UCI: Milky Way spiral product of intergalactic collisions
Posted: Thu Sep 15, 2011 8:45 am
Milky Way’s spiral arms are the product of an intergalactic collision course
University of California, Irvine | 2011 Sept 14
The Sagittarius impact as an architect of spirality and outer rings in the Milky Way - CW Purcell et al
Star-Crossed: Milky Way's Spiral Shape May Result from a Smaller Galaxy's Impact
Scientific American | John Matson | 2011 Sept 14
Milky Way Owes Its Shape to Crashes With Dwarf Galaxy
Space.com | Charles Q. Choi | 2011 Sept 14
Multiple dwarf strikes gave Milky Way its spirals
New Scientist | Justin Mullins | 2011 Sept 14
University of California, Irvine | 2011 Sept 14
UC Irvine models show dark matter packs a punch
UC Irvine astronomers have shown how the Milky Way galaxy’s iconic spiral arms form, according to research published today in the journal Nature.
A dwarf galaxy named Sagittarius loaded with dark matter has careened twice through our much larger home galaxy in the past two billion years, according to telescope data and detailed simulations, and is lined up to do it again. As the galaxies collide, the force of the impact sends stars streaming from both in long loops. Those continue to swell with stars and are gradually tugged outward by the Milky Way’s rotation into a familiar ringed arm.
It’s the weighty dark matter from Sagittarius that provided the initial push, the researchers said.
“It’s kind of like putting a fist into a bathtub of water as opposed to your little finger,” said James Bullock, a theoretical cosmologist who studies galaxy formation.
The smaller galaxy pays a steep price though – sucked inward repeatedly by the Milky Way’s mightier gravity, it’s being ripped apart by the blows, sending huge amounts of its stars and dark matter reeling into the new arms.
“When all that dark matter first smacked into the Milky Way, 80 percent to 90 percent of it was stripped off,” explained lead author Chris Purcell, who did the work with Bullock at UCI and is now at the University of Pittsburgh. “That first impact triggered instabilities that were amplified, and quickly formed spiral arms and associated ring-like structures in the outskirts of our galaxy.”
The Sagittarius galaxy is due to strike the southern face of the Milky Way disk fairly soon, Purcell said – in another 10 million years or so.
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The Sagittarius impact as an architect of spirality and outer rings in the Milky Way - CW Purcell et al
- Nature 477 301 (15 Sep 2011) DOI: 10.1038/nature10417
Star-Crossed: Milky Way's Spiral Shape May Result from a Smaller Galaxy's Impact
Scientific American | John Matson | 2011 Sept 14
Milky Way Owes Its Shape to Crashes With Dwarf Galaxy
Space.com | Charles Q. Choi | 2011 Sept 14
Multiple dwarf strikes gave Milky Way its spirals
New Scientist | Justin Mullins | 2011 Sept 14