Dark Twin of the Milky Way Galaxy, Discovered
An international team of astronomers discovered a massive galaxy composed of dark matter, an opposite of Milky Way's bright and teeming composition.
Called 'Dragon 44,' the galaxy is about the size of Milky Way galaxy but with fewer stars.
"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," astronomer Pieter van Dokkum, lead author of a paper said in a statement.
The latest discovery led by an astronomer at Yale University was published in the Astrophysical Journal Letters. The study was conducted using W.M. Keck Observatory and the Gemini North telescopes in Hawaii. An 8-meter Gemini North telescope was used to study the halo of the clusters of stars around the galaxy's core. The velocities of stars are used to measure a galaxy's mass.
What the astronomers found out is not what is expected of a dark or dim galaxy. "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," Roberto Abraham said in a press release.
The massive galaxy is about one trillion times the size of the Sun, similar to the size of Milky Way. Based on the study, only one-hundredth of one percent of the galaxy is made up of stars and normal matter, the rest are in the form of dark matter. The paper described dark matter as "hypothesized" materials that remain unseen but is believed to make up for more than 90 percent of the universe.
Although finding a dark matter-consumed galaxy is not new, astronomers were surprised it is not common to find massive galaxies dominated by dark matter. Some of them are 10,000 times less massive as compared to Dragonfly 44. Dragonfly 44 was discovered in the Coma constellation about 300 million light-years away, according to CNN.
Astronomers are still surprised with the fact that this type of galaxy, composed of mostly dark matter can exist. The astronomers' next venture is to find out more about the dark matter.