# Do nebula's move? (Help calculating where things will be in the future)?

1. Jan 24, 2012

### piareround

Hey guys I been trying to figure out the location of various objects from a galatic perspective using celestia.

One particular object that has been of help to me is the Horsehead Nebula.

While doing this, I quickly realized that star's move, so a galactic map (if you could make one large enough) of all the major stars would be inaccurate in something like 500,000 years.

However, this thought experiment has got me wondering. If star's move and drift around the galaxy with a set total velocity, do nebula's and gas clouds also have measurable velocities? A velocity besides their constant expansion?

If they do move, how could one figure out the new Declination, Right Ascension, or any of the angular/distance coordinates of a nebula 100,000 sidereal years or some long time in the future?

Is it a simple kinetmatics or dynamics problem using proper motion? Are there any tutorials that would help?

Last edited: Jan 24, 2012
2. Jan 24, 2012

### piareround

Ok seriously this might sound too easy to you guys. Nonetheless, every time I try too look up and search for the proper motion of a major nebula like the crab, horsehead, or even the hourglass nebula, I come up empty handed.

3. Jan 24, 2012

### obafgkmrns

There's no doubt that they move -- supernova remnants will have some trace of the original star's proper motion, for example. The problem is that nebulae all lie at large distances (the Gum Nebula, one of the nearest, is about 700 parsecs off), and they are all, well, nebulous. That makes any proper motion exceeding small while at the same time making it difficult to define a center of mass.

Note, however, that nebulae can be observed to change in time. See http://hubblesite.org/newscenter/archive/releases/1996/22/video/a/ for example.

4. Jan 26, 2012

### piareround

Cool thanks for the insight obafgkmrns

5. Jan 27, 2012

### shifty88

isn't our solar system orbiting around the galaxy in unison with all the other stars and nebula?
resulting in the position of stars relative to earth at the same distance constantly

6. Jan 27, 2012

### Fuzzy Logic

I wouldn't say in unison. They all move relative to one another, but there are other effects besides galactic orbit that affect their movement. Most importantly would be gravity. Eventually all matter converges under gravity (barring inflation). So while the stars (and the nebulae) orbit the galaxy, they are also being drawn into the center and attracted to each other.

7. Jan 27, 2012

### Fuzzy Logic

@ the OP,

Mass is mass. If you know the mass of the nebulae, you can calculate the same as you would for any other celestial body.

8. Jan 27, 2012

### HallsofIvy

When I first read this, I thought you meant "look up" in the sky to see the motion!:tongue: