Astronomers may have found the dark matter-dominated 'Galaxy X'

Astronomers may have found the dark matter-dominated "Galaxy X," it has been revealed.

A cluster of young, pulsating stars discovered in the distant regions of the Milky Way may mark the location of a previously unseen dark-matter dominated dwarf galaxy hidden behind clouds of dust, on the far side of our galaxy.

A team, led by Sukanya Chakrabarti from Rochester Institute of Technology, analyzed near-infrared data collected by the European Southern Observatory's survey VISTA to find four young stars approximately 300,000 light-years away. These young stars are Cepheid variables "standard candles" that astronomers use to measure distances.

According to Chakrabarti, these are the most distant Cepheid variables found close to the plane of the Milky Way.

The stars appear to be associated with a dwarf galaxy Chakrabarti predicted in 2009 based on her analysis of ripples in the Milky Way's outer disk. Chakrabarti's earlier study predicted the mass and 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.

Invisible particles known as dark matter make up 23 percent of the mass of the universe. The mysterious matter represents a fundamental problem in astronomy because we don't understand what it was, Chakrabarti said.

VISTA's infrared eyes allow scientists to study unexplored regions close to the galactic plane that are inaccessible to optical surveys. Optical wavelengths cannot penetrate the dust and gas in these regions.

This next-generation sky survey helped 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.

The study is published in Astrophysical Journal Letters.