How do nebulae keep their shape,such as the horsehead nebulae ?

Question

How do nebulae keep their shape,such as the horsehead nebulae ?

Answer 1

The shape is random, made by gases that are slowly coming together. They light up because young stars are beginning to form within them and exciting the gas. They don't keep their shape, its changing over time. Its just too slow for anybody to notice within one human lifetime. In a few million years, the shapes may have changed enough to warrant a new name for some of them.

Answer 2

Nebulae don't keep their shapes, they are constantly changing.  But because they are so large and so far away we don't see the changes in the short time we have been observing them.

Most nebula are either expanding due to their own internal motion, or being eroded or blown around by the radiation of nearby stars.

And minute changes in the Pillars of Creation in the Eagle Nebula have been detected since Hubble imaged them in 1995.  And in 2007 scientists using the Spitzer discovered evidence that they were likely destroyed by a supernova explosion about 6,000 years ago, but the light showing the changes won't reach Earth for another thousand years.

Answer 3

Nebula keep their shape due directly to the fact that they are in space and there is no atmosphere there, therefore, shapes, sizes, etc., etc., maintain itself.  Anyway, dust and gas maintain the shape, in which they were created.  However they will diffuse over time.  

Stars that blow up, or supernova, or "whatever" that blew up to cause the nebula, just do exactly that----there is no conscienceness involved.  The "shape" they have upon the explosion, is the "shape" they maintain, well, almost forever!  Mainly, because they did this "thing" in space!

Answer 4

They don't, they are clouds of gas and dust which are constantly changing shape. Currently it looks like a horses head but in a few million years it won't.

It will change it's shape, but it will do it very slowly, since it is 3.5 x 2.6 light years. A light year is a VERY long way, so that is one HUGE horses head.

Answer 5

Magic! ...

Sorry, couldn't resist ;)

They do change, but over time.