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Gabriele Menefee
Gabriele Menefee

Fascinating.  Really, it's amazing that we can see that so clearly.  I can't wait until they land some probes there.

Susan Cronk
Susan Cronk

I'm curious as to what keeps the Crab Nebula together if it's just a collection of gases and space dust? Surely other objects moving through space would interact with it and cause it to shift or dissipate. Is it completely inert? It must have been in motion at some time and what caused it to stop?

V. Ali-Lagoa
V. Ali-Lagoa

@Susan CronkGood questions! To add to J H's answer: gravity affects everything, including gases and dust; in fact, stars are the result of the gravitational collapse of unstable portions of interstellar clouds. 

About the interactions with other objects, even though the nebula spans interstellar distances, space is mostly empty and I'd guess that gravitational interactions with other stars would be very weak compared to the forces driving the expansion. However, even if it was interacting with other stars we might take some very long time to notice, for the same reason that J H pointed out.


@Susan Cronk The crab nebula is in motion. It is expanding. It is only a thousand years since the nebula exploded. The material surrounding the core is moving outwardly at 1500 kilometers per second. Since it has a diameter of 11 light years, even that very rapid motion is not visible except over long periods of time. It has taken the full 1000 years for it to get to the current size.

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