A curious dwarf galaxy may have originated from a bullet-like collision in the universe.

Michael Keim from Yale University and his team employed the Keck Observatory in Hawaii to examine the distinctive trails of 12 small dwarf galaxies located approximately 75 million light-years from the Milky Way.

The orientation and velocity of the galaxies indicate that they resulted from a head-on impact between two galaxies known as NGC 1052-DF2 and NGC 1052-DF4. This collision expelled gas, which eventually coalesced into a group of stars due to gravitational attraction.

“They’re exceptionally unique,” states Kayme. “This is the only known system of its kind.”

Keim and his colleagues named this system after a similar cluster of large galaxies referred to as Bullet Clusters.

It is believed that the two galaxies collided at a speed of 350 kilometers per second around 9 billion years ago. As they passed through one another, gas was stripped from each galaxy. “While it’s improbable for two stars to collide,” notes Kayme, “the same does not apply to gas clouds.”

Interestingly, the remnants of stars left after the collision appear to lack dark matter. This is quite unusual, as most galaxies contain a substantial amount of dark matter, often comprising over 90% of their total mass.

Keim and his team theorize that this anomaly may stem from dark matter’s inability to interact with regular matter during the gas stripping process or because it remained unaffected by the interaction.

This finding may challenge alternative theories regarding dark matter, which posit that discrepancies in stellar and galactic behavior stem from gravitational effects rather than the existence of dark matter particles. “This suggests that dark matter is indeed a particle that can be separated from a galaxy,” explains Kayme.