The Discovery Of Milky Way's 'Dark Twin' Could Lead To A Detailed Study Of Dark Matter
The astronomers discovered a vast galaxy made up of entirely of dark matter, which they dubbed Dragonfly 44. This could unravel the mysteries of dark matter as the researchers could study them in detailed.
The Dragonfly 44 is the collection of stars lies about 330 million light-years from earth in a group of galaxies, which is known as Coma cluster. It is about the size of Milky way and comprises of about 1 billion stars, which is about 1 percent the numbers of stars in the galaxy. The Milky Way has about thousands of millions of stars and there are more millions of stars in the galaxies.
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The study was printed in the Astrophysical Journal Letters. It was led by Pieter van Dokkum astronomer from Yale University and other colleagues. Van Dokkum said that very soon after its discovery, they realized this galaxy had to be more than meets the eye. He further said that it has so few stars that it would rapidly be ripped apart unless something was holding it together.
Dragonfly 44 is in the form of dark matter, which is an invisible substance that is believed to make up 85 percent of everything in the universe. Van Dokkum told the Huffington Post that they knew about other galaxies that are wholly dark matter, but those are tiny dwarf galaxies that are about a million times less massive than Dragonfly 44.
"It is an exciting discovery," said Jeremiah Ostriker, an astrophysicist at Columbia University. "It gives us a chance to study [dark matter] in detail - close-up."
According to Yale News, the astronomers identified the Dragonfly 44 with a telescope invented by van Dokkum and Roberto Abraham from University of Toronto, which is known as Dragonfly Telephoto Array. Dragonfly 44's mass is approximately 1 trillion times the mass of the Sun. This is similar to the mass of Milky Way. On the other hand, only one-hundredth of 1 percent of that is in the form of stars and "normal" matter. They said that the other 99.99 percent is in the form of dark matter. This means that Milky Way's dark twin is a vast amount of unseen mass.
Van Dokkum said that scientists have been searching for distinctive signal in dwarf dark galaxies. On the other hand, the signal would be much stronger in a big dark matter galaxy like Dragonfly 44. "The race is on to find massive dark galaxies are even closer to us than Dragonfly 44, so we can look for feeble signals that may reveal a dark matter particle."