Femtolensing

Femtolensing is a phenomenon in astrophysics that occurs when a gravitational lens, such as a galaxy or a cluster of galaxies, bends the path of light from a distant source, typically a quasar or a gamma-ray burst. This bending causes the light to be magnified and distorted, creating multiple images of the same source. The term "femto" in femtolensing refers to the extremely small angular separation between these multiple images, which can be as small as a few microarcseconds. This phenomenon is particularly useful for studying the distribution of mass in the lensing galaxy or cluster, as well as for probing the structure of the universe on very small scales. Femtolensing has been observed in various astrophysical systems, and its study has provided valuable insights into the nature of dark matter and the evolution of galaxies.