Mysterious Galaxy X Found Finally? Dark Matter Hunters Would Like To Believe So

Excerpt from techtimes.com


Astronomers

have long suspected strange ripples in hydrogen gas in the disk of our

Milky Way galaxy are caused by the gravity of an unseen dwarf galaxy

dominated by dark matter — and now they think they’ve found this

“Galaxy X.”

The prediction of an invisible dark matter dwarf galaxy orbiting our

Milky Way, made in 2009, may have had its “observational confirmation,”

say researchers at the Rochester Institute of Technology in New York.

RIT astronomer Sukanya Chakrabarti and her colleagues analyzed

near-infrared data from the European Southern Observatory’s VISTA

telescope to discover four young stars clustered in the constellation

Norma.

The stars are 300,000 light-years distant, well beyond the edge of the Milky Way’s disk, they report in the Astrophysical Journal Letters.

“They can’t be part of our galaxy because the disk of the Milky Way terminates at 48,000 light years,” says Chakrabarti.

“These young stars are likely the signature of this predicted

galaxy,” she says, suggesting the dwarf galaxy is difficult to see

through the obscuring dust of our own galaxy and because the majority of

its mass is invisible dark matter.

Chakrabarti was the first to predict its existence in 2009 based on

her analysis of the ripples seen in our home galaxy’s outer disk.

“I decided to see if I could actually find the thing,” she says.

“It was a difficult prediction to test because it was close to the

plane [of our Milky Way galaxy], and therefore difficult to see in the

optical.”

The infrared capability of the VISTA telescope

allowed Chakrabarti and her fellow astronomers to peer into previously

unexplored regions close to our galaxy’s disk plane that are

inaccessible using visible light.

Dark matter is a hypothetical but never directly observed form of

matter believed to account for most of the matter and mass of the

universe.

Its existence has been inferred from effects observed on visible

matter and on the structure of the universe, attributed to dark matter’s

gravitational pull.

Large galaxies like our own Milky Way likely have many small

satellite galaxies dominated by dark matter that are thus difficult to

see, astronomers have suggested.

Chakrabarti’s 2009 study had predicted a specified mass and location

for the unseen galaxy, and radiation from the four news discovered

stars, known as Cepheid variables, allowed her to derive accurate

distances and test her prediction.

“The discovery of the Cepheid variables shows that our method of

finding the location of dark-matter dominated dwarf galaxies works,” she

says.

“It may help us ultimately understand what dark matter is made up of,” she adds.

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Mysterious Galaxy X Found Finally? Dark Matter Hunters Would Like To Believe So