In HUbble vs Webb pictures we see the dying start picture. Why after 24 years it is still is a dying explosion scene. Shouldn’t be an instant?

Question

NASA released the latest pictures from Webb. You can see a link to a dying start here:
https://webbtelescope.org/contents/news-releases/2022/news-2022-033?Collection=First%20Images

I am not sure, how it is possible that after 24 years, it seems the dying star explosion is still in a very similar size and shape. Can someone please what exactly we are observing in this picture.

In: 2

Answer 1

Quite simply it’s scale.

The gas cloud is expanding at a considerable rate, say 30 km/s.

But that particular cloud is about 300 light years across already.

thats about 3,000,000,000,000,000 km across

At 30 km/s for 24 years, the edge has moved… 22,720,986,720 km.

That’s about… 0.001% larger. A bit hard to notice.

Edit for clarity: Numbers above for the “carina” nebula, that big one. My mistake!

Numbers for the southern ring nebula: At 0.4 ly across (thanks cornflakes_91) we adjust the numbers to 20 km/s expansion, and get ~0.1% increase in size. Still hard to notice.