Immigrant Sun: Our star could be far from where it started in Milky Way

Sep 15, 2008
This image is from a computer simulation showing the development and evolution of the disk of a galaxy such as the Milky Way. Credit: Rok Roškar

A long-standing scientific belief holds that stars tend to hang out in the same general part of a galaxy where they originally formed. Some astrophysicists have recently questioned whether that is true, and now new simulations show that, at least in galaxies similar to our own Milky Way, stars such as the sun can migrate great distances.

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 Roškar, a doctoral student in astronomy at the University of Washington.

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

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.

Roškar is lead author of a paper describing the findings from the simulations, published in the Sept. 10 edition of the Astrophysical Journal Letters. Co-authors are Thomas R. Quinn of the UW, Victor Debattista at the University of Central Lancashire in England, and Gregory Stinson and James Wadsley of McMaster University in Canada. The work was funded in part by the National Science Foundation.

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 simulations of the formation and evolution of a galaxy disk from material that had swirled together 4 billion years after the big bang. (See a simulation video at www.astro.washington.edu/roska… M_hr_rerun_angle.mpg">www.astro.washington.edu/roska… M_hr_rerun_angle.mpg.)

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.

Migrating stars also help explain a long-standing problem in the chemical mix of stars in the neighborhood of our solar system, which has long been known to be more mixed and diluted than would be expected if stars spent their entire lives where they were born. By bringing in stars from very different starting locations, the sun's neighborhood has become a more diverse and interesting place, the researcher said.

Such stellar migration appears to depend on the galaxy having spiral arms that twist their way through the galaxy, as are present in the Milky Way, Roškar said.

"Our simulated galaxy is very idealized in the formation of the disk, but we believe it is indicative of the formation of a Milky Way-type of galaxy," he said. "In a way, studying the Milky Way is the hardest thing to do because we're inside it and we can't see it all. We can't say for sure that the sun had this type of migration."

However, there is recent observational evidence that such migration might be occurring in other galaxies as well, he said.

Roškar noted that the researchers are not the first to suggest that stars might be able to migrate great distances across galaxies, but they are the first to demonstrate the effects of such migrations in a simulation of a growing galactic disk.

The findings are based on a few runs of the simulations, but it is expected additional runs using the same parameters and physical properties would produce largely the same results.

"When you swirl cream into a cup of coffee, it will rarely look exactly the same twice, but the general process, and the resulting taste, is always the same," said Wadsley, the team member from McMaster University.

The scientists plan to run a range of simulations with varying physical properties to generate different kinds of galactic disks, and then determine whether stars show similar ability to migrate large distances within different types of disk galaxies.

Source: University of Washington

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User comments : 14

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ofidiofile
4 / 5 (1) Sep 15, 2008
i take it the whole planetary system is pulled along by the star?

interesting when you think about it: the word for "planet" comes from the greek for "wanderer". it'd be awesome is the whole damn solar system wandered!
disco
2 / 5 (4) Sep 15, 2008
two balloons one inside other. pop inside one.implosion explosion?
disco
4.3 / 5 (3) Sep 15, 2008
i was born under a wonderin star.lee marvin
brant
1.8 / 5 (5) Sep 16, 2008
Why dont they simulate GOD??
jeffsaunders
5 / 5 (1) Sep 16, 2008
I thought the standard model included that our sun rotated through the spiral arms already. Looks like I was getting behind the times and the times have now caught up.

Its a bit like fashion - If I keep that old jacket it will become fashionable again one day.
EarthScientist
1 / 5 (10) Sep 16, 2008
Here We go again,Morons that were there ,got it all figured out,just took 100 thousand hours of computer time ,while they chewed on energy bars and checked their e-mails for dates they fished for. My,My, who did this, such foolish boys believing their goom-ba Phd. who thinks the
"Big bang" did the big thing.Morons,who just cannot see the engineered system that was designed here and everywhere else,Stars ,my boys sit on cymatic nodes,and are the circuit connectors to provide continuity of process throughout the system,Old Papa Doc here is bettah than your little Doc-Tah. He just is, you poh boys actually pay for that garbage,and I continually state you ah needs a ree-fund.
Might try 1 -800 Call Sam
Trippy
4.7 / 5 (3) Sep 16, 2008
Here We go again,Morons that were there ,got it all figured out,just took 100 thousand hours of computer time ,while they chewed on energy bars and checked their e-mails for dates they fished for. My,My, who did this, such foolish boys believing their goom-ba Phd. who thinks the
"Big bang" did the big thing.Morons,who just cannot see the engineered system that was designed here and everywhere else,Stars ,my boys sit on cymatic nodes,and are the circuit connectors to provide continuity of process throughout the system,Old Papa Doc here is bettah than your little Doc-Tah. He just is, you poh boys actually pay for that garbage,and I continually state you ah needs a ree-fund.
Might try 1 -800 Call Sam


Did you read the article?
The results are not dependent on the BBT being accurate.

The BBT doesn't even enter into it, apart from as a reference point for time.
Pogsquog
not rated yet Sep 16, 2008
This is hardly surprising.

We already know that Stars wander around under influence of gravity, just like planets, moons, asteroids, etc.

When they come close to each other, they interact. I expect that there are some stars in retrograde orbits, many in elliptical orbits, some get ejected from the galaxy, etc. In any case, the orbital period around the galactic centre must follow Kepler's laws, which means that the ones closer to the centre must orbit faster than those further out, hence gas and stars that 'started' next to each other would become stretched out into a swirl over time.

The only difference between the galaxy and any other system behaving under gravity is that it is very 'young' - i.e. there haven't been all that many interactions since it formed (the sun has only orbited the galactic centre about 20 odd times since it formed)... which is fortunate for us, since any interaction between stars has a fair chance of putting both into elliptical orbits that might end with them plummeting into the galactic core.

I would point out that some nearby stars, such as wolf 424, are moving at tremendously different speeds to the Sun (it is moving at 555Km/s relative to the Sun, or 1/540 light speed). In 7000 years, it will have moved to within a light year of the Sun, from its current position 14.2 light years away.
D666
5 / 5 (4) Sep 16, 2008
Did you read the article?
The results are not dependent on the BBT being accurate.


Do you seriously think he cares? Whack-a-doodle alert, big time.
robbycoats
2.3 / 5 (3) Sep 16, 2008
Yes, yes ,yes stars move we all know, orbits, gravitational interaction, etc. You all are missing the point... The article is referring to a unique interaction between stars and the spiral arms of the galaxy that they pass through. Spiral arms of a galaxy are NOT formed the same way they would be in a whirl-pool; the stars are not in this formation because they are all being sucked toward the center. Stars are in fact all mostly in nice circular orbits around the center of the galaxy just like our earth around our sun. The spiral arms of the galaxy are formed by gravity waves propagating from a super-massive, and rapidly spinning black hole at the center of the galaxy. If you were to take a stick (each end representing a pole) and float it in a pool and spin it rapidly, waves would propagate from each end and spread out into the pool. As a wave is formed at any point in time and sent outward, another is not far behind, and thus the waves will look like spiral arms. This interference of gravity waves in a galaxy actually expands and shrinks space itself on a local level; where you see stars grouped together in arms is where space itself is actually more dense and thus the distances between stars shrink.

So, no we have discovered that this is also maybe having an effect on a stars orbital period around, or its distance from, the center of the galaxy.

duh.
MGraser
3 / 5 (2) Sep 16, 2008
Nothing of value to contribute, but I couldn't help thinking...imagine being, say, 60,000 hours into it and thinking, "Oh, cr*p! I forgot to change the [fill in code change here] before I pressed execute!" Sorry, just struck me as funny and I had to make you read it...
KB6
not rated yet Sep 16, 2008
"Why dont they simulate GOD??"

--
They don't need to because, according to the Bible, we already ARE the simulation of God.

"So God created man in his own image, in the image of God created he him; male and female created he them." Genesis 1:27 (KJV)

That's why, contrary to popular opinion, it's OK to play God.
robbycoats
3 / 5 (2) Sep 16, 2008
f u whoever rated me a 1, the effect of these waves has been directly observed in distant galaxies.
EarthScientist
1 / 5 (2) Sep 17, 2008
Oh Yes, Senor, Trippy ,I did read the article,and their whole hypothesis is ganged with their big bang time frame,and by the way Senor Trippy,we at Earth Service have told your kinda folks over and over that the system is approx. 50 thou years old,and we were not kidding.

Ya see Senor Trippy,when Papa here understands the growth of the salts and the growth of the spheres,of course including the Sun,which must be replaced at 10 K intervals,he really does chuckle at the big bang Idiots(Capitaslized for specific emphasis) Have you pondered the eco-system provided by my people and of course you just do not seem to grasp the cymatic nodes bringing forth the processes of this eco-system and the gases from light frequency,does it not smell pretty good? Big Bangs,my ,my.........