In 2009, Sukanya Chakrabarti predicted the existence of ‘Galaxy X’, a dwarf galaxy orbiting the Mily Way. Now, using data from the European Southern Observatory’s near-infrared survey VISTA, she appears to have found it. A research team, led by Chakrabarti, found four young pulsating stars approximately 300,000 light years away.

The young stars are called “Cepheid variables” which translates as “standard candles”. They are used by astronomers to measure distances. According to the researchers these are the most distant Cepheid variables found close to the plane of the Milky Way.

The stars appear to belong to the dwarf galaxy Chakrabarti predicted based on an analysis of ripples in the outer disk of the Milky Way. Radiation emitted by the Cepheid variable stars allowed Chakrabati to derive accurate distances to test her earlier predictions.

The Visible and Infrared Survey Telescope for Astronomy (VISTA) telescope is a reflecting telescope with a 4.1 metre mirror, which has been operating since 2009. It is located at the Paranal Observatory in Chile.

The telescope works at infrared and near-infrared wavelengths and is the largest survey telescope in the world used for this purpose.

Using the 3-ton VIRCAM camera, researchers are able to see objects that would otherwise be invisible because they are obscured by dust, cool or because their light is in the redder wavelengths.

Chakrabarti analyzed the VISTA database to find the Cepheid stars in the Norma Constellation. All of them were found within one degree of each other.

“These young stars are likely the signature of this predicted galaxy. They can’t be part of our galaxy because the disk of the Milky Way terminates at 48,000 light years,” said Chakrabarti, assistant professor in Rochester Institute of Technology’s School of Physics and Astronomy in a statement.

The ‘Galaxy X’ described by Chakrabati and her team in Astrophysical Journal Letters is believed to be dominated by dark-matter and hidden by clouds of dust. Dark matter is believed to make up 23 percent of the universe’s mass. Dark matter is a fundamental problem in astronomy because little is understood about it according to Chakrabati.

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

VISTA’s infrared lens allow researchers to study regions close to the plane of the Milky Way that cannot be seen with the naked eye because of dust and gas. Infrared survey’s frequently help resolve discrepancies between predicted and visible observations.

“I decided to see if I could actually find the thing. 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 lift the veil and see these young pulsating stars,” said Chakrabarti.