Astronomers Uncover Dark-Matter Dominated Galaxy X Marked with a Cluster of Stars

Astronomers may have discovered a hidden galaxy, called Galaxy X. Veiled behind clouds of dust, the dark-matter-dominated galaxy is marked by a cluster of young, pulsating stars.

Actually spotting the galaxy wasn't easy. The researchers analyzed near-infrared data collected by ESO's survey, VISTA, to find four young stars that are located about 300,000 light-years away. These young stars are Cepheid variables, which means that they're "standard candles" that astronomers use to measure distances.

"These young stars are likely the signature of this predicted galaxy," said Sukanya Cakrabarti, one of the researchers, in a news release. "They can't be part of our galaxy because the disk of the Milky Way terminates at 48,000 light-years."

Earlier studies actually predicted the location of the dark-matter dominated dwarf galaxy. The recent discovery of these Cepheid variable stars allowed the researchers to derive accurate distances and test this prediction.

"The discovery of the Cepheid variables shows that our method of finding the location of dark-matter dominated dwarf galaxies works," said Chakrabarti. "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."

Optical wavelengths can't penetrate dust and gas in regions of space that are close to the galactic plane. That's why infrared was necessary. In fact, new 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.

"I decided to see if I could actually find the thing," said Chakrabarti. "It was a difficult prediction to test because it was close to the plane, and therefore difficult to see in the optical. This new survey, VISTA, was able to help us to life the veil and see these young pulsating stars."

The findings are published in the Astrophysical Journal Letters.

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