Scientists discovered a massive galaxy named Dragonfly 44 that is primarily composed of dark matter. To determine the amount of the material, they measured the speed of its composing stars.
The galaxy contains 99.99% dark matter, which is a new record in the Universe as the average proportion of dark matter is only 27%.
Dark matter had been forever elusive, and no scientist has ever been able to determine its existence or its properties.
Dragonfly 44 is situated 300 million light years away from Earth. While it has the same mass as the Milky Way, it has very few stars, which made it stay hidden for decades.
The tiny dwarf galaxies also have a great quantity of dark matter. However, this would be the first time a massive galaxy would display such a density of the unknown material.
Dragonfly 44 had been discovered in 2014, and the scientists were amazed that nothing seemed to be holding it together.
A recent study recorded the speed of stars, as the faster the stars, the more massive the galaxy should be. The measurements had been done using the Keck Observatory on Mauna Kea in Hawai’i, and the monitoring was done during six nights.
The researchers used the DEIMOS instrument to measure star velocities in order to determine the mass of the galaxy.
The recorded speed of the stars was of 30 miles per second. Therefore, the researchers say that the stars themselves do not represent the only mass inside the galaxy. The only conclusion left was that the rest of it was dark matter.
The previous record in terms of dark matter content belonged to a galaxy in the Virgo cluster that had 99.96% dark matter. However, to settle things down, Dragonfly 44 is made of 99.99% dark matter.
The scientists believe that these galaxies are placed in a dense and violent region, and the dark matter that is included in their composition is protecting them from other galactic forces.
Whereas the formation of this type of galaxies remains a mystery, the researchers focus on the fact that their stars appear to exist in compact clusters.
Having objects of study that are created almost exclusively by dark matter might help astronomers explore the properties of the elusive material. Until now, the researchers had only small galaxies to analyze. The existence of massive galaxies will offer them new study premises.
Image Source: Wikipedia
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