Astronomy/Physics Question?

Yes, it's possible, but the situation is rare.

Unfortunately, most of the time objects are in either relatively dust-free areas (so we don't see the light expanding), or the dust is so heavy that it's difficult to image at all.

However recent observations have used this effect to give some information about a supernova that wasn't imaged directly. The dust isn't homogeneously arrayed for us to directly see the expanding shell of light, but it is enough for us to gather data on it.

http://www.youtube.com/watch?v=9Cp4uNnUrCo

EDIT:

"If somebody flashed an extremely bright laser through dust at a great distance from us, would we see the light travel through the dust?"

If the dust was continuous, sure. Different patches would light up at different times. We should be able to map this as the motion of the light.

I assume you're asking about this because the astronomical distances allow you to see the motion of the light at a more human timescale. But in principle, if you had a fast enough camera, you could do similar things in the laboratory.

http://web.mit.edu/newsoffice/2011/trillion-fps-ca...

Do you mean a pulsar when you say 'pulsing light'? If so you as an observer with your own eyes would see simply the star itself, and since light travels through the EM field at 'c' you as the observer would see everything illuminate at the same time.

However due to red-shift and hubble's work we could find evidence for this spreading out of light.

I suppose you mean to ask if the length of gas or dust would appear to bands of brightness like a type of ripple. Yes and no. Your mind would present the effect because it its logical to you but in reality even if you were going the speed of light, light would still be travelling that much faster. The only reasons we see twinkling stars is because of stuff moving through the light. In the end, if you watched a beam of light travel through gas or dust, the entire thing would seem to dim and brighten as a whole.

because light get scattered in dusty like medium