A team of Keio University astronomers has discovered that the mysterious ultra-high-velocity molecular feature in the Milky Way known as the "Bullet" is not alone. Located about 10,000 light-years from the Sun, the Bullet exhibits an extraordinarily broad velocity width of about 120 km s−1 and an enormous amount of kinetic energy. Because of these extreme properties, scientists have proposed that the Bullet may have been formed by an isolated black hole without a companion star.
Using the Atacama Large Millimeter/submillimeter Array (ALMA), the team identified eight additional high-velocity components, dubbed “Petit-Bullets,” which surround the main Bullet. Analysis of their spatial distribution and velocity structures indicates that these Petit- Bullets likely share a common origin with the Bullet. The team’s discovery suggests that these features were not produced by a single compact object, but rather by a group of compact massive objects plunging at high speed into a molecular cloud.
This study presents the first high-resolution observational evidence of the interaction between a high-velocity object group, possibly including a black hole, and a molecular cloud in the galactic disk. The findings suggest that high-velocity molecular features may serve as indicators of otherwise invisible object populations in our Galaxy, offering new insights into the distribution of black holes and their role in galactic evolution.
These findings were published in The Astrophysical Journal Letters on February 23, 2026.
