Dark Galaxies Discovered Hiding in the Coma Cluster May Shed Light on Dark Matter

First Posted: Jun 23, 2015 12:45 PM EDT

Astronomers have discovered a staggering number of more than 800 dark galaxies in the famous Coma Cluster. The "ultra dark galaxies" may reveal a bit more about these mysterious features in space.

These galaxies appear very diffuse and remarkably extended, as seen by the light of stars they contain. Many are similar in size to the Milky Way, but have only a thousandth of the stars that our galaxy does. The population of stars within such fluffy, extended galaxy is subject to rapid disruption due to a strong tidal force detected within the cluster. This means that something invisible must be protecting the fragile star systems of these galaxies; in fact, researchers believe this "something" could be an excessive amount of dark matter.

In this latest effort, the Subaru Telescope revealed that these large galaxies contain old stellar populations. They also show a spatial distribution similar to brighter galaxies in the Coma Cluster. This suggests that the dark galaxies have been a long-lived population of galaxies within the cluster. The amount of visible matter they contain-less than one percent-is extremely low compared to the average fraction within the universe.

So why are these galaxies dark in the first place? It's likely they lost the gas they need to create new stars during or after their formation process. However they lost this gas, what matters is that the dark galaxies may offer insight into the model of galaxy formation.

The findings not only reveal a bit more about galaxies, but may also tell researchers a bit more about dark matter. Scientists hope to continue researchers these dark galaxies and measure the stellar motions of the galaxies, which may expose the distribution of dark matter.

The findings are published in the Astrophysical Journal Letters.

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TagsGalaxy, Dark Matter, Dark Galaxy, space