According to Gaia, a space observatory launched in 2013, there is something that appears to have ripped a huge hole into the Milky Way, our Galaxy.
While analyzing Gaia’s observations, a Harvard-Smithsonian Center for Astrophysics’ scientist, Ana Bonaca , noted an enormous gap , a “dark structure” in one of the tidal streams. Last month she presented her research findings at the American Physical Society’s meeting in Denver.
The scientist was focusing on tidal streams produced by stars escaping from globular clusters which are usually found at the edges of a galaxy.
The evidence for the “dark impactor” is a series of holes in our galaxy’s longest stellar stream names GD-1. The stellar streams are lines of stars moving across a galaxy and many times they originate in smaller blobs of stars that collided with that very galaxy. The streams have a uniform density usually, if there is nothing to interfere with them. However, Bonaca detected a hole in one of them. As per her report “the on-sky morphology suggests a recent, close encounter with a massive and dense perturber”.
The hole is enormous, so whatever made it must have been huge as well. “It’s much more massive than a star”, she said. “Something like a million times the mass of the sun. So there are just no stars of that mass. We can rule that out. And if it were a black hole, it would be a supermassive black hole of the kind we find at the center of our own galaxy.” The trouble with this information is that there are no visible signs of a supermassive black hole anywhere in the surrounding area, therefore the “perturber” is unknown.
“It’s a dense bullet of something” Bonaca told LiveScience. Telescopes failed to find the source so is fair to wonder what it could possibly be.
Telescope observations do not show any large luminous object (meaning a structure made from ordinary matter that reflects light) moving away from the hole. This led Bonaca to consider that perhaps the perturbation was caused by a dark matter. Dark matter is a form of matter that is thought to account for at least 27 percent of the universe. The primary evidence for dark matter is that calculations show that many galaxies would fly apart instead of rotating if they did not contain a large amount of unseen matter. The scientists hypothesized that it exists because of the gravitational force it exerts on normal matter, being “dark” and not reflecting light, it cannot be seen.
“Observations permit a low-mass dark-matter subhalo as a plausible candidate,” Bonaca said.
A dense blob of dark matter that crashed through the tidal stream would be an exciting find for scientists, as it would provide them the opportunity of studying this substance so difficult to find. The finding at last of a dark matter “bullet” would fit with current predictions about what dark matter is like and the research suggests that it is “clumpy,” signifying that it is not smooth and evenly dispersed around our universe.
Identifying a clump of dark matter “opens up the possibility that detailed observations of streams could measure the mass spectrum of dark-matter substructures and even identify individual substructures,” the researcher added.
However without s clear confirmation the possibility of being a luminous object is not to be ruled out. It could be that it’s a luminous object that went away somewhere, and it’s hiding somewhere in the galaxy,” her abstract concluded.
As her research is still in early stages and her findings are yet to be published in a peer-reviewed journal, LiveScience has reported that her presentation was welcomed by the conference attendees.
Chris Mcfadden is the lead editor for Swerd Media. Chris has written for several online publications including the Huffington Post, Vanity Fair and Bleacher Report. Chris is based in Los Angeles and covers issues affecting California. When he’s not busy writing, Chris enjoys traveling and hiking.