New theory of evolution for spiral galaxy arms

Apr 21, 2011
Image Caption: Snapshots of face-on view of a simulated disc galaxy. A Brighter colour indicates higher density. The Image shows two examples of star particles: the red star are travelling at the leading side of the arm, and the blue star are at the trailing side. It can be seen that the blue and red stars interchange their radial distances, with rapid migration within 40 million years. The dotted lines trace circles with radii of 4, 5 and 6 000 parsecs (1 parsec = 31 trillion kilometres), to guide the eye.

(PhysOrg.com) -- A study of spiral patterns found in galaxies like our Milky Way could overturn the theory of how the spiral arm features form and evolve. The results are being presented by postgraduate student, Robert Grand, at the Royal Astronomical Society’s National Astronomy Meeting in Llandudno, Wales this week.

Since 1960s, the most widely accepted explanation has been that the features move like a Mexican wave in a crowd, passing through a population of stars that then return to their original position.  Instead, computer simulations run by Grand and his colleagues at University College London’s Mullard Space Science Laboratory (MSSL) suggest that the stars actually rotate with the arms. In addition, rather than being permanent features the arms are transient, breaking up and new arms forming over a period of about 80-100 million years.

"We have found it impossible to reproduce the traditional theory, but stars move with the spiral pattern in our simulations at the same speed. We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years. We found that stars are able to migrate much more efficiently than anyone previously thought. The stars are trapped and move along the arm by their gravitational influence, but we think that eventually the arm breaks up due to the shear forces," said Grand.

In the simulations, Grand found that some stars gradually move outwards and inwards along the spiral arms. Stars travelling at the leading side of the spiral arm slide in towards the centre of the disc, whereas the travelling at the trailing side are kicked out to the edges.

"This research has many potential implications for future observational astronomy, like the European Space Agency's next corner stone mission, Gaia, which MSSL is also heavily involved in.  As well as helping us understand the evolution of our own galaxy, it may have applications for regions of star formation," said Grand.

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User comments : 16

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6_6
1.3 / 5 (15) Apr 21, 2011
I don't know about anyone else, but I feel lied to when I learned photos of galaxies are all fabricated and photo-shopped and actually don't look that in real life.
Pyle
4 / 5 (8) Apr 21, 2011
@6_6 I have no idea what you are talking about. Go to Hubblesite.org. Those images aren't "fabricated and photo-shopped" They really look like that in real life.

The image on the article is a "simulated galaxy". It isn't real and wasn't presented as such. The only real galaxy that I am sure is fabricated in every "outside looking in" image is the Milky Way and that is on account of us being in it and not having a very good vantage point to see it.
FrankHerbert
1.1 / 5 (56) Apr 21, 2011
6_6 is pretty stupid. Just look through his post history.
Pyle
3 / 5 (4) Apr 21, 2011
Yes, but to leave that offal for those unfamiliar with history seemed an offense to the authors of the article.
Moebius
3.5 / 5 (4) Apr 21, 2011
He probably means the addition of colors.
omatumr
1 / 5 (8) Apr 22, 2011
I see evidence that the galaxy originated from fragmentation of a central object.

Neutron repulsion is the powerful repulsive nuclear force that probably caused this:

In March 2001 it was first reported: Excess nuclear rest mass shows that neutron repulsion is the source of nuclear energy that powers the Sun, heats Earth, and sustains life ["The Sun's origin, composition and source of energy" by Manuel, Bolon, Zhong and Jangam, 32nd Lunar Science Conference]:

http://xxx.lanl.g.../0411255

This empirical finding in nuclear rest mass data from the Brookhaven Nat'l Lab was ignored by mainstream scientists for 10 years, until earlier this month when excess nuclear mass was reported in proton/anti-proton collisions ["Invariant mass distribution . . . 1.96 TeV" by 499 scientists (Aaltonen, . . . Zeng, and Zucchelli)

http://arxiv.org/...4.0699v1
astrobobo
5 / 5 (2) Apr 22, 2011
Well this may sound silly but I managed to "simulate" a spiral galaxy by rotating my beer glass :) Try it! There should be just a little foam left.
Modernmystic
4.4 / 5 (8) Apr 22, 2011
I see evidence that the galaxy originated from fragmentation of a central object.


When I saw this, I KNEW this was coming...

Neutron repulsion is the powerful repulsive nuclear force that probably caused this:


:)

Is non-existent neutron repulsion responsible for global warming too?
LKD
not rated yet Apr 22, 2011
I look at the simulations and it feels wrong. I don't see the form defined enough structurally. Am I alone in this opinion?
Pyle
4 / 5 (4) Apr 22, 2011
I see evidence that the galaxy originated from fragmentation of a central object.

It is a SIMULATED galaxy. Resultant of a computer simulation. I am pretty sure fragmentation of a central object as you suggest isn't in their model in the way you mean. Nice try though.

Is non-existent neutron repulsion responsible for global warming too?

My understanding is that omatumr feels solar activity is likely a major cause of climate change and that we can understand it better if we embrace NR and give him a Nobel Prize.
omatumr
1 / 5 (6) Apr 22, 2011
Neutron repulsion is the powerful repulsive nuclear force that probably caused this:

Is non-existent neutron repulsion responsible for global warming too?


See experimental evidence below:

http://xxx.lanl.g.../0411255

www.springerlink....6685079/

http://xxx.lanl.g.../0410168

http://arxiv.org/.../0609509

http://arxiv.org/...2.1499v1

http://arxiv.org/...4.0699v1

With kind regards,
Oliver K. Manuel
that_guy
5 / 5 (2) Apr 22, 2011
Neutron repulsion is the key. It is more powerful than snake oil, yet soft as a baby's bottom.

With Warm Regards,

That Stratovarius-octavio-strunheimer the third Guy.
(AKA That_Guy)
Beard
5 / 5 (1) Apr 25, 2011
We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years.


I just want you to stop for a moment and reflect upon the fact that this quoted sentence exists.
kaasinees
3 / 5 (2) Apr 25, 2011
Well since matter happens to clump together i think its naturally that under the right conditions you ge a spiral arm galaxy. Meaning that if the galaxy is young and nothing interfered with its evolution than in its event horizon, matter will "clump" together and look like arms.

Correct me if i am wrong?
frajo
3.7 / 5 (3) Apr 25, 2011
We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years.


I just want you to stop for a moment and reflect upon the fact that this quoted sentence exists.
My reflection says that natural languages lack the bracket feature of less-natural languages. Otherwise, it would be easy to tell
"We simulated {the evolution of spiral arms for a galaxy with five million stars} over a period of 6 billion years."
from
"We simulated the evolution of {spiral arms for a galaxy with five million stars over a period of 6 billion years}."
that_guy
not rated yet May 05, 2011
I see evidence that the galaxy originated from fragmentation of a central object.

It is a SIMULATED galaxy. Resultant of a computer simulation. I am pretty sure fragmentation of a central object as you suggest isn't in their model in the way you mean. Nice try though.

Nice catch pyle