Gravitational lensing

Gravitational lensing happens when light is distorted by the presence of a massive object. The gravitational field of a massive object extends far into space, and causes light rays passing close to that object (and thus through its gravitational field) to be bent and refocused somewhere else. The more massive the object, the stronger its gravitational field and hence the greater the bending of light rays. Gravitational lenses change the apparent position of a background object and can also magnify it, making it easier to study.