First galaxy sans dark matter challenges longstanding belief about universe

To the uninitiated, the galaxy NGC 1052–DF2 is just another galaxy among billions that adorn the observable universe. Behind the mundane name hides a peculiar aspect that not only sets it apart from any other galaxy in the universe, but might also fundamentally challenge established ideas about how galaxies form and evolve.

Scientists announced Wednesday that NGC 1052–DF2, or just DF2, located about 65 million light years away, is the first galaxy ever observed to have little or no dark matter, making it a complete mystery for astronomers and cosmologists.

The finding is likely to disrupt dominant notions of galaxy formation as contemporary science believed the presence of dark matter to be a pre-requisite for the formation of galaxies. In case the findings n DF2 are confirmed and a similar lack of dark matter is observed in other galaxies too, human understanding of galaxy formation would have to be fundamentally re-imagined.

What is dark matter?

Dark matter in itself is one of the universe’s biggest enigmas. Despite never having been observed directly, scientists have inferred its presence through the gravitational influence it has on other matter that populates the universe. It is believed that dark matter is responsible for the vast majority of all the mass in the universe. In fact, most of what we claim to know about the universe rests on this belief. Based on observations of other galaxies, DF2 was expected to have about 100 times more dark matter than regular matter. Instead researchers found almost none according to a paper published March 28 in the journal Nature.

The researchers used a combination of lenses called the Dragonfly Telephoto Array which enabled them to track the motion of 10 embedded star clusters. This gave the team an estimate of how much mass the galaxy contains. To their surprise, scientists found that there wasn’t much deviation between the observed mass of the galaxy and combined mass of the star systems indicating the lack of the unseen matter seen in every other observed galaxy.

The absence of dark matter in DF2 and the disparity in characteristics of different galaxies paradoxically confirms the presence of dark matter in other parts of the universe laying to rest a longstanding doubt on the existence of dark matter itself.