Our sun could be far from where it started in the Milky Way

Washington, September 16 : New simulations have shown that a least in galaxies similar to our own Milky Way, stars such as ours can migrate great distances, which implies that our sun could be far from where it started.

This questions a long-standing scientific belief holds that stars tend to hang out in the same general part of a galaxy where they originally formed.

What's more, if our sun has moved far from where it was formed more than 4 billion years ago, that could change the entire notion that there are parts of galaxies - so-called habitable zones - that are more conducive to supporting life than other areas are.

"Our view of the extent of the habitable zone is based in part on the idea that certain chemical elements necessary for life are available in some parts of a galaxy's disk but not others," said Rok Roskar, a doctoral student in astronomy at the University of Washington.

"If stars migrate, then that zone can't be a stationary place," he added.

If the idea of habitable zone doesn't hold up, it would change scientists' understanding of just where, and how, life could evolve in a galaxy, he said.

Using more than 100,000 hours of computer time on a UW computer cluster and a supercomputer at the University of Texas, the scientists ran a simulation of the formation and evolution of a galaxy disk from material that had swirled together 4 billion years after the big bang.

The simulations begin with conditions about 9 billion years ago, after material for the disk of our galaxy had largely come together but the actual disk formation had not yet started.

The scientists set basic parameters to mimic the development of the Milky Way to that point, but then let the simulated galaxy evolve on its own.

If a star, during its orbit around the center of the galaxy, is intercepted by a spiral arm of the galaxy, scientists previously assumed the star's orbit would become more erratic in the same way that a car's wheel might become wobbly after it hits a pothole.

However, in the new simulations the orbits of some stars might get larger or smaller but still remain very circular after hitting the massive spiral wave.

Our sun has a nearly circular orbit, so the findings mean that when it formed 4.59 billion years ago (about 50 million years before the Earth), it could have been either nearer to or farther from the center of the galaxy, rather than halfway toward the outer edge where it is now.

ANI