Can we See changes in Nebula's?

[Woggles]

Hi Everyone. I was just read the article posted here at space about the Orion Nebula ( http://www.space.com/spacewatch/orion-c ... 00203.html ) and a question popped up! lol. Ok here goes. We all seen many pictures of different nebulas, but from my perspectives is that, those pictures never seem to change. The pictures shown on different webs site all seem the same. i.e. Orion nebula pictures taken say 5 years ago look the same as the one shown here today. Now is it the same picture shown over and over again or are the sizes and distances so great that we can’t discern the changes?

 

[MeteorWayne]

It's the latter. The sizes and distances are so great, that we can't see any changes.

We can see changes in individual stars and supernova remnants, where the distance scales are much smaller.

 

[Saiph]

definetley a size issue.

Found a link about the pillars of creation (another popular nebulae image) saying that those pilars are about 4 light years tall...


They'd have to have gas velocities a good fraction of the speed of light (1% or more) to see any changes over the span of a few years.

As the motion is a lot less than that, you won't notice any change over a human lifetime, maybe something small over a thousand years...but not much at all.

 

[SpaceTas]

I can think of 2 cases, aside from novae/supernovae shells; Hubble's variable nebula, and some of the clouds around TY-Corona Australis. Both are reflection nebulae, so it is really shadows/light moving about, rather than physical motions. A shadow can move a lot faster than the object. It is possible to get apparent faster than light changes in illumination.

link to image of TY R-Corona Australis region http://antwrp.gsfc.nasa.gov/apod/ap090605.html
with a close up of the 2 variables and nebulahttp://www.physics.adelaide.edu.au/~pmcgee/wpics/tyvri.jpg
and a link to Hubble's variable nebula showing changes http://www.asahi-net.or.jp/~rt6k-okn/nebulae/hubblem.jpg

 

[Woggles]

Thanks everyone. Hey SpaceTas wow those links were awesome!! Thanks