2021 REWIND of the highlights from the field of astronomy. 

Gravitational lensing: When light passes one of these objects, such as a cluster of galaxies, its path is changed slightly. This effect, called gravitational lensing, is only visible in rare cases and only the best telescopes can observe the related phenomena. Smaller objects, like individual stars, can also act as gravitational lenses when they pass in front of more distant stars.