's 3300 light years away, then all the light we're seeing from it is 3300 years old. Light from it has reached us already because the actual supernova event that produced the nebula happened more than 3300 years ago.
That is, our information is delayed. Based on how it looks to us now, it looks to us like it's 1000 years old. But the actual nebula is 4300 years old. It's just that we won't get to see the 4300-year-old picture of it for a long time.
This is always the case with stuff that's way out in interstellar or intergalactic space. What we see is thousands, millions, or even billions of years younger than those things actually are. Astronomers are so used to this time-delay that it's easy to end up using sloppy wording that confuses the difference between the actual and the apparent age of these objects.
That makes sense. Thank you!