Researchers have proposed a new method to detect compact dark matter clusters, known as microhalos, which are currently too small to be identified by standard astronomical techniques. The approach relies on precise astrometry, specifically measuring the shifts in the positions of quasar images caused by gravitational lensing.
The method focuses on how massive foreground galaxies warp spacetime, creating multiple images of distant quasars. Small dark matter structures along the line of sight can cause subtle changes in the apparent positions of these images. Scientists plan to track these positional shifts over time to distinguish them from other gravitational disturbances.
The calculations cover structures with radii ranging from 0.005 to 2 parsecs and masses between 3 × 10⁻⁶ and 100 solar masses. The lower mass limit is comparable to that of Earth. Detecting these objects would help verify whether dark matter structure formation continues at such small scales.
The study evaluates the method using two gravitationally lensed quasars: B1422+231 and SDSS J1029+2623. The required measurement precision for these systems is approximately 0.1 and 1 microarcsecond, respectively. Achieving this level of accuracy remains a significant challenge for current observational technology.
Practical implementation faces obstacles, as individual stars within the lens galaxy can cause similar positional shifts, known as microlensing. Furthermore, the signal depends on the long-term stability of microhalos throughout the evolution of the universe. Researchers note that these estimates demonstrate potential rather than current detection capabilities.
