Astrophysicists have recently discovered something that has left them completely baffled. Something is causing massive bullet-like holes in the Milky Way’s GD-1 stellar stream. This utterly strange phenomenon has been observed in a long string of stars. The astrophysicists have suggested that an extremely large object could have possibly collided violently with the Milky Way’s stream. This has raised new questions as to the forces that shape our galaxy.
The Secrets of the Milk Way’s GD-1 Stellar Stream

What is the GD-1 Stellar Stream, anyway? Well, it is believed that the gravitational forces of the Milky Way tore apart a globular star cluster, leaving behind remnants that are now referred to as the GD-1 stellar stream. This stream stretches across the galaxy and provides researchers with an excellent opportunity to study the effects of gravitational forces. While observing the stream, they noticed strange gaps, flanked by spurs of displaced stars. To them, this potentially suggests some kind of powerful and unknown disruption. Due to their unique nature, the existence of these gaps makes the GD-1 stream a focal point of interest, especially regarding the dynamics of our galaxy.
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The Unexplained Dense Bullet

Ana Bonaca, the astrophysicist who first identified these gaps, described them as “dense bullets.” Although the object left no trace, it is thought to have a mass a million times greater than the sun! According to Bonaca, there are no known black holes or stars that match these characteristics. This led the researchers to look for other possible explanations for this anomaly. What they do know is that the sheer scale of the disruption caused is a sure indication that the object was incredibly dense and powerful.
Ruling Out the Usual Suspects

Conventional explanations for this anomaly, including black holes and massive stars have already been ruled out. A star does not exist that has the mass to cause the gaps and a supermassive black hole would be part of a galaxy core, not simply roaming around through space. Even molecular clouds, which occasionally interfere with star trajectories, are far too weak to explain the observed gaps. This glaring lack of potential suspects really makes it clear why this is such a mystery to many.
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Could Dark Matter Be the Answer?

So far, the most plausible theory seems to be dark matter – an invisible substance theorized to make up the majority of the mass of the universe. If a dense dark matter clump collided with the GD-1 stream, it could potentially produce these disruptions. The ΛCDM cosmological model predicts that dark matter creates dense substructures in galaxy halos, which this hypothesis aligns with. If this turned out to be correct, it would provide us with new evidence for the very nature of dark matter.
The Challenges of Studying This Milky Way Mystery

The lack of concrete evidence makes investigating the GD-1 anomaly particularly difficult. Dark matter is invisible and therefore can only really be detected through its gravitational effects. Researchers employ advanced simulations to explore various possibilities, however, limits in observational technologies prevent definitive results. Yet, upcoming missions, like the Vera C. Rubin Observatory, could contribute important information to help solve this great mystery.
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Alternative Explanations For the Gaps in the Milky Way Stream

Dark matter may be the current leading contender, but other possibilities are still being looked into. For example, exotic astrophysical objects may yet offer alternative explanations. These objects include self-interacting dark matter and primordial black holes. Self-interacting dark matter models predict that dark matter particles can collide and produce dense clusters, which may possess the qualities required to disrupt the GD-1 stream in the Milky Way.
The Potential Implications For Astrophysics

Understanding the gaps in GD-1 means revolutionizing our understanding of the universe. If a dark matter subhalo is verified as its cause, it will validate crucial aspects of existing cosmological models and shed light on the properties of dark matter. The peculiar “bullet holes” in the GD-1 stream serve as a cosmic puzzle that continues to intrigue researchers in astronomy This discovery, whether driven by dark matter or some other undiscovered phenomenon, has opened up new lines of investigation. As researchers probe deeper into this mysterious riddle, their results could lead to significant advances in our knowledge of the universe’s hidden forces. The journey to finding the truth about the Milky Way is only just beginning!