Overview
- A Yale-led team used the Keck Cosmic Web Imager to measure stellar velocities in NGC 1052-DF9 and found the star motions match the visible stellar mass, indicating little or no dark matter in the galaxy.
- DF9 is now the third claimed dark‑matter‑deficient object in the same thin linear chain as DF2 and DF4, a pattern that strengthens the idea of a shared, unusual origin.
- Study authors favor a 'bullet‑dwarf' collision in which gas and stars were ripped away from their dark‑matter halos, producing dark‑matter‑poor remnants and implying dark matter behaves like a physical substance.
- Teams are carrying out follow-up observations with instruments including the Mothra telescope and radio arrays to look for residual gas and to test whether other galaxies in the trail show the same dynamics.
- Separately, recent simulations and the January detection of a starless, HI‑rich object called Cloud‑9 motivate searches for nearby ‘dark galaxies’ that contain gas and dark matter but no stars and could be found by radio telescopes.