Around 27% of our universe is made up of dark matter. In our home-galaxy, there’s about 5 times more dark matter than regular matter. But now scientists have discovered a distant galaxy that’s made almost entirely out of dark matter.
Dark matter is a very mysterious substance. So far, scientists don’t really know much about it. The reason why it’s called that is because it does not emit or interact with electromagnetic radiation, such as light. For this reason, it remains invisible to regular scans. We know of its existence from the way in which its gravity affects regular matter.
The newly discovered galaxy is quite different than our own. It has the same mass as the Milky Way. But nearly all of it made up of this enigmatic dark matter.
Scientists speculate there might be more like it out there. The Dragonfly 44 galaxy is located 300 million lightyears away. Unfortunately, that makes it difficult for scientists to study dark matter firsthand. To put that into perspective, one lightyear is about 93 million miles.
The scientists who made this discovery stumbled upon more or less by accident. And interestingly enough, they used a telescope built out of camera parts to do it.
The Dragonfly Photo Array that captured the images was built by a group of Yale astronomers. The first impulse to build it came more out of a frustration with how expensive and cumbersome modern-day astronomical equipment is.
The lenses used by these cameras were very well suited to spot cosmic objects that aren’t very well lit. they’re coated with a special that filters out errant light. It makes images sharper and crisper, and removes lens flare effects. It took them a while to raise the money to build the array, but it 2012 they managed to do that.
After studying several nearby galaxies, they decided to turn their sights towards the Coma Cluster, and were surprised to discover multiple galaxies, roughly the same size as the Milky Way, but much less bright.
The Surprising Properties of Dark Matter
According to Pieter van Dokkum, one of the lead authors of the study, “They are so diffuse, these galaxies, so tenuous, that they would be ripped apart. There just wasn’t enough mass to hold them together”
Normally, the bulk of a galaxy is made up of dark energy and dark matter. These two unknown substances make up around 95% of the universe. Like dark matter, dark energy has not been studied, and cannot be observed.
Scientists assume it exists because of the universe’s tendency to continuously expand. This type of energy is what pushes matter apart. Without regular matter, galaxies would tear up.
So what keeps Dragonfly together?
It seems the answer is dark matter. As mentioned earlier, we don’t really much about dark matter, other than the fact that it exists. And that it’s different from normal matter.
But this new galaxy throws a spanner in the works. According to Dokkum, “We thought that that ratio of matter to dark matter was something we understood. We thought the formation of stars was kind of related to how much dark matter there is, and Dragonfly 44 kind of turns that idea on its head.”
He concludes, “It means we don’t understand, kind of fundamentally, how galaxy formation works.” This discovery could change the way in which we understand the universe.
Image Source: Caelum Observatory