How is the mass of a galaxy cluster determined using gravitational lensing?

The mass of a galaxy cluster can be determined using gravitational lensing by analyzing the distortion of light from background galaxies as it passes near the massive galaxy cluster. According to general relativity, massive objects, such as galaxy clusters, can curve the fabric of spacetime around them, causing light from more distant objects to bend.

When astronomers observe the background galaxies, they notice that their shapes are distorted—this effect is known as gravitational lensing. By studying the degree of this distortion, scientists can infer how much mass is present in the galaxy cluster. The stronger the lensing effect, the more massive the galaxy cluster is likely to be. This relationship allows for an estimation of the cluster's mass, making gravitational lensing a powerful tool in astrophysics to understand the distribution of mass in the universe.

Other choices do not directly relate to the method of using light distortion to determine mass. Calculating distances to nearby stars and examining colors do not provide information about the mass of objects in a distant cluster, and measuring temperature pertains more to the dynamics of the cluster's gas rather than the determination of mass through lensing effects.