Dragonfly 44 Galaxy Consists Almost Entirely of Dark Matter

Posted on August 28, 2016

Astronomers say Dragonfly 44 is a dark Milky Way sized galaxy that consists almost entirely of dark matter. The images above show the galaxy as seen by the Sloan Digital Sky Survey (left) and the Gemini telescope (right). The Gemini long exposure image reveals the galaxy as a faint elongated object.

Dragonfly 44 is located in the Coma constellation. It is about the same size as the Milky Way but has far fewer stars. Astronomers discovered the galaxy using the world's most powerful telescopes.

Yale University astronomer Pieter van Dokkum, lead author of the study, says in a statement, "Very soon after its discovery, we realized this galaxy had to be more than meets the eye. It has so few stars that it would quickly be ripped apart unless something was holding it together."

The mass of the galaxy was determined by using the velocities of the stars in the galaxy. The Gemini telescope revealed a halo of spherical clusters of stars around Dragonfly 44's core. The galaxy has a mass estimated to be 2 tredecillion kilograms or 1 trillion times the mass of our Sun.

Study co-author Roberto Abraham of the University of Toronto says, "Amazingly, the stars move at velocities that are far greater than expected for such a dim galaxy. It means that Dragonfly 44 has a huge amount of unseen mass."

A research paper on the findings was published here in the journal, The Astrophysical Journal Letters.

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