Astronomers have discovered a “dark twin” of the Milky Way that is made up almost entirely of dark matter. In a study, published in The Astrophysical Journal Letters, researchers found that a population of large galaxies was identified in the Coma cluster, calling the ultra-diffuse galaxy Dragonfly 44.
According to CNN, Dragonfly 44 is 300 million light years away and this “dark twin” comes in direct contrast to the sparkling Milky Way galaxy. “Dragonfly 44 is an incredibly large but diffuse and dim galaxy,” the article says. “Encircling its core is a halo made up of clusters of stars, much like what we see in the Milky Way. But this galaxy is only 0.1% stars. The Milky Way has more than a hundred times that.”
The other 99.9 percent, according to the article, is made up of dark matter. That’s why, despite its size being similar to that of the Milky Way, it cannot be seen, given that it is nearly entirely “cloaked in darkness,” comprised of much fewer stars. According to the Science World Report, dark matter is believed to comprise 85 percent of everything in the universe.
Lead study author Pieter van Dokkum told CNN that the discovery is exciting, albeit very misunderstood, and could pave the way to finding other galaxies to study. “It’s very exciting because we thought we had sort of figured out what the relationship is between galaxies and dark matter. This discovery turns that on its head.”
According to YaleNews, scientists initially spotted the “dark twin” with the Dragonfly Telephoto Array, built by van Dokkum and fellow study author Roberto Abraham. They were then able to get a closer look with the help of the W.M. Keck Observatory and Gemini North telescope in Hawaii. The researchers also pointed out that the discovery of a galaxy comprised of dark matter isn’t new, however, the other galaxies that have been discovered were far less massive.
The researchers now hope to find galaxies a little closer to home in order to research dark matter in a bit more detail. Van Dokkum told the Washington Post that he hopes someday darker galaxies will be detected, including ones made entirely of dark matter.
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Dragonfly 44, ‘Dark Twin’ of Milky Way, Discovered