The Absolute Cosmos: Mystery behind a galaxy containing 99.99% dark matter solved

The formation and evolution of galaxies is impossible to decode without the presence of dark matter. Scientific calculations show that dark matter presence in the galaxies varies ten to three hundred times the total quantity of visible matter.

However, this ratio was found out of line in case of a galaxy, which was thought to be containing 99.99 percent dark matter. The galaxy is called Dragonfly 44 and it was found in 2016.

Dragonfly 44 lies about 330 million light years away in the Coma Cluster, a cluster with thousand other galaxies. DF44 is an ultra diffuse galaxy with luminosity much less than that of our Milky Way galaxy.

Since its discovery, the galaxy was thought to be the peculiar as the quantity of dark matter measured was almost equivalent to that of Milky Way. However, compared to Milky Way’s hundred thousand million stars, DF44 only contains a hundred million stars.

Meaning, the galaxy has ten thousand times more dark matter than its stars. This changed the whole perspective of dark matter presence in galaxies.

This huge amount of dark matter in DF44 challenged the current models of galaxy formations. This prompted scientists to further study the galaxy and to check whether if it is really anomalous or if it was wrongly measured.

Thus, to solve this mystery, an international team of scientists from Kapteyn Institute of the University of Groningen (Netherlands), the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL) re-examined the galaxy.

The team re-counted the number of globular clusters bound to DF44 using Hubble Space Telescope. They found only twenty clusters which is way too less than previous count of eighty.

For some unknown reasons, the total number of globular clusters is connected to the total mass of a galaxy. This enable scientists to measure mass of a galaxy.

The low number of globular clusters reduces the total amount of dark matter in DF44. Furthermore, this amount of dark matter in DF44 is consistent with what is expected for this type of galaxy.

The ratio of visible matter versus dark matter has come down from 1:10,000 to 1:300.

Prior to this study, scientists were not able to explain the Dragonfly 44 anomaly using the current galaxy formation models. Now, with previous results turning out to be wrong, the DF44 has now become a normal galaxy.




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Absolute Cosmos

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