Milky Way


Human understanding of the Milky Way is an ongoing process. The more we learn about it, the more we realize how much we still have left to discover. Recently, research that was presented by Harvard-Smithsonian astrophysicist Ana Bonica underscores this point in dramatic fashion. Bonica shared information indicating that a mysterious, unknown force is punching holes into the Milky Way. At this point, neither she nor anyone else is sure of what is causing the interruptions which are said to look like cosmic bullet holes or like something caused by a hammer.

What Do “Bullet Holes” In The Galaxy Look Like, Anyway?

What does a hole in a galaxy look like and how do you know when you’ve found one? That may be one of the first questions that everyday astronomy fans may have when they consider Bonica’s evidence. To better understand Bonica’s findings, it helps to consider that stars are arranged in the galaxy as what’s known as a “stellar stream” or a line of stars that travels through the galaxy as a group with a single gap in the middle. The longest of these in the Milky Way is called GD-1. For her research, Bonica studied GD-1 closely and noticed that there was at least one additional hole in it, different than the original gap in the center. This new hole was ragged as if something that been dragged through the string punching a hole in the center. Whatever had punched through it seemed to have dragged everything, including stars and other matter, behind it after it passed through.

Ruling Out Some Causes Of The Hole

Bonica and other scientists are using the term “impactor” to describe whatever it was that caused the hole in GD-1. They can’t give it a different term because, as of yet, they’re not quite sure what it is. However, while they can’t rule anything out 100%, they believe it likely is NOT either another star or a black hole.

How do they know this? For starters, they can tell that whatever the impactor is more massive than any other star in the galaxy. and is in the range of a million times larger than the mass of Earth’s sun. That helps to rule out the possibility that it is, itself, a star. Experts have also run detailed comparisons between the impactor and what they know about the black hole at the center of the galaxy. The comparison shows that whatever caused the jagged hole in GD-1 doesn’t have the trademark flares or radiation that most black holes show. While it’s not impossible that the Milky Way has a second black hole, most other galaxies have just one. A second in our galaxy would be highly unlikely.

Is It Made Of Dark Matter?

After ruling out that the hole is likely not a star or a black hole, the one possibility for what it could be is dark matter. While this possibility is exciting to researchers they’re careful not to jump to that conclusion entirely, in part, because there’s so much left to learn about what dark matter is. If it turns out that they can confirm the impactor is dark matter, it would add to the base of information about what dark matter is and how it acts. For example, it would show that dark matter has the potential to clump together, which is consistent with other theories scientists currently hold.

Still A Mystery

Though scientists are working to rule things out and develop new theories on the impactor, nothing is known for certain. The only thing that scientists do know is that something incredibly large is punching holes in the Milky Way. As they continue to analyze their findings and watch for new evidence, what that something is will hopefully become clearer.