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#Science

Researchers lift the veil off the dark-matter laden galaxy. Is it the ‘Galaxy X’?

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Researchers over at the Rochester Institute of Technology may have found the location of a dark-matter rich dwarf galaxy whose location was previously unknown using data from European Southern Observatory’s survey VISTA.

The location of the dwarf-galaxy was given away by hot pulsating stars which the researchers studies. Astronomers call such young stars Cepheid variables or “standard candles” that they use to measure distances. According to Sukanya Chakrabarti, assistant professor in RIT’s School of Physics and Astronomy these are the most distant Cepheid variables found close to the plane of the Milky Way.

The reason for using VISTA’s survey data was that it allows scientists look at the structure of the galaxy and distant stars at low latitudes. Infrared surveys may help resolve current discrepancies between observations and the current cosmological paradigm by giving us a more complete view of the structure of the Milky Way, Chakrabarti said.

Back in 2009, Chakrabarti had predicted the existence of a dwarf-galaxy based on her analysis of ripples in the Milky Way’s outer disk. The latest discovery is an extension of her previous research wherein she had predicted the location of the dark-matter dominated dwarf galaxy.

Radiation emitted by the Cepheid variable stars allowed her to derive accurate distances and test her prediction. Chakrabarti analyzed VISTA’s database of tens of millions of stars to find these clustered Cepheid variables in the Norma constellation, all within one degree of each other.

Chakrabarti calls the young stars as signature of the new predicted galaxy and she says that these young stars can’t be a part of our Mikly Way as our galaxy terminates at 48,000 light years.

“The discovery of the Cepheid variables shows that our method of finding the location of dark-matter dominated dwarf galaxies works,” she said. “It may help us ultimately understand what dark matter is made up of. It also shows that Newton’s theory of gravity can be used out to the farthest reaches of a galaxy, and that there is no need to modify our theory of gravity.”

Researchers added that earlier they were not able to test their prediction as the galaxy is too close to the plane “and therefore difficult to see in the optical”, however, “VISTA, was able to help us to lift the veil and see these young pulsating stars.”

The paper announcing the discovery appears in Astrophysical Journal Letters and is available online.