Thanks for the invite OWN
Are the stars stationary, or do they move?
The answers given so far have been excellent
Simply put the stars move. Take our star (good old Sol) for example, we are in a spiral galaxy in which our star wonders around at a speed of roughly 200 km/s making one orbit every (number could be high or low here) 230 odd million years. So, stars rotate within their own galaxies, and believe it or not, there are some stars wondering between
galaxies - ours potentially could be heading in that direction in a few billion years, give or take a couple of million
Ah ha, he says, but a little bit more movement occurs (I LIKE
your question joshilewis
) In addition to the movement within our own galaxy, the galaxies themselves, as a whole, are in motion. For example, our galaxy (the Milky Way Galaxy) and the Andromeda Galaxy are moving towards each other and will likely merge in 4 to 6 billion years. So, the stars as a whole in a galaxy are in motion, not just orbitally within the galaxy but as the galaxy moves. The estimated velocities of this movement are in the region of 600km/s for our galaxy and about 110 km/s for the Andromeda galaxy. I say estimated because of the peculiarities of requiring a frame of reference for measuring velocity of which there really is'nt for galactic movement.
For all we know there may be multiple universes and these universes are moving around each other providing yet another motion.
So, as I said, simply put, stars do move but at such a slow rate that for all intents and purposes, as Siobain said, in our lifetime we could consider them stationary for observational purposes.
For further information there are two methods of "seeing" star motion – the movement along the plane of the sky called "proper motion" and the movement along our line of sight called "radial motion". Previously discussed was redshift / blueshift which is the change in wavelength of the object. This is the measurement of radial motion. Proper motion is measured by taking the movement of an object relative to another distant "fixed" object. (JJ's initial statement :thumbs up: ). The "fastest" moving object visible to us is Barnard's Star (4th nearest star to Earth) which moves at a relative speed of about 10 arcseconds per YEAR) (1 arcsecond is approximately 0.0003 degrees – therefore 10 arcseconds is approximately 0.003 degrees). That's NOT a lot of motion – how many years before it has moved 1 degree?! I think that most stellar objects have a proper motion in the region of 0.1 arcseconds per year, ie. 0.00003 degrees per year!
I may be off a little in the figures I've given but that's as close as I can remember them.
Sorry if I've gone further than you required OWN but it's a lovely topic