A line of galaxies formed after two dwarf galaxies collided head-on, ripping gas from each other
Keim et al./DECaLS
Astronomers have discovered a peculiar line of dwarf galaxies that might have been formed as a result of a high-speed cosmic collision resembling a bullet in space.
Michael Keim and his team from Yale University utilized the Keck Observatory in Hawaii to observe a distinctive trail of 12 small and faint dwarf galaxies located approximately 75 million light years away from our own Milky Way galaxy.
The trajectory and velocity of these dwarf galaxies suggest that they emerged from a direct collision between two specific galaxies known as NGC 1052-DF2 and NGC 1052-DF4. The collision caused gas to be stripped from the galaxies, leading to the formation of clusters of stars due to gravitational forces.
Michael Keim mentions, “They’re very unique. It’s the only system like this that’s known.” The researchers have given this system the nickname “bullet dwarf,” drawing parallels to a similar assemblage of larger galaxies referred to as the Bullet Cluster.
The collision between NGC 1052-DF2 and NGC 1052-DF4 is estimated to have occurred around 9 billion years ago, with the galaxies colliding at a speed of 350 kilometers per second relative to each other. During this encounter, gas was torn away from each galaxy, resulting in the formation of star clusters devoid of dark matter.
It is highly unusual for galaxies to lack dark matter, as it typically constitutes a significant portion of their total mass, sometimes exceeding 90 percent. Keim and his colleagues speculate that dark matter, unlike gas, does not interact with regular matter or even itself, which explains its absence in the aftermath of the collision.
This discovery challenges alternative theories regarding the nature of dark matter, suggesting that it is indeed a distinct particle that can be separated from galaxies. Keim states, “This is saying dark matter is a particle, and it can become separated from a galaxy.”
Topics:
