When the stars move out to more exterior parts of the galaxy, perhaps it is then when solar systems are born as on their journey they pick up orphan planets along the way. I wonder if solar systems even poach planets from other solar systems?
I'm sure someone will point to imaginary dark matter and dark energy as an explanation for erratic orbits. I would be more inclined to think that larger and smaller stars could have their orbits changed by the gravitational slingshot effect of simply passing near each other.
Some good research and a good demonstration of evaporative cooling but on a galactic scale. As a galaxy evolves and matter is collected into discrete particles (stars) its begins to exhibit the behaviours of an ideal gas. In that it has a 'temperature' measured as the average motion of the particles.
This is not like the temperature you can measure with a spectrograph or a thermometer, its just a way of stating the average orbital velocities of the particles due to gravitation. Thus it becomes possible for particle on particle interactions (slingshots) to transfer kinetic energy from one star to another. The star with the greater energy migrates outwards (or even leaves the galaxy altogether), while the other migrates inwards.
Thus over time, as stars age there is a general tendency for them to migrate towards the barycentre, 'cooling' while a small number escape entirely 'evaporate'.
Maybe we just don't understand what we're looking at. Time for a new model.
Dave Mikulec
Geez, I'm so tired of moving.
I'm more inclined to believe that these start were originally plotted incorrectly. Seems to me that a proper "Orbit" tends to be more or less fixed. Sure it may be eccentric, and gravity from transients would throw off a few, but for a whole constellation (30%!) to shift orbits, there's a fundamental mistake somewhere in the original calculations. The rationale provided for the change seems specious.

Personally, if 30% of the stars in the universe really HAVE shifted, I think we're headed for a lot of trouble in the future.

God is an amazing artist and designer! :)
Dave Lawrence
I dunno, you turn your back for 5 MINUTES . . . . .
How much of a shift could have occurred? I mean it supposedly takes 250 million years for our solar system to orbit the Milky Way. then of course once everything completes one orbit there will be some various changes. Isn't it pretty much the same way a hurricane works? When it rotates, it may still look like a hurricane, but the outer bands alter as they expand and contract.
Ernani Medenilla
How about Dark Matter, must have made particle move to other direction? How about an invisible hand... Dark Matter is an invisible hand! Who decides where this things go? We only observe and marveled over it, we can't do anything about it except we try to figure, nothing more. Same goes with life here on Earth I'm sure, with or without Evolution theory ideas.