Dwarf Galaxies Found to Harbor 1,000 Times More Dark Matter

Thursday, September 12, 2013

Dwarf Galaxies Found to Harbor 1,000 Times More Dark Matter

Astronomers at The University of Texas at Austin believe they have discovered the answer to a 20-year debate over how the mysterious cosmic “dark matter” is distributed in small galaxies. They found that the distribution, on average, follows a simple law of decreasing density from the galaxy’s center, although the exact distribution often varies from galaxy to galaxy. The findings are published today in The Astrophysical Journal Letters.

Dark matter is matter that gives off no light, but that astronomers detect by seeing its gravitational tug on other objects (like stars). Theories abound on what dark matter might be made of — unseen particles, dead stars, and more — but nobody knows for sure. Though mysterious, understanding the nature of dark matter is important, because it makes up most of the matter in the universe. The only way to understand how the cosmos evolved to its present state is to decode dark matter’s role.
For that reason, astronomers study the distribution of dark matter within galaxies and on even larger scales. Dwarf galaxies, in particular, make great laboratories to study dark matter, say astronomers John Jardel and Karl Gebhardt, because they contain up to 1,000 times more dark matter than normal matter. Normal galaxies like the Milky Way, on the other hand, contain only 10 times more dark matter than normal matter.

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Multiple streams of Sagittarius dwarf galaxy

Uploaded on Nov 26, 2011

The illustration of multiple streams produced by the disruption of the Sagittarius dwarf galaxy in the Milky Way halo. The orange sphere shows the location of the Sun in the Galaxy. The Sagittarius dwarf galaxy itself is located in the middle of the stream.The size of the area shown in the movie is approximately 600 thousands light years (200 kiloparsecs)