bullet dwarf

Meanings

1. An ultradiffuse galaxy and dwarf galaxy with little or no dark matter, but with young very luminous globular clusters, about the same age as most of the stars in the galaxy.
2. An ultradiffuse dwarf galaxy that resulted from the collisions of two dwarf galaxies, where the stars, gas, and, dust, collide, bind, and shocked together, creating a new single dwarf galaxy and starburst, while the companion dark matter haloes continue onward on their former paths, separating from the now singular galaxy.
3. Any of a series of ultradiffuse dwarfs lined up on the path of the two dark matter haloes after collision, the remnants of the collision of two, perhaps not dwarf, galaxies, falling behind due to matter shockwave interactions the dark matter did not experience.

Etymology

Blend of Bullet Cluster + dwarf galaxy. From being a situation analogous to the Bullet Cluster of galaxies, except involving a single dwarf galaxy. Where the Bullet Cluster is a galaxy cluster shorn of its dark matter the result of two galaxy clusters colliding and combining, but their dark matter haloes passing through each other and continuing on their way.