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Press Release 11-103

Just Four Percent of Galaxies Have Neighbors Like the Milky Way

Our home galaxy belongs to a rare subset among the billions that populate the cosmos

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Visualization of the Milky Way galaxy at 16 million to 13.7 billion years old.

This image, taken from a visualization created by the Advanced Visualization Laboratory at the National Center for Supercomputing Applications (NCSA), shows the formation of the Milky Way galaxy at 16 million to 13.7 billion years old. Brian O'Shea of Michigan State University (formerly of Los Alamos National Laboratory) and Michael Norman of the University of California at San Diego collaborated on this research.

Credit: National Center for Supercomputing Applications


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Image showing the Milky Way with Magellanic Clouds circled.

Researchers are interested in the cosmological context of the Milky Way--is it a special galaxy in any way? They found thousands of galaxies like it in the Sloan Digital Sky Survey, and also thousands of matching halos in the Bolshoi simulation, and asked, how many have neighbours like the Milky Way's Magellanic Clouds? In the real and simulated universes they found that roughly five percent of Milky Way-like galaxies have two satellites like the Magellanic Clouds. In this video, see why our galaxy is a bit unusual!

Credit: Busha, Kaehler, Marshall & Wechsler, KIPAC/Stanford University

 

Image and text showing galaxies mapped by the Sloan Digital Sky Survey.

Researchers see galaxies in the sky, but cannot see the dark matter clumps surrounding them. However, they can simulate them as they form in a model universe. In this video, they show how well the observed distribution of galaxies in the SDSS sky survey, and the predicted distribution of model galaxies in the Bolshoi simulation agree.

Credit: Busha, Kaehler, Marshall & Wechsler, KIPAC/Stanford University

 

Image and text showing the Milky Way with the Magellanic Clouds circled.

How did our galaxy form, and and when did its neighbors arrive? Researchers found all the dark matter halos in the Bolshoi simulation that had subhalos with speeds, distances and masses that matched the Magellanic Clouds, and then visualized one of them to show what the Milky Way's development may have been like. The Magellanic Clouds likely arrived together, recently! See the formation of the Milky Way and the Magellanic Clouds in this video.

Credit: Busha, Kaehler, Marshall & Wechsler, KIPAC/Stanford University